Influence of Lightweight Aggregate on Properties of Cement Concrete Road and Bridge

摘要

Replace normal weight aggregate (NWA) with lightweight aggregate (LWA) in the ratios of 25%, 50% and 75% respectively by volume content, and the influence on properties of strength, early shrinkage cracking and anti-chloride ion penetration of concrete were investigated. The results show that, mixing part of LWA into normal weight concrete within a range that the strength and elastic modulus could meet the construction request, can lighten the dead load of structure, and increase the specific strength of concrete. Under this test condition, the suitable LWA content is 25%~50%. The anti-cracking property of concrete can be improved by the mixing of pre-wetted LWA as well, for concrete with w/b of 0.28 and 0.43, when the LWA content are greater than 50% and 25% respectively, the improve effect is obviously. With the increase of LWA content, the hydration degree of cement paste around aggregate increased apparently in concrete with low w/b ratio, and the pore structure of hardened cement paste refined gradually. The adverse effect of weak interfacial zone around NWA on concrete impermeability can be made up by the good interfacial structure between LWA and cement paste, consequently the impermeability of concrete can be improved, and more obviously for concrete with higher w/b ratio. When w/b ratio is lower, the permeability of concrete could be affected by the permeable LWA, and excessive LWA content would reduce the permeability of concrete.