relevant micro-concepts of common nigerian civil engineering

RELEVANT MICRO-CONCEPTS OF COMMON NIGERIAN CIVIL ENGINEERINGMATERIALSProfessor Danladi Slim MatawalAbubakar Tafawa Balewa University Bauchi5 th November, 2001ABSTRACTOf all the disciples of engineering, the greatest strides, and the most independent practice inNigeria, has been in the branch of Civil Engineering. This is because windfall profits andincomes of oil revenue, since the middle sixties, resulted in huge developmental projects/effortsto provide basic, essential and service infrastructure, office and housing accommodation for thepopulation and for their desire to improve. This has led, up to date, to completed and ongoingconstruction of over 5,000 kilometres expressways, 12,000-15,000 kilometres of cross countryfreeways as well as a large volume of urban roads and infrastructure. Additionally, there are 7major bridges across the rivers Niger and Benue, not less than 80 bridges on their tributaries andup to 20 bridges across the distributaries on the Niger-delta. Major bridges like the third axial,Mainland and Eko are in Lagos, similar ones in Warri (e.g. the link across the creek from NNPCto Aladja Steel complex), Sapele, Port Harcourt and Calabar in the creeks off the Atlantic oceanhave been built while major seaports and airports, huge buildings, drainages, housing estates,dams, water plants and even a new Federal Capital city of Abuja as well as many state and LGcapitals have sprung up. A thriving and vibrant private sector together with frequent shortlivedrise in the living standards of the populace has also resulted in private corporate and individualinvestment in housing and office buildings. All the activities have involved constructionutilizing many civil engineering materials.The civil engineering materials that have been most commonly used for these activities are soils,stone aggregates, cement, structural steelwork and reinforcement rods, asphalt and timber/woodas well as water. The ubiquitous use of these materials has imparted upon the generality ofNigerian developers the technical know-how, skills and confidence to apply them frequentlywithout the need for references. It has also led to a complacent attitude as to the utilization of1

these materials, which are frequently applied, with many avoidable misapplications resulting inuneconomical, shoddy, cracked, failing and collapsed structures and infrastructure for both theindividual/private as well as the corporate developers. Many micro concepts; relevant andsignificant, have been ignored that could improve the quality of our developments, if known andapplied. These relevant micro concepts of in-situ materials used in foundations, concrete worksas well as those of water applied everywhere for mixing and drinking are espoused in thislecture. Manufactured and uncommonly used materials are mentioned but not elaborately delvedinto since they should always be subjected to industrial and factory quality controls whereprofessionals are involved. However, if they have to be remolded in application, like cement,then the concepts of remolding (often with changes in the material chemistry) are presentedwithout emphasis on purely technical issues that are taught in classes. Finally, the results ofpersonal research works and knowledge gained from years of field experience, related tomaterials, are presented. It is hoped that the stuff of this lecture will be found useful and basicby the common Nigerian developer including those aspiring to build personal homes andbusinesses, as well as managers of corporate public and private enterprises, and those inGovernment.1.0 INTRODUCTIONCivil engineering is that field of engineering concerned with the planning, design, andconstruction for environmental control, development of natural resources, buildings,transportation facilities, and other structures required for the health, welfare, safety, shelter,employment, and pleasure of mankind. As a result of this focus of the profession, the scope offunctions undertaken by the civil engineer are quite wide and varied including land drainage,water supply, rivers, canals, harbors, docks, marine construction, water power, sewage disposal,sewerage, bridges, tunnels, railways, roads, traffic engineering, foundations, airports, municipalengineering, soil mechanics, structural engineering, town planning, and transportationengineering. In the course of implementing the functions of civil engineering, intensive andextensive use is made of natural resources, in the form of materials, for the design andconstruction of necessary structures and infrastructures. Some of these materials used in civilengineering include soil, water, steel and metal alloys, timber, cement, stone and stone2

aggregates, sand, admixtures, fabric and synthetic geo-textiles, plastics, bitumen and so forth andso on.The application of these materials for design and construction can be in a monolithic orcomposite form. The type, nature and quantity of materials used also depends largely on thecomplexity of the engineering scheme as certain structures, due to large forces and stresses inmembers, may require modification of common materials to suit the peculiar application. Forexample, alloys can be used rather than normal steel; soil can be stabilized rather than apply it inhomogenous state, while cement concrete may need to be improved to give it higherstrength/grade. It is also true that the use of Civil Engineering materials, in whatever format,must be applied, molded and cared for according to certain engineering principles, governingtheir behaviour and characteristics, so that optimal objectives can be attained. These principlesrelate to strength of the material, its elasticity and plasticity properties, water absorption andcompressibility/swelling phenomena, matters related to deflection and fatigue, life-span etc. Theprinciples could be theoretical or practical or both but which, when observed, will lead to betterperformance of the designed structure. It is the objective of this lecture to expose some of thevery relevant micro-concepts of the use and application of Civil Engineering materials in theNigeria environment in such a manner that it will be useful to our many people involvedeveryday in the building of homes for shelter, roadways for transportation, land drainage for asafe environment, water supply for life sustenance, retaining wall structures for sea, ocean andriver defences and numerous other structures for the benefit of mankind.It is important, at the outset, to reiterate that the list of Civil Engineering materials is almostlimitless as almost every natural and artificial item that has form, and/or strength (however low),is a potential material for building one object or another. However, when scanning them, it isalways obvious that some are more abundant, cheaper and more commonly used than others.For these, their use is virtually an ubiquitous phenomenon and they are usually utilized byprofessionals and non-professionals, alike. It is also significant to understand that while someare manufactured and, therefore, rigorously subjected to professional factory quality control,others are actually manufactured or built or mixed on the site (in-situ). The latter include soiland cement, being the most common Civil Engineering materials. The application is usuallysubject to certain micro-concepts that improve their performance. Some of these micro-3

concepts, considered relevant, are treated in this lecture. The concept of water supply fordrinking and domestic applications is also treated since water can also be considered anothervery ubiquitous commodity for the health, welfare and pleasure of mankind. Not really relevantis the mention, and scanty treatment, of the other civil engineering materials notably steel, timberand bitumen. It is believed that the audience as well as readers of this lecture will, no doubt, findthat many of the micro-concepts are so relevant that it will change, positively, our perception andposture in the use of Civil Engineering materials for our personal estates, and businessdevelopments. It will also result in better physical development for the public enterprises that weably manage.2.0 NIGERIAN CIVIL ENGINEERING VERSUS THE WORLDBefore the discussion of the micro-concepts of civil engineering materials, let us look at some ofthe prominent structures of the world, compare them with Nigerian structures and assess whatmaterials are used in construction. This is easily made using the categories as set out below.2.1 Structures above ground: include bridges, dams, towers, masts and tall as well as largeclear span buildings. The world’s longest span bridge is the Honshushikoku link at Akashistraight in Japan with a main span of 1780 metres made of steel trusses. As a matter of fact, theWorld’s long spanning bridges are ally suspension types made principally of steel mainframe. InNigeria, the longest bridge is the third axial bridge from Lagos Island linked to HerbertMacaulay way in Yaba made of concrete and passing right through the Atlantic Ocean. Theworld’s long span bridges are all suspension types made principally of steel. Nigeria’s largebridges are either at Lagos or other coastal cities or the many arch bridges crossing the riversNiger and Benue and are all made of concrete: a mixture of cement, stone aggregates and fineaggregates with water, reinforced with structural rods. Their foundations sit on soil via speciallypiled footings ad caissons.The World’s largest dams are in the Russia or their breakaway republics like Bratsk (withvolume of reservoir 169.2km 3 ) at Angara river, Irkutsk; and Nourek dam (highest dam at 317metres) on the Vakhsh river in Tadjikistan close to the Afghanistan border. There are numerousother large dams like Aswam, Kariba etc. but the Kainji dam is Nigeria’s largest. Large damsare generally mainly of earth fill embankment with a clay core but will usually have a central4

