Influence of additives on strength enhancement and greenhouse gas emissions of pre-cast lime-based construction products

Abstract Strength properties of laboratory scale lime-based samples enhanced with additives such as nanomaterials (nanofibrillated cellulose, nanosilica, nanoclay, expanded graphite), hemp & glass fibres, hemp shiv and polyvinyl acetate (PVAc) are determined. Samples were cured for 26 days in air at 20˚C / 60% RH after casting before being oven dried for a further two days at 50˚C (28 days total). Results show that the nanomaterials on their own had a mixed effect on the strength although nSiO 2 as a solo additive performed exceptionally well. The combination of fibres in conjunction with PVAc also greatly enhanced the strength due to increased bond between the fibres and the matrix. In addition, Greenhouse Gas emissions (GHG, kgCO 2 eq) of an arbitrary block was determined for all composites and compared to the GHG of a commonly used lightweight aerated concrete block. Comparison of the normalised compressive strengths to the different loading conditions as outlined in BS EN 8103 shows that a more widespread use of pre-cast lime composites is possible and without unduly increasing GHG emissions.