Effect of heat treatment on mechanical behavior and scaling resistance of slag impregnated low strength recycled compacted concrete

Recycling concrete waste via high-pressure compaction is a new way of producing recycled concrete, which is developed in 2016. However, it is limited in that the compressive strength of the compacted product is less than 21 MPa. This study focuses on the characterization of recycled compacted concrete (also referred to as compact) quantified according to mechanical behavior, including compressive strength, flexural strength, tensile strength, and scaling resistance, quantified based on a salt scaling test. Investigations were conducted to enhance the strength of compact from previous studies by observing the influence of byproducts such as granulated blast furnace slag and base course materials of iron and steel slag (as replacements for natural fine and coarse aggregates) using water immersion and heat treatment. At 100% replacement, heat treatment increased the compressive, tensile, and flexural strengths by 1.77, 2.23, and 2.32 times, respectively than that of the untreated specimens. Also, morphological observation through Scanning Electron Microscopy indicated that bond performance of compact is improved by incorporating slag materials. This study experimentally demonstrated the potential of heat treatment in the strength enhancement of compacts after specified water immersion period and thus, rendered heat treatment as a prospective experimental method of increasing the strength of compact.