Bond Development in Burnt Clay and Fly Ash-Lime-Gypsum Brick Masonry

Abstract

Fly ash bricks are used for load-bearing masonry. The bond development between the masonry unit and the mortar is mainly due to the mechanical interlock of cement hydration products in the brick pores. This paper deals with the investigations in understanding the phenomenon of bond development between the fly ash-lime-gypsum (FaL-G) brick and the mortar. The bond strength of the FaL-G brick masonry and the burnt clay brick masonry was determined. Apart from quantifying the bond strength of FaL-G and burnt clay brick masonry, microstructure analysis of the materials at the brick-mortar interfaces was carried out using scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) techniques to establish the evidence and to quantify the chemical bond development between the FaL-G brick and the mortar. The results show that the flexure bond strength of FaL-G brick masonry is an order of magnitude higher than that of the bond strength of burnt clay brick masonry. This is attributed to the chemical bond between FaL-G brick and the mortar, which has been demonstrated in this study.