2010 NRMCA - National Ready Mixed Concrete Association

ConcreteJanuary/February 2011A PUBLICATION OF THE NATIONAL READY MIXED CONCRETE ASSOCIATION2010NRMCAQualityBenchmarkingSurveyHighlights of the2010 NRMCA IndustryData SurveyTake Control of Your2011 Fuel BudgetWinter Freezes Water, NotYour Employees’ Brains

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infocusConcreteJanuary/February 2011, Vol. 10, No. 1contentsConcrete infocus is published for:National Ready Mixed ConcreteAssociation900 Spring StreetSilver Spring, Maryland 20910Phone: (301) 587-1400Fax: (301) 585-4219www.nrmca.orgPresident: Robert A. Garbini, P.E.Managing Editor:Kathleen Carr-SmithAssociation Editor:Frank CavalierePublished by:Naylor, LLC5950 NW 1st PlaceGainesville, Florida 32607Phone: (800) 369-6220Fax: (352) 331-3525www.naylor.comPublisher: Jill AndreuEditor: Sean GarrityProject Manager: Heather CioccaMarketing Research:Amanda NiklausAdvertising Director:Maureen HaysAccount Representatives:Lou Brandow, Krys D’Antonio,Ryan Griffi n, Norbert Musial,Christine Ricci, Rick Sauers,Jamie Williams, Chris ZabelLayout and Design:Emma LawAdvertising Art:Jean-Baptiste Bonnelame©2010 Naylor, LLC. All rightsreserved. The contents of thispublication may not be reproducedby any means, in whole or in part,without the prior written consent ofthe publisher.PUBLISHED DECEMBER 2010NRC-S0610-9979features11 2010 NRMCA Quality Benchmarking Survey16 Inch by Inch19 Highlights of the 2010 NRMCAIndustry Data Surveydepartments9 Truck Tracs: Take Control of Your 2011 Fuel Budget23 Education Matters: Winter Freezes Water,Not Your Employees’ Brains26 Advertisers’ Index/Advertiser.comPlease visit the electronic version of Concrete Infocus at http://www.nrmca.org/news/connections/ for bonus features, including Who to Call at NRMCA, Tech Talk,Quality Corner and an assessment of pervious concrete maintenance techniques.Cover ©www.istockphoto.comVisit our Buyers’ Guide online at NRMCA.OfficialBuyersGuide.netCONCRETE in focus ı 7

THE LEARNINGSTARTS NOWPut down this magazine and flip on your computer for somefree industry webcasts. They’re crammed with practicalinformation you can use right now. Sure makes waiting forthe sunny days of CONEXPO-CON/AGG 2011 a little easier.MARCH 22-26LAS VEGAS USACheck out any or all of these webcasts free (each a $70 value).Concrete Always CracksPrevent callbacks by eliminating thisperennial problem.Project Management FundamentalsBecome a better project manager,whether you’re a rookie or a veteran.Paydirt: Mass Excavating Alternativesfor Mass ProfitChoose the right equipment to pile up profits.Best Practices for Fleet ManagementSave 2% to 5% in your fleet maintenancebudget with these efficiencies.Register to view whenever atwww.conexpoconagg.com/tasteof2011Co-locatedwith© 2010 Association of Equipment Manufacturers

truck tracsTake Control of Your 2011 Fuel BudgetFuel price protectionoffers a new, uniqueapproach to fuel budgetcontrol.With the downturn in the economy,the ready mixed concrete industry isbeing forced to price bids competitivelywith little room for error—any inaccuracyin your cost estimates can hurt your cash flowand earnings. And while many are diligent incapturing the cost of materials and labor in theirbids, most struggle with estimating fuel costs.As a major cost, fuel poses aunique challenge to the ready mixedconcrete industryWhile many fleets track their fuel usage inmiles per gallon, this does not provide a truepicture of fuel usage for ready mixed concretecompanies like yours. Mixer trucks spend varyingamounts of time at idle, mixing concrete oroff-road travel. And this is before we even considerpower-take-off (PTO) energy use. A 2006NRMCA study found that PTO accounts for20-25% of total fuel consumption alone.Ready mixed concrete companies, along withother businesses, have found it extremely difficultto accurately pin down fuel costs. Since 1999,the average annual price movement from lowto high as reported by the U.S. Dept. of Energy(DOE) is $0.7544/gallon. Even if we disregard2008, which presented unprecedented fuel pricefluctuations, the yearly average fluctuation isapproximately $0.61 since 1999. As many know,even small fuel price increases can result in large,unbudgeted fuel cost variance.These dramatic price fluctuations coupledwith a longer construction season (from whatused to be a nine month season to now 12months) makes it even more difficult for you toforecast future fuel prices to accurately price abid upfront.With growing emerging market demand,weakened U.S. dollar, geopolitical realities of theMiddle East combined with unexpected naturaldisasters, fuel prices are anyone’s best guessand continue to expose companies to significantoperating risk. As a result, it’s crucial for yourcompany to adopt a more strategic and proactiveapproach to protecting your fuel budgets.Introducing fuel price protectionHistorically, most companies were not ableto hedge their fuel costs because they did nothave large enough fuel budgets or the necessaryin-house expertise to decipher and navigate thefuel commodities market. This is changing withadvances in technology and fi nancial instrumentsgiving companies of all sizes more control overtheir fuel budgets.Fuel price protection offers a new, uniqueapproach to fuel budget control. You select aprotection price that represents the most yourcompany wants to pay for fuel. When fuel prices(as measured by an index such as the U.S. DOEnational average fuel price) go above that protectionprice, your company receives a payment equalto the difference. This allows you to accuratelypredict your company’s maximum fuel costs.With this fi nancial arrangement, there is nochange to how you fuel your fleet and no pre-purchaseof fuel. Fuel is still purchased at the pump,in bulk, or via a discount fuel card. Fuel price protectionis not tied to actual usage. If the predictedamount of fuel is not used, there is no cost to yourcompany. And if fuel prices drop, you can stillbuy fuel at the current, lower market price.Fuel price protection offers some specificadvantages to the ready mixed concrete industry:° Increases competitive advantage: Remainprofitable by locking in your project marginsupfront without worrying about cost overrunsdue to fuel. Ultimately, this may enable youto undercut the competition with fi xed bids/contracts and gain market share.° Helps mitigate risk: Better upfront risk planningcan help you cap your fi nancial exposure,prevent detrimental damage to your fuel budgetand protect your bottom line.° It’s proactive: Protect your most volatileexpense upfront and redirect your limitedresources to focus on strategic initiatives.Why are we discussing fuel priceprotection now?Since 1999, the lowest fuel prices have occurredon average within a six week timeframe—betweenCONCRETE in focus ı 9

three weeks before year-end and threeweeks after the New Year. After that point,fuel prices typically rise and continue in abell curve pattern reaching their peak inJune and July.STOPLOSINGBUSINESS!Don’t let hot water shortages slow you down,ensure your hot water supply keeps up withYOUR demand.The RM99 Direct Contact Water Heater• 99.7% fuel efficient• Instantaneous hot water• Stainless steel, non-pressurized unit• Convenient 4-point connectionTo schedule an on-site plant analysis orfor information contact Kemco Systems800.633.7055www.kemcosystems.comsales@kemcosystems.comIf history is our guide, right now is thebest time for you to cap your company’sfuel costs. By taking advantage of lowerprice levels, your company can continue tobenefit from low fuel prices next year andKemco Systems is a proud memberand supporter of the NRMCAKEMCO SYSTEMSRM99DirectContactWaterHeaterturn one of your biggest fi nancial risks intoa competitive advantage.About PricelockPricelock, headquartered in RedwoodCity, CA, is a proud member of the NationalReady Mixed Concrete Association and hasintroduced a new way for businesses largeand small to incorporate stability and predictabilityinto their fuel budgets with itsfuel price protection program. Bringingtogether expertise in commodities, riskmanagement and technology, Pricelock hasprice protected over 100 million gallons offuel for Chrysler, Hyundai and other leadingbusinesses.The Pricelock program is simple andsafe: businesses get paid when fuel pricesrise above their protection price. When fuelprices fall, there are no hidden costs and theycontinue to buy at lower fuel prices unlikefi xed price programs. With Pricelock, planscan be created in any size allowing businessesto accurately estimate their fuel costseven for a specific project.■For more information, visit www.pricelock.com or call us at 650-517-5416.254429_Kemco.indd 17/31/06 9:38:12 AMwww.humboldtmfg.com1.800.544.7220if this looks familiar……get familiar withHUMBOLDT10492563_Humboldt.indd ı JANUARY/FEBRUARY 1 20119/15/10 10:56:50 AM

feature2010NRMCA QualityBenchmarking SurveyIntroductionThe 2010 NRMCA Quality BenchmarkingSurvey was conducted in the summer of2010. The need for this survey resulted fromdiscussions within the NRMCA ResearchEngineering and Standards Committee andthe survey questions were established by atask group of the committee. Surveys werecompleted by a ready mixed concrete producercompany or division. The survey had3 sections.• Section 1 - General company information• Section 2 - Quality indicators• Section 3 - Quality benchmarksThis report establishes averages and otherbenchmark from this survey. For this surveyrespondents were asked to use data from themost recent fi scal year. Respondents wereasked to avoid guessing and not to respondto questions where information was notavailable. This survey is intended to providebenefits to concrete producers in termsof industry statistics for quality initiatives.There were 28 respondents to this surveyfrom 16 companies. Some large companiessubmitted survey responses for several oftheir divisions.Section 1 - General companyinformation1.3 Annual Concrete Volume(cubic yards)The respondents to this survey produced acumulative 21.7 million cubic yards in 2009representing approximately 8.4% of estimatedready mixed concrete produced inthe U.S. for that year. The breakdown wasas follows:Annual Concrete Volume, Number ofcubic yardsRespondents≤100,000 1100,001 to 250,000 5250,001 to 500,000 6500,001 to 1 Million 121 to 3 Million 2>3 Million 21.4 Number of PlantsThe respondents to this survey supplied concretefrom a total of 670 plants. Company ordivision size ranged from 3 to 179 plants.1.5 Market served by companies – percentof annual productionAll respondedPercent of AnnualMarketProductionPublic (FAA, DOT,city, county) 37Commercial 37Residential 23Other 3Numbers represent the average value. Volumefor the residential market is lower thanexpected due to the overall drop in constructionin that market sector.1.9 Are you in a weathering region requiringair entrained concrete?All respondedPercent ofCold Weather Region RespondentsYes 68%No 32%Section 2 - Quality indicators2.1 Provide information on top 5 sellingmixtures.QuestionAverage2.1a Weighted averagestandard deviation (SD), psi 5052.1b Weighted average Avg.strength, psi* 37732.1c Weighted averagecoefficient of variation,COV, % 10.3%2.1d Average increment, % 28.6%2.1e Number air entrained 2.4*Even though 2.1b asked for averagestrength all respondents provided specifiedstrength. So the number reported is theweighted average specified strength.Weighted average statistics were determinedby multiplying the percent volume of each mixlisted and the individual mix statistic.2.1a and as a result 2.1c had 26 respondents.Other questions were responded to byall 28 respondents. Among the respondentswho answered 2.1a and 2.1c information wasprovided for 90% of the maximum possible130 mixtures. The weighted average SD was505 psi. According to ACI 214R-02, SD of500 to 600 psi would qualify as a good standardof concrete control for general constructiontesting.Average increment represents the incrementof the average strength above the specifiedstrength for the five mixtures reported bythe respondent. On average, the increment ofthe average strength of the mixtures over theaverage specified strength is 28.6% (1079 psi).For mixture submittals according to ACI 318CONCRETE in focus ı 11

