Preparation Of High Density Sulphoaluminate Cement-based Materials

Concrete is a porous material which contains gas-liquid-solid three phases. Under theharsh environmental conditions, the external harmful ions and water are easily got into theconcrete to destroy the structure and short concrete serveice life, resulting in huge economiclosses. At present, optimizing concrete pore structures and increasing concrete densitybecome the effective way to improve the concrete durability. The research contents the gradedoptimization of cementitious materials and the properties of cementitious materials, theoptimization of aggregate gradation and its effect on performance of concrete, preparation andproperties of high density sulphoaluminate cement concrete. The main findings are showed asfollows:(1) Sulphoaluminate cement-based materials with smaller Q presented a higher strength,a homogeneous and denser microstructure than those of reference cement at the samewater-binder ratio, adding mineral admixture can optimize the grain size distribution andimprove the density of hardened cement past. The1d,3d and28d compressive strength of thecementitious materials when Q was equal to1.219were29.4MPa,38.9MPa and45.2MPa,respectively,13%,5%and2%higher than reference cement；its1d and3d flexural strengthwere5.4MPa and5.8MPa,20%and5%higher than reference cement.The relationship between packing densities of sulphoaluminate cement-based materialsand compressive strength curing for1d,3d and28d were fitted by y=-4645.8x~2+6531.5x-2266.4, y=-8686.3x~2+12234x-4268.7and y=-10484x~2+14698x-5105.4, respectively,with the high correlation coefficients. The relationship between packing densities ofsulphoaluminate cement-based materials and flexural strength cured for1d,3d and28d werefitted by y=-811.94x~2+1147x-399.71、y=-1479.4x~2+2067.6x-716.53and y=-2992.1x~2+4140.3x-1425.5. The correlation coefficients were greater than0.9and became lower asthe prolongation of curing ages.(2) Compared with the blank concrete sample, the aggregate, considering total aggregategradation that met Fuller distribution with h=0.33, had the biggest bulk density which was1720Kg/m~3. The1d,3d and28d compressive strength were14%,19%and18%higher thanthe blank concrete, respectively, the resistance to sulfate attack of concrete were increased by 9%. And its depth of permeable to water was41.6mm under the2.1MPa pressure.The fitting formula between bulk density of aggregate and compressive strength ofsulphoaluminate cement concrete curing for1,3and28d were y=0.0159x+6.7906,y=0.0293x-10.46and y=0.0446x-26.18, the correlation coefficients were greater than0.9. Thefitting formula between bulk density of aggregate and water penetration depth ofsulphoaluminate cement concrete was y=0.002x~2-6.8638x+5862.3with R~2=0.9799, indicatingnotable correlation. The fitting formula between bulk density of aggregate and sulfateresistance coefficient of sulphoaluminate cement concrete was y=0.0005x+0.3704with R~2=0.9585(3) The high density concretes were prepared by optimizing concrete mix ratios based ondense mix design and using a four-step mixing process with paste wrapped sand method. Thebiggest apparent density of the prepared concrete was2540Kg/m~3. The porosity can bereduced to less than7%, having a very density structure.