Mechanical and physical properties of concrete made of alkali-activated lightweight aggregates from construction demolition waste

Abstract

Dwindling natural resources combined with the increasing amount of construction waste is one of the major challenges of the current time. In concrete production, attempts are being made to tackle both problems by obtaining new materials from construction and demolition wastes (CDW).In previous studies, cold-bounded alkali-activated aggregates were formed of the fine fraction (≤4 mm) of concrete and brick demolition waste and determined regarding mechanical and physical properties. In this paper, these aggregates were used to produce concrete prisms at water-to-binder ratios of 0.5. The concrete prisms were compared to prisms containing natural aggregates regarding compressive and flexural strength, density, water absorption and thermal conductivity following EN standards. Compressive and flexural strength were evaluated after 7 and 28 days. Additionally, flow spread was determined.The results show that the concrete samples made with concrete powder aggregates possess higher compressive strength with 42 MPa than the brick powder aggregate samples with around 30 MPa. Natural aggregates achieve the highest compressive strength with 56 MPa. The water absorption of the concrete prisms ranges between 6 and 15 wt-%. The lower density of the concrete prisms made of brick powder aggregates leads to lower thermal conductivity than the concrete prisms made of concrete powder aggregates.