the average increment should be 1.34XSD(677 psi) over the specified strength when atest record is available to calculate the SD. Thefact that concrete producers are providing anexcess of 402 psi above that is not unusual andcould be due to several reasons –1. Producers are reducing their risk of failingtest results compared to ACI 318’s 1%probability of strength tests failing theacceptance criteria.2. Producers could be supplying to concretewith a minimum w/cm and/or minimumcementitious content, which resultsin a higher average strength than thatrequired;3. Producers are unable to use SD informationin their mixture submittal, eitherbecause test record data are not available,not documented or specifications requiredesigning concrete mixtures to a fixedincrement above specified strength.2.1e shows that the data provided was splitequally among air entrained and non airentrained concrete mixtures. This questionwas asked because the strength variability ofair entrained mixtures is typically higher.2.2 Concrete rejected at jobsite as percentof production.Report percent based on total volume or loads.Include all rejected loads for reasons associatedwith quality, specification or delivery requirements,including the amount beneficiallyreused. Do not include concrete returned dueto ordering excess quantities. 24 respondedand the average was calculated as 0.57%. Thedistribution of responses was as follows:Percent ConcretePercent ofRejectedRespondents0% 7%0.001 to 0.1% 11%0.1 to 0.49% 21%0.5% to 0.99% 7%1% 39%Did not respond 14%Approximately 40% reported that rejectedconcrete is less than about 0.5% which is avery low number. Verbal estimates of returnedconcrete, which includes quantities returneddue to excess ordered, tend to be higher, suggestingthat a primary reason for returnedquantity is based on customers ordering practicesrather than for quality reasons.2.3 Cost to company to resolve customerproblems, in $ per yd3 produced.Include cost to repair, replace or mitigate hardenedconcrete issues because concrete did notmeet purchaser’s or specification requirements,expectation, etc. For example, if the companyproduced a total of 20,000 yd3 of concreteand the total cost paid for the above reasonswas $20,000 the cost should be calculated andreported as $1/yd3. 23 responded and the averagewas calculated as $0.42/yd3. The distributionof responses was as follows:Cost to Company. Percent of$/yd3Respondents0 7%0.01 to 0.2 29%0.21 to 0.5 25%0.51 to 0.99 7%1 14%Did not respond 18%2.4 Perception of company’s quality levelby customer in annual quality survey (orother means)All respondedQualityPercent ofPerceptionRespondentsNot Applicable 50%Excellent 18%Very Good 25%Good 7%Fair 0%Poor 0%Of the survey respondents, 50% of thecompanies report a quality perception that isExcellent, Very Good or Good. The remaining50% of the respondents do not track theircustomers’ perception of their quality level.While most companies survey their customersor otherwise attempt to annually gage theircustomers’ perception of the company, it isclear that such survey responses are related todelivery and other service-related issues.It is suggested that concrete producersincorporate the above or a similar question aspart of annual customer surveys or by othermeans. Why is the customer’s perception ofcompany quality level important? It conveysthe company’s emphasis on quality and continualimprovement. When customers associatequality with a ready mixed concreteproducer, they are less likely to assign blamefor problems and will attempt to identify othercauses for those problems. Owners and designprofessionals will be more likely to involvethe concrete producer in product requirementsin specifications for desired concreteperformance; or to solicit their advice whenproblems occur. The attention to quality initiativeswill foster increased business.Section 3 - Quality benchmarks3.1 Does your company maintain a qualityplan?All respondedQualityPercent ofPlanRespondentsYes 86%No 14%3.2 Is there a process in place to collect customerfeedback regarding company qualityand act on it?All respondedCustomer Feedback Percent ofProcessRespondentsYes 68%No 32%3.3 Total number of employees with qualitycontrol/technical function, includingfield and laboratory techniciansAll responded and the average was calculatedas 1.6 employees for every 100,000 yd3 ofannual production. An alternative estimateis there is one person with a quality control/technical service function for 62,500 cubicyards. The average for respondents below500,000 yd3 production was 2.3 (1 person per45,000 cubic yards) and average for respondentsabove 500,000 yd3 was 1.1 (1 personper 91,000 cubic yards). The distribution ofresponses was as follows:No. of QC/Tech per 1 person Percent of100,000 yd3 per, yd3 Respondents≤ 0.5 ≥ 200,000 7%0.5 to 1 199,000 to 25%100,0001 to 2 99,000 to 39%50,000> 2 < 50,000 29%3.4 Number of field and laboratorytechniciansAll responded and the average was calculatedas 1.2 for every 100,000 yd3 of annual production.Technicians are a subset of employeesreported in 3.3. An alternative estimateis there is one field/laboratory technician for84,000 cubic yards. The average for respondentsbelow 500,000 yd3 production was12 ı JANUARY/FEBRUARY 2011

1.8 (1 technician for 56,000 cubic yards) andaverage for respondents above 500,000 yd3was 0.7 (1 technician for 143,000 cubic yards).The distribution of responses was as follows:No. of field/lab techs per 1 technician Percent of100,000 yd3 per, yd3 Respondents≤ 0.5 ≥ 200,000 21%0.5 to 1 199,000 to 36%100,0001 to 2 99,000 to 32%50,000> 2 < 50,000 11%3.5 Average volume of concrete underresponsibility of one technical manager.Divide the total volume by the number oftechnical managers to represent an averagevolume for each manager’s responsibility. 26responded and the average was calculated asone technical manager with responsibility for326,000 yd3. The average for respondents withproduction less than 500,000 yd3 productionwas one technical manager with responsibilityfor 179,000 yd3 and average for respondentswith production above 500,000 yd3 was oneindividual for 434,000 yd3. The distributionof responses was as follows:Average volume underresponsibility ofPercent of1 technical manager, yd3 Respondents≤100,000 11%100,000 to 200,000 21%200,000 to 350,000 25%350,000 to 600,000 25%>600,000 11%Did not respond 7%3.6 Percent of quality control/technicalemployees above technician level withNRMCA Concrete Technologist Level 2certification or equivalentAll respondedPercent of Employees Percent ofwith NRMCA Level 2 Respondents< 20% 32%20% to 50% 32%>50% 36%3.7 Quality control costs, in terms of $ /average sales price of cubic yard.Include lab costs and all quality control staffsalaries, including corporate level technicalmanagers. Do not include back charges orpenalties. 24 responded and the average wascalculated as $1.14/yd3. The breakdown wasas follows:QC Cost to Company. Percent of $/yd3Respondents0 to 0.75 7%0.76 to 1.25 50%1.26 to 1.75 21%>1.75 7%Did not respond 14%3.8 Percent of production facilities that areinspected or certified - NRMCA or statehighway departmentAll respondedPercent ofPercent ofProduction Facilities Respondents< 20% 4%20% to 50% 7%>50% 89%3.9 Frequency of verifying accuracy ofmeasuring devices - scales, water metersadmixture dispensers, etc. (calibration orinternal checks) per plantAll respondedFrequency ofPercent ofVerifying Accuracy Respondents6 months or less 75%More than 6 months 25%3.10 Frequency at which mixers are inspectedfor wear and build-up per plantAll respondedFrequency ofPercent ofVerifying Accuracy Respondents6 months or less 86%Annually 14%3.11 Frequency at which technical managersreview batch records and mixture performanceper plantAll respondedFrequency ofPercent ofVerifying Accuracy Respondents< 1 month 36%1 to 6 months 61%7 to 12 months 0%> 12 months 4%3.12 Number of company laboratory facilitiespossessing at least one strength testingmachineAll responded and the average was calculatedas 0.34 for every 100,000 yd3 of annualproduction. An alternative estimate is thereis one laboratory with at least one strengthtesting machine for 295,000 cubic yards.The average for respondents with productionbelow 500,000 yd3 production was 0.40(one lab for 250,000 cubic yards) and averagefor respondents with production above500,000 yd3 was 0.30 (one lab for 330,000cubic yards).No. of labs Concreteper 100,000 volume per Percent ofyd3one lab, yd3 RespondentsNone 11%≤ 0.2 ≥ 500,000 14%0.201 to 0.4 499,000 46%to 250,0000.402 to 0.6 249,000 to 14%167,000>0.6 < 167,000 14%3.13 Number of laboratory facilities thatare inspected and participate in proficiencysample (CCRL) or regional round robintesting27 respondedThis question assumes the existence of alab that would conform to some of the requirementsof ASTM C1077 and will have a higherlevel of testing capabilities than lab facilitieslisted in 3.12. Of the respondents, 19 did nothave a lab in this category.Annual ConcreteNumber ofVolume, Number of respondentscubic yards Respondents with labs*≤100,000 1 0100,001 to 250,000 5 0250,001 to 500,000 6 2500,001 to 1 million 12 31 to 3 million 2 2**>3 million 2 2****Unless otherwise noted, respondentsreports one lab in this question.**One respondent reports 6 labs***Both respondents report 2 labs each.3.14 Frequency of measuring aggregatemoisture contentAll responded. This question resulted insome misinterpretation. Respondents couldmake only one of the four choices listedbelow. It is likely that some respondents havesome of their plants with moisture probesinstalled and selected that choice. The intentof the question was to gain an idea of the frequencyat which aggregate moisture is measured.The percentage of respondents thatindicate use of moisture probes is not in linewith the respondents in 3.15 that indicatethat they did not use the probes. In general,it appears that the respondents do pay closeattention to measuring the moisture contentof aggregates.CONCRETE in focus ı 13