portion of gravity masonry construction for overflow purposes and electricity generation, if it ismeant for hydropower. It always sits on the parent soil, which constitutes its foundation.The World’s tallest buildings are the 109 storeys twin Sears Towers in Chicago, Illinois (442metres), until September 11, 2001 there was the 110 Storeys twin World Trade Centre at NewYork city, USA, (411.5 metres); the 102 storeys Empire state building, New York city (381metres), 89 Storeys Standard Oil Building, Chicago (346 metres) etc. In fact, the eight World’stallest buildings up to September 10, 2001 were either in Chicago or New York city with the 49storeys National Westminster Bank’s headquarter in London being the tallest (183 metres) inBritain. A set of twin towers was commissioned in 2001 in Malaysia which, when the details areavailable, will make an impression. In Nigeria, the NITEL building in Lagos has been the tallest(37 storeys) while many other tall structures have been built along the Marina, in Lagos, as wellas in the city of Abuja. The modern practice in the design and construction of skyscrapers is touse structural hybrids of masonry, iron and steel that depends partly on load-bearing walls and isthe situation with world and Nigerian buildings. They use high-strength steels-alloys (up to 100percent stronger than normal steel). The World’s tallest towers and masts are generally built forcommunications purposes such as radio and television transmission. They exist in Nigeria andother parts of the world mainly in form of structural steel framework. The world’s talleststructures are either masts or towers namely: Warszawa radio mast at Plock, Poland (645.38m),Stayed television mast in North Dakota, USA (629m), CN Tower at Toronto, Canada (553m),Ostankino TV tower in Moscow, Russia (537m), Stayed television mast at Knoxville, US(533m), Stayed television mast at Columbus, US (533m), Stayed television mast in Missouri, US(510m). The tallest structure in Nigeria is the Plateau stayed television mast at Rayfield, Joswith the author of this paper as the Soil/geotechnical consultant of the project in 1981.The World’s largest buildings are assessed in terms of floor area, frequently the clearest longspan and the USA has the most of the world’s largest building. The Boeing Assembly hall withcubic content of building of 5.8 million m 3 is the largest. In Nigeria, the National theatre atIganmu, Lagos, the International Conference Centre, Abuja, the Multipurpose Indoors Sportshall in Bauchi and many lecture theatres, like the one in A.T.B. University built with the authoras Consultant, are large buildings in Nigeria. They are constructed of concrete and steelframes/space truss to span their large centre to centre roof supporting mechanisms.5

2.2 Structures below ground: include tunnels, underground workings, excavation anddredging, foundations and ground engineering. The world’s longest tunnels are scattered inUSA, South Africa, Europe and Japan for water supply, irrigation, submarine railway, drainages,aqueducts, diversion works and reclamation. The Delaware aqueduct in New York at 169kilometres is the world’s longest while the 57 kilometre submarine railway tunnel from Englandto France made a big construction news in the last decade though it may be only the forth longestin the world. No tunneling activities of significance have, to date, been recorded in Nigeria butin the future they will be necessary to cross some of the difficult obstacles in transportation.Tunnels driven beneath the beds of rivers, estuaries and the sea are the most difficult but alltunnels involve extensive excavation (tunneling or cut-and-fill techniques) in soft ground (soil)and in rock. Subsurface drainage is an important feature of tunnels as well as the associatedunderground workings.Muck-Shifting, which is the odd name for excavation and dredging, is always the starting pointof civil engineering and yet the records tend to be held in mining. The world’s largestexcavation record for many years was the Bingham Canyon copper-mine, near salt lake city,Utah, USA, from which 3500 million tones (1200 million m 3 ) of material (soil/rock) wasexcavated. I have only recently watched the documentary film of the Hansai international airportproject for which a new Island 4 kilometres x 1.5 kilometres was created from an 18 metres deepsea in Japan. The soil fill was obtained by completely demolishing mountains and transportingthe material to create the new Island. In Nigeria, gargantuan mining pits and valleys from whichmillions of cubic metres of soil was excavated, some still existing as spoil mounds, have beenmined on the Jos Plateau for tin and columbite. Excavations are associated with city building,earth dams and road works and these construction edifices can be sited near major cities ofNigeria in the form of borrow pits. We are also probably all acquainted with huge dredgingactivities by National Westminster Company along the river Niger as well as those thataccompanied the construction of coastal ports at Lagos (Apapa and Tin-can Island); PortHarcourt (main Port and Onne terminal); Warri, Calabar, Sapele and Koko. The single mostimportant civil engineering material in excavation works is soil followed by rock.Foundations generally comprise of the direct bearing and piled foundations, which are structuralelements intended to transmit the super structural loads to the ground. Even though common6

eference is usually made to them, nonetheless foundations include the sophisticated types liketrench or pier foundations, buoyant foundations, caissons, cylinders and monoliths, as well as thevery important sheet-piling works. There are also cut-off wall/trenches, drainage blankets andother forms of construction. In terms of foundation practice, it can be argued that wherever thereis a human habit, there is always a foundation to design and construct. The Sears towers, asexample, are pinned down to four basements (underground storeys) into the ground and thefoundation is made of 4 metres thick raft on top of basement complex. The most commonfoundations in Nigeria are strips and pads but there is a very established piled practice associatedwith large/tall structures as well as difficult ground. The Agriculture faculty building by A.T.B.University at Gubi site is on bored piled foundation, designed by the author, because it waslocated on a displaced stream valley. However the lecture theatre of the university is on padfoundation as are the bigger structures like Zaranda hotel and NIDB buildings here in Bauchi.For foundations of buildings generally, the main civil engineering material is concrete reinforcedwith structural rods and interacting directly with soil. The soil, which in such instances is thefoundation material, actually becomes the construction material as fill on ground floors and inroadways. Foundation techniques are very complex processes and involve rigorous concepts ofanalysis of shear capacity, structural competence, compressibility and settlement principles, andthe comprehensive modeling of water seepage forces and flow patterns. The difficultfoundations in literature include the deepest caissons and monoliths like the South Bisansetobridge (75m x 64m caissons), in Japan, the San Francisco-Oakland Bay bridge (60m x 28mcaisson) central anchorage in USA; etc. Caissons are concrete or steel containers of soil and theabove quoted ones were sunk to depths of 129 metres and 66 metres, respectively, in fast flowingwater ways. On the other hand, sheet piles which are common in city building are principallyreinforced thick strong gauge steel sheets retaining soil. Major piling associated with buildingsand bridges are usually concrete but can be steel and also timber.2.3 Ground engineering: are geotechnical processes like cofferdams, control of ground water;diaphragm walls, grouting and chemical treatment (Stabilization). Much of ground engineeringhas to do with improving properties of poor soils or the science of movement of water in the soilfor control purposes. Ground engineering techniques are very common procedures on Nigerianroads and many significant construction projects.7

2.4 Hydraulic works: include harbours, canals, barrages, spillways, flood control, sea defence,civil works associated with hydro-electric power, pumping stations, irrigation, aqueducts,pipelines, water supply and treatment, main drainage and sewage treatment. Even though thecentral theme in hydraulic works is the beneficial harnessing of the properties of water formankind, nonetheless many of the associated structures required are very huge engineeringedifices of soil, rock, concrete and steel. Jetties, Terminals and deep water ports are verycomplex hydraulic structures to construct: the Rotterdam, as example, is the world’s largest port(by length of quay or berth in the port). There are also canals and Inland Navigations, thenotable ones being St. Lawrence Seaway, Europe canal, Grand Canal, Amazon, Mississippi,Suez, Panama, etc. In Nigeria, dredging has been undertaken for inland navigation on the Niger,Imo and Cross Rivers. Flood control and sea defences are great schemes for protection againstriver floods and tidal waves. Their main material is sand/soil and rock boulders as well as sheetpiles of steel or gravity walls of masonry. Pipelines can be of asbestos-cement, galvanized ironand plastic: recently, some Nigerians have been writing on bamboo soil pipes.3.0 MICROCONCEPTS OF SOIL AS FOUNDATION AND CONSTRUCTIONMATERIALFrom the account of structures presented above, it is clear at this stage that one of the versatilecivil engineering materials is the soil. Later on, when I shall be listing an account of my personalcontributions in research and practice, it would then be observed that Nigerian soils exist inmany varieties exhibiting different properties and characteristics, some attractive and otherproblematic. Basically, in summary, soils are applied in practice as:i) Foundations of buildings and all forms of structures.ii) Construction material for road base, sub base and sub grade courses in roadways.iii) Construction material for the foundations of paved areas, parking spaces, airporttarmacs etc.iv) Construction material for earth dams, cutoff walls, central core of rock fill dams andcertain seepage and erosion control structures.v) Construction material for earth fills beneath the floors of structures.vi) Construction material for backfills behind retaining wall structures.8

