The properties and performance of polymer modified GRC

Abstract

Recently, there has been increasing interest in the potential advantages of adding a polymer to the matrix of GRC formulations, especially for use in cladding. This paper describes some experiments, carried out in order to provide specific information on the moisture movement and mechanical properties of GRC materials reinforced with 5% weight of cem-fil fibre and modified by forton polymer. Three mix formulations were tested: (1) a high polymer content mix, with 10% of polymer by weight; (2) a low polymer grey cement mix, with about 5% of polymer; (3) a polymer-free mix, used as a control. After adding the cem-fil fibre, the test boards were produced by a normal hand spray/rolling process. Tests were carried out on: (1) cure shrinkage and moisture movement; (2) accelerated ageing and laboratory durability; (3) effects of wet and dry testing and different curing conditions. The conclusions reached included the following: (1) drying shrinkage and moisture movement on subsequent exposure can be reduced significantly by adding appropriate polymers to GRC mixes; (2) for GRC containing a polymer, the mechanical properties of samples tested in 'wet' and 'dry' conditions are significantly different; (3) relatively crude covering or wrapping of polymer GRC materials (e.g. polythene sheet) is effective in creating a damp cure environment. (TRRL)