Frequency ofPercent ofMeasurementRespondentsUse moisture probes 50%At least daily 39%Weekly 7%> Weekly 4%3.15 Frequency of calibration of moistureprobes per plantAll responded. As indicated above, there weresome problems with the wording of 3.14 and3.15 that could have resulted in some misinterpretation.The intent here was that companiesusing moisture probes should estimatethe frequency at which the accuracy of theseprobes were checked. This is generally done bycomparing the moisture probe reading withan aggregate moisture test. It is assumed fromthis question that most of the respondents douse moisture probes and for the most partcheck their accuracy relatively often.Frequency ofPercent ofMeasurementRespondentsDo not use moisture probes 7%Weekly 29%Monthly 29%Quarterly 21%Annually or Greater 14%3.16 Frequency of aggregate grading testsper plantAll respondedFrequency ofPercent ofMeasurementRespondentsUse aggregate suppliers data 25%Weekly 54%Monthly 14%Quarterly or Greater 7%3.17 Information collected on primarycements usedAll respondedInformationPercent ofCollectedRespondentsNone 4%Mill Test Reports 64%Mill test and C917 reports 25%Other cement company info 7%3.18 Frequency of quality control testingof cementitious materials from primarysourcesAll respondedFrequency ofPercent ofMeasurementRespondentsDo not test 57%Weekly 4%Monthly 7%Quarterly or Greater 32%3.19 Do you test cement in mortar or labconcrete batches?27 respondedPercent ofRespondentsYes 46%No 54%Did not respond 4%3.20 Typical number of unique classes ofmixtures maintained at a plant27 responded and the average number ofunique classes of mixes maintained was calculatedas 184 for each respondent. Responsesranged from 5 to 1000.3.21 Number of internal strength tests per10,000 yd3 of production concrete21 responded and the average was calculatedas 13.9 internal strength tests per 10,000 yd3of concrete produced. Assuming that averagetruck load is 8 yd3 this works out to about onetest for every 90 truck (1.1%) loads. Since theaverage plant in this survey produced 624 yd3of concrete in one week it can be calculatedthat one strength test is being conducted every1.1 weeks. The above calculations are for theaverage reported. It should be noted that somerespondents did not test their concrete at allwhile some tested at the rate of 50 strengthtests per 10,000 yd3 of production (4% of alltruck loads).3.22 Frequency of yield checks per plantAll respondedFrequency ofPercent ofMeasurementRespondentsNever test it 4%Weekly 43%Monthly 21%Quarterly or Greater 32%3.23 Do you evaluate independent labs’testing proficiency through documentationof within test variation (pair difference)?All respondedEvaluate independent Percent oflab test dataRespondentsYes 50%No 50%3.24 What percent of total concreterequires a mixture submittal in accordancewith ACI or DOT requirements?All responded and on average 69% of thetotal concrete furnished required a mixturesubmittal. The responses ranged from 40%to 100%.3.25 What percent of total concrete doyou use the standard deviation from pastrecords to establish the required averagestrength in accordance with ACI?All responded and on average for 51% of thetotal concrete furnished the average strengthused to design the mixture were based on usingstandard deviation from past test records. Theresponses ranged from 0% to 100%.3.26 What percent of total concrete hassome level of jobsite acceptance testing bya commercial laboratory?All responded and on average 66% of the totalconcrete furnished had some level of jobsiteacceptance testing. The responses ranged from40% to 95%.3.27 How many core sets have you had tocut in the last year because of low strengthresults or other reasons?All responded and on average 1.14 core setsare extracted for every 100,000 yd3 because oflow strength results or for other reasons. Threerespondents did not have to cut any cores duringthe last year.No. of core setsPercent ofper 100,000 yd3Respondents0 11%0.1 to 0.5 25%0.51 to 1.20 29%1.21 to 2.0 32%>2.0 4%3.28 What percentage of core tests resultedin the strengths being acceptable?21 of the 25 producers who had to cut coresresponded and on average 80% of the coretest results indicated that the concrete as furnishedcomplied with the acceptance criteriafor cores. The responses ranged from 0% to100%.3.29 What percentage of time when coretests are acceptable when full payment isreceived?21 of the 25 producers who had to cut coresresponded and on average 97% of the timesfull payment was received.3.30 When concrete is rejected at the jobsite,what percentage is due to:14 ı JANUARY/FEBRUARY 2011

All responded and the distribution of responsesis as follows:Percent ofCauseRespondentsSlump 43%Air content 32%Delivery time or exceedingrevolution limits 14%Other 8%Some reasons listed in the other categoryby respondents are• unit weight,• color,• temperature,• plant/mechanical breakdown,• mixture being too rocky or too sandy(contamination) or pumpability (or lackthereof),• dispatch order entry error,• wrong mix,• missing fibers,• wrong delivery time,• truck malfunction,• operator error,• cement content out of tolerance3.31 What percentage of call backs due tohardened concrete are related to:All responded and the breakdown is asfollows:Percent ofCauseRespondentsCracking 46%Strength 21%Scaling 20%Other 12%Some reasons listed in the other categoryby respondents are:• delamination, • color,• set time, • dusting,• workmanship, • finishing errors,• aesthetics, • contamination,• soft particles, • finishability,• yields,• workmanshipof contractor.ConclusionThis was the first survey on quality initiativesconducted by NRMCA under thedirection of the Research Engineering andStandards Committee. The goal of thesurvey is to evaluate typical resources andbenchmarks that support quality initiativesin ready mixed concrete companies. Consideringthat this survey represents informationwhen the industry was operating duringa period of downturn in the constructionindustry, it may not represent benchmarkvalues as one might expect during “normal”times. The goal of this survey is to measurequality benchmarks on company resourcesassigned for quality management systems andto provide for continual improvement in theindustry. NRMCA expects to conduct thissurvey once every two years. Questions willbe improved for clarity and other questionsmight be developed in future surveys.The following members of the Task Groupthat helped develop the survey are gratefullyacknowledged:Mark Williams, Williams Concrete Inc.Steve Ragan, Concrete Supply CompanyJeff O’Leary, Vulcan Materials CompanyChris Wolf, Shelby MaterialsJohn Vaughan, Irving MaterialsGodwin Amekuedi, ARGOS USAMike Epifano, Cemex■498524_Solomon.indd 1CONCRETE 10/4/10 in focus 4:15:32 ı PM 15

featureInch by Inch(Reprise)Introduction by Amy Miller, National Resource Director, NRMCAArticle by Randell Riley, P.E., Executive Director/Engineer for Illinois Chapter of ACPA and consultant toIllinois Ready Mixed Concrete AssociationIntroductionIn the “old days”(prior to 2008) we wereforced to sell concrete parkinglots based primarily on longtermcosts savings, or so we thought.We would perform life cycle costs analysesshowing those savings to engineers and ownersand anyone else that would listen. We wouldtout the longevity of the product citing examplesof concrete structures from the days of JesusChrist. Short of off ering our fi rst-born, wewould resort to any means of selling concretepavement advantages only to have the fi rst-costissue thrown back in our face. We thought wewere just fi ghting price but perhaps we werereally fi ghting our own lack of education.Various economic factors have drivenasphalt prices higher so now we believe wecan fi nally face fi rst-cost competition head-on.According to Randell Riley, P.E., executivedirector/engineer for the Illinois Chapter ofACPA and consultant to Illinois Ready MixedConcrete Association, we’ve always been ableto do this, yes, even in the “old days.” Belowis a reprint of Randy’s article entitled “Inchby Inch” explaining why we always had theoption to be cost competitive on concrete parkinglots. Randy cites examples from the IllinoisDepartment of Transportation, but franklythe example is apropos for most any state asRandy uses AASHTO 1993 Guide for Designof Pavement Structures as the basis of hisdiscussion.At NRMCA we endorse use of ACI 330The Guide for Design and Construction ofConcrete Parking Lots as the fi rst option forconcrete parking lots. The Guide and associatedspecifi cation off er an all-inclusive approach todesign and construction. Often engineers citeuse of AASHTO 93 as their design choicebecause they feel there is some comfort in usingthe same source as their DOT. We feel there aremany smarter reasons to use ACI 330 instead,but I will leave that for another discussion ( orWebinar, see below). When dealing with engineersand designers that refuse to move awayfrom AASHTO 1993 in designing their concreteparking lots, Randy’s article might do justthe trick in getting a reasonable specifi cation.Inch by InchI’d like to take a couple of minutes ofyour time to show you how concrete hasalways been fi rst-cost competitive if youwere designing the sections to actually carryroughly the same traffic and getting thesame life.Let’s take a typical Illinois parking lotpavement section. How many of you haveroutinely seen a section of 3-inches of bituminoussurface on 6-inches of granularmaterial? How many of you have seen evenless? How many inches of concrete would ittake compared to what the engineers andarchitects frequently pull out of their mysteriousdesign manual? And why? Let’s startwith the why.Most engineers and architects start oneof two places in Illinois: either Chapter 54 ofthe Illinois Department of Transportation’s(IDOT) Bureau of Design and EnvironmentManual (BDE Manual) for highways orChapter 37 of IDOT’s Bureau of LocalRoads Manual. (BLR Manual) Are thesereally appropriate for parking lots? Probablynot! IDOT designs for controlling vehiclesthat are principally trucks – and usually a lotmore than we are inclined to see on a typicalparking lot.For example, if you look at either of thesereferences they start at the bottom traffic levelswith about 12 percent truck traffic. Thereare provisions if you know what you aredoing to go below this level, but even thenthe minimum thickness for concrete fromthe design charts in the BDE Manual is currentlyabout 7.5 inches for soil conditionstypical of parking lot construction and 6.5inches for the BLR Manual. Both proceduresare mechanistically based and incorporateextremely high levels of reliability. Both also16 ı JANUARY/FEBRUARY 2011

