Experimental Study of the Impact of Particle Packing Density Optimization on Strength and Water Absorption Properties of Concrete

Abstract

The packing characteristics of concrete ingredients (cementitious materials and aggregates) have great influence on the performance of a concrete mix. Herein, a new method, called the wet packing method, developed by H.H.C Wong and A.K.H. Kwan is used to measure and optimize the packing density of ordinary Portland cement and coarse aggregates. It mixes the cementitious materials with water and then measures the apparent density of the resulting mixture at varying water/cementitious materials ratio to characterise the packing behaviour of the cementitious materials. It also measures the aggregate packing in its dry state and its wet state. Using this method, the packing density of pure cement, and blended cementitious materials, single sized 20mm aggregate and blended aggregates under same conditions have been measured. The best three optimizations realized from each category were used to cast concrete cubes in other to determine the impact of the optimization on strength and water absorption. The results show that the best optimized aggregate resulted in a concrete strength increase of 16.63% for 7-days strength and a 6.17% increase in the 28-days strength for grade M20. When OPC was optimized with 20% Silica Fume, an increase in strength of 4.27% (7 days) and 2.78% (28 days) was observed for grade M20 concrete. Water absorption is seen to decrease up to 23.22% as the packing density increased. Based on the results so obtained, it is advocated that packing density optimizations for concrete ingredients should be practised for improved concrete performance.