双层抛填轻骨料混凝土力学及微结构研究

Mechanical and micro-structural properties of hydraulic concrete based on Double-layer Placed-Fill process

摘要:

本研究运用双层抛填法在混凝土浇筑过程中分两层抛入骨料，通过优化浮石轻骨料混凝土骨料骨架结构。提升混凝土强度，构建抛填骨料粒径区间与抛填率量化评价体系。研究表明，抛填骨料最大粒径为19mm、31.5mm，抛填率为10%及20%时，混凝土抗压强度分别提升16.45%、8.98%，劈裂抗拉强度同步增强。微观分析表明，抛填骨料优化了基体微观结构。随着抛填率的提升，有害孔隙减少，界面微裂纹宽度减小。对应力应变曲线无量纲化拟合分析显示，R2最高达 99%，拟合精度良好。进而建立的韧性分析体系表明，4.75 - 19mm粒径抛填率20%时，韧性分析结果表明，抛填骨料最大粒径为19mm，抛填率为20%时，韧性指数I较基准组提升51.9%，脆性指数B降低47.2%，抛填骨料混凝土实现脆—韧性转变。研究为轻骨料混凝土的工程应用提供了工艺优化方案与理论支撑。

Abstract:

This study utilized a Double-layer Placed-Fill method to introduce aggregates in two layers during the concrete pouring process, with the aim of optimizing the aggregate skeleton structure of pumice lightweight aggregate concrete. This method improved the concrete strength and established a quantitative evaluation system for the particle size range and Placed-Fill rate of the aggregates. The research showed that when the maximum particle size of the aggregates was 19mm and 31.5mm, and the Placed-Fill rates were 10% and 20%, the compressive strength of the concrete increased by 16.45% and 8.98% respectively, and the splitting tensile strength also improved concurrently. Microscopic analysis revealed that the aggregates optimized the microstructure of the matrix. As the throwing-in rate increased, the number of harmful pores decreased, and the width of interfacial microcracks narrowed. Dimensionless fitting analysis of the stress-strain curve showed that the R2 value reached up to 99%, indicating a good fitting accuracy. Furthermore, the established toughness analysis system indicated that when the particle size range of the aggregates was 4.75-19mm and the Placed-Fill rate was 20%, the toughness index I increased by 51.9% compared to the control group, while the brittleness index B decreased by 47.2%. The aggregate concrete achieved a brittle-to-tough transition. This research provides a process optimization scheme and theoretical support for the engineering application of lightweight aggregate concrete.