vii)viii)Construction material in caisson foundations and land reclamation schemes as well asdredging and other works.Construction material for buildings of mud, compressed earth and burned bricks/firedclay.In all theoretical and practical applications of soil, the fundamental considerations and principlesare aimed at assessing the strength (shear) and consolidation/compressibility characteristics ofthe material. It is interesting to have known that when the twin world trade centre towers of 110storeys (411.5 metres) collapsed following the terrorist attacks of September 11, 2001, thesubstructure supported by the soil was quoted to be undamaged. Indeed the soil has atremendous capacity to take impacts from crushes of explosives, plane crashes, shuttle machinesand, of course, the world’s structures of all sizes and heights. The soil takes the loads imposedby these situations quite comfortably: frequently it does so with very prominent and noticeabledeformations and settlements depending on the material plasticity. Because the strength andconsolidation characteristics of the soils are so influential, I have found it convenient to classifythe theorems and principles associated to these properties (i.e. shear and settlement) as macroconcepts.However, there are certain micro-concepts related to the behaviour and response of thesoils to loading conditions that affect their strengths tremendously but which we frequentlyeasily overlook. One of these micro-concepts deals with the influence of water within the voidspaces of the soils. The concept is easily explained by the piston and spring analogy.A load (stress), σ is applied on the piston. The loads taken by the spring and water are σ / and u,respectively. At the beginning, as long as the weep hole is closed, σ = 0 and σ = u; i.e. the wholeload is taken up by the water. When the weep hole is opened gradually, stress is transferred fromthe water to the spring so that σ / > 0 so that at any finite time, t, σ = σ / + u and at t = ∞, u = 0 andσ = σ / .9

Applying our analogy to practical conditions, the spring is, in reality, the soil skeleton or solidparticles, in nature, while the water in the container is the pore water in the soil voids spaces. σ isknown as the effective stress while u is the pore water pressure. The rate at which water seepsout of the weep hole can be compared to the practical permeability of the soil. This concept;known as the principle of effective stress, was explained, in detail, by Matawal (1990). Theeffective stress theorem is a basic practical situation that is easily appreciated by the followingillustrations:a) Foundations on low permeability soils (clay and tropical laterites, as example), areknown to exhibit continuous time-dependent settlement. Under constant load, longafter application of full service conditions but which is not creep. This is due togradual dissipation of the initial excess pore water pressures: a phenomenon that canbe illustrated using the mathematical model of consolidation which we can use topredict the time-settlement responses of slow draining soil media subjected tochanges in loading conditions.b) Of considerable importance; but usually less obvious, are the regional settlementsresulting from ground water lowering in compressible soils either due to pumping forwater supply (as in boreholes) or due to other engineering situations. Regional10

settlements were quoted in London around 1942, in Oslo, Norway in 1953 andMexico city in 1953, Matawal (1990). The settlements resulting from landreclamation and dredging for ports construction projects at Warri, Lagos (Tin-CanIsland), Calabar, Sapele and Koko, all in Nigeria, in 1979 are quoted by Matawal(1987).c) The settlement of light foundations, which are generally shallow, in Nigeria, in thedry season, due to negative pore pressures set up by drying or by suction of plantroots or; in certain instances, complete drying out is one other result of the effectivestress principle.The role of water in the void space, as explained in the effective stress principle also assists us toundertake ground improvement schemes on soft soil to enhance their strengths. It isunderstandable that if the normal stress on a shear plane can be increased, then the shearresistance can also improved upon and, consequently in the case of soils, their strengthsenhanced. The normal stress on the shear plane of a soil mass is essentially the inter-particlecontact force which is about the same as the effective stress. It clearly follows that when weaccelerate drainage conditions, we can then speedily dissipate the excess pore water pressures setup and thus increase the effective stresses in the soil. This is a fundamental micro-concept that isfrequently used to solve recurring instability and failure problems associated with slopes in earthdams, cuts and fills, or roads and other embankments. The acceleration of drainage to improvestrength and reduce the long term settlement of structures can be achieved using drainage filters:sand drains, plastic drains and cardboard drains. Conversely, slow dissipation of excess porewater pressures; as well as poor drainage of embankments, can lead to catastrophes in thefollowing ways:• Failure of downstream slopes of earth dams through rotational slips e.g. Gubidam at inception and Bauchi – Jos highway.• Failure or road and other earth foundations structurally by the development ofpotholes e.g. City roads in Nigeria as well as Federal and State highways.• Failure of fills beneath the floors of buildings noticeable in many structures.• Failure and severe cracking of building structures, particularly walls on stripfoundations.11

• Failure of pile foundations due to inadequate shaft friction on the skin of thepile.There is a phenomenon, a micro-concept, of soil relationships with water that is quite importantto highlight at this juncture. It is observed in the compaction of soils, an operation that mustalways be undertaken when soils are used as construction material namely: fills under floors,base and sub-base courses beneath the pavements of roadways and parking lots; the generalconstruction process involving soil placement in compacted layers. A typical compaction curveshown reveals that when soil is mixed with water and compacted, the dry density (representing astate of compaction) rises, peaks up abruptly and then drops again. Every soil exhibits thistypical behaviour as confirmed in numerous studies by the author and which will be presentedlater.The implication of this compaction phenomenon is that for every compaction effort, there is a‘maximum dry density (MDD)’ of any particular soil which is found to correspond to a moisturecondition known as the ‘optimum moisture content (OMC)’. In fact, this typical relationship canbe represented by a mathematical model known as the compaction formula (ρ d = ρ b / (1 + m)),correlating dry density, ρ d , to the known and measured bulk density, ρ b , with the water content,m, as the variable. It always gives a perfect curve. If, for some reason, the moisture content is12

too much on the wet side of optimum, the soil rebounds or swells on application of thecompaction effort and it becomes near impossible to compact the soil practically andtheoretically speaking. It has led to the practice over the years in which construction worksinvolving soil compaction, and consequently remolding, are normally suspended in periods ofinclement weather. It is easily observed from the compaction curve that the density, andtherefore soil strength, falls so rapidly from peak with an increase or decrease of the moisturecontent. In dry weather, the moisture content can be increased, in a controllable manner, on soilfills and layers to meet the optimal conditions. However in periods of inclement weather whenrainfall is fierce, heavy and persistent, it is impossible to achieve optimal moisture contents.Therefore construction must either be stopped for the period (i.e. suspended) or deterioration ofthe constructed facility must be expected immediately the inclement weather or rainy/snowyseason passes. Infact, this together with poor soil usage as well as the poor water-proofingqualities of the asphalt cement pavements are principally responsible for potholes on ourroadways in highways.Another micro-concept is related to the passage of water through soil media, a process known asseepage. Forces above the normal hydrostatic level are known as excess pore water pressures.However, in the process of seepage, certain damages are usually posed to the earth structure ifnecessary remedial measures are not put in place. One of these, which is significant, is theinstallation of toe filters in the form of sand blankets, relief wells, and any similar improvisators,at the downstream end of earth dams and earth embankments. In the absence of these towprovisions, seepage flows/pressures usually wash out fines from the compacted soils of the earthstructure. The result is usually devastating because there is what is commonly referred to as coreerosion resulting in soil pipes. It does not take long before huge voids are created in the body ofthe earth structure emanating at the surface in the form of collapses and holes.It is also easy in practical situations of soil construction to trap huge hydrostatic pressures,beneath embankments, which emanate elsewhere at low points in the form of boils and quickcondition. If relief wells are not installed, they can lead to blow-ups when a huge accident wouldhave taken place.13

