Impact of particle size of fly ash on the early compressive strength of concrete: Experimental investigation and modelling
Impact of particle size of fly ash on the early compressive strength of concrete: Experimental investigation and modelling
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DOI：
10.1016/j.conbuildmat.2022.126444
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发表时间：
2022-02-01
影响因子：
7.4
通讯作者：
Pang, Bo
中科院分区：
文献类型：
--
作者：
Cui, Yunpeng;Wang, Licheng;Pang, Bo
粉煤灰由于其稀释效应、增强火山灰反应效应、成核效应和物理填充效应，常被用作混凝土掺合料，以改变混凝土的耐久性和工作性。基于颗粒大小的粉煤灰的有效利用已成为目前的研究热点。本文采用筛分法制备了具有间隙级配的粉煤灰颗粒，并将其用于混凝土搅拌。采用等温量热法、压汞法研究了混凝土的水化热、抗压强度和孔结构。以水化度为中间变量，基于Neville理论，对粉煤灰颗粒级配混凝土的水化度进行了计算，初步建立并验证了粉煤灰颗粒粒径与混凝土早期（7天）抗压强度的数学模型。但由于Neville理论中没有考虑孔隙率的影响，该模型只能粗略地反映粉煤灰粒径与混凝土早期抗压强度的关系。因此，为了提高模型的精度，将孔隙特征参数模型的计算误差作为修正系数。计算误差从30个近似于70%显著降低到3个近似于17%。修正后的模型可有效预测不同粒径粉煤灰混凝土的早期抗压强度。这对混凝土强度的预测和粉煤灰的有效利用具有重要意义。
Fly ash (FA) was commonly used for admixture in concrete to change the durability and workability of concrete due to its dilution effect, enhanced pozzolanic reaction effect, nucleation effect and physical filling effect. The efficient utilization of FA based on particle size has now become a hot research topic at present. In this work, FA particles with gap-graded sizes were prepared by sieving method and then prepared for concrete mixing. The hydration heat, compressive strength and pore structure of concrete were studied using isothermal calorimetry, mercury intrusion porosimetry (MIP) analysis. Hydration degrees of the concrete with gap-graded FA particles were calculated, and a primary mathematical model was tentatively established and verified according to the particle sizes of FA and early compressive strength (7 days) of concrete based on Neville's theory, where the hydration degree was used as an intermediate variable. However, the mathematical model can just roughly reflect the relationship between FA particle sizes and the early compressive strength of concrete due to the lack of consideration of porosity in Neville's theory. Therefore, to improve the accuracy of the model, calculation error of the model with pore characteristic parameters were used as correction coefficients. The calculation error was significantly reduced from 30 similar to 70% to 3 similar to 17%. The modified model was proved to be effective to predict the early compressive strength of concrete prepared with gap-graded sizes of FA. It is of great significance to the prediction of concrete strength and the efficient utilization of FA.