Investigation of mixing techniques for full-strength-grade engineered cementitious composites (ECCs): Mechanical properties and microstructure

Abstract

Mixing techniques significantly influence the performance of ECC by affecting both macro- and microstructural properties. Despite its importance, research on ECC mixing techniques remains limited, restricting broader exploration and application. This study investigates the effects of three mixing techniques using pan, handheld, and planetary mixers on the performance of full-strength-grade ECC, focusing on flowability, compressive strength, elasticity, tensile and flexural properties, and fiber bridging ability. CT scan-based 3D reconstructions provided insights into pore and fiber distribution. The findings indicate minimal variations in flowability, compressive strength, and elasticity across mixer types, all within 10 % of optimal performance. However, tensile strength showed significant variability at higher strength levels, with pan mixers exhibiting up to 72.25 % performance drop, while handheld mixers showed reductions of up to 25.78 %. Flexural performance remained robust across all mixers, with pan and handheld mixers achieving over 82 % and 92 % of the performance seen with planetary mixers, respectively. While porosity was similar across mixers at identical strength levels, pore size diversity increased with higher strength levels. Additionally, fiber distribution varied significantly. Planetary mixers achieved superior uniformity, whereas pan mixers exhibited significant clustering. These results provide a quantitative assessment of the mixing performance of different mixers, offering valuable guidance for both research and practical engineering applications.