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In this paper, a novel kind of cement blend with high temperature resistance and self-healing abilities is tailored by incorporating fly ash (FA) and calcium carbonated whisker (CW). The physiochemical changes after high temperature exposure and water re-curing were examined in this blended cement. Incorporation of FA and CW would be able to lower carbon dioxide footprint of cement manufacture and the resulting cementitious composite demonstrates high temperature resistance and self-healing performance. Due to pozzolanic effect of FA, formation of ceramic phases, rehydration process, and carbonation, the deterioration in residual strengths and microstructure after high temperature exposure can be partially recovered during the self-healing process. [ABSTRACT FROM AUTHOR]

Polyvinyl alcohol (PVA) fiber with high elastic modulus and toughness can act as a reinforcing material to improve the brittleness of cement-based materials. However, the difficulty of fiber dispersion in the matrix is correspondingly increased due to its bending and clustering. Poor fiber dispersion not only deteriorates the mechanical properties of PVA fiber-reinforced cementitious composites (PVA-FRCCs) but also increases the difficulty in determining the relationship between fiber dispersion and hardening properties. Rheology, as a vital method to supervise the mixture properties, can improve the fiber distribution and optimize the hardening performance. This paper investigated rheological performance, fiber dispersion, and strengths of three types of PVA-FRCCs and discussed the effect of different fiber factors on the materials properties. Results showed that the rheology of a mixture can affect fiber dispersion and uniform fiber dispersion can be achieved through the experimental design of PVA-FRCCs. Besides, the quantitative relationship between fiber distribution parameters and flexural strengths of PVA-FRCCs was proposed, which showed a superior reliability than the composites theory formula and other traditional fitting equations. However, the relationship between fiber dispersion and compressive strengths was hardly founded due to the deterioration in compressive strength caused by the addition of PVA fibers. [ABSTRACT FROM AUTHOR]

The relationships between the reinforcing index (RI: the product of volume fraction and length-to-diameter ratio of fibers) and rheological parameters (hysteresis loop area, yield stress, plastic viscosity, flow spread, and flow rate) of a single type of fiber-reinforced cementitious composites (SgFRCCs) and hybrid fiber-reinforced cementitious composites (HyFRCCs) with steel, polyvinyl alcohol (PVA) fibers, and calcium carbonate (CaCO3) whiskers, were systematically studied for the first time. After shearing action, short whiskers between cement particles prevented the cement particles from coming close to each other, leading to more irreversible broken structures in the entire rheological test process, which means higher hysteresis loop areas than those of longer fibers. The new hybrid fiber system decreased the yield stress and plastic viscosity to a certain extent, as a result of the "grading effect" of hybrid fibers and whiskers. Based on the theoretical framework of random loose packing, the critical RI values for single PVA fibers and hybrid fibers were approximately 1.0 and 2.0, respectively, which supports this theoretical framework and the effect of critical RI values in fiber-reinforced mortar. The influence of the RI on the characteristics of fresh HyFRCCs can be quantified well into a multivariate linear relationship. Moreover, these findings can be used to optimize fiber mixtures in practical project applications. [ABSTRACT FROM AUTHOR]