Water film thickness and paste film thickness: key factors for mix design of high-performance concrete

Although in recent years, great advancement in high-performance concrete (HPC) has been achieved, research on the governing factors affecting the performance of HPC is still progressing slowly without much success. As a result, the mix design of HPC has remained a difficult task. To overcome this problem and simplify the design progress, the authors have proposed a three-tier mix design method, which divides the mix design of HPC into three tiers. They are the paste tier, mortar tier and concrete mix tier. At each tier, the factors affecting the performance of paste/mortar/concrete mix are investigated thoroughly so as to find out the governing factors affecting the performance of HPC. At the paste and mortar tiers, it has been found that the water film thickness (WFT) is the governing factor determining the rheological performance. On the other hand, at the mortar and concrete tiers, it has been found that the paste film thickness (PFT) has significant effects on the rheological properties. Hence, it is advocated that the WFT and PFT are the key factors to be considered in the mix design of HPC