As an end to the discussion on soil as construction material, it is important to be acquainted withsome procedures of ground improvement. Because we deal with soils of all form of properties,some with very undesirable characteristics, it is usually necessary to improve these properties tomeet with the minimum specifications required for construction. This matter is treated under thetopic of stabilization, which is considered in a separate chapter.4.0 SOIL IMPROVEMENT BY STABILISATIONStabilization of soils have been extensively pursued by three (3) Nigerian researchers namelyBalogun, Matawal and Ola; in separate studies quoted in the references. Stabilization has beenwith the use of either cement or lime to improve the properties of soils.One of the important micro-concepts of soils engineering is the influence of the crystal structureon the properties of the material. All soils of the earth are formed from either 2 layer or 3 layerminerals. Whereas such soils like illite are formed of 2 layer minerals, others like kaolinite andmontmorillonite are from three layer minerals. A 2 layer arrangement comprises of anoctahedral sheet on top of a tetrahedron crystal. The basic building units of soils stack togetherto form the mass of soil. In the stacking arrangement of the basic units, the crystals are heldtogether at their interfaces by certain forces. If these forces are metallic, example bonding withpotassium irons, then they are usually very strong forming stiff soils with high shear strength andlow compressibility characteristics. On the other hand, the bonding can be weak as is the casewith adsorbed water in between the crystals. It gives rise to soils of low shear strength and highcompressibility. Some of these properties are clearly undesirable and frequently need to beimproved through the process of stabilization as follows:i) Cement stabilization is a common process of soil/ground improvement by spreading,mixing and compacting cement with the poor soil. However, studies by Ola (1978,1974); Matawal (1996, 1991 and 1990) and Balogun (1991) have revealed that theeconomic use of cement as a stabilization agent must stop at 9 percent beyond whichwe are dealing with concrete (presented later in this lecture). All the studies show avaried benefit via improvement of the strength, permeability, compressibility andswelling properties of the soils. Cement stabilization actually affects the crystalstructure of the soil resulting in what the author calls ‘soil cement’. Calcium, from14

the cement, replaces the absorbed water layer resulting in stronger keying or bondingof the soil basic building units together giving rise to better construction material.Cement stabilization is a very common process in the construction of roads inNigeria.ii) Lime stabilization studies have been undertaken by Ola (1974) and Balogun (1991)and involve the addition, mixing and compacting of lime to poor soil. The resultingmixture has vastly improved properties by the same changes in crystal structure of thesoil as in cement stabilization. It is possibly easy to understand that cement and limestabilization are very similar because lime is a basic raw material of cement.iii) Mechanical stabilization processes are essentially similar to compaction or even meancompaction. It is common and because compaction has already been presented needsno further elaboration.5.0 MICRO-CONCEPTS OF CEMENT AND CONCRETE AS CIVILENGINEERING MATERIALConcrete is essentially a mixture of cement with natural aggregates of sand/quarry dust andstone. When the mixture is of cement and sand or quarry dust only, the resultant is calledsancrete and if it is cement and soil only, it is soilcrete. The most interesting thing about thesemixtures is that the prime objective is to attain bonding of the coarser aggregates (which providestrength) with cement (which provides the glue). The strength of natural aggregates, particularlystone, is a macro-concept and so to gain insight into this aspect of civil engineering materials, itwill be sufficient to look into the micro-concepts of the cementatious material, which is regulatedby the engineer.Cement, like other cementatious materials, contains inorganic nonmetallic products that aremixed with water or another liquid to form a paste. The paste, which is temporarily plastic andmay be molded, may or may not have aggregate added to it. Later, it hardens or sets to a rigidmass. Driving off a liquid or gas from the natural mineral produces the simple cementingmaterials, such as limes and plasters. Their cementing properties arise from the re-absorption ofthe liquid or gas that has been expelled and the formation of the same chemical compounds ofwhich the original raw material was composed. The more complex hydraulic cements derivetheir cementing properties from formation of new chemical compounds during the15

manufacturing process. The term hydraulic applied to cements means capable of developingstrength and hardening in the presence of water. Limes, plaster and hydraulic cements are notwidely used.The most widely used is Portland cement concrete which is the most important constructionmaterial employing a cement. Understanding of the factors affecting the constituents ofconcrete, the Portland cement and aggregates, is essential to a fundamental understanding of theproduction and behaviour of concrete and the influence of water on its properties.5.1 Portland Cement Manufacture: Portland cements are made by blending a mixture ofcalcareous (lime containing) materials and argillaceous (clay) material. The raw materials arecarefully proportioned to provide the desired amounts of lime, silica, aluminum oxide, and ironoxide. After grinding to facilitate burning, the raw materials are fed into a long rotary kiln,which is maintained at a temperature of about 1482 o C. The raw materials, burned together, reactchemically to form hard, walnut-sized pellets of a new material, clinker. (Lime) + (Silica +Alumina + Ferric Oxide + Water) + Heat Tricalcium silicate + Dicalcium silicate +Tricalcium aluminate + Tetracalcium Aluminoferrite = Cement.[Lime = CaO + CO 2 , Silica = SiO 2 ; Alumina = Al 2 O 3 ; Ferric Oxide = Fe 2 O 3 , Water = H 2 O].[Tricalcium Silicate = 3CaO. SiO 2 , Dicalcium silicate = 2CaO. SiO 2 , Tricalcium aluminate =3CaO. Al 2 O 3 ; Tetracalcium aluminoferrite = 4CaO. Al 2 O 3 . Fe 2 O 3 ]. The clinker, after dischargefrom the kiln and cooling, is ground to a fine powder ( ≥ 1600 cm 2 /gm specific surface). Duringthe grinding process, a retarder (usually a few percent of gypsum) is added to control the rate ofsetting when the cement is eventually hydrated. The resulting fine powder is Portland cement.It is important to understand that because Portland cement is derived from unrefined rawmaterials, additional compounds are usually present in addition to the major essential ones. Fourcompounds, however, make up more than 90 percent of cement, by weight namely: Tricalciumsilicate, Dicalcium silicate, Tricalcium aluminate, and Tetracalcium aluminoferrite. Each ofthese four compounds is identifiable in the highly magnified microstructure of Portland-cementclinker, and each has characteristic properties that it contributes to the final mixture.16

5.2 Hydration of Cement: When water is added to cement, the basic compounds present aretransformed to new compounds by some chemical reactions like:Tricalcium Silicate + Water Tobermorite gel + Calcium hydroxide Dicalcium Silicatealuminoferrite + Water + Calcium hydroxideCalcium aluminoferrite hydrateTetracalcium aluminate + Water + Calcium hydroxide Tetracalcium aluminate hydrateTricalcium aluminate + Water + Gypsum Calcium monosulfo aluminate.Two calcium silicates, which constitute about 75 percent of Portland cement, by weight, reactwith the water to produce two new compounds: tobermorite gel and calcium hydroxide. In fullyhydrated Portland cement paste, the calcium hydroxide accounts for 25 percent of the weight andthe tobermorite gel makes up about 50 percent. The third and fourth reactions above show howthe other two major compounds in Portland cement combine with water to form reactionproducts. The final reaction involves gypsum: the compounds added to Portland cement, duringgrinding of the clinker, to control set.Each product of the hydration reaction plays a role in the mechanical behaviour of the hardenedpaste. The most important of these, by far, is the compound called tobermorite gel, which is themain cementing component of cement paste. This gel has a compound and crystal structure tothose of a naturally occurring mineral, called tobermorite, named for the area where it wasdiscovered, Tobermory in Scotland. The gel is an extremely finely divided substance with acoherent structure.The average diameter of a grain of Portland cement, as ground from the clinker, is about 10microns (0.010mm). The particles of the hydration product, tobermorite gel, are in the order of1/1000 of that size (10 x 10 -6 mm). Particles of such small size can be observed only by using themagnification available in an electron microscope. The enormous surface area of the gel (about3 million cm 2 /gram) results in attractive forces between particles since atoms on each surface areattempting to complete their unsaturated bonds by adsorption. These forces cause particles oftobermorite gel towards each other as well as to particles of aggregates introduced into thecement paste. Thus, tobermorite gel forms the heart of the hardened cement paste and concrete,in that it cements everything together.17

Each of the four major compounds in Portland cement makes a contribution to the behavior ofthe cement as it proceeds from the plastic to the hardened state after hydration. Knowledge ofthe behaviour of each of these major compounds upon hydration permits us to understand theprocess on sites.• Tricalcium Silicate is primarily responsible for the high-early strength ofhydrated Portland cement undergoing initial and final set within a few hours.The reaction is exothermic giving off large quantity of heat (heat of hydration)attaining most of its strength in 7 days.• Dicalcium Silicate exists in alpha, beta and gamma forms but only the beta issignificant. It takes several days to set being primarily responsible for thelater developing strength of Portland cement paste with low heat of hydration.It is known that it produces little strength until after 28 days but the finalstrength is equivalent to that of Tricalcium Silicate.• Tricalcium aluminate exhibits an instantaneous or flash set when hydrate. It isprimarily responsible for the initial set of Portland cement and gives off largeamounts of heat upon hydration. It shows little strength increase after 1 daybut the gypsum added combines to control the time of set. Though it developsvery low strength, nonetheless it is desirable in Portland cement as anincreased amount results in faster sets and also decreases the resistance of thefinal product to sulfate attack.• Tetracalcium aluminoferrite also hydrates rapidly and develops only lowstrength but, unlike tricalcium aluminate, does not exhibit flash set.In addition to composition, speed of hydration is affected by fineness of grinding of clinker,amount of water added, and temperatures of the constituents at the time of mixing. To achievefaster hydration, cements are ground finer. Increased initial temperature, as revealed fromresearch by Matawal and Abba-Gana (1998); and the presence of a sufficient amount of water,also speed the reaction rate.18

