Cracking occurs when the tensile stress developed in the member exceeds the tensile capacity of the material. The mechanisms that occur during the maturing of fresh concrete causes change in volume of the concrete itself. If the concrete is allowed to expand and contract without any form of restraint, it will not crack. However, fresh concrete, even at its earliest age has some internal restraints due to aggregates and reinforcement, which usually cause minute cracking.
These early age effects can be broadly divided into two stages. Firstly, cracking that occurs before the concrete has set (i.e. concrete is in a fluid or semi-fluid state), and secondly, cracking that occurs after the concrete has begun to set [1]. In the plastic stage (or the early age), plastic shrinkage cracking and plastic settlement cracking causes the most significant problems. Initial cracking age is delayed when low percentages of fibers are added to the concrete. Fibers prevent cracks from widening and propagating throughout the concrete. However, there is no significant reduction in free shrinkage observed with polymer fibers [2]. Zhang & Li [3] used steel fibers to show that long-term
Cracking occurs when the tensile stress developed in the member exceeds the tensile capacity of the material. The mechanisms that occur during the maturing of fresh concrete causes change in volume of the concrete itself. If the concrete is allowed to expand and contract without any form of restraint, it will not crack. However, fresh concrete, even at its earliest age has some internal restraints due to aggregates and reinforcement, which usually cause minute cracking. These early age effects can be broadly divided into two stages. Firstly, cracking that occurs before the concrete has set (i.e. concrete is in a fluid or semi-fluid state), and secondly, cracking that occurs after the concrete has begun to set [1]. In the plastic stage (or the early age), plastic shrinkage cracking and plastic settlement cracking causes the most significant problems. Initial cracking age is delayed when low percentages of fibers are added to the concrete. Fibers prevent cracks from widening and propagating throughout the concrete. However, there is no significant reduction in free shrinkage observed with polymer fibers [2]. Zhang & Li [3] used steel fibers to show that long-term
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