Experimental study on mechanical properties of compression casting concrete after freeze-thaw cycles

Compression Casting Concrete (CCC) significantly improves the mechanical properties of concrete and presents favorable application prospects in precast concrete components. However, studies on the toughness evolution and compressive strength prediction models of CCC after freeze-thaw (F-T) cycles are still insufficient. In this study, CCC specimens with three compression levels (5, 10, and 15 MPa) and reference NC specimens were prepared and subjected to 0-300 and 0-105 F-T cycles, respectively. The mass loss rate, relative dynamic elastic modulus (RDEM), load-displacement curves, compressive strength, peak secant modulus, and toughness were measured and analyzed. Scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP) tests were used to analyze the microstructure and porosity of CCC. F-T damage models were proposed based on RDEM and compressive strength, respectively. The results show that when RDEM decreases to 60%, the F-T resistance of CCC is 150.67% higher than NC on average. After 100 F-T cycles, the compressive strength and peak secant modulus of CCC are 59.63% and 75.45% higher than NC, respectively. The toughness of both CCC and NC first increases and then decreases with the increase of F-T cycles. Compared with NC, the porosity of CCC decreased from 19.76% to 11.44%. The R ² value of the RDEM-based WANG Model is 0.609, which is improved to 0.822 for the Corrected WANG Model after modification by compressive stress. The R ² value of the compressive strength-based LV Model is 0.440, and it is enhanced to 0.841 for the Corrected LV Model with the compressive stress modification.