Research On Properties Of Self-compacting Lightweight Concrete

Self-compacting lightweight concrete(SCLC) combine the advantages of normal self-compacting concrete(SCC) and normal lightweight aggregate concrete(LWAC), it has the characteristics of vibration-free, light weight and high strength. As a new type of building material, there are very few studies on SCLC. The researches on the workability and durability of SCLC are not comprehensive. It has been a hot topic for concrete researchers to solving the nonuniform distribution of lightweight aggregate in concrete on the basis of ensuring the self compacing properties of SCLC.This paper is devoted to the study of SCLC with different density. SCLC is designed by the absolute volume method with fixed fine and coarse aggregate contents, mixed with different W/B ratio. The workability of SCLC is evaluated by the slump flow diameter, slump flow time(T500), J-ring flow diameter, V-funnel flow time. The uniformity of distribution of SCLC is evaluated by the sieve segregation and segregation column test. The result shows that the liquidity of the concrete with ground slag(GS) increases, but the uniformity of distribution decreases; in contrast to GS, the uniformity of distribution of the concrete with silica fume(SF) increases, but the slump flow decreases greatly. SCLC with 30% fly ash(FA) has a good uniformity, at the same time ensures the self compacting properties. On the basis of the concrete composition with 30% FA, three proportions for SCLC with density 1700 kg/m3, 1800 kg/m3, 1900 kg/m3 are designed.Then the study of the influence of material on the rheology of SCLC is conducted. The rheology of SCLC with different content of FA, GS, fine lightweight aggregate, S/C ratio is tested. With the combination of the result of workability, the reasonable yield shear stress and viscosity values of SCLC are calculated.Finally, the studies of the strength and durability of three designed SCLCs are carried on. The result shows that the designed SCLCs have excellent properties of frost resistance and permeability resistance. By the analysis of the pore structure of concrete, three designed SCLCs have reasonable pore size distribution, the porosity of SCLC decreases with the decrease of the density of SCLC. In addition, SCLC has a good interface transition zone according to the water absorption of lightweight aggregate.