2CHART 2 ASPHALT BASESUBBASE2,000 2,000LANE 16,000LANE 21”0” 3” 6”0” 4” 0” 4” 0” 4”52 80 552 2.5 2.8 3.22 2 70 73 106 5702,0002,0006,000LANE 1LANE 2SURFACE2½”0” 3” 6”PLAIN REINFORCED PLAIN REINFORCED PLAIN REINFORCED4.3 4.2 4.4 4.2 4.4 4.4555469 2.2 8403.13.80.0SERVICEABILITY INDEXAT END OF TEST000LOAD APPLICATIONSTO FAILURE (1,000’S)ALL SECTIONSIN SECOND ROWARE REPLICATESASPHALT SURFACE THICKNESS2”3”645743.01041.7873.31063.82502.41203.87103.55823.31.83.82.73.43.53.72.53.63.13.63.23.32.63.93.60.0SERVICEABILITY INDEXAT END OF TEST000LOAD APPLICATIONSTO FAILURE (1,000’S)LOOP2ALL SECTIONSIN SECOND ROWARE REPLICATESCONCRETECONCRETE THICKNESS3½”5”4.2 4.4 4.0 4.1 4.2 4.53.7 4.1 4.0 4.1 4.0 4.64.54.24.1 4.3 3.9 4.6 4.1 4.34.1 4.5 4.1 4.6 4.0 4.33.53.6imply that granular sub-base is “optional”at traffic levels typical of parking lots, butexplain “optional” to most engineers and theword “required” seems to take its place.What about the asphalt designs? Whatare the minimums there? The BLR Manualsays 3 inches on 8 inches of stone is adequate.So how do you actually compare these competingsections? Clearly, IDOT methods arenot the answer!There are a number of competing designsystems for concrete pavement in this designniche. Many of you are familiar with theConcrete Pavement Analyst (CPA) softwareavailable from National Ready MixedConcrete Pavement Association. It hasbeen discussed on several occasions at theIRMCA annual short course and seminarshave been conducted on its use by your association.CPA is largely based on a variationof the results of the road test conducted bythe American Association of State HighwayOfficials (AASHO). I will not go into detailhere, but CPA uses a variation on the structuralcoefficient approach to assign a structuralcoefficient to concrete.However, since the AASHO Road Testwas conducted right here in Illinois, whynot use the data, the methods and the equationslaid out in the 1993 Guide for Designof Pavement Structures? If it is meaningfulanywhere, it should be here in Illinois.First, a little history. The engineers at theRoad Test conducted testing on sections ofboth asphalt and concrete pavements underthe same traffic loadings at the test site westof Ottawa, IL. Interestingly, some of thesesections included loadings restricted to automobilesand light trucks; loads more typicalof convenience store and mall parkinglots. The concrete thicknesses on these sectionsranged from 2.5 inches of concrete upto 5 inches. How did they fare? One of mypersonal favorites, an out of print publication,Pavement Performance in the NationalRoad Test, produced by Portland CementAssociation in 1962 offers some insight. (Ihave a pdf if you are interested.)The tables above demonstrate how thepavement sections performed. The tables area little busy, but they are jampacked withexciting information for pavement geeksinterested in promoting concrete pavementsfor parking lot applications.During the Road Test vehicles ran overthe traffic loops until the loops had receivedroughly 1,114,000 axle load repetitions orthe pavement section had failed. Periodically,engineers at the Test Road would evaluatethe “serviceability” of the sections on a5-point scale, five being a smooth pavementin new condition and 1.5 having been determinedto be failure of a section in need ofserious repair. The vehicles ran in adjacentlanes restricting the specific loads to thoselanes. In our table you will see that one laneoperated with 2,000 lb. axle loads; the otherwith 6,000 lb. axle loads. By conducting thetest in this manner is was possible to compareperformance of different loads to oneanother while simultaneously evaluating theaffect of those loads on different pavementsections. The asphalt and concrete pavementsof different sections received identicalloadings under identical traffic for roughlytwo years.The tables as laid out depict the serviceabilityafter 1M plus axle loads shown as agrade ranging from 1.7 to 4.4. If the sectionfailed, i.e. reached a serviceability of 1.5, thenumber of axle-load repetitions in thousandsis shown. In addition, various subbasethicknesses were evaluated for both asphaltand concrete. For concrete sections meshreinforcementwas also evaluated as thatwas popular at the time of the test. (Meshreinforcement turned out to not make a difference,but that is perhaps an article foranother time. Needless to say, we no longeruse mesh in Illinois.)Let’s work left to right for the concretesection of Loop 2 and the 2½-inch concretepavements. Yes, they tested them that thin.Serviceability of the pavement sections for2,000 lb. axle loads similar to that of anautomobile were in very good condition, i.e.serviceability greater than 4.0 after 1M plusrepetitions. This was regardless of whetherCONCRETE in focus ı 17

featureHighlightsof the 2010NRMCA IndustryData Survey(Analysis of 2009 Data)By Michael J. Olivarri, CPA, Senior Vice President of Finance and Administration, NRMCAIntroductionThe Business Administration Committeeof the National Ready Mixed ConcreteAssociation annually administers theIndustry Data Survey. The survey is a benchmarkingtool against which companies inthe ready mixed concrete industry can measuretheir performance. The survey is confidentialin that all information submitted byeach company is submitted directly to andcompiled by an independent certified publicaccounting fi rm. Individual company detailsare restricted to the company submitting thesurvey and the accounting fi rm.The survey provides performance andratio analyses by which to analyze a company’sfi nancial performance in relation toother companies of similar size, scope orgeographic region. The survey is presentedin four sections: Company Size analysis (bycubic yards), Regional Analysis, CompanyArea Type Analysis and Trend Analysis.Content includes presentation of incomestatement items as a percentage of sales anddollars per cubic yard, fi nancial ratios, balancesheet data, company demographics,employee productivity data and five-yeartrend analysis of various fi nancial data.Although participation levels and companymix vary from year to year, bothnationally and regionally, the survey resultsare deemed statistically valid based on thenumber of responses and grow more statisticallyvalid as increased numbers of producersparticipate. The National Ready MixedConcrete Association continues to stress theconfidentiality of individual data submittedby participants and encourages increasedparticipation, which is vital for the continuedsuccess of the survey as a benchmarkingtool for the industry.Summary of ResultsThere were 189 respondents to the2010 survey, a slight increase over 2009participation levels. Average sales of onlythe ready mix component of a cubic yardof concrete for the 189 respondents was$38,832,739, or 442,607 cubic yards, down30% and 25%, respectively, from 2008levels of $55,759,785 and 592,244 cubicyards. Average sales for all components ofa cubic yard of concrete were $42,512,402,which is 31% lower than the $61,859,845for 2009.The average net sales price per cubic yardof concrete for a “Typical NRMCA Member”increased just over 2% from $94.15/cyd in2008 to $96.05/cyd in 2009, a net gain of$1.90/cyd. For 2009, “Industry Leaders” orthe “Upper Quartile” that fell into the top25% of overall performance had an averagenet sales price of $99.74/cyd, consistent withthe 2008 number of $99.66.For the “Lowest Quartile”, the averagenet sales price per cubic yard of concretedecreased from $94.47 to $94.36, whiletotal costs for this group increased over 6%from $98.84 to $105.07/cyd. The increasein those costs reflects the inability to trimfi xed costs in line with the decrease incubic yards sold as fi xed costs represented30% of a cubic yard of concrete for 2009versus just 21% in 2008. That translatedinto an additional $9/cyd in fi xed costsfor the lowest quartile over the 2008 levelof $20.03/cyd or an almost 45% increasefrom 2008. In contrast, fi xed costs percyd for the highest quartile representedonly 20% of a cubic yard of concrete andan increase of only 22% from 2008 levels.For both the lowest and highest quartilesas well as the typical member, variablecosts were in line with 2008 levels with thedecrease in fuel and cement costs offsettingother increases.Pre-tax profit for the typical NRMCAmember decreased from $0.20 to $-3.07(-1,635%), while pre-tax profit for industryleaders fell 26% in 2009 to $4.26/cyd.For the “Lowest Quartile”, pre-tax lossesof $4.37 in 2008 increased further to$-10.37/cyd.The following pages show the majorchanges in costs for a typical member percubic yard of concrete from 2008 to 2009.CONCRETE in focus ı 19

The included tables show the breakdown and the key variances forthe current and past surveys.Change,2009 vs.2008Income Statement, Dollars per Cubic Yard 2007 2008 2009 % $Material Costs (including freight)Cement costs 24.39 24.61 23.77 -3.4% (0.84)Fly Ash 1.77 1.99 2.13 7.9% 0.14Coarse Aggregates 12.77 14.23 13.55 -5.3% (0.68)Fine aggregates 8.58 9.29 9.51 2.6% 0.22Plant CostsPlant/Yard wages (hourly only - reg & OT) & Fringes 1.95 2.32 2.77 23.1% 0.45Delivery CostsDriver wages (for all on-duty time) 6.77 7.44 7.85 6.1% 0.41Fuel expenses (gas, diesel & oil for all truck mixers) 2.66 3.75 2.63 -42.1% (1.12)Direct Fixed Costs - PlantQuality Control (incl. salaries, fringes & lab) 0.59 0.70 0.85 25.4% 0.15Superintendent wages (or other wages not above) 0.74 0.94 1.51 77.0% 0.57Other direct plant expenses 0.53 0.72 0.96 45.3% 0.24Selling ExpensesSales salaries (commissions & bonuses) & Fringes 1.04 1.29 1.61 30.8% 0.32General & Administrative ExpensesOffice salaries and wages 0.80 1.10 1.31 26.3% 0.21Fringes (p/r taxes, FICA, Wrkr Comp, health., etc.) 0.38 0.55 0.59 10.5% 0.04Chart 1AComponents of A Cubic Yard of ConcreteTypical Co. vs. Upper & Lower Quartiles - 2009Chart 1BComponents of A Cubic Yard of ConcreteTypical Co. vs. Upper & Lower Quartiles - 2008Lower QuartileAvg Selling Price$9436 cyd$51.7154.8%$18.4319.5%$5.976.3%$28.9630.7%$-10.37-11%Upper QuartileAvg Selling Price$99.74 cyd$54.1054.24%$16.1916.23%$5.685.69%$20.1320.18%$4.264.27%Typical MemberAvg Selling Price$96.05 cyd$52.7054.9%$17.3518.06%$6.006.25%$23.0223.97%$-3.07-3.2%$0.00 $10.00 $20.00 $30.00 $40.00 $50.00 $60.00 $70.00 $80.00 $90.00 $100.00Material Costs Delivery Costs Plant Costs Fixed Costs Pre-taxChart 2: Pre-Tax Profit as a % of Sales byCompany Size - 2007 through 200915.0%10.0%5.0%0.0%-5.0%-10.0%-15.0%4.1%1.3%-4.7%Under 100,000cyd4.1%0.5%-0.9%100,000 -299,999 cyd5.7%4.6%300,000 -500,000 cyd-2.5%7.1%-0.4% -3.7%Over 500,000cyd6.7%0.2%-3.1%Typical NRMCAMember1.8%-4.6%Lowest Quartile-11.0%10.6%5.9%Upper Quartile4.3%Chart 3: Pre-Tax Profit as a % of Sales by Region2007 through 200920.0%15.0%10.0%5.0%0.0%-5.0%4.8%2.8%-0.6%7.0%-4.8%3.6%-1.9%1.8% 3.0% 2.1%2.3%1.9%-2.5%-4.7%10.9%3.7%0.6%15.2%5.2%5.7%6.9%2.5%6.7%0.2%-3.1%1.8%-4.6%10.6%5.9%4.3%2007 2008 2009-10.0%-15.0%-12.1%NE/MA SE Nth Ctrl Sth Ctrl Grt Lakes RockyMtnPac.Nthwst-11.8%Pac.SthwstTypicalMember-11.0%LowestQuartileUpperQuartile20 ı JANUARY/FEBRUARY 2011

