Integral quality indicators of waste concrete for reuse

Abstract

Introduction. Waste concrete is one of the main heavy construction waste having good recycling prospects with regard to rational nature management related to reducing the consumption of natural resources. However, the widespread introduction of waste concrete is hindered on the one hand by the variety of compositions and structures of recycled scrap, and on the other hand by the lack of quantitative criteria to choose the most rational area of its use (a binder component, coarse and fine aggregate, finely dispersed filler, etc.). Materials and methods. Case studies of experimental powders obtained by mechanical grinding from the concrete scrap of internal wall panels and floor slabs (heavy concrete) and external wall panels (light concrete) of a five-storey residential panel house built in 1979 in the Obozersky village, Arkhangelsk region, demonstrated the possibility of choosing the optimal secondary use of waste concrete fractions featuring residual compressive strength. The indicators of residual strength, grindability and contraction of mineral powders were used as optimization criteria. Results and discussions. The applicability of the mathematical model for calculating the raw material grindability index is shown. A criterion for grinding equipment selection is proposed to obtain powders with an extended active surface. Conclusions. Powders obtained from the fraction of waste light concrete featuring low strength properties and grindability by mechanical grinding to a specific surface area comparable to that of Portland cement used and having a higher value of contraction can be rationally used as a composite binder component. Concrete scrap fractions featuring by higher grindability and strength properties are optimally suited for crushed aggregate preparation in the concrete composite production process.

Keywords

• concrete scrap
• recycled concrete
• grindability criterion
• composite binder
• mineral powder contraction