Study On Preparation And Application Of High Strength And High Flowability Concrete

In this paper, three rheometers were used for investigating the rheologicalproperties of cementing material paste, mortar, and concrete. The effect ofdifferent particle size on the cement-based materials has been discussed from theview of rheology. After that, the optimized mix proportion of mineral admixtureand grading curves of the fine aggregate and coarse aggregate which may besuitable to prepare the high strength and high fluidity concrete were given. Therheological results of the investigation shown that, when the weight ratio of flyash to slag was2:1and the total weight substitution rate of mineral admixture was30%, the paste had higher flowability and compressive strength than otherproportion. Meanwhile, a relative wider particle size distribution of the powdersshould contribute to improve the flowability of the blended cement paste. Thestudy also found that, the medium sand was suitable for the preparation ofordinary high fluidity concrete. However it’s best to choose the coarse sand withfineness modulus less than3.30to prepare the high strength and high fluidityconcrete. In the preparation of high fluidity concrete，much attention must be paidto the mass percentage of each particle size range. Generally, the best masspercentage was15%～30%for the sand particle which is smaller than0.315mm,30%～45%for smaller than0.60mm, and55%～75%for smaller than1.18mm,respectively. The rheological results of coarse aggregate indicated that, the coarseaggregate grading had the greatest effect on the fresh concrete fluidity whereas alittle on the compressive strength. While preparing the high strength and highfluidity concrete, the best mass percentage was30%～50%for the coarseaggregate particle size between4.75mm and9.5mm,20%～30%for the particlesize between16mm and19mm. In the fluidity demand was not very high cases,the limit of particle size between16mm and19mm could be broaden to10%～40%.On the basis of a large number of pre-experiment, C60pumping concrete, C80pumping concrete and C80self-compacting concrete which are in line with therequirement of project are prepared. Finally, the rheological parameters of C80pumping concrete and C80self-compacting concrete are measured by rheometer.This part of experiment found that the thickness of mortar which bind up the coarse aggregate is the primary factor for leading to the rheological differencesbetween C80pumping concrete and C80self-compacting concrete. When thethickness of the mortar is beyond2mm，the self-compacting concrete possessesfavorable fluidity and excellent self-compacting performance. If the mortarthickness of the C80pumping concrete is more than2mm, it also has the ability ofself-compacting. The flowability of the concrete largely depends on the limitingsize of coarse aggregate.