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

Mo Li,Victor C Li

doi:10.1617/s11527-012-9909-z

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 strain-hardening 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.

Highlights

In the past decade, great strides have been made in the development and testing of Engineered Cementitious Composites (ECC), a class of high-performance fiberreinforced cementitious composites (HPFRCC) featuring high intrinsic tensile ductility and moderate fiber content [1]
This study investigates the correlation between the rheological parameters of ECC mortar before adding polyvinyl alcohol (PVA) fibers, dispersion of PVA fibers, and ECC composite tensile properties
This study systematically established the strong correlation between the ECC mortar plastic viscosity, fiber dispersion and composite tensile properties

Summary

Introduction

Great strides have been made in the development and testing of Engineered Cementitious Composites (ECC), a class of high-performance fiberreinforced cementitious composites (HPFRCC) featuring high intrinsic tensile ductility and moderate fiber content [1]. ECC exhibits tensile strain-hardening behavior through multiple micro-cracking with self-controlled crack width, leading to fracture toughness similar to aluminum alloys [2]. Tensile strain capacity in the 3–5 % range, about 300–500 times that of concrete and fiber reinforced concrete (FRC), has been demonstrated in ECC materials using polyvinyl alcohol (PVA) fibers with fiber volume fraction at 2 % [3]. ECC’s high tensile ductility, deformation compatibility with existing concrete, and self-controlled micro-crack width lead to its superior durability under various mechanical and environmental loading conditions such as fatigue, freezing and thawing, chloride exposure, and drying shrinkage [8,9,10,11,12]. ECC is emerging in full-scale structural applications in Europe, Japan, and the US [13,14,15,16]

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