Abstract
Ultra-High Performance Concrete (UHPC) is a new generation of concrete characterized by its high strength, high durability, and high stiffness. Autogenously shrinkage represents one of the issues of UHPC that occurred at early ages. It occurs particularly during the first 48 hours after casting. This paper focuses on the ways that can be depended on to mitigate the autogenously shrinkage and obtain the outstanding mechanical properties of UHPC. The results showed that the use of coarse sand and high dose of high range water reduced the admixture above 5% of cementations of materials weight, and high ambient temperature at the time of mixing and casting led to increasing the autogenously shrinkage. While using fine sand, silica fume at 25% of cement weight, and crushed ice at 50% of mixing water to control the mixing temperature can reduce autogenously shrinkage significantly.
Highlights
The modern generation of concrete called ultra-high-performance concrete (UHPC) depends primarily on optimizing the packing density [1]
The properties of cement, silica fume, and fly ash are presented in Table 1.The mitigation of passive effects of autogenously shrinkage on UHPC has been studied by adopting the modifications in the types of the materials, their proportions, and controlling the placing and initial curing temperatures
From the results of the mixtures, the following conclusions can be drawn for mitigation of the autogenously shrinkage and production of UHPC: 1) The optimum percentage of cement-to-sand (c/s) was 1.0
Summary
The modern generation of concrete called ultra-high-performance concrete (UHPC) depends primarily on optimizing the packing density [1]. Volume changes occurred due to low water content which induces a capillary pressure and leads to forming glimmer voids It results from self-desiccation and reactions of cementations materials hydration [14]. Despite the outstanding properties that UHPC possesses, high autogenously shrinkage might occur during the first 48 hours after casting This shrinkage occurs because of the initial hydration that may cause hairline cracks at early ages [11]. Many factors influence the autogenously shrinkage such as; the size of fine aggregate used, the dose of high range water reducing admixture, the ambient temperature, the percent of cementations materials used, and the use of fibers as a micro reinforcement inside the matrix. This research focuses on studying the factors that affect the presence of autogenously shrinkage in UHPC and the possible ways to minimize its inverse effects on the mechanical properties by adjusting the mix proportions and without other additives
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