为解决标准试验方法难以测定大坝混凝土早期热膨胀系数的难题,采用温度-应力试验,以等效龄期为桥梁计算得到粉煤灰掺量分别为35%,80%的2种常态大坝混凝土的温度差与应变差曲线,并分段进行线性拟合,确定粉煤灰混凝土的早龄期热膨胀系数。结果表明:①2种粉煤灰混凝土在硬化初期热膨胀系数值在(20～30)×10-6/℃范围内变化,而后期则稳定在(4.6～10.0)×10-6/℃;②高掺粉煤灰混凝土的热膨胀系数低于基准混凝土(即35%粉煤灰掺量混凝土),更有利于大坝混凝土的抗裂;③基于已确定的热膨胀系数,建立热膨胀系数模型,可较好地反映混凝土早期热膨胀系数发展规律,并用于计算2种混凝土的温度变形。
Abstract
In an attempt to overcome the difficulty of determining the thermal expansion coefficient of dam concrete at early age by standard test method, temperature-stress test (TST) was conducted. The early-age thermal expansion coefficients of fly ash concrete were determined by segmented linear fitting of the temperature difference and strain difference curves of conventional dam concrete dosed with 35% and 80% fly ash volumes. Results demonstrated that (1) the thermal expansion coefficients of the two kinds of concrete varied in the range of (20~30)×10-6 /℃ at the stage of initial hardening, and tended to be stable in the range of (4.6~10)×10-6/℃ at late stage. (2) The thermal expansion coefficient of high-volume fly ash concrete (80% fly ash concrete) is lower than that of reference concrete (35% fly ash concrete), which is conducive to crack resistance of dam concrete. (3) On the basis of the determined thermal expansion coefficients, a model of thermal expansion coefficient is proposed to better reflect the development law of thermal expansion coefficient at early age and to calculate the temperature deformations of the two kinds of concrete.
关键词
高掺量粉煤灰混凝土 /
热膨胀系数 /
温度-应力试验 /
等效龄期 /
早龄期
Key words
high-volume fly ash concrete /
thermal expansion coefficient /
temperature-stress test (TST) /
equivalent age /
early age
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基金
国家自然科学基金项目(51479178,51879235);浙江省自然科学基金项目(LY14E090006);广东省滨海土木工程耐久性重点实验室开放基金(GDDCE15-01)
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