Influences of fiber length and water film thickness on fresh properties of basalt fiber-reinforced mortar

Abstract

In plain mortar, the water film thickness (WFT) has been found to play a key role in the fresh properties. However, in fiber-reinforced mortar, the role of WFT has not been investigated yet. In this research, basalt fibers of different lengths were added to the mortar, and the dynamic and static flowability, cohesiveness, adhesiveness, and packing density were tested to study the effects of fiber length on the packing density and WFT, and the combined effects of fiber length and WFT on the fresh properties. The results showed that in fiber-reinforced mortar, the WFT also plays a key role, whereas the fiber length exerts its influences through the indirect effects on the packing density and WFT and the direct effect on fiber-mortar interaction. Basically, an increase in fiber length decreases the packing density and WFT, decreases the dynamic and static flowability needed for placing, increases the cohesiveness needed for avoiding segregation, and, quite unexpectedly, decreases the adhesiveness needed for rendering and spraying applications. Regression analysis yielded good correlation of the fresh properties to fiber length and WFT, and best-fit formulas for the mix design for basalt fiber-reinforced mortar were obtained.

目的: 纤维增强水泥基材料新拌性能的关键影响因素仍有待探明. 本文以玄武岩纤维增强砂浆为研究对象, 旨在研究纤维长度与水膜厚度对砂浆新拌性能的综合影响, 进而推动水泥基材料流变学“膜厚度与纤维因子理论”的发展.

创新点: 1. 通过试验分析, 发现水膜厚度与纤维长度是砂浆新拌性能的重要影响因素; 2. 通过回归分析, 建立玄武岩纤维增强砂浆新拌性能的预测模型.

方法: 1. 通过调整纤维长度和水灰比, 制备20组试验砂浆, 并对其进行各项新拌性能试验(表4); 2. 采用堆积密实度湿测法, 对砂浆固体组分的堆积密实度进行测定(图3), 并计算水膜厚度(图4); 3. 通过回归分析方法, 系统分析水膜厚度和纤维长度对砂浆各项新拌性能的综合影响, 并建立玄武岩纤维增强砂浆新拌性能的预测模型(图5∼9).

结论: 1. 水膜厚度是影响玄武岩纤维增强砂浆新拌性能的主要因素; 2. 纤维长度也对各项新拌性能有重要影响: 纤维长度的增加, 会降低砂浆的堆积密实度与水膜厚度, 降低流动性和粘附性, 但会提升粘聚性; 3. 通过回归分析, 建立了基于纤维长度和水膜厚度的玄武岩纤维增强砂浆新拌性能预测模型.