TYPICAL PROPORTIONS (%) OF MAJOR COMPOUNDS IN PORTLAND CEMENTTYPE OF PORTLAND CEMENTCOMPOUNDS I II III IV V3CaO.SiO 2 53 47 58 26 382CaO. SiO 2 24 32 16 54 433CaO. Al 2 O 3 8 3 8 2 44CaO. Al 2 O 3 . Fe 2 O 3 8 18 8 12 8Total (%) 93 94 90 94 93Recollect that there are Hydraulic, simple and Portland cements. Hydraulic cements includeAluminous cements, Natural cements, White Portland cement and Hydraulic lime. Simplecements include Plasters, Limes (Quicklime and Hydrated limes) and others (Gypsum cementsand oxychloride cements). Portland cements as shown in the table are: Type I – GeneralPurpose, Type II – Modified general purpose, Type III – High early strength, Type IV – Lowstrength and Type V – Sulfate resisting.RELEVANT STRENGTHS OF CONCRETE AS FUNCTION OF CEMENT TYPEComprehensive Strength %, of Type I Portland CementTYPES OF PORTLAND 3 days 28 days 3 monthsCEMENTI. General Purpose 100 100 100II. Modified 80 85 100III. High-early strength 190 130 115IV. Low heat 50 65 90V. Sulfate-resisting 65 65 65There are also air-entraining Port land cements, by addition of air-entraining agent, designatedtypes IA, IIA and IIIA, for the manufacture of concrete for exposure to severe frost action.5.3 ENHANCING PERFORMANCE OF CONCRETE: The user of concrete, a veryversatile building material made from cement and aggregates, desires adequate strength,controlled set and consequently workability (placeability), and durability at minimum costs. Theprincipal variables are the water to cement ratio, cement-aggregate ratio, size of coarseaggregate, ratio of fine aggregate to coarse aggregate, type of cement, and use of admixtures.19

i) Water – cement ratio is a very important micro-concept for assessing strength andworkability of concrete and it is easy to understand the influence of water in thehydration process of concrete from preceding discussions. Water – cement ratio,expressed by weight, affects the comprehensive strength of normal concrete.Strength decreases with an increase in the w-c ratio. The relationship is linear ifconcrete strength (log. scale) is plotted against w-c ratio, the slope is unity.TYPICAL VARIATION OF STRENGTH OF CONCRETE WITH W-C RATIOW-C ratio 0.35 0.40 0.50 0.60 0.80 1.00Average 28 day comprehensive strength, 42 37 30 24 15 9N/mm 2ii)iii)iv)Cement content: there is a general decrease of strength with decrease in cementcontent.Type of cement affects the rate at which strength develops and the final strength.Curing conditions are very important in the development of strength of concrete.Since cement hydration reactions proceed only in the presence of an adequate amountof water, moisture must be maintained in the concrete during the curing period. It isfor these reasons that watering and wrapping with wet jute bags is required forconcrete elements after construction. Furthermore, the strength of concrete isdetrimentally affected by early transfer from a moist atmosphere to a dry one asexperiments by the U.S Bureau for reclamation shows, Merritt (1976).TYPICAL CONCRETE STRENGTH (N/mm 2 ) AS FUNCTION OF CURINGCONDITIONSComprehensive Strength (N/mm 2 ) at No. ofConcrete curing/storage conditionsdays3 7 14 28 90 1801. Continuously in laboratory air 10 14 17 18 17 172. In air after 3 days 10 17 24 26 26 243. In air after 7 days 10 17 26 31 31 294. In air after 14 days 10 17 26 34 35 345. In air after 28 days 10 17 26 31 39 376. Continuously moist cured 10 17 25 31 37 4020

v) Temperature for curing also affects concrete strength: a phenomenon amplydemonstrated in experiments by Matawal and Abba-Gana (1998). Lower periods arerequired at lower temperatures to develop a given strength. Although continuedcuring at elevated temperatures results in faster strength development at 28 days, atlater ages the trend is reversed as concrete cured at lower temperatures developshigher strengths.6.0 MICRO-CONCEPTS OF STEEL AS CONSTRUCTION MATERIALSteel is used as reinforcement in reinforced concrete structures and as structural steelwork inframes, towers, trusses (including space tresses), bridges etc. In concrete, it is taken thatconcrete, being weak in tension, does not take such loading so that whenever direct or flexuraltension occurs, then reinforcement must be introduced. As a manufactured material subjected toa lot of quality supervision and specifications, matters related to its uses and applications arerather too technical for a public lecture of this nature: they are macro-concepts to civil engineerstaught rigorously in classrooms. Moreover, it is not a common material to the society who maynever need elaborate reinforcement or structural steelwork for any work related to their housingand businesses. It is then only noteworthy to emphasise that, in use of this type of materials inthe civil engineering industry, certain points must be observed to make optimal application ofsteel. These points are:• They must be free of rust or corrosion and where they have rusted, the scalesshould be thoroughly cleaned.• The dimensions must be comprehensively monitored to ascertain that theyconform to standards of the structural designs.• The yield stresses should be checked because tests by Matawal (1990)revealed that while rods of smaller diameters (12mm and below) tend to giveyield values equal or above specifications, the higher diameter rods (16mmand above) fall grossly below specifications.21

7.0 MICRO-CONCEPTS OF TIMBER AS CONSTRUCTION MATERIALTimber is remarkable for its beauty, versatility, strength, durability, and workability. It possessesa high strength-to-weight ratio and has flexibility. It performs well at low temperatures andwithstands substantial overloads for short periods and has low electrical and thermalconductance. It resists the deteriorating action of many chemicals that are extremely corrosive toother building materials and is abundant in Nigeria. However timber differs in severalsignificant ways from other civil engineering materials for which its cellular structure isresponsible, to a considerable degree. As a result of this, structural properties are dependent onorientation. While most structural materials are essentially isotropic, with nearly equalproperties in all directions, timber has three principal grain directions: longitudinal, radial andtangential. Loading in the longitudinal direction is referred to as parallel to the grain, whereastransverse loading is considered across the grain. Parallel to the grain, timber possesses highstrength and stiffness (be it shear, tension or compression); while across the grain, strength ismuch lower.Timber is unlike most other structural materials in regard to the causes of its dimensionalchanges, which could be primarily from gain or loss of moisture; not temperature. A newlyfelled tree is green (contains moisture). In removing the greater part of the moisture, seasoningfirst allows free water to leave the cavities of the timber. A point is reached when these cavitiescontain only air, and the cell walls are still full of moisture. The moisture content at which thisoccurs, known as the fiber-saturation point, FSP, varies from 25 to 30% of the weight of theoven-dry timber.During removal of the free water, the timber remains constant in size and in most properties, butthere is a weight decrease and it is called green timber. Once the fiber-saturation point has beenpassed, it is dry timber, and shrinkage of the timber begins as the cell wall loses water.Shrinkage continues nearly linearly down to zero moisture content. Eventually, the timberassumes a condition of equilibrium, with the final moisture content dependent on the relativehumidity and temperature of the ambient air. Timber relationship of timber moisture content,temperature, and relative humidity can actually define an environment.22

