Effect of Fly Ash with Different Particle Size Distributions on the Properties and Microstructure of Concrete

Fly ash has become an important component of concrete as a supplementary cementitious material. Fly ash, as an admixture in concrete, has a great impact on the improvement of concrete properties and utilization of resources. In this work, fly ashes with different particle size distributions (S. Tsivilis, Andersen, normal and F distributions) were selected to prepare concrete. The relationships among the particle size distribution of the fly ash, compressive strength, hydration, pore structure and microstructure of the concrete were studied. The results showed that the compressive strength of the concrete increased at 28 d with fly ashes with the S. Tsivilis and F distributions. Moreover, the porosity of the concrete at 28 d was reduced, and the pore structure of the concrete was improved. The early compressive strength of the concrete increased with the fly ash with a normal distribution. The second hydration heat release rate of the concrete with fly ashes with a normal distribution and an F distribution was obviously faster. In addition to the Andersen distribution, other distributions of fly ash had obvious improvement effects on the pore structure of the concretes. High-performance concrete can be made from fly ash with different particle sizes, which avoids the need for ultrafine grinding with a high energy consumption and high-cost chemical excitation processes.