Study on the effect of fly ash and polycarboxylic acid water reducer on the properties of recycled concrete

Abstract

By testing the compressive strength, tensile strength, permeability coefficient, carbonization depth and relative dynamic elastic modulus, the influence of fly ash and polycarboxylic acid superplasticizer on the performance of recycled concrete was studied. The mechanism of action of fly ash and polycarboxylic acid superplasticizer on concrete properties was also analyzed by SEM. The results indicate that the compressive strength, tensile strength, permeability coefficient relative and dynamic elastic modulus of recycled concrete are increased by 7.1%, 8.3%, 81.0% and 16.7% respectively, the carbonization depth decreased by 34.4%, when the cementitious materials is replaced by 20% (by mass) of fly ash and 1.2% (by mass) of polycarboxylic acid superplasticizer. Therefore, fly ash and polycarboxylic acid superplasticizer can effectively promote the hydration of cement particles and improve the pore structure of concrete along with the bond between cement paste and recycled aggregate in the interface transition zone, which is suitable for the preparation of high performance recycled concrete.