关键词: CO2碳化;CO2封存;水泥水化;抗压强度;软化系数;耐久性;

Abstract: The combined technology of CO2 carbonation and cement hydration is a novel approach for soil solidification and CO2 permanent storage.Until now, there are few reports on the strength, durability and micro-mechanisms of CO2 carbonated cement-solidified soils.By using compressive strength, scanning electron microscopy, water immersion, cyclic dry-wet and cyclic freeze-thaw tests etc.,the strength and durability of CO2 carbonated solidified soil is evaluated according to the morphology, compressive strength and strength softening coefficient.The compressive strength of solidified sample tends to grow with increasing cement content, while the strength of carbonated sample is higher than that of standard curing sample and the optimal cement content is 25%.An increase in CO2 concentration can accelerate the diffusion rate of CO2 and carbonation degree, and it can induce an increase in carbonation depth and compressive strength of carbonated sample, and the strength of carbonated sample is greater than that under standard curing.The formation of calcite and aragonite crystals is the intrinsic reason that the compressive strength of carbonated sample significantly increases.From the viewpoint of strength softening coefficient, the resistance of solidified sample to water immersion, cyclic dry-wet and cyclic freeze-thaw is higher than that of carbonated sample.The durability of freezing resist of 3-day carbonated sample is the worst, and the large-scale block spalling appears on the sample surface after testing.The 7-day standard curing and 1-day carbonated samples have good durability.For the short-term immersion, the strength of carbonated sample is higher than that of standard curing sample.For the cyclic dry-wet tests, the softening coefficient of carbonated solidified sample remains above 0.8(maximum 0.9)and the strength exceeds 5.5 MPa.For the cyclic freeze-thaw tests, the strength of carbonated solidified sample is higher than that of standard curing sample.The obtained results provide a theoretical basis for the development and engineering application of combined solidification technology based on CO2 carbonation and cement hydration for ground reinforcement.

Key words: CO2 carbonation; CO2 storage; cement hydration; compressive strength; softening coefficient; durability;