Study on the shrinkage mechanism and prediction model of high-strength specified density concrete based on the internal curing micro-pump effect of MSW incineration tailings

Abstract

As an effective substitute for high-strength concrete, high-strength specified density concrete can prevent and reduce the autogenous shrinkage cracking of high-strength concrete caused by low water-binder ratio or dry environment. In this paper, the early-stage shrinkage law of high-strength specified density concrete prepared from the lightweight aggregate of municipal solid waste (MSW) incineration tailings was explored through autogenous shrinkage and non-contact dry environment shrinkage tests. Combined with the tests of relative humidity, capillary negative pressure, penetration resistance, mesoporous structure and hydration products, the shrinkage reduction mechanism of internal curing micro-pump effect of incineration tailings in high-strength specified density concrete was revealed systematically and comprehensively. What’s more, the shrinkage prediction model of high-strength specified density concrete was established accordingly. The results show that replacing high-strength concrete with high-strength specified density concrete can effectively reduce the autogenous-shrinkage value by more than 68.5%, and incineration tailings can be widely used as internal curing material in cement concrete. It deserves to be mentioned that incineration tailings have significant internal curing micro-pump effect in high-strength specified density concrete. More importantly, the micro-pump water releases effect before the critical humidity point (RH = 100%) ameliorates the hydration degree of high-strength specified density concrete (SDC-25, SDC-50 and SDC-75) by 34.9%, 69.9% and 103.4%, and the self-expansion effect produced compensates for the volume shrinkage resulted from chemical shrinkage. Nevertheless, after the critical humidity point (RH < 100%), the water release effect of micro-pump lessens the pore negative pressure. The difference between the critical point test results of SDC-25, SDC-50 and SDC-75 relative humidity and the modified predicted shrinkage values of Zhang Jun-Hou Dongwei is 2.4%, 1.8% and 1.3%, respectively. The deviation between the two is within 20%, and the correlation coefficient (R2) is 0.943, which suggests that the modified Zhang Jun-Hou Dongwei model is applicable to the shrinkage prediction of high-strength specified density concrete of the shrinkage reduction type of internal curing. By adjusting the aggregate composition structure of traditional high-strength concrete and introducing internal curing micro-pump effect, it is helpful to improve the shrinkage resistance of high-strength concrete and the technical progress of the resource utilization of bulk solid wastes (incineration tailings) in cement concrete.