Research on Nigerian timber has been initiated in the university by the author and is continuingeven though collation and analysis of results is still incomplete for presentation at this stage.8.0 MICRO CONCEPTS OF ASPHALT AS CONSTRUCTION MATERIALAsphalt materials have been known and used in road and building construction since ancienttimes. Each type of asphalt was of natural origin, found in pool and asphalt lakes, but currentsupplies come mainly from the residues of refined petroleum. Asphalt, which is the black ordark brown petroleum derivative of fractional distillation process, is distinct from tar, the residuefrom destructive distillation of coal.Bituminous pavements result from asphalt refined to meet specifications for paving purposes,called asphalt cements. At normal temperature, it is semi-solid, with a degree of soliditymeasured by a penetration test. It is heated until liquefied before being blended with aggregatein paving mixtures. If asphalt is so soft that a penetration test is not an appropriate means formeasuring consistency, it is called liquid asphalt. Several types of liquid asphalt are produced:• Rapid curing (RC) asphalt, which is liquefied with naphtha or gasoline, bothof which are highly volatile and evaporate quickly to leave asphalt cement.• Medium curing (MC) asphalt, which is asphalt cement liquefied with akerosene dilutant.• Slow curing (SC) asphalt, which is blended with low-volatile oil.• Emulsified asphalt, which is produced by mixing together water with anemulsifying agent and asphalt cement. This heterogeneous system ofspherical globules in the water medium hardens as the water evaporates.Asphalt pavements are composed of asphalt, aggregate, and voids (2 to 7%). An asphaltpavement carries applied load by particle friction and interlock. Its strength is a function of thesurface texture (particularly of the fine aggregate) and density (compactness) of the aggregate. Arough surface texture is desirable.23

TYPICAL ASPHALT – AGGREGATE COMPOSITIONConstituentProportion (%) byWeightVolume1. Asphalt 6 14.42. Coarse aggregate 53 43.73. Fine aggregate 35 33.44. Mineral dust 6 4.95. Air 0 3.6Dense mixtures are obtained by using well-graded aggregates, where the fine aggregate fills thevoids in the coarse aggregate structure. Coarse aggregate is that retained on a 0.01 mm sieve,fine aggregate passes the 0.01mm sieve, and quarry/mineral dust passes a 0.063mm sieve. Theasphalt cement binds the aggregate particles together and waterproofs the pavements. The airvoids allow the expansion of the asphalt cement or compaction of the composite by providingspace for the asphalt cement to move into instead of pushing the aggregate further apart.9.0 MICRO-CONCEPTS OF WATER AS CIVIL ENGINEERING TOOLIn the treatment of civil engineering materials, water is more of a tool as well as a medium formany human activities. It is an essential constituent of life that is unevenly distributed on ourplanet, earth. It is in excess in certain regions while there is desertification in many other parts ofthe world. The total estimate of the world’s water resources, as example, is 1.45438 x 10 9 sq.km.A large proportion of these resources comprises of salt water contained mainly in the oceans,about 97.2 percent. 2.8 percent of the world’s water is available as fresh water (salinity is due todissolved salts: NaCl (80%) and MgCl 2 , MgSO 4 , CaSO 4 all constitute 20%). Of the 2.8 percentfresh water, 2.2 percent is available as surface water while the remaining 0.6 percent as groundwater representing the major influence in the interstices, voids and pore spaces of oursubstructures and the world’s soils. Much of the engineering of water and water resources is inform of macro-concepts dealing with such topics like evaporation and transpiration, infiltration,stream characteristics, ground water hydrology, water conservation and other topics. Moreover,what is considered of micro-significance is the influence of water on the characteristics andprocessing of other civil engineering materials like soil and cement, already elaborately dealtwith. Therefore what this lecture will touch on is the water for domestic use (drinking, washingetc) processed in large treatment plants for urban supplies. This is considered directly relevant to24

the health of the common man and certain micro-concepts of water treatment may be appreciatedfor individual self-help.Matawal and Kulack (2001) have undertaken a comprehensive study of water from differentsources of human consumption. Colony counts were made, temperatures taken, as well as testsfor pH, biochemical oxygen demand (BOD) and total solids (TS) to ascertain their degrees ofinfection. The results of the tests reveal that these water sources; used for drinking by humansand animals as well as domestic applications, are in reality polluted above World Health (WHO)standards, some even over polluted.WHO BACTERIOLOGICAL STANDARDS FOR DRINKING WATERS/No SPECIFICATION1. Throughout any year, 95 percent of samples should not contain any coliformorganism in 100ml specimens.2. No sample should contain more than 10 coliform organisms per 100mlspecimens.3. No sample should contain Escherichia-coli bacteria in a 100ml specimen4. Coliform organisms should not be detectable in two consecutive samples of100ml each.WHO TENTATIVE LIMITS FOR TOXIC SUBSTANCES IN DRINKING WATERToxicSubstanceMaxConcentration,mg/lArsenic Cadmium Cyanide Lead Mercury Selenium0.050 0.010 0.050 0.100 0.001 0.01025

RESULTS OF WATER TESTS ON RAW WATER SOURCES by Matawal and Kulack(2001)SourcesTemp. pH BOD Colony per TS( o C)(mg/l) ml x 10 6 (mg/l) x 10 61. Drinking well 27 7.7 4.4 1.10 0.5172. Flowing stream 28 7.9 7.8 1.16 1.1043. Borehole 26 7.1 1.0 0.00 0.0044. Stagnated pond 30 7.9 9.6 1.39 0.9875. Pipe borne 25 7.0 0.4 0.03 0.002It is significant to know that pipe borne water, relied on by most of the population as hygienic, isin fact polluted in spite of treatment by the water works. This is quite significant but for goodobservers, is nothing new since, in periods of shortages, maggots have been known to flow out ofour pipelines with the reestablishment of first traces of water supplies.10.0 PERSONAL WORKS OF SIGNIFICANCEThe contributions that the author has made to knowledge of Nigerian civil engineering materialshave been extensive in some areas while they are continuing on others. Accounts of thesecontributions are going to be presented without regard to any sequence.The influence of water in the microstructure of soils was exposed, in detail, in the presentationon effective stress principle, Matawal (1990). The influence of pore water pressures and theconcept of effective stress as it affects shear strength, compressibility and other applications wereresearched into while the basic mathematical and physical relationships were presented andillustrated. Matawal (1990) undertook some physical and index measurements of concrete andsteel elements used on construction projects in Bauchi town including reinforcement rods for theNew Lecture Theatre Complex in the University campus at Yelwa. While the concrete wasfound to be in conformity with specifications for strength and durability, certain deficiencieswere observed in the results of the reinforcement rods. As example, in addition to otheranalytical and professional shortcomings, it was observed that while the yield of the smallerdiameter (below 16mm) rods showed agreement or even exceeded the code specifications ofindustry, the higher diameter (16mm and above) fell below the standards by 5 to 10 percent.Furthermore, the nominal diameters of the bars rolled out of steel industries always fell below26

the specification by as much as 0.8mm, which is a substantial reduction of the cross-sectionalarea required to carry tensile stresses in reinforced concrete elements.Matawal (1990) subjected five (5) soil specimens from the Jos Plateau and from Bauchi tocompaction and strength studies. Details of some tests on these soils are shown in the tablebelow:RESULTS OF IDENTIFICATION TESTS ON SOILS FROM BAUCHISample CONSISTENCY LIMITS (%) SOIL FRACTIONS (%)No. LL PL PI SL CLAY SILT SAND GRAVEL1 30.30 18.7 11.59 9.07 24 3 22 512 35.80 25.66 10.14 6.43 40 6 32 243 32.70 26.65 6.05 3.57 27 9 33 314 31.40 N.P. 0.00 3.21 57 11 28 35 38.60 20.51 18.09 8.93 34 5 33 27Laboratory research was conducted on both the Jos and Bauchi soils and it was observed thatthey obey the perfect compaction model described previously. A theoretical correlation wasestablished between a strength index, CBR, and the OMC of the soils. Matawal (1991)undertook shear strength studies, using Vane apparatus, on borrow pit specimens used on theuniversity construction sites. The soil data is shown below:UNIVERSITY CONSTRUCTION SOILSDepth (m) LL % PL (%) PI (%) LS (%)1.0 44.0 29.0 15.2 7.11.9 N. P. N.P. N.P. N.P.Matawal (1991) in separate studies subjected northern Nigerian soils to shear strength,compressibility and permeability analyses. Again, the compaction curves were perfectconfirmation of the pattern exposed in the micro-concept studies.27

