A line graph showing flow test results of reactive powder concrete (RPC) with varying pumice content. The red line shows spread diameter (mm) on the Y-axis decreasing as pumice content (%) on the X-axis increases, with annotations explaining the impact of pumice on workability and hydration.

The flow test results presented in Figure 7 indicate that, in general, increasing the pumice content in reactive powder concrete (RPC) gradually reduces the spread diameter. However, mixtures containing up to 30% pumice still exhibit an acceptable spread diameter. According to the flow table results, increasing the pumice content decreases the workability of RPC. The primary reason for this behavior is that a portion of the pumice, consisting of very fine particles with high specific surface area, absorbs part of the free water available in the mixture. Since part of the pumice passing through the 1.18 mm sieve is very fine and can be considered pozzolanic, it reacts in the presence of cement and undergoes hydration reactions, thereby consuming some of the mixing water. Meanwhile, the total pumice replacing silica sand is considered as aggregate, and no additional water for hydration is accounted for these particles. Furthermore, the specific surface area of pumice particles is higher than that of the silica sand they replace; therefore, the water demand increases, leading to a relative water deficiency in the mixture. Mehr sehen