Enhancing the Mechanical and Frost Resistance Properties of Sustainable Concrete Using Fired Pumice Aggregates

This study addresses the problem of pumice deposits in the southern Kyushu region, which can cause landslides during heavy rainfall. To reduce this hazard, it is important to expand pumice applications and promote its use before disaster events occur. Among construction materials, this study explores the possibility of using pumice as a concrete aggregate, considering the global shortage of natural aggregates. Because of the low strength and difficulty of use, pumice must be fired to improve its properties. In our experiment, it was fired at 1000 or 1100 °C, and the performance of the resulting concretes was compared. Concrete incorporating pumice fired at 1100 °C achieved a maximum compressive strength of 54.6 N/mm2 with an increase in the amount of cement, whereas concrete with pumice fired at 1000 °C remained within the 20–24 N/mm2 range even when the amount of cement was increased. This difference arises because pumice has a lower strength than the cement paste, leading to material failure. Furthermore, freeze–thaw tests showed that concrete made with pumice fired at 1100 °C was resistant to frost damage. These results suggest that pumice fired at 1100 °C has an excellent potential as a sustainable building material.