Effects of thickener on macro- and meso-mechanical properties of ECC

This paper focuses on studying the influences of thickener (hydroxypropyl methyl cellulose, HPMC) on ECC performance, with the adding dosages of 0%-0.1% by mass of the reference mix. The tensile properties (including the tensile strength, the tensile strain capacity, and the cracking characteristics) and the compressive strength were thoroughly evaluated. Particularly, the matrix toughness and the fiber-matrix bridging behaviors were further studied by a varies of so-called meso-scale experiments. Meanwhile, the fibers dispersions in the mixes with HPMC were analyzed. The results showed that, both the tensile strength and the tensile strain first increased and then decreased, with the largest values at the 0.05% HPMC (the strain value was up to 8%); while the compressive strength gradually declined according to the HPMC contents. After adding 0.05% HPMC, the crack numbers reached a stable level of around 100 with the average crack width of approximately 60μm, and the dispersion coefficient of fibers tended to a higher level of around 0.35. The variation trends of the matrix fracture toughness and the maximum fiber bridging stress were almost agreement with that of the compressive strength and the tensile properties, respectively. Therefore, no more than 0.05% HPMC was recommended to be used into ECC (or 3D printing ECC).