TABLE 1: Efficiency Ratios by Company Size - 2007 through 2009CompanySize500K20092008200720092008200749454650.748.460.7-1.20%9.10%12.30%-2.90%20.00%10.40%2.53.02.92.82.73.14,1454,6634,9404,3535,4655,914$243,467$279,923$290,909$238,822$284,730$317,347$0.78$0.89$0.87$0.78$0.77$0.78TypicalMemberLowestQuartileUpperQuartile20092008200720092008200720092008200751.148.859.946.344.58153.643.550.1-2.50%80.00%10.10%-11.70%-6.10%3.40%6.90%8.90%16.40%2.72.73.12.33.13.23.03.13.04,0985,1585,5953,9275,1205,5833,9284,8165,818$230,900$276,054$304,003$222,693$275,837$273,832$225,633$291,643$315,995$0.77$0.79$0.79$0.72$0.95$0.90$0.80$0.95$0.76TABLE 2: Efficiency Ratios by Region - 2007 through 2009Region Year Days SalesOutstandingEBIT toTotal AssetsYardsper HourYardsperTruckSales perEmployeeVar. DeliveryCosts/MinuteNortheasternMid-AtlanticSoutheasternNorth CentralSouth CentralGreat LakesRockyMountainPacificNorthwestPacificSouthwestTypicalNRMCAMemberLowestQuartileUpperQuartile200962.7 0.10% 2.7 3,747 $232,000200859.4 5.70% 2.7 4,374 $271,0002007 63.2 8.60% 2.3 4,329 $255,000200945.2 -6.10% 2.1 4,160 $225,000200844.8 -3.20% 2.1 5,248 $266,0002007 41.8 10.20% 2.9 5,601 $307,000200952.1 2.80% 2.8 2,898 $216,000200845.8 -1.50% 2.8 4,199 $244,0002007 121.8 5.10% 3.0 4,493 $216,000200946.2 2.80% 2.8 5,408 $262,000200855 2.60% 3.2 6,985 $318,0002007 65.3 6.40% 3.5 7,398 $295,000200969.2 -2.90% 3.0 3,825 $202,000200869.3 -1.00% 2.9 4,561 $230,0002007 102 3.90% 2.8 4,644 $243,000200943.1 0.50% 2.6 4,023 $236,000200840.3 5.30% 3.0 5,082 $286,0002007 77.3 8.30% 2.7 5,831 $293,000200950.4 9.00% 3.5 3,621 $232,000200838.3 7.40% 3.6 4,740 $251,000200762 16.10% 4.1 6,611 $314,000200944.6 -20.00% 3.0 4,040 $234,000200832.9 4.60% 3.1 5,326 $364,0002007 50.7 15.00% 3.5 6,092 $412,000200951.1 -2.50% 2.7 4,098 $231,000200848.8 0.80% 2.7 5,158 $276,000200759.9 10.10% 3.1 5,595 $304,000200946.3 -11.70% 2.3 3,927 $223,000200844.5 -6.10% 3.1 5,120 $276,000200781 3.40% 3.2 5,583 $273,000200953.6 6.90% 3.0 3,928 $226,000200843.5 8.90% 3.1 4,816 $292,000200750.1 16.40% 3.0 5,818 $315,995$0.82$0.83$0.69$0.58$0.59$0.69$1.03$0.95$0.92$0.65$0.73$0.74$1.01$0.99$0.88$0.74$0.88$0.75$1.06$1.12$0.86$0.94$0.93$0.93$0.77$0.79$0.79$0.72$0.96$0.90$0.80$0.95$0.7622 ı JANUARY/FEBRUARY 2011

education mattersWinterFreezesWater,Not YourEmployees’BrainsBy Eileen Dickson, VicePresident of Education, NRMCAUse the Cold Months to YourAdvantage: Train andCommunicate. Winter traininghas critical advantages. The simplest is thatit changes the training pattern becausetime is on your side. The adage, “communicate,communicate, communicate,”really comes into play because frontlinesupervisors have the time to work and talkwith employees side-by-side in a slowerpace, solicit suggestions and positively correctmistakes. A clear message is sent thatthere is an atmosphere where employeesare willing and able, to talk with superiors,and mutually learn. These personaldiscussions are a great gage to tell you howthe business is doing and how to improveit. Second, for those companies who takeadvantage of instructor-led or computerbasedtraining, the slow business cycleallows your employee to spend more timeto really engage, master the curriculum,and personalize it to the company’s way ofdoing business. Let’s look at two commonscenarios ready mix producers face thistime of the year.Chicago plant manager Jack McKinleyfelt the cold blow right through him as he“A clear message is sent that there is an atmospherewhere employees are willing, and able, to talk withsuperiors, and mutually learn. ”walked the yard. Stan Adamczyk, his seniormixer driver, fi nished shoveling the snowmounted around the steps’ railing up tothe batch house. He had also chipped offbig patches of ice elsewhere in the yard todecrease a chance of anyone slipping. Stanand the other senior driver kept on all winterwere getting bored with the little, nondrivertasks. It looked like not one yardof concrete would be poured in the nextcouple of days. In fact, business had beenpretty awful for the last three weeks. Jackwanted to keep them occupied to both his,and their, advantage.Eight hundred fi fty miles south inDallas, the weather was a mild 48°F andbatchman Raul Perez was having his thirdcan of Dr Pepper with drivers Jose Delgadoand Jimmy Dawes. They only had a fi rstround on the books so afterward Jose andJimmy swept up debris around the conveyorbelts and emptied the trash cans. With theyard work well in hand, Raul needed tofi nd them something to do.Each of these plant operators startedout as mixer drivers so they saw value inthe drivers’ delivery skills and yard work.It was an added bonus to their mutual relationship.Yet each plant operator knew thatwith the experienced drivers, winter was agood time to to brush up on mixer driverskills and knowledge as well as refresh theircross training as substitute batchmen.In the case of cross-training for batching,adding responsibility increases subordinates’confidence in their ability toperform well, not only as a substitute, butwhen acting in their primary mixer driverrole. It also assures that when productivityis of utmost importance in low revenuetimes, someone competent is on reserve tostep in when needed.CONCRETE in focus ı 23

As for training specific to the mixerdriver job function, producers have two newoptions to consider, both from NRMCA.Recognizing that a producer’s greatest performanceliability lies within 50%+ of staffwho have the same job function, NRMCAupdated and adapted its premier mixer drivertraining curriculum, the Concrete DeliveryProfessional (CDP) Certification Program©,to an individualized, self-paced online learningtool. The online accessibility allows companiesto train individual drivers withoutdirect interaction with a trainer/supervisor- aperfect fit when that computer is not batchingand a driver is being paid to do nothingbetween loads! CDP Online is also accessibleanywhere, 24/7, from any computer.Originally developed with input from readymix concrete producers of all sizes throughoutNorth America, the material still focuses oninstructing drivers in their core competenciesas well as relaying why specific actionsare important and what the ramifications ofcompliance/non-compliance are to themselves,their company and their customers in less than20-minute units. It measures and documentsindustry-based standards, a positive reinforcementto the driver and company managementthat there is a measured training record for anemployee’s file.Additionally, in Winter 2011 NRMCAwill release a new series of Mentor Driver©lessons. As many are aware, there are 80+video titles in the series. Each will be reformulatedinto individual, interactive lessons,available on a CD. Drivers do NOT needsupervision or a peer driver to go through thematerial. Each lesson comes with two quizzesand one final test. When done, the driverprints a certificate if he/she passed, showingthe company measured and documented thetraining.With the pressure of so many wearingmultiple hats, NRMCA believes both programswill continue driver training and mitigateany possible “failure to train” citationsfrom EEOC or OSHA. NRMCA envisionsproducers will use the interactive lessons inone of two ways: after training a group ofdrivers, each driver can be assigned to takethe CDP Online certification or reviewin the accompanying individual interactiveMentor Driver© lesson to review what wastaught; or if a driver as a “problem” in oneperformance area, he/she could be assignedto go through that lesson as part of a performancerequirement, again showing the companyhas been pro-active to address a hole ina driver’s performance.Results, measurement, return on investment,testing, behavior change, performanceimprovement, expectations, accountabilityand learning applied on the job are the industry’sfuture for performance development andenhancement. Let the colds winds of Winter2011 be your company’s best friend. ■For more information on NRMCA’s educationaloff erings, please visit www.nrmca.org.IF YOU ARE PAYING FOR STORAGE ORHAULING PROCESS WATER OFF YOUR SITE,FORTRANS CAN HELP REDUCE ORELIMINATE THOSE COSTS!Fortrans process water management can provide solutionsto treat process water so that the water can be released tothe environment, recycled or returned to themunicipal wastewater treatment system.Our patented carbondioxide diffusion injectionsystems can treat andproduce process waterthat meets EPA standards.Fortrans systems aredesigned to be affordableand cost effi cient withminimal maintenance.All systems are guaranteedto perform to our customers’satisfaction!866-958-7267919-365-8004www.fortransinc.com357719_Enviro.indd 24 ı JANUARY/FEBRUARY 120113/10/08 4:12:08499960_Fortrans.indd PM111/4/10 8:32:43 AM

AdmixturesReason #42 - Increase ProductivityReason #18 - Improve Concrete PropertiesReason #1 - Reinforce Your Bottom LineThe Euclid Chemical Company has been providing field-proven concreteadmixtures for over 100 years. Our century-old dedication to continued researchand development of cutting edge admixture productsputs us on the forefront of concrete technology.It comes down to one thing, you need a companythat has been there, and will continue to be there.1-800-321-7628100 YEARSofEXPERIENCEONE SOURCE. Hundreds of Reasons.www.euclidchemical.com491241_TheEuclid.indd 1Instant Steam GeneratorDesigned specifically for heating water andaggregates, all with the one unit.Ultra-ConcreteWashout Filter®NEW8/18/10 11:47:03 PM“Will not makeaggregateMUSHY”Fuel savings up to 50%Low carbon monoxidelevelsFull bore steam in 15secondsNo stationary engineerrequiredNo chemical treatment ofwaterfor More infoCall: 1-800-388-1339or visit: www.steamengineering.ca• Reduce turbidity• Reduce pH• Recycle aggregate• Solve your washoutdilemmabefore and afterUltraTech International Inc.800-764-9548www.ConcreteFilter.com419624_Steam.indd 12/12/09 8:51:46480496_Ultratech.indd PM1CONCRETE 5/26/10 in focus 11:09:07 ı 25 AM

advertisers’ index/advertiser.comADMIXTURESBASF ConstructionChemicals. . . . . . . . . . . . Inside Front Coverwww.masterbuilders.comThe Euclid Chemical Company . . . . . . . . . 25www.euclidchemical.comSolomon Colors . . . . . . . . . . . . . . . . . . . . . 15www.solomoncolors.comCEMENTHolcim. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3www.holcim.usCONCRETE CHIPPINGCoast 2 Coast . . . . . . . . . . . . . . . . . . . . . . 26www.C2C-chipping.comCONCRETE COLORANTSDavis Colors . . . . . . . . . . . . . . . . . . . . . . . 18www.daviscolors.comCONCRETE CURING EQUIPMENTKemco Systems, Inc.. . . . . . . . . . . . . . . . . 10www.kemcosystems.comCONCRETE WASH-OUTUltraTech International, Inc.. . . . . . . . . . . . 25www.spillcontainment.comENVIRONMENTALEnviro-Port, Inc. . . . . . . . . . . . . . . . . . . . . 24www.enviro-port.comFortrans, Inc.. . . . . . . . . . . . . . . . . . . . . . . 24www.fortransinc.comFLY ASHHeadwaters Resources . . . . . . . . . . . . . . . 26www.fl yash.comMERGERS & ACQUISITIONS/INVESTMENT BANKINGFMI Corporation. . . . . . . . . Inside Back Coverwww.fminet.comMIXER TRUCKSContinental Mixers . . . . . . . . . . . . . . . . . . . 4www.continentalmixers.comSTEEL FIBERSBekaert Corp. . . . . . . . . . . . . . . . . . . . . . . . 6www.bekaert.comSUSPENSIONS - TRUCK LIFT AXLEHendrickson Auxilliary Axle Systems. . . . . . 5www.hendrickson-intl.comTESTING EQUIPMENT & MATERIALSHumboldt Mfg. Company. . . . . . . . . . . . . . 10www.humboldtmfg.comWATER HEATING EQUIPMENTHeatec, Inc. . . . . . . . . . . . Outside Back Coverwww.heatec.comKemco Systems, Inc.. . . . . . . . . . . . . . . . . 10www.kemcosystems.comSteam Engineering . . . . . . . . . . . . . . . . . . 25www.steamengineering.caHOW TOcombatreduce theglobal warming,production ofgreenhouse gases,and buildastronger infrastructure.SPECIFY FLY ASH(a recovered resource)as a replacement for cementin concrete.When you specify fly ash as replacement for cement in concrete,you help reduce CO 2 emissions from cement production, conservelandfill space, and decrease water usage. You also enhanceworkability and chemical attack resistance, increase strengthand produce more durable concrete.Contact Headwaters Resources for free technical literature and informationon how fly ash use benefits the environment and produces better concrete.MEMBERwww.flyash.com I 1-888-236-6236373895_Headwaters.indd 26 ı JANUARY/FEBRUARY 120113/13/08 4:32:4465116_Infocus.indd PM12/12/10 8:34:23 AM

