基于水化程度的早龄期混凝土拉伸徐变模型研究

RESEARCH ON TENSILE CREEP MODEL BASED ON DEGREE OF HYDRATION FOR EARLY-AGE CONCRETE

研究了早龄期混凝土的拉伸徐变特性,首先对基于水化程度的开尔文模型进行改进,并建立拉伸徐变的增量计算方法;然后采用门式加载设备对早龄期混凝土的直接拉伸强度、拉伸弹性模量以及拉伸徐变进行试验研究,通过热重分析得到水泥浆体的水化程度;最后利用1 d龄期的徐变试验结果确定改进模型的计算参数,并对其他龄期拉伸应变进行验算。研究结果表明,早龄阶段混凝土的水化程度发展较快,拉伸徐变对早龄混凝土的加载龄期非常敏感,加载龄期越早,混凝土的徐变度越大;基于水化程度包含3个开尔文单元的徐变模型可以较好地描述早龄期混凝土拉伸徐变特征。

This paper investigates the tensile creep of early-age concrete. Firstly, improvements are made on the Kelvin model based on degree of hydration. An incremental calculation approach is given for computing tensile creep. Then tests concerning the direct tensile strength, the tensile modulus of elasticity and tensile creep are conducted through a custom-made loading frame. Moreover, the degree of hydration of the cement paste is obtained by thermogravimetric analysis. Lastly, the calculated parameters of the improved creep model are determined through the creep results of the specimens loaded for 1 day. This improved model is used to check the development of the strain at other loading ages. The results show that the degree of hydration develops rapidly during the early age, and the tensile creep is very sensitive to the loading age; the earlier the loading age is, the greater the specific creep of concrete becomes; the creep model containing three Kelvin units based on degree of hydration could be used to describe the tensile creep of early-age concrete well.