Abstract:

In order to investigate the influences of moisture content w, water cement ration W/C(W is water mass, C is cement mass) and cement content P_s on the thermal conductivity l of cement-bonded calcareous sand, thermal conductivity of cement-bonded calcareous sand under different test conditions were determined by thermal probe method. The change rule of thermal conductivity under the influence of various factors was analyzed, and the microcosmic mechanism of the change trend was explained by scanning electron microscope (SEM). On this basis, a calculation model of the thermal conductivity of cement-bonded calcareous sand, which takes into account the water content, water cement ratio and cement content, was proposed. The experimental results show that the thermal conductivity of cement-bonded calcareous sand is significantly higher than that of natural calcareous sand. The l value of former increases with increasing the cement content, but the increase rate decreases in turn. The l value of cement-bonded calcareous sand increases with increasing water content as positive correlation. However, a larger W/C leads to a smaller l. The results of SEM show that the macroscopic thermal conduction characteristics of cement-bonded sand depend on the variation of size and quantity of its micro-pores. The gel-like hydration product continuously fills the internal pores of the bonded sand, causing a reduction in porosity and thereby improving internal heat transfer of the sand sample. At macro level, the thermal conductivity increases with the increase of degree of cementation. Finally, the novel calculation model for the thermal conductivity of cement-bonded sand having a comprehensive consideration for P_s, w, and W/C has a good applicability, whose coefficient of determination R² is 0.916 4.

Key words: cement-bonded calcareous sand, thermal conductivity, influence factors, thermal probe method, calculation model