Rheology, fiber dispersion, and robust properties of Engineered Cementitious Composites

Abstract

The capability of processing robust Engineered Cementitious Composites (ECC) materials with consistent mechanical properties is crucial for gaining acceptance of this new construction material in various structural applications. ECC's tensile strainhardening behavior and magnitude of tensile strain capacity are closely associated with fiber dispersion uniformity, which determines the fiber bridging strength, complementary energy, critical flaw size and degree of multiple-crack saturation. This study investigates the correlation between the rheological parameters of ECC mortar before adding PVA fibers, dispersion of PVA fibers, and ECC composite tensile properties. The correlation between Marsh cone flow rate and plastic viscosity was established for ECC mortar, justifying the use of the Marsh cone as a simple rheology measurement and control method before fibers are added. An optimal range of Marsh cone flow rate was found that led to improved fiber dispersion uniformity and more consistent tensile strain capacity in the composite. When coupled with the micromechanics based ingredient-tailoring methodology, this rheological control approach serves as an effective ECC fresh property design guide for achieving robust ECC composite hardening properties.

Effect of elevated temperature on strain-hardening engineered cementitious composites

“…The ECC design theory requires the simultaneous satisfaction of steady state cracking criteria [37] and maximized micro-cracking density [38]. The ingredient particle size distribution and the combined amount of water and admixtures were first determined to achieve a homogeneous cementitious composite material at fresh state, with plastic viscosity and yield stress tailored to an optimal level [38] that favors uniform dispersion of micro-scale polyvinyl alcohol (PVA) fibers.…”

“…The ECC design theory requires the simultaneous satisfaction of steady state cracking criteria [37] and maximized micro-cracking density [38]. The ingredient particle size distribution and the combined amount of water and admixtures were first determined to achieve a homogeneous cementitious composite material at fresh state, with plastic viscosity and yield stress tailored to an optimal level [38] that favors uniform dispersion of micro-scale polyvinyl alcohol (PVA) fibers. Then, the micro-parameters of the hardened material, including matrix properties (e.g., fracture toughness, flaw size distribution, hydration products), the fiber/matrix interfacial properties (e.g., interfacial chemical and frictional bonds, slip-hardening coefficient, fiber debonding and pullout behavior), and fiber properties (e.g., aspect ratio, strength, Young's modulus) were tailored to ensure the strain-hardening criteria [37] were satisfied.…”

Toward modeling anisotropic yield stress and consistency induced by fiber in fiber-reinforced viscoplastic fluids

“…It is well established that fiber orientation depends on both process and material rheology [5,9,10,13,15,22,[27][28][29][30][31][32]. Then, some works have been carried out on the effect of fibers on the concrete rheology [11,28,30,[33][34][35] and on the prediction of fiber orientation during processing [29,31,36,37].…”

Latex-modified Engineered Cementitious Composites (L-ECC)

“…Higher viscosity tends to entrap more air during mixing resulting in higher air content when EVA is used in the mixture. On the other hand, however, increased viscosity can potentially improve fiber dispersion of ECC (Yang et al 2009;Li and Li 2013). As compared to poor fiber dispersion (e.g.…”