FMI is pleased to have served as advisor on the following transactions:MERGERS & ACQUISITIONS | FINANCIAL ADVISORY SERVICEShas been acquired byhas been acquired byThe assets, barging,quarry and constructionaggregates operations ofJim Smith Contracting•Superior Asphalt &Concrete•Western States Asphalt•Transtate Asphalt•Mid Columbia Asphalt•Blue Mountain Asphalt•Basin AsphaltThe assets ofandMirimec Trucking Inc.has been acquired byhave been acquired byhave been acquired byhas been acquired byhas sold itsGunnison County Coloradooperations toOldcastleMaterials, Inc.(a U.S. subsidiary of CRH,Dublin, Ireland)The stock ofGibraltar NationalCorporation(a subsidiary ofTriss Corporation)has been acquired byandTom Brook, Inc.were acquired byElmer Larson, LLChas been acquired byFlorida Rock Industries, Inc.has been acquired byNally & Haydon, LLCand its affiliatessold itsEastern Kentuckyoperations to asubsidiary of(a Rinker GroupLimited company)Selected assets ofHeavy Civil Divisionhave been acquired byJ.C. Compton Company(dba Riverbend Sand & GravelValley Concrete & Graveland Salem Road & Driveway)has been acquired byOldcastleMaterials, Inc.(a U.S. subsidiary of CRH,Dublin, Ireland)has been acquired byFlatiron and Turner jointventured for the acquisition*Company noted has been represented by FMIFMI is the premier investment banking and managementconsulting firm serving the worldwide engineering andconstruction industry.For more than 55 years, FMI hasbuilt a reputation for assisting our clients in the creationand realization of value in their firms.For more information, visit our Web site at www.fminet.com, or contact:George Reddin at 919.785.9286 / greddin@fminet.comWill Hill at 303.398.7237 / whill@fminet.com

FUEL TANKFIRESTORM HEATERPRODUCTSFORCONCRETEPRODUCERSHOT OIL HEATERCHILLERWE offera numberof products forFIRED TANKconcrete producers.Our heating productsenable you to extend your workingseason into cold-weather months by makingconcrete mixes that are much warmer than ambienttemperatures. This is achieved by heating mix water.Or by heating stock piles. Or both.Our Firestorm heater is our most popular waterheating product. It is a direct-contact water heaterwith extremely high thermal effi ciency: up to 99percent.Our fi red tank is an economical alternative to theFirestorm heater. It combines a burner and fi re tubewith a fully insulated storage tank.HOT OILPIPE COILSOur hot oilheater can beused to heat mixwater stored in tanksthat have hot oil pipe coils.Or it can preheat stockpiles ofsand or aggregate. Or it can do both.Our chillers, which are made by Carrier, cool mixwater during hot summer periods.We also make fuel tanks that meet UL-142 standards.And we make hot oil pipe coils that can be embeddedunder stockpiles or installed in tanks.Please contact us to discuss productsmost suitable for your heating andcooling needs.HEATEC®HEATEC,INC. an Astec Industries Company5200 WILSON RD • CHATTANOOGA, TN 37410 USA 800.235.5200 • FAX 423.821.7673 • heatec.com

tech talkVariation in Concrete StrengthDue to Water and Air Content VariationPart IV of Concrete Quality SeriesBy Karthik Obla, Ph.D., P.E., VP, Technical Services, NRMCAParts I and II of the Concrete Qualityseries 1,2 discussed that to attain goodconcrete quality a concrete producerneeds to target a low standard deviation ofcompressive strength. In order to reduce thestrength standard deviation the material,manufacturing and testing variations needto be lowered. This article discusses concretestrength variability due to variation inwater and air contents.Water Content Variation and itsEffect on Strength VariationCompared to other ingredients, thereare several sources (and potential errors)by which mixing water is incorporated ina concrete mixture. These sources and waysto ensure that the batch water is withintolerance of the designed amount will bediscussed in a later article. ASTM C94 3and ACI 117 4 state that the total mixingwater should be within ±3% of the quantityrequired by the mix design. ASTM C94also requires that the added water should bewithin ±1% of the design total mixing water.These standards do not establish accuracyrequirements for individual sources of water,such as for water added from the water tankon the concrete truck. The NRMCA PlantCertification inspection process has accuracyrequirements for water measurement inthe plant and for water tanks that are basedon target quantities. For the purpose of thisdiscussion, it is assumed that for plants andconstruction practices operating under agood standard of control the mixing watercontent can vary within ±5% of the requiredquantity 95% of the time. In other wordsfor a concrete mixture with a design mixingwater content of 250 lb/yd 3 , the actual watercontent can vary by ±12.5 lb/yd 3 .During a field evaluation conducted byNRMCA the mixing water content calculatedfrom the batch records and otherreported sources of water was found to rangefrom 227 to 256 lb/yd 3 with an average of243 lb/yd 3 . This was determined from 12loads of the same mixture. From this evaluation,94% of the values were within the rangeof ±12.5 lbs. One could also consider theASTM C94 and ACI 117 allowable slumptolerance of ±1.5 in. (for concrete of slumpgreater than 4 in.), with all else being equal,as roughly resulting from a ±5% variation inwater content. As part of a different studythe author received project test data fromseveral concrete producers. Each project testdata consisted of slump, air content, temperature,7 and 28 day strengths measuredon the same concrete sample over a period ofseveral months. Some of that data are summarizedin Tables 1-3. Table 1 shows thatbarring Producer C the remaining four datasets met the slump requirement within toleranceexceeding 95% and averaged 96.3%.So, the assumption that plants and constructionpractices operating under a good standardof control have a mixing water contentvariation of ±5% of the required quantity95% of the time seems reasonable.For a concrete mixture at a given w/cm, a±5% variation in mixing water will have thesame effect on the w/cm as a ±5% variationin the cement content. A commonly usedrule of thumb is that one pound of cementequates to a compressive strength between8 to 12 psi. (This is a simplistic assumptionthat is valid only for w/cm around 0.50 to0.60 or for concrete with 28-day compressivestrength ranging from 4000 to 5000 psi;for lower w/cm concrete, a pound of cementcontributes lesser to compressive strength ascompared to higher w/cm – see AppendixA for more discussions). This means that a±5% variation in cement content will resultin a ±5% compressive strength variation(based on the discussions in Appendix Athis is valid only for w/cm around 0.50). Ifthe mixing water content varies by ±5% ofthe target value 95% of the time, the effectis that the resulting compressive strengthvariation should be within ±5% of the averagestrength 95% of the time.Air Content Variation and itsEffect on Strength VariationASTM C94 and ACI 117 state thatfor air entrained concrete the tolerance is±1.5%. Table 2 has only two data sets withair entrained concrete. Both the data setsshow that there is a higher compliance withair content tolerances compared to slumptolerances. Based on that data one couldconservatively assume that for plants andconstruction practices operating under agood standard of control the air contents ofair entrained concrete can vary within ±1.5%of the average 95% of the time. Table 2 has3 data sets with non air entrained concrete.ASTM C94 and ACI 117 do not state tolerancesfor non air entrained concrete. Theair content variations in non air entrainedconcrete are expected to be lower than in airentrained concrete. Assuming a tolerance of±0.75%, the 3 data sets show that for plantsand construction practices operating undera good standard of control the air contents ofnon air entrained concrete can vary within±0.75% of the average 95% of the time.A common rule of thumb is every 1%increase in air content will reduce the concretecompressive strength by 5%. So the aircontent variation of ±1.5% will result in aCONCRETE in focus ı 29

±7.5% compressive strength variation. In the case of air entrainedconcrete since the air content is within ±1.5% of the specified value95% of the time the resulting compressive strength variation shouldbe within ±7.5% of the average strength 95% of the time.Combined Effect of Water and Air Content Variationon Strength VariationIt is assumed the mixing water and air content and the resultingcompressive strength are normally distributed.So far we know the following:95% of the time the water content is between 0.95W and 1.05Wwhere W is the target mixing water content. Assuming a normalprobability distribution this would result in 97.5% of the time thewater content is less than 1.05W and as a result97.5% of the time the strength is greater than 0.95Xwhere X is the average compressive strength.In the same way it can be concluded that 97.5% of the time theair content is less than (A+1.5) where A is the specified air contentand as a result97.5% of the time the strength is greater than0.925X (1-0.075).Combining the water and air content probabilities we can statethat:95% (0.975x0.975) of the time the water content is lesser than1.05W and the air content is lesser than (A+1.5) and as a result95% of the time the strength is greater than 0.875X(1-0.05-0.075).This is somewhat of a conservative approach since the aboveapproach assumes that high slump and high air content are mutuallyexclusive events where as in reality a high water content is likely tolead to a high air content and vice-versa.“To attain a low SD of 28-day strength, it is important for the producer to attaina low variation in water content and air content, as they contribute significantlyto the variation in strength.”Let us assume the compressive strength test results are normallydistributed with a standard deviation (s). So, for the 95% probabilityit follows that:X – 1.64s = 0.875X. Simplifying we gets = 0.0762XIf the average measured compressive strength (X) is 5000 psi thens = 381 psi. ACI 214R-02 5 states that s

