Combined effects of water film thickness and polypropylene fibre length on fresh properties of mortar

Among the various characteristics of fibre, the fibre length is no doubt a major factor affecting the fresh properties of fibre-reinforced cement-based material. In previous studies, it has been revealed that the water film thickness (WFT) is the most important factor governing the fresh properties of plain cement-based material containing no fibres. However, there has been little research on whether the concept of WFT can be applied when fibres are added and thus the combined effects of WFT and fibre length are still not known. In this study, a number of fibre-reinforced mortar samples containing polypropylene (PP) fibres of different lengths were produced for packing density, flowability, cohesiveness and adhesiveness measurement. It was found that the fibre length has significant effects on the packing density and WFT, and substantial effects on the flowability, cohesiveness and adhesiveness. Good correlations of these fresh properties to the WFT and fibre length have been obtained, indicating that the WFT and fibre length are together the governing factors.