Properties of Modern Rendering Systems based on Mineral Binders

Doktorsavhandling, 2007

Composite mineral–organic materials and in particular cement-organic materials are increasingly used in today’s construction applications and civil engineering projects. Polymer-modified render is a material that possesses several properties superior to conventional renders, such as better workability, crack resistance, adhesion to substrate and flexural strength. This improves the durability of the material. The importance of understanding the mechanisms behind the materials behaviour is crucial when designing new and advanced products for the industry. In this thesis the influences of different organic admixtures on the early age and hardened properties of mortars, such as water retention, plastic shrinkage and drying shrinkage, are investigated. The mechanisms of the hardening process, from plastic to hardened state, moisture transfer and obtained structure are examined. The results show that the cellulose water retainer not only improves water retention, but also significantly introduce air content in both the cement and the cement-lime binder systems. Styrene-butylacrylate-based copolymer significantly increased the flexural strength as expected, but revealed a high dry shrinkage. The combined effect of the air-entrainer and the cellulose ether reduce the plastic shrinkage of all compositions, but increase the drying shrinkage, due to their high air contents, but also the lower elastic modulus created by the entrained air. Styrene-butylacrylate copolymer and vinyl acetate/ethylene copolymer also contribute to improving water retention, but have a significant effect on moisture transport properties.