Abstract
This article reviews the tailoring of engineered cementitious composites (ECC), a type of high performance fiber reinforced cementitious composites with a theoretical design basis, for special attributes or functions. The design basis, a set of analytic tools built on micromechanics, provides guidelines for tailoring of fiber, matrix, and fiber/matrix interfaces to attain tensile ductility in ECC. If conditions for controlled multiple cracking are disturbed by the need to introduce ingredients to attain a special attribute or function, micromechanics then serve as a systematic and rational means to efficiently recover composite tensile ductility. Three examples of ECCs with attributes of lightweight, high early strength, and self-healing functions, are used to illustrate these tailoring concepts. The fundamental approach, however, is broadly applicable to a wide variety of ECCs designed for targeted fresh and/or hardened characteristics required for specific applications.
Highlights
We review the essence of the micromechanics based analytic tool set, emphasizing its use in controlling the composite matrix, fiber, and fiber/matrix interface ingredients for achieving targeted properties and special attributes
The 4 % strain capacity at 4 h was reduced to about 1 % after 3 days. This suggests that the binder modification for high early strength leads to time-dependent micromechanical parameters that negatively impact the long term engineered cementitious composites (ECC) tensile ductility performance, by violating one or both multiple cracking criteria (1) and (5)
To investigate the underlying reason for the progressive loss of tensile ductility, a detailed investigation (Li 2009) was launched to determine the time-dependence of micromechanical parameters. This is a case where the multiple cracking criteria were satisfied at early age, but continuous changes in matrix and/or fiber/matrix interface micromechanical parameters as a result of continuous hydration of binder leads to a gradual reduction of the ratio of J0b/Jtip and/ or r0/rcr
Summary
While the fundamental characteristic of ECC is its extreme tensile ductility, a variety of useful attributes/ functions have recently been designed into particular members of this material family These special attributes/functions include light-weightedness, low carbon footprint, selfhealing, self-sensing, self-thermal control, impact resistant, fire resistive with low thermal conductivity, pigmentability, rapid setting, self-consolidating, sprayability, extrudability, Tensile Stress (MPa) Crack Width (μm). We review the essence of the micromechanics based analytic tool set, emphasizing its use in controlling the composite matrix, fiber, and fiber/matrix interface ingredients for achieving targeted properties and special attributes For illustration of this approach, we shall discuss three example ECC materials with the attributes/ functions of light-weightedness, high early strength, and self-healing, respectively. It is emphasized that the availability of the micromechanics based analytic tool set removes a lot of guesswork, which allows systematic and effective tailoring of material ingredients to efficiently attain the desired material behavior
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