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自收缩是引起低水胶比高性能混凝土早期开裂的主要原因。通过不同掺量粉煤灰混凝土自收缩的测定,研究粉煤灰对高性能混凝土自收缩的抑制作用。通过水化结合水和内部孔含量的测定以及微观结构形貌分析,研究粉煤灰抑制自收缩的作用机理。研究表明:粉煤灰通过改变胶凝材料体系水化速度、徐变系数、弹性模量,可以有效抑制早期混凝土的自收缩。粉煤灰掺量在0~20%范围内,混凝土自收缩随着粉煤灰掺量的增加而减少,但粉煤灰惨量超过20%后自收缩减少的幅度变小。粉煤灰抑制自收缩的作用在初凝至1 d龄期内非常突出。
Self-shrinkage is the main reason for early cracking of high-performance concrete with low water-cement ratio. Through the determination of self-shrinkage of fly ash concrete with different dosage, the inhibition of self-shrinkage of high performance concrete with fly ash was studied. Through the hydration combined water and the determination of the content of the internal pores as well as microstructure and morphology analysis, to study the mechanism of fly ash inhibition of self-shrinkage. The results show that fly ash can effectively suppress the self-shrinkage of early concrete by changing the hydration rate, creep coefficient and elastic modulus of the cementitious material. The content of fly ash in the range of 0 ~ 20%, the self-shrinkage of concrete decreases with the increase of fly ash content, but the decrease of self-shrinkage decreases when the amount of fly ash exceeds 20%. The effect of fly ash on inhibiting self-shrinking is very prominent during the initial setting to 1 day of age.