Effects of ambient temperature, relative humidity and wind speed on interlayer properties of dam concrete

Abstract

Dam concrete is usually poured layer by layer. Interlayer as a “weak section” or “defect” inside the concrete, may lead to an increase in the risks of seepage and bedding slip of dams. This study investigated effects of environmental condition (i.e. ambient temperature, relative humidity and wind speed) on interlayer properties of dam concrete, in terms of tensile splitting strength, resistance to chloride ion penetration and pore structure. In addition, damage degree of concrete caused by the interlayer was evaluated by means of ultrasonic non-destructive test. The results show that increasing temperature or wind speed on the lower layer surface decreases the interlayer tensile splitting strength and resistance to chloride ion penetration of concrete significantly. Meanwhile, reducing relative humidity has an adverse effect on the interlayer properties of concrete. It is attributed to that higher temperature or wind speed, or lower relative humidity can accelerate water evaporation, reducing surface water content and speeding up hardening process of the lower layer concrete obviously. It causes not only a worse bonding quality but also a pore-structure coarsening effect near the interlayer. Moreover, the reduction of surface water content of the lower layer concrete may decrease final degree of hydration reaction, which should be responsible for the decrease in the interlayer properties as well. Furthermore, there was a linear relationship between the damage degree and loss rate of tensile splitting strength of concrete. Therefore, the damage degree calculated from wave velocity can be adopted to predict the loss rate of tensile splitting strength effectively.