TOUGHENING OF HIGH PERFORMANCE CEMENT SYSTEMS: INFLUENCE OF MATRIX - AGGREGATE BINDING

摘要

It has been shown recently that the bond between aggregate and matrix in cement mortars can influence composite toughness by controlling the extent of aggregate bridging taking place. Aggregate bridging is widely known to be an effective crack wake mechanism that increases the toughness of brittle materials. This paper describes the effectiveness of this mechanism in high strength cements which are known to exhibit increased brittleness due to the higher levels of strain energy stored prior to failure. Pore Reduced Cement (PRC) and silica fume blended cement are used as model high strength matrices. The increased density of conventional high strength pastes that results from the lower water cement ratio and better particle packing does not immediately lend itself to this toughening mechanism because of the increased physical bond developed between matrix and aggregate. However, the present study has shown that the measured toughness can also be used as a means of assessing the relative strength of the matrix- angular aggregate interaction.