Investigation into low density fly ash aggregate in micro-concrete for lightweight concrete repair

Abstract

This paper presents the effect of low density aggregate (LDA) made from fly ash on compressive strength, flexure strength, flexure bond strength, drying shrinkage and shrinkage due to raised temperature for accelerated drying of the micro concrete for concrete repair. Sintered fly ash lightweight aggregate were crushed to required sizes and replaced by weight partially to fully; 50, 60, 70 and 100 percent of the natural aggregate to prepare the micro concretes. The results were compared with the normal weight micro concrete. It was observed that the strengths of the light weight micro concrete were comparable with the strength of normal weight micro concrete with less cement content. The drying shrinkage percentage was also within permissible value. The flexure bond strength was higher and the drying shrinkage due to raised temperature for accelerated drying was also lower in the partial replacement of the LDA. The partial replacement of LDA showed encouraging results for the light weight micro concrete mix for the concrete repair particularly under the beam or slab to reduce gravity load on the bonding interface of the substrate concrete and the micro concrete.