碳纳米管增强堆石坝面板混凝土早龄期热膨胀系数研究

Thermal Expansion Coefficient of Carbon Nanotubes Reinforced Face Slab Concrete of Rockfill Dam at Early Age

热应力是引起堆石坝混凝土面板非结构性开裂的主要原因之一,热膨胀系数(CTE)与混凝土的热变形和热应力直接相关。碳纳米管(CNTs)具有良好的力学性能和一维纳米材料独有的纳米效应,有望改善面板混凝土的CTE。制备施工配合比基准混凝土(JC)和掺质量分数为0.1%的CNTs的面板混凝土(NC),采用温度-应力试验机(TSTM)测量早龄期混凝土在温度匹配(TMC)模式和恒温模式下的自由应变,计算早龄期混凝土的CTE值,提出面板混凝土时变CTE模型。结果表明,两种面板混凝土的CTE在终凝后快速降低至最小值,最后缓慢增至一个稳定值。CNTs的掺入提高了面板混凝土在终凝附近的CTE值,但能降低混凝土CTE的稳定值。

Thermal stress is the main cause of non-structural cracking of rockfill dam face slab concrete.The coefficient of thermal expansion(CTE)is directly related to the thermal deformation and thermal stress of concrete.Carbon nanotubes(CNTs)have good mechanical properties and unique nano-effects of one-dimensional nanomaterials.CNTs also have great potential in improving the CTE of face slab concrete.The construction mix concrete(JC)and the face slab concrete(NC)with 0.1%(mass fraction)CNTs were prepared,and the temperature stress testing machine(TSTM)was used to measure the free strain of the early age concrete under temperature matching curing(TMC)mode and the constant temperature mode.The CTE value of early age concrete was calculated and a time-varying CTE model of face slab concrete was proposed.The results show that the CTE of two kinds of face slab concretes quickly decrease to a minimum value after final setting,and finally slowly increase to a stable value.The incorporation of CNTs increases the CTE of the face slab concrete near the final setting,but reduces the stable value of the concrete CTE.