References1Obla, K.H., “How Good is your QC – Part I of Concrete Quality Series,” Concrete InFocus, May-June 2010, Vol. 9, No. 3, NRMCA, pp.17-18.2Obla, K.H., “Sources of Concrete Strength Variation – Part II of Concrete Quality Series,” Concrete InFocus, July-August 2010, Vol. 9, No. 4,NRMCA, pp. 21-23.3ASTM C94, “Standard Specification for Ready Mixed Concrete,” Volume 4.02, ASTM International, West Conshohocken, PA, 2009, www.astm.org.4ACI Committee 117, “Specifications for Tolerances for Concrete Construction and Materials and Commentary,” American Concrete Institute,Farmington Hills, MI, 2006, 70 pp.5ACI Committee 214, “Evaluation of Strength Test Results of Concrete (ACI 214R-02),” American Concrete Institute, Farmington Hills, MI,2005, 20 pp.Table 1. Statistical Summary of Project Slump Test Results Sent by 5 Different Concrete ProducersProducer ID # of measurements Average Slump, in. Slump Range, in. Percent in compliance with C94 tolerance of ±1.5 in.A 305 5.2 1.75 – 6.75 98.0B 57 6.9 5.00-8.00 94.7C 41 7.6 3.50-10.50 73.2D1 304 4.8 2.00-8.00 97.4D2 62 8.4 6.25-9.50 95.2Table 2. Statistical Summary of Project Air Content Test Results Sent by 5 Different Concrete ProducersProducer ID # of measurements Average Air Content, % Air Content Range, in. Percent in compliance with C94 toleranceof ±1.5%A 302 5.6 3.4-6.9 99.7B 57 5.4 3.9-7.1 96.5C 41 2.9 2.2-4.0 90.2*D1 302 2.0 1.0-4.5 92.1*D2 17 1.0 0.8-1.4 100**Non air entrained concrete does not have C94 air content tolerances. So ±0.75% was assumedTable 3. Statistical Summary of Project Test Results Sent by 5 Different Concrete ProducersProducer ID Slump, in. Air Content, % Temperat., o F SD of SD of 7 d 28 day StrengthDensity, Strength,AVG SD AVG SD AVG SD lb/ft3 psi AVG, psi SD, psi Standard ofControl*PredictedSD, psi**A 5.2 0.67 5.6 0.46 68.3 6.3 NA 485 5578 438 Very Good 307B 6.9 0.73 5.4 0.81 68.5 6.8 1.36 624 4952 536 Good 362C 7.6 1.69 2.9 0.46 63.0 10.8 1.26 1701 9450 1258 Fair 890D1 4.8 0.59 2.0 0.45 72.0 6.4 1.51 594 5213 474 Very Good 281D2 8.4 0.76 1.0 0.18 78.0 5.7 0.52 1167 6632 938 Poor 294*Standard of Control per ACI 214**Predicted SD based on slump and air content compliance probabilitiesCONCRETE in focus ı 31

Appendix A – Calculation of Strength VariationFrom Water Content VariationThe ACI 211 table of strength versus w/cm for non air-entrainedconcrete and the best-fit straight line has been plotted below.The slope is -9600 psi. The following table shows the calculatedchange in strength (based on the straight line equation) for a onepound change in cement content for concrete with a water contentof 300 lb/yd 3 and for different target w/cm values. The numberswould be slightly higher for lower water content.w/cm Change in Strength, psi/lb of cement0.4 50.5 80.6 120.7 16It is seen that the strength change for a change in one pound ofcement is 8-12 psi for concrete in the 4000 to 5000 psi range andfor w/cm of 0.50 to 0.60.Using the straight line equation, the percentage change instrength for a ±5% change in cement content for concretes for agiven water content is calculated and is shown below:w/cm Change in Strength, %0.4 3.3%0.5 4.9%0.6 7.4%0.7 11.4%Thus it is clear that a 5% change in cement content will result ina 5% change in compressive strength only around w/cm of 0.50.A similar situation occurs when the variation in strength is calculatedfor variation of water-content with the cement held constantat the target cement content. If the water content varies 5% fromthe target value, the strength variation will depend on the w/c andalso slightly on the target value of the water content. From the tablebelow it becomes clear that a 5% change in water content will resultin a 5% change in compressive strength only around w/cm of 0.50.32 ı JANUARY/FEBRUARY 2011Variation in Strength at Different Water Contentsw/cm 280 lbs 300 lbs 310 lbs0.4 3.1% 3.3% 3.4%0.5 4.6% 4.9% 5.1%0.6 6.9% 7.4% 7.6%0.7 10.6% 11.4% 11.8%Higher w/cm concrete mixtures appear to be more vulnerableto cement and water content variations as compared to lower w/cm concrete mixtures. A given percent change in cement or watercontents does not lead to the same percent change in compressivestrength because strength is related inversely to water-cementitiousratio and not directly to cement or water content as commonlyassumed.■Who to Call at(301) 587-1400TOLL-FREE: 1 (888) 846-7622NRMCALOCAL:WEB SITE: www.nrmca.orgCODES AND SUSTAINABILITYErin Ashley, Ph.D., LEED AP(240) 485-1306eashley@nrmca.orgCOMMUNICATIONSFrank Cavaliere(240) 485-1141fcavaliere@nrmca.orgCONCRETE PROMOTIONGlenn Ochsenreiter(240) 485-1140gochsenreiter@nrmca.orgDan Huffman(503) 292-7729dhuffman@nrmca.orgJon Hansen(515) 266-1058jhansen@nrmca.orgPhil Kresge(610) 966-7220pkresge@nrmca.orgDoug O’Neill, LEED AP(585) 436-8310doneill@nrmca.orgVance Pool(281) 557-8415vpool@nrmca.orgAmy Miller, P.E.(904) 264-8850amiller@nrmca.orgENGINEERINGColin Lobo Ph.D., P.E.(240) 485-1160clobo@nrmca.orgLionel Lemay, P.E., S.E., LEED AP(847) 918-7101llemay@nrmca.orgKarthik Obla, Ph.D., P.E.(240) 485-1163kobla@nrmca.orgREGULATORY AFFAIRSGary Mullings(240) 485-1161gmullings@nrmca.orgFINANCIAL ACTIVITIESMichael Olivarri, CPA(240) 485-1130molivarri@nrmca.orgNick Muzzatti(240) 485-1131nmuzzatti@nrmca.orgTamara Waugh(240) 485-1132twaugh@nrmca.orgGOVERNMENT AFFAIRSKerri Leininger(240) 485-1159kleininger@nrmca.orgKevin Walgenbach(240) 485-1157kwalgenbach@nrmca.orgINDUSTRY RELATIONSNicole Maher(240) 485-1158nmaher@nrmca.orgINFORMATION TECHNOLOGYLawrence Afable(240) 485-1167lafable@nrmca.orgJake Zhu(240) 485-1144jzhu@nrmca.orgMARKETINGGlenn Ochsenreiter(240) 485-1140gochsenreiter@nrmca.orgGillian McBurney(240) 485-1166gmcburney@nrmca.orgMEETINGSNicole Maher(240) 485-1158nmaher@nrmca.orgJessica Moore(240) 485-1152jmoore@nrmca.orgMEMBERSHIPKathleen Carr-Smith(240) 485-1145kcarrsmith@nrmca.orgKimberly Pittmon(240) 485-1146kpittmon@nrmca.orgOFFICE OF THE PRESIDENTRobert Garbini, P.E., President(240) 485-1139rgarbini@nrmca.orgDeana Angelastro(240) 485-1138dangela@nrmca.orgOPERATIONS/EQUIPMENTMAINTENANCEGary Mullings(240) 485-1161gmullings@nrmca.orgPUBLICATIONSJacques Jenkins(240) 485-1165jjenkins@nrmca.orgRMC RESEARCH & EDUCATIONFOUNDATIONJulia Garbini(240) 485-1150jgarbini@rmc-foundation.orgJennifer LeFevre(240) 485-1151jlefevre@rmc-foundation.orgSAFETYDavid Ayers, CHMM, CSP, MS(240) 485-1155dayers@nrmca.orgGary Mullings(240) 485-1161gmullings@nrmca.orgTRAINING/EDUCATION/CERTIFICATIONEileen Dickson(240) 485-1164edickson@nrmca.orgShawnita Dickens(240) 485-1154sdickens@nrmca.org

quality cornerWater Demand – What is it?And what’s it used for? PART IBy Fernando Rodriguez, Rowen Concrete, Inc. and Jack Hoy, Swope & Associates (SIKA Admixtures)What is the water demand of thesand that your company is usingto produce concrete? Is it 33 gal/cy or 42 gal/cy? Can there possibly be adifference of this magnitude? What factorscontribute to the water demand of theconcrete? How do you determine the waterdemand of the sand? How can it be used tosave money?Water demand is primarily impacted bythe characteristics of the sand. The primarycharacteristics of sand that impact waterdemand are its particle shape, surface textureand grading. In general, crushed manufacturedsand requires a higher mixing watercontent than natural river sands that have amore rounded shape and smoother surfacetexture.Ground granulated blast furnace slag(slag) and fly ash enhance the slump of a concretemix. A mix design containing 564 lbs/cy of portland cement has less slump than amix that contains 50% Class F fly ash. Flyash, because of its rounded particle shape,reduces the water demand of a concretemixture for a target slump. Air-entrainersand most water reducers also contribute toa higher slump.A standard concrete mixture must beevaluated when estimating the water demand.One might choose a portland cement contentof 564 lbs/cy, coarse aggregate, water, andthe production sand. The concrete mixtureis tested in laboratory conditions to estimatethe quantity of water required to produce a4-inch slump. The following describes proceduresused by the authors.A Type II (MH) cement conforming toASTM C150 is used.The coarse aggregate is manufacturedstone from southern Pennsylvania, conformingto ASTM C33 Size #57.The sand used was washed, naturalsand produced in northeast Maryland andconforms to the requirements of ASTM C33and approved for use by the Maryland StateHighway Administration.turn for five revolutions. Approximately 10pounds of water was weighed, and smallamounts were introduced and allowed tomix with the other constituent materials.We added these small increments until itappeared that a 4-inch slump was attainedupon visual assessment. Slump tesing wasperformed in accordance with ASTM C143.Once a 4-inch slump was obtained, the mixingwas terminated. The unit weight and aircontent was measured and recorded. A setof five compressive strength cylinders wasalso fabricated. All testing was performed inaccordance with ASTM standards.From this trial batch evaluation procedure,the amount of mixing water requiredto obtain the 4-inch slump was equivalentSize ∑ Wt Ret %Pass3/8” 0 100No. 4 2.0 98.0No. 8 15.6 84.4No. 16 26.5 73.5No. 30 42.7 57.3No. 50 77.7 22.3No. 100 96.3 3.7PAN 100.0 0.0Total 2.61Listed below are the mixture proportionsused;Material SP GRAV SSD Wts per cubic yard(lbs) Absolute Volume(cf)Cement 3.15 564 2.87SSD Stone 2.87 1800 10.05SSD Sand 2.59 1454 9.00Mixing Water 1.00 264 4.23Air,% 3.00 0.81A non-air entrained concrete batch of avolume of 0.8 cubic foot was mixed in thequality control laboratory at the author’s productionplant. The moisture content of thecoarse and fi ne aggregate was determined.From experience and past performance,1800 lbs/cy of coarse aggregate was used.For optimum pumping placement, it is estimatedthat 10.0 - 10.3 cubic feet of stone ina cubic yard of concrete appears to providethe best performance.All of the constituents were weighedaccording to design mixture proportions.The stone, sand and small amount of waterwere placed in a 2.0 cubic foot mixer. Themixer was allowed to turn for five revolutions.The cement was then added to themixer. Again, the mixer was allowed toto 300 lbs/cy or 36 gallons per cubic yard.It should be noted at this point that theconcrete sands available in this one smallregional marketplace have a range of as lowas 33 gallons per cubic yard up to as high as44 gallons per cubic yard. With this in mind,it is easily demonstrated how important it isto be well informed as to the demands ofyour concrete sands.Now that the water demand has beendetermined, it can be used for developmentof concrete mixtures and mix optimization.The information can be used to establish thecementitious materials required for differentwater cement ratios, admixture dosagerates and yield targets. Knowing the waterdemand of the local materials can help optimizecementitious material contents andCONCRETE in focus ı 33

