Mechanical properties and antifreeze performance of cement-based composites with liquid paraffin/diatomite capsule low-temperature phase change.

• The influence of liquid paraffin/diatomite capsule phase change material on the compressive strength of cement matrix is far less than the flexural strength. • The mass loss of the capsule phase change material cement-based test block after freeze–thaw cycles is reduced by 47% compared with the pure cement paste. • The liquid paraffin/diatomite capsule phase change material has a certain effect on improving the frost resistance of concrete. Freezing-thawing cycles is one of the most common and severe factors to concrete in service. The research focuses on breaking through the bottleneck of passive frost resistance of traditional concrete materials. Based on the principle of phase change heat storage and release, liquid paraffin/diatomite microcapsule phase change material was prepared by controllable assembly method. Its physical and chemical properties and thermal properties were explored by modern characterization methods. At the same time, it is introduced into the cement matrix to explore its specific effects on the thermal conductivity, mechanical properties and frost resistance of concrete materials. The results show that liquid paraffin/diatomite capsule phase change materials (CPCMs) cement-based test block has stable chemical properties and excellent thermal properties. The heat resistance limit is 280 ℃. Adding liquid paraffin/diatomite capsule phase change material will weaken the thermal conductivity and mechanical properties of cement matrix, but at the same time, it will significantly improve the frost resistance of cement matrix. The mass loss after freeze–thaw cycles can be reduced by 47%, the compressive strength loss and flexural strength loss are reduced by 186% and 99%, respectively. The negative effect of liquid paraffin/diatomite capsule phase change material on the flexural strength of the cement matrix is greater than the compressive strength. [ABSTRACT FROM AUTHOR]