Cold-bonded fly ash aggregate concrete

The subject of the experimental research is concrete with cold-bonded fly ash aggregate from fly ash of Novosibirskaya GRES Thermal Power Plant (Novosibirsk, Russia). Cold-bonded fly ash aggregate has the true specific gravity of 2.50 g/cm³, an average density of 1.53 g/cm³, water absorption by weight of 18.4 %, and an opened porosity of 28.15 %. Concrete with cold-bonded fly ash aggregate has a compressive strength after 28 days of 37.8 МPa, a flexural strength of 4.9 MPa, a coefficient of linear expansion of 14.8*10^-6 K^-1 and modulus of elasticity of 18*10⁹ Pa. The water presoaking of lightweight aggregate did not affect the kinetics of heat emission and, consequently, the kinetics of hydration of cement. The shrinkage of concrete with dry aggregate was higher than concrete with presoaking lightweight aggregate. Moreover, the evaporation loss was also less for concrete with dry aggregate. The shrinkage of concrete with presoaking aggregates is much less than the shrinkage of concrete with dry aggregates with the same evaporation loss. The usefulness of presoaking aggregates in working conditions, as “internal curing”, has been confirmed. This will reduce the likelihood of shrinkage cracks during concrete drying.