featureappropriate percentages of portland cementand supplementary cementitious materials.All these evaluations that result in mixtureoptimization helps lower the material costof a cubic yard of concrete. Having the correctwater content in your mixture establishesthe necessary input into the batchingand production process and provides anidea of the possible impact to fresh concreteproperties such as strength and durability.Getting the proper water slump in theconcrete is also important for more effectiveuse of water-reducing admixtures andto minimize problems like stickiness orballing in the batch process. Getting thecorrect slump out of the plant also reducesthe amount of time your CDPs (ConcreteDelivery Professionals) spend on the washrack adjusting their slump. Remember,the quicker the CDPs leave the plant, thequicker they reach the job site, creatinggreater customer satisfaction.Do not rely on the sand producer toknow the water demand. As a qualitycontrol manager or engineer, you shoulddevelop a water demand testing programand update this information as often aspossible. A good rule of thumb would beto perform these tests once every threemonths or whenever you notice a dramaticchange in the appearance or sieve analysisof the sand. Develop simple processes, likethe sand void content test, that will giveyou an idea if the characteristics of the sandhave changed significantly to impact mixingwater demand.In the second part of this article, we willdiscuss the confirmation of the Type A andF admixture’s ability to reduce the amountof mix water. Knowing how effective yourwater reducers are is another way of savingmoney. Reducing the mixing water contentthrough the judicious use of these admixtureswill help reduce cementitious materialscontent that can cause increased shrinkage,heat of hydration or otherwise increase thepotential for cracking. These “leaner” mixturescan be designed to perform as well asor better than the reference mixture that youstarted with. It all starts with a good estimateof the water demand of your mixture! ■For more information, contact Mr. Rodriguezat concretemechanics@gmail.com.ASSESSMENT OF PERVIOUSConcreteMaintenanceTechniquesBy Lev Khazanovich, Kevin MacDonald and Mary VancuraINTRODUCTIONImpermeability is a distress commonto all pervious concrete pavements regardlessof application or climate. Over time,material such as tree leaves, sand, soil andgarbage becomes entrapped in the perviousconcrete’s interconnected voids and contributesto decreasing the permeability of waterthrough pervious concrete. Ideally, perviousconcrete is built away from sources of organicmatter and shielded from soil and sand particles.However, even pervious concrete thatis shielded from a constant source of fi ne andorganic material, still experiences a decreasein permeability over time. Furthermore,sometimes the purpose of installing perviousconcrete is to capture fi ne and organicmaterial from stormwater runoff.Pervious concrete is distressed when itno longer infi ltrates the amount of rainfallor runoff that it was designed to infi ltratebecause it is partially permeable or impermeable.The good news about impermeability isthat, in most instances, it is a distress thatcan be remedied. Maintenance that periodicallyremoves the entrapped fi nes from theinterconnected voids will typically maintainacceptable permeability through the perviousconcrete.BACKGROUNDDuring inspection of 22 pervious concretepavement sites, it was discovered thatthe owners’ methods of maintaining theirpervious concretes’ permeability were determinedby what was available in the utilityshed rather than by purchasing the idealinstrument or machine. There was interestamong the some of the owners to compare theefficiency with which the different machinesremoved the entrapped fines from the interconnectedvoids in pervious concrete.The machines compared were an 8-inchvacuum hose attached to a vacuum truck(Figure 1), a regenerative air street sweeper(Figure 2) and a vacuum street sweeper(Figure 3). The machines’ abilities to removeclogging material from the pervious concretewere evaluated by taking core samplesof the pervious concrete before and aftermaintenance by each machine. To ensurethat the entrapped fi nes did not get washedout of the interconnected void areas duringthe coring process, a non-viscous and clearepoxy was placed in the pervious concreteat least three hours prior to taking the cores(Figure 4). Once the cores were extracted,they were cut in half, polished and observedwith a stereomicroscope. The magnificationallowed observation of the location of thefi ne and organic matter within the perviousconcretes’ interconnected voids before andafter maintenance.Comparison ofMaintenance TechniquesBefore and after photomicrographs ofthe pervious concrete pavements on which34 ı JANUARY/FEBRUARY 2011

FIGURE 1. Vacuum truck with an 8-inch diameter hose nozzle used for maintenance of impermeable pervious concrete.FIGURE 2. Regenerative air street cleaner used toremediate pervious concrete.FIGURE 5. (L) Before maintenance and (R) aftermaintenance with the 8-inch diameter hose nozzleconnected to a vacuum truck.FIGURE 3. Vacuum street sweeper used to remediatepervious concrete impermeability.FIGURE 4. Residual epoxy on the surface of perviousconcretemaintenance was performed with an 8-inchdiameter vacuum hose, a regenerative airsweeper or a vacuum sweeper are shownbelow. Letters represent a representativesample of concrete matrix constituentsrather than all the constituents.Key for Photomicrograph LabelsP = PasteA = AggregateV = Interconnected voidE = EpoxyD = Fine and organic material in voidVacuum Truck with 8-inchDiameter Hose NozzleIn both the before and after photomicrographsof pervious concrete that was maintainedby an vacuum truck with an 8 in.diameter hose (Figure 5), the consolidated,entrapped fi nes reach a maximum depth of¼ in. In the before photomicrograph, theentrapped fi nes are almost flush with thepervious concrete surface. The after photomicrographshows that the 8 in. vacuumhose removed approximately 1/16-1/8 in. ofthe consolidated entrapped fi nes.Regenerative Air Street SweeperFigure 6 shows the entrapped fi nes inpervious concrete before and after maintenancewas performed with a regenerativeair sweeper. The before photomicrographshows that some entrapped fi nes hadmigrated into the triangular void markedby the letter D, but that the entrapped fi neshad not consolidated in the area. A smallnotch on the surface, marked with theletter V, harbors no fi nes. The after photomicrographshows a large void area thatis half-full with epoxy (marked by E) thatis accessible from the pervious concrete’ssurface. The regenerative air sweeper likelyremoved the entrapped fi nes from withinthe area occupied with epoxy. Consolidatedentrapped fi nes remain in this void below1/8 to ¼ in. A smaller void on the left sideof the photomicrograph was also accessiblefrom the surface. Either it harboredno entrapped fi nes before maintenance or itFIGURE 6. (L) Before and (R) after photomicrographsof pervious concrete that had been maintained with aregenerative air street sweeper.FIGURE 7. (L) Before and (R) after photomicrographs ofpervious concrete maintained by a vacuum sweeper.was cleared of entrapped fi nes by the regenerativeair sweeper.Vacuum Street SweeperThe photomicrograph in Figure 7 showsthat before maintenance with the vacuumstreet sweeper, a majority of the entrappedfi nes were consolidated within the top 1/8in. of the pervious concrete’s interconnectedvoids, although a small tail of fi nes extendsto ¼ in. deep. The after photomicrographshows that the vacuum sweeper likelyCONCRETE in focus ı 35

emoved the entrapped fi nes from the top1/8 in. of a ¼ inch-deep void.Other Photomicrographs fromAfter MaintenanceThe photomicrographs in Figure 8 wereadditional photos taken of pervious concretefollowing maintenance by the 8 in. vacuumhose, regenerative air sweeper, or vacuumsweeper. The photos reinforce that theentrapped fi nes were mostly concentrated inthe top ¼ in. of the pervious concrete and,regardless of the maintenance performed,only the top 1/16-1/8 in. of entrapped fi neswere removed.FIGURE 8. Photomicrographs of pervious concretefollowing maintenance by 8 in. vacuum hose, regenerativeair sweeper, or vacuum sweeper.Coarse Sand FinesWhile small fi nes and organic matterremained within the top ¼ in. of theinterconnected void spaces and tended toconsolidate into tightly packed masses, thelarger fi nes such as coarse sand particleswere observed in interconnected voidsthroughout the depth of the cores. Figure9 shows an example of coarse sand particlesthat migrated 3 in. into a pervious concretepavement.FIGURE 9. Pervious concrete exposed to sand during thewinter and spring snow melt. Sand particles migratedthree inches into the pervious concrete voids.CONCLUSIONThree possible methods of pervious concretepavement maintenance were attempted,and all were equally effective at removing thetop 1/8” of fine and organic material from thepervious concrete pavements. The fine andorganic materials that were responsible forthe partial or total impermeability of the perviousconcretes typically consolidated within¼ in. of the concrete’s surface. Pervious concretevoids deeper than ¼ in. were rarely fi lledby these materials. If fines were found in theinterconnected void areas beneath ¼ in.,these fines were typically larger sand particlesand did not appear to impede permeability ofthe pervious concrete.Entrapped fines were not entirely removedduring maintenance. Instead, the total thicknessof consolidated fines within a void spacewas decreased and the remaining fines weredisturbed enough so that the pervious concretewas able to infiltrate water according todesign. The rate at which the voids were fi lledwith fine and organic matter depended on theexposure of the pervious concrete to fine andorganic material, which varied by site.ACKNOWLEDGEMENTSThis research was completed with a grantfrom the Ready Mixed Concrete (RMC)Research & Education Foundation.Mark Maloney, Tom Wesolowski andMike Shaughnessy, City of Shoreview PublicWorks Department.Andjela Tomovic, City of Saint CloudDepartment ofEngineering.For more information contact:Mary VancuraGraduate Research AssistantUniversity of MinnesotaDepartment of Civil Engineering500 Pillsbury Drive S.E.Minneapolis, MN 55455Phone: 612-597-3431E-mail: vanc0060@umn.eduKevin MacDonaldVice President of Engineering ServicesCemstone Products Co.2025 Centre Pointe Blvd #300Mendota Heights, MN 55120Phone: 612-363-7111E-mail: kmacdonald@cemstone.comLev KhazanovichAssociate ProfessorUniversity of MinnesotaDepartment of Civil Engineering500 Pillsbury Drive S.E.Minneapolis, MN 55455Phone: 612-624-4764E-mail: khaza001@umn.edu■The research taking place at the University of Minnesota was funded bythe RMC Research & Education Foundation. The Foundation supportsresearch and educational programs that will increase professionalismand quality in the concrete industry. Additional information about theFoundation’s work may be found at www.rmc-foundation.org.Additional pervious concrete resources available from theRMC Research & Education Foundation include:■ Pervious Concrete Research Compilation■ Construction & Maintenance Assessment of Pervious Concrete■ Hydraulic Performance Assessment of Pervious Concrete Pavements forStormwater Management Credit■ Portland Cement Pervious Pavement: Field Performance Investigationon Parking Lot and Roadway PavementsAll of the reports noted above are included on the Foundation’sResearch Supporting Sustainable Development deliverables CD.Other pervious concrete research projects currently underwayinclude:■ Heat Island Mitigation Through Use of Pervious Concrete■ Pervious Concrete Mix Design for Wearing Course Applications36 ı JANUARY/FEBRUARY 2011