Balogun and Matawal (1997) undertook theoretical analytical studies on reinforcing strips ofmetal for sheet pile wall design. Matawal et al (1996) undertook studies on the response oftropical laterites to ground improvement techniques using cement stabilization.SOILS USED FOR STABILISATION STUDIESSOIL SOURCE AND COMPOSITION (%) GRAVEL SAND SILT CLAYGubi Campus 8 59 2 31Yelwa Campus 11 63 5 21Ningi 22 56 7 15Birshin Fulani 21 57 0 22These soils were stabilized with cement contents of 1.5, 3.0 and 6.0 percent, in addition to thehomogenous specimen. Detailed consolidation, compaction, CBR and swell studies wereconducted on the homogenous and stabilized samples. Matawal and Daspan (1997) undertookstudies on the design, construction and cost-benefit of reinforced earth wall and concluded thatthe basic cost of materials was only 7.24 percent of the cost of an equivalent gravity wall. Metalstrips were used for reinforcement with thin facing wall of aluminum foil.Matawal and Abba-Gana (1998) undertook studies to ascertain the effects of high tropicaltemperatures on concrete from Ashaka Type I cement. The results confirmed that hightemperatures result in increased strength at early ages but lower strengths at late curing ages thanlow temperatures. The temperatures of experiments were 28, 32, 38 and 42 o C for which theresults totally confirmed the effects of temperatures on the strength of concrete i.e. that there ismuch long term benefit, by the grain in strength, in the use of low temperatures for concreteworks. High temperatures merely encourage accelerated hydration process for the formation oftobermonite gel at the outset of concrete batching which gives high early strength but lower longterm resistance.28

MEAN CUBE STRENGTHS FOR VARYING TEMPERATURESMean Compressive Strength (N/mm 2 ) at indicated agesCuring Temperature o C 3 days 7 days 14 days 28 days28 23.60 27.22 34.55 38.5632 24.00 28.78 35.00 37.7838 24.89 29.78 37.45 37.5642 25.22 29.22 34.89 36.67MEAN CUBE STRENGTH AS RATIO OF 28 DAY STRENGTH AT ROOMTEMPERATURERatio (%) of 28 day – 28 o C strength at age:Curing Temperature o C3 days 7 days 14 days 28 days28 61.2 70.6 89.6 100.032 62.2 74.6 90.8 98.038 64.5 77.2 97.1 97.042 65.4 75.8 90.5 95.1Tricalcium silicate component of cement is responsible for high early strength of concrete and itsreaction exothermic, favored by high temperatures.Matawal and Ajala (1966) tackle, explicitly, the influence of pore water pressures on the stabilityof slopes for which computer solutions are proffered for the associated problems. Matawal andOkere (2001) map out soils, ground water and rocks of the University campus using electricalresistivity methods (the terrameter utilizing the Schlumberger fixed array configuration).Matawal and Gboganiyi (2000) analyse six (6) specimens of soils from locations in Bauchi andGombe, identifying them and undertaking laboratory measurements to ascertain some of theirproperties.29

SOILCOLOUR LL % PL PI SL IDENTIFICATION ClassificationSOURCE% % %Yelwa, Bauchi Reddish 25.8 22.8 3.0 4.8 Laterite A-2-6brownWunti, Bauchi Brown 26.3 21.6 4.7 5.0 Laterite A-2-7Miri, Bauchi Dark brown 29.6 16.1 13.5 7.1 Laterite A-2-6Gombe Town Dark 36.4 21.1 15.3 10.4 Black Cotton A-6Kari, Bauchi Light brown 33.1 14.0 19.1 7.9 Laterite A-2-7Bayara, Bauchi Reddishbrown28.3 14.3 14.0 10.0 Laterite A-2-6Stabilisation studies were undertaken on the soils with cement contents of 0, 1.5, 3.0, 4.5, 6.0,7.5 and 9.0 percent based on which the linear relationship q = q o + K.c was derived for stabilizedsoils.Matawal and Enunoya (2001) have undertaken sensitivity measurements on ten (10) soilspecimens from Delta, Edo, Bauchi, Gombe and Plateau states to ascertain their stability asfoundation and construction material under a cycle of dry and wet conditions.SOIL SOURCEDepth LL% PI (%) GS CLASSIFICATION(m)1. Warri, Delta State 2.00 33.10 14.16 2.63 A-2-62. Warri, Delta State 2.00 22.50 9.50 2.67 A-2-43. Benin city, Edo State 2.00 45.40 24.65 2.62 A-2-74. Bauchi, Bauchi State 2.25 35.50 17.10 2.51 A-2-45. Bauchi, Bauchi State 1.60 35.00 18.15 2.42 A-66. Bauchi, Bauchi State 1.60 46.00 16.74 2.30 A-7-67. Dadin Kowa, Gombe State 2.00 26.70 NP 2.74 A-1-68. Baure, Gombe State 1.50 36.40 15.56 2.47 A-2-69. NNPC, Gombe State 1.60 48.41 22.50 2.48 A-2-710. Fed. Low Cost, Jos, Plateau State 1.60 36.10 13.74 2.38 A-6It is interesting to note the existence of black cotton soils in Bauchi State somewhere in Wunti(5) and Wuya dam (6) sites.The quality of water for human consumption and domestic applications had been of concern formany years particularly with incessant reports of the unacceptable water being consumed bymany communities in the North East zone. This prompted the research by Matawal and Kulack30

eported on earlier in Chapter 8. Following the discovery that even pipe borne water is not fit forhuman consumption as it fell below the WHO standards for drinking, an alternative method ofpurification was explored. The research describes, in detail, the use of ultraviolet radiation fordisinfection of water particularly for commercial purposes and is recommended for householdand small community applications in addition to the old age tradition of boiling. Matawal andKulack (2001) bombarded all the poor water sources with ultraviolet rays and discovered that itresulted in total disinfection and had no known side effects.RESULTS OF WATER TESTS SUBJECTED TO ULTRAVIOLET TRADITIONSOURCE Temp. ( o C) pH BOD, mg/l Colony per mlx 106Total solids, TS, x10 3 , mg/lDrinking well 26 7.2 0.1 0.0 0.502Flowing25 7.1 0.1 0.0 0.502streamBorehole 25 7.1 0.2 0.0 0.502Pond 26 7.1 0.2 0.0 0.508Pipe mains 25 7.0 0.1 0.0 0.002The dissolved and suspended solids were reduced by filtration.The accounts given above are details of researches that are relevant to the theme of common civilengineering materials. There have been accounts of applications and results of tests on newmaterial called spunbonded polypropylene, a fabric geotextile for construction on difficultgrounds, by Matawal (1997, 1990 and 1991). Additionally, in the course of construction of civilengineering projects in which numerous materials were used in Abuja, Gombe, Bauchi, Warri,Jos, Yola, Maiduguri, Keffi, Makurdi and on rural roads, numerous experiences have beengained that are immensely valuable to the development and welfare of the society. NITELresistivity tests undertaken in Bauchi, Jos, Maiduguri, Yola and Jimeta, and at Gombe werebacked by direct borings and the gains were that the soils of these locations were known firsthand. Many technical reports that will be useful to planners and practitioners have beenproduced while mapping of construction materials have been well defined particularly in NorthEast Nigeria.31

11.0 CONCLUSIONIt is a fact that common civil engineering materials are used by professionals, knowledgeable inthe science of application of these materials, as well as non-engineers. The latter do not havemuch knowledge of the properties and characteristics of these basic materials that they canharness economically for building their homes, improving the environments in which they liveand upstaging the organisations which they administer or serve. That is not all, water is soessential to life and yet in harnessing this resource for drinking, particularly, very little attentionis often given to the quality and degree of disinfection of the commodity. It is in this regard thatthe micro-concepts enumerated and exposed in this lecture can be harnessed for the benefit ofmankind whether privileged or underprivileged. The earth’s soils, cement used in concreteconstruction, timber and, to a lesser extent, steel and asphalts are considered common enoughmaterials to warrant the micro-details of this lecture. A little more knowledge on one or more ofthese materials could make the difference between dilapidated housing, roads and otherinfrastructure of our generation and a new generation of gratified Nigerians.12.0 ACKNOWLEDGEMENTSThe author, Professor Danladi Slim Matawal, is particularly thankful to Professor A. S. Sambo,the Vice Chancellor of ATBU University, Bauchi, who initiated the inaugural lecture series andenergetically propelled it. Appreciation is also made to the various compatriots in the universitywho have given encouragement and counsel when it was necessary. The family warmth andenticement to keep working on, when the spirit is willing but the body is weak, needs mentionespecially from my wife, Rose D. Matawal. And to those whose contributions came after writingthe lecture: typists and those who will assist with teaching aids materials, projector and the like,I say thank you all.13.0 LIST OF REFERENCES1. Abba-Gana, M. (1997) “The effect of High curing temperatures on the strength ofconcrete prepared using Nigerian cements”, B. Eng. Project report, ATBU, Bauchi.2. Atkinson, J. H. and Bransby, P. L. “The mechanics of soils”, McGraw hill, Maidenhead.32

