The results of research on the effectiveness of a multistage crushing of concrete scrap by the "soft" regime are given. It was found that the processing of concrete scrap by this technology can significantly improve some properties of recycled concrete aggregate, particularly crushability, water absorption, shape factor "average thickness of the grain" and porosity. The result of this treatment is the formation of a significant amount of particulate material. This material can be used as a fine filler in the technology of self-compacting concrete. It was found that self-compacting concrete based on products of crushing concrete scrap has a strength of 50 MPa after 28 days of curing in normal conditions, and more than 70 MPa after one year of storage in dry-air conditions. It was established that received concrete has a lower modulus of elasticity, which should be considered when choosing the fields of its application.
Keywords: self-compacting concrete, concrete scrap, secondary aggregates, multi-stage crushing, crushability, water absorption, elastic modulus
This article presents the results of comparative studies of the effectiveness of superplasticizers (SP) of different chemical nature in the flooring mixes. The mixes were prepared by using of blended binder based on Portland cement, alumina cement and gypsum. The effect of the type of superplasticizer and its dosage on the spreadability of the mixture, strength and shrinkage of building flooring mortar at different ages was investigated. It was found that all additives, with the exception of SP Sika Viscocrete 105P, characterized by rapid loss of fluidity of the mixture. The strength of the mortars does not depend on the type and dosage of additive at last age and strength decreases in mixes with additive of SP Melflux PP 100 F based on polyethylene glycol at early age. It was investigated the influence of the type and dosage of SP on the shrinkage of flooring mix on the basis of a blended binder. The received dependence is due to the relationship between the degree of dispergating of the cement suspension with different type of SP and shrinkage of binder stone.
Keywords: superplasticizer, blended cement, alumina cement, cement flooring mix, spreadability of mix, strength, shrinkage