Effect of different ice contents on heat transfer and mechanical properties of concrete

Abstract

With annually decreasing shallow mineral resources, development and utilization of deep mineral resources are critical. However, heat hazards in deep mines pose hidden dangers to health and safe operation of equipment. Therefore, a suitable cooling method is an urgent concern in deep high-temperature mines. This study proposes a cooling method that introduces ice into concrete for phase change cooling and improved strength characteristics. It can be used in deep high-temperature mines, and is known as iced-concrete technology. Based on temperature monitoring, mechanical strength tests, and microstructure tests, this study explores the influence of different ice contents (0 %, 10 %, 20 %, 30 %, 40 %, 50 %, 60 %) on heat transfer and mechanical properties of concrete, and analyzes the mechanism of heat transfer and the mechanical properties of concrete under the action of ice particles. The results show that: (1) the temperature evolution law of concrete with different ice contents takes 18 h–26 h and has a temperature change inflection point interval that first increases and then decreases. With an increase in ice content, the lower the initial temperature, the greater the rate of temperature change. (2) Ice particles have an obvious positive effect on the uniaxial compressive strength and splitting strength of concrete; the final mechanical properties of concrete are positively correlated with the ice content with a constant water (ice)–cement ratio. (3) Compared with ordinary concrete, the initial low-temperature water storage capacity of iced concrete promotes formation of hydration products in the later stage to some extent, improving the content of hydration products in the curing stage, promoting the full filling of internal concrete pores, reducing the content of harmful macropores and mesopores, optimizing the pore structure, and improving the compactness and mechanical strength of the concrete. (4) The cooling efficiency of concrete was increased with an increase in ice content. The cooling efficiency of concrete with 60 % ice content was six times that of ordinary concrete. When the ice content exceeded 20 %, the cooling capacity generated by ice–water phase change was greater than the heat absorbed by the temperature change of the water.