3. Balogun, L. A. (1991) “Effect of sand and salt additives on some geotechnical propertiesof lime-stabilised black cotton soils”. The Nig. Engr. 26 (4), 15-25.4. Balogun, L. A. and Matawal, D. S. (1997). “New application of reinforced earth studiesin the design and construction of retaining walls”. Journal of Engineering Res. JER, 5(1), 16-345. Bhatia, H. C. (1967). “Soil-cement: a material of construction for road and airfieldpavements”. Tech. Paper 1, Building and Road res. Inst. Ghana.6. Bitrus G. P. Philips (1989). “Geotechnical properties and behavior of some stabilizedNigerian Lateritic soils,” B. Eng. Project report, A.T.B. University, Bauchi.7. Brand, E. W. and Brenner, R. P. “Soft clay engineering” Elsevier scientific Company,Amsterdam.8. Bureau of Reclamation: “Concrete manual”. Government printing Office Washington,D. C.9. Dugdak, D. S. and Ruize, C. “Elasticity for engineers”. McGraw hill, London.10. Emesiobi, F. C. (2000). Testing and quality control of materials in civil and highwayengineering”. Blueprint Ltd. Port Harcourt.11. Hughes, B. P. “Limit state theory of reinforced concrete design”. A Pitman Internationaltext, London.12. Ketkukah, T. S. (1990). “Long term effect of lack of curing on structural concrete”, B.Eng. Project report, A.T.B. University, Bauchi.13. Lea, F. M. and Desch, C. H. “The chemistry of cement and concrete”. Edward ArnoldPub., London.14. Matawal, D. S. and Enunoya, E. (2001). “Sensitivity evaluation of some tropical soils”.Journal of Engineering Tech. And Ind. App. Vol. 2.15. Matawal, D. S. and Kulack, P. A. (2001). “Alternative methods to chlorination fordisinfecting water: Case of ultraviolet radiation”. Journal of Engineering Tech. and Ind.App. Vol. 2.16. Matawal, D. S. and Okere, C. N. (2001). “Results of subsurface exploration using theterrameter”. Journal of Engineering Tech. and Ind. App. Vol. 2.17. Matawal, D. S. and Gbobaniyi, M. M. (2000). “Theoretical relationships in cementstabilized soils”. Journal of Engineering Tech. and Ind. App., 1 (1).33

18. Matawal, D. S. and Abba-Gana, M. (1998). “Curing age versus concrete strengthrelationships in tropical temperatures”. 5 th National Engineering Conference Series, 5(2), 297 – 303.19. Matawal, D. S. and Ajala, E. O. (1998). “Computer solutions for the Bishop methods ofslope stability analysis”, 5 th National Engineering Conference Series, 5 (2), 276-281.20. Matawal, D. S. et al. (1996). “Response of some tropical laterites to cementstabilization”. 3 rd National Engineering Conference Series, 3(1), 90-95.21. Matawal, D. S. (1992) “Earth response of embankments in soft ground”, NationalSeminar (Earthdam monito0ng and Management).22. Matawal, D. S. (1991a) “The compaction characteristics of some stabilized NorthernNigerian laterite soils”. Permeability and shear strength response. The Nig. Engr. 26(2),41-54.23. Matawal, D. S. (1991b). “The use of field and laboratory methods for the shear strengthanalysis of tropically weathered soils”. Journal of Engineering research, JER 3(1), 1-9.24. Matawal, D. S. (1990). “Compaction characteristics of some tropical laterite soils”OMC-CBR relationship, Journal of Engineering Research, JER 2(2), 1-9.25. Matawal, D. S. and Bhalla, S. N. (1990). “Some suggested areas of practical applicationof reinforced earth material on civil engineering projects”. Conference on utilization ofengineering in rural development, Nsukka.26. Matawal, D. S. (1990). “Qualitative national development through standardization”.Cont. of quality con. Soc. of Nigeria, Ile-Ife.27. Matawal, D. S. (1990). “The concept of effective stress as an engineering principle”.Civil engineering seminar, 1.12.90, A.T.B. University, Bauchi.28. McCormac, J. C. “Structural analysis”. In text education publishers, New York.29. Merritt, F. S. “Standard handbook for civil engineers”. McGraw hill Company, NewYork.30. Mustafa, S. and Yusuff M. I. “A textbook of hydrology and water resources”; Jenas printsCo. Abuja.31. Neville, A. M. and Brooks, J. J. “Concrete technology”. Longman Ltd. Singapore.32. Neville, A. M. “Properties of concrete”. Pitman books, London.34

33. Ola, S. A. (1978). “The geology and geotechnical properties of the black cotton soils ofNorth-Eastern Nigeria”. Engineering Geology, Vol. 12, 375-391.34. Ola, S. A. (1974). “Stabilisation of cement in Nigeria”. Nigerian Journal of Engineering1(1), 19-30.35. Ononuju, E. M. (1988). “Effects of cement stabilization of soils for highwayconstruction”. B. Eng. Project report, A.T.B. University, Bauchi.36. Portland Cement Association. “Soil cement laboratory handbook”, Portland cementassociation, 33 West Grand Aven., Chicago, IL, 60610.37. Scott, C. R. “Soil Mechanics and Foundations”. Applied Science Pub. Ltd, London.38. Scott, J. S. “The Penguin dictionary of civil engineering”. Penguin books Ltd.Harmondsworth.39. Smith, G. N. “Elements of soil mechanics for civil and mining engineers”. Granada Pub.London.40. Stephens, J. H. “The Guinness book of structures”. Guinness superlatives Ltd, London.41. Wajahat, M. N. (1988) “Growth of comprehensive Strength of Concrete under adverseeffect”. B. Eng. Project report, A.T.B. University, Bauchi.42. World Health Organisation, WHO. “International Standards for drinking water”, WHOGeneva, Switzerland.35

ABOUT THE AUTHORProfessor (Engr.) DANLADI SLIM MATAWALB. Eng. (ABU), M. Sc. (London), DIC, Ph.D.,C. Eng., MNSE, MNIM, MSESNProfessor of Civil EngineeringBorn on Sunday, October 30, 1955, i.e. 46 years ago, in Bokkos, Bokkos LG of Plateau State ofNigeria, Professor Matawal had his primary school education at the N. A. Primary School inBokkos from 1963 to 1968. He was born to Mama Undong Matawal (mother) and Pa YakubuMatawal Yakwal (father, then adult education teacher in the defunct pankshin N.A.). Fromprimary school, young Matawal proceeded to the Government College at Keffi in 1969 fromwhere he passed out, in 1973, with a WASC division ONE with excellent (E1) in Mathematics,Physics and Chemistry. His best results were usually in the three subjects because he never paida lot of attention to his other subjects like Geography, English and Bible Knowledge in which henonetheless obtained credit 6 scores. He salvaged the Benue Plateau State prize for the bestbeginner of Technical drawing in 1972.He proceeded to Ahmadu Bello University at Zaria in 1974 where he spent some one and halfyears in the School of Basic Studies in the same class with many useful colleagues today. InSeptember 1975, he registered for Civil Engineering in the same institution from where hegraduated, in 1978, with a FIRST class honors degree earning the final year spectacularperformance prize. He studied, on the Commonwealth of nations’ scholarship scheme, M.Sc.and DIC at the Imperial College of the University of London where he had special departmentalcall for the best examination score in the course ‘Foundation engineering’ in 1981. He registeredfor the Ph.D. in 1989 and was successfully awarded the advanced degree in Civil engineering in1992.Professor Matawal has practiced mostly in the area of Structural engineering but has had vastand sufficient research and practical experience in Foundation, Soil Mechanics, Water andtransportation engineering. He worked as consultant in the field for five (5) years and was one of36

pioneer young consultant engineers for the city of Abuja in 1981. He has designed andsupervised construction projects in Nigeria in all disciplines of Civil engineering. He has alsoserved on various Government, University, Polytechnic and Voluntary agency boards, taskforces, Visitation panels, Accreditation teams/panels and technical groups. His last majornational assignment has been as Chairman (Civil engineering team) of the UNESCO-NIGERIAtechnical revitalization program for technical-vocational education in Nigeria from April toSeptember 2001. He has lectured and researched in the University (at A.T.B. University,Bauchi) from 1987 and was promoted to the Chair of Professor of Civil Engineering on October1, 1999. He is happily married with seven (7) vibrant children.37