Effect of freeze-thaw cycles on the mechanical behavior of geopolymer concrete and Portland cement concrete containing micro-encapsulated phase change materials

The effect of frost conditions on the physical and mechanical properties of geopolymer concrete (GPC) and Portland cement concrete (PCC) containing two different micro-encapsulated phase change materials (MPCM) was examined. Microstructural studies revealed that the freeze-thaw induced concrete deterioration can be contributed to microcracks appearing at the weak interfacial transition zones between paste/aggregate and paste/MPCM. The addition of MPCM provided an excellent resistance against freeze-thaw cycles with minor reduction of the compressive strength, unlike the samples without MPCM where a stronger reduction was observed. When the temperature was reduced to 0 °C, the initial setting time of Portland cement pastes became longer due to the low temperature and the high viscosity. For geopolymer pastes, the initial setting time became shorter due to phase separation of the alkaline solution at low temperatures. Increasing the MPCM concentration reduced the final setting time for both Portland cement and geopolymer pastes.