Influence of substrate in rendering with crushed fine aggregates

This paper discusses the influence of brick water absorption on the performance of renders made of basalt crushed fine aggregates. Six mortar admixtures in a 1:1:6 proportion (cement:lime:crushed fine aggregate), with three particle size distributions and two proportions of microfines were produced. The physical characteristics of these mortars, susceptibility to cracking (especially due to shrinkage) and bond strength of the rendering mortars applied over brick walls measuring 60 × 60 cm were determined. The study indicates that water absorption of the substrates is very important for shrinkage and adhesion strength of mortars made of manufactured fine aggregates. Bricks with higher initial rate of absorption increase the bond strength. On the other hand, bricks with higher water absorption (but lower initial rate of absorption) have higher shrinkage and cracking. With higher microfines proportion, the mortar increases bond strength but demands higher water content, resulting in higher shrinkage and cracking.