Roles of water film thickness and polypropylene fibre content in fresh properties of mortar

Previous studies on the fresh properties of the mortar portion of concrete have revealed that the water film thickness (WFT) is the key factor governing the rheological performance of mortar. However, such studies were limited only to plain mortar containing no fibres. For mortar containing fibres, such as polypropylene (PP) fibres, there have been no similar studies. To investigate the combined effects of WFT and fibre content on the fresh properties of mortar, a number of mortar samples with various water/cement ratios and PP fibre contents were produced for measurements of packing density, flowability, cohesiveness and adhesiveness. It was found that the fibre content has certain effects on the packing density and WFT. Apart from the indirect effects through the change in WFT, the fibre content also has direct effects on the flowability, cohesiveness and adhesiveness. Overall, very good correlations of the fresh properties of mortar to the WFT and fibre content have been obtained and the concept of WFT has been extended to fibre-reinforced mortar.