compatibility of ultra high performance concrete as repair material

Ductal® premix is typically comprised of Portland cement, silica fume, ground quartzand quartz sand already mixed. The constituents (Ductal® premix, water, superplasticizerand steel fibers) that were added are described in Table 3.2 along with the mixingschedule. To obtain a proper UHPC material, it is essential to prolong the mix to ensurethat the turning point is reached. This point is defined as the time at which all of theDuctal® premix, water and half of the superplasticizer are entirely mixed so that theUHPC begins clumping together and falling from the sides of the mixing bowl(Kollmorgen 2004).Table 3.2Ductal® (BS1000-Grey Premix) mix process18 l batchProcessestimateAdd Premix, time start mixing with Speed 1 over two minutes to breakup any clumps 0:00Add water blended with half of the superplasticizer over 2 mins 2:00Increase to Speed 3, mix for 30 secs 4:15Increase to Speed 4, mix for 2 min and 30 secs 4:45Increase to Speed 5, mix 3 min and 30 secs 7:15Increase to Speed 6, mix until the turning point/mixer attains 12 amps 11:15When mixer attains 12 amps (turning point), add the other half ofsuperplasticizervariableContinuing mixing until motor evens out 6-7ampsvariableSlow speed 3, add fibers over 2 minsvariableSlow speed 1, mix for 2 minsvariableThe flow test was utilized after mixing UHPC in order to control the quality of theconcrete in its plastic state. The equipment utilized is shown in Figure 3.1. The test wascarried according to ASTM C230/C230M-08 (Standard Specification for Flow Table forUse in Tests of Hydraulic Cement). The cut down steel cone was filled with UHPC.Afterwards, the cone lifted off slowly to allow UHPC to flow evenly on the table. Fourmeasurements of the flow diameter were taken. The static flow of the material is theaverage of these measurements. Afterwards, 20 shocks were applied to the sample, andthe diameter was measured four times again. The dynamic flow of the material is the44