Influence of concrete depth and surface finishing on the cracking of plastic concrete

Published on Jun 30, 2018in Construction and Building Materials6.141
路 DOI :10.1016/J.CONBUILDMAT.2018.04.225
Riaan Combrinck12
Estimated H-index: 12
(Stellenbosch University),
Lourens Steyl2
Estimated H-index: 2
(Stellenbosch University),
William P. Boshoff17
Estimated H-index: 17
(Stellenbosch University)
Sources
Abstract
Abstract Settlement and shrinkage cracking occurs in plastic concrete once cast up to around the final setting time. This paper reports on the influence of element depth and surface finishing operations on the cracking of plastic concrete. Deeper concrete elements are shown to have less severe shrinkage cracking when no settlement cracking is present, while when combined with settlement cracking at similar cover depths the cracking is more severe in deeper concrete. Surface finishing operations are shown to only close the surface of plastic cracks and not the crack below the surface, therefore temporarily hiding the true severity of the cracking.
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#1Riaan CombrinckH-Index: 12
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Abstract Plastic shrinkage cracking (PShC) is one of the earliest forms of cracking in concrete as it occurs within the first few hours after the concrete has been cast. Concrete elements with large exposed surfaces are especially vulnerable to PShC. Many researchers have proposed models to simulate plastic shrinkage, bleeding and to predict the occurrence of PShC. In this paper a model to predict the degree of PShC is proposed. This model, the so called PShC Severity Model, is based on the volu...
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Plastic shrinkage cracking (PShC) is one of the earliest forms of cracking in concrete. Concrete structures with large exposed surfaces are especially vulnerable to PShC and the cracks formed are unsightly and can lead to premature durability issues. Although various precautionary methods exist, they are often neglected or ineffective due to the fundamental lack of knowledge regarding PShC. This paper investigates and describes the typical behaviour of PShC in conventional and low-volume synthet...
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In this paper, the plastic settlement of mortar is analyzed on the basis of small strain consolidation theory and the approach is compared with experimental data. The amount of settlement caused by the self-weight of bulk mortar was measured using a noncontact laser measurement device. In addition, tests were performed on systems containing different geometries of embedded reinforcement to measure the effect of specimen and inclusion geometry on settlement. The influence of mixture proportions a...
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Plastic shrinkage cracking, which occurs during the first several hours after the casting of concrete, is of considerable economic significance in the concrete construction industry. In this paper, the mechanism of plastic shrinkage cracking and its related phenomena of evaporation and bleeding are first reviewed. Then, together with tensile strength of early-age concrete, the concept of matric suction, its effect on plastic shrinkage and an empirical relationship for its estimation are discusse...
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Plastic shrinkage in fresh cement-based materials is caused by capillary pressure in the pore system. Within the first few hours after casting, evaporation results in the loss of water and possibly in the formation of menisci in the water surface between the superficial solid particles. With decreasing radius of the menisci the capillary water pressure rises. At a certain pressure, the system becomes unstable and air penetrates into the system. This event is called air entry and assumed to be th...
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In the present paper, the influence on plastic shrinkage cracking of many factors related to concrete mixture properties and weather conditions are analysed through parametric studies using the numerical models introduced in the companion paper. First of all, through a systematic calculation of bleeding, a relationship between the bleeding constants and the concrete mixture is proposed on the basis of the experimental data previously obtained by many researchers. Moreover, an equation is introdu...
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Comprehensive, up-to-date coverage of the properties, behavior, and technology of concrete Fully revised to include the latest advances in concrete technology, Concrete: Microstructure, Properties, and Materials provides complete details on the microstructure-property relationship approach to provide scientific explanation for the strength and durability of concrete. This in-depth resource discusses the microstructure and properties of hardened concrete; concrete-making materials and concrete pr...
The influence of mix constituents (including corresponding concrete grade), retarding and air entraining admixtures and PFA additives, and the effect of environmental factors on plastic shrinkage cracking of mortar specimens is reported, supplemented by concurrent evaporation and bleeding tests. The dominant effect of environmental factors on evaporation, and that of corresponding concrete grade on plastic shrinkage cracking, were clearly established. Both retarding and air entraining admixtures...
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Abstract Plastic cracking is probably one of the earliest defects for concrete structures, and is capable of reducing a structure鈥檚 durability and service life if not prevented. Over the last 60鈥痽ears, researchers have attempted to unravel the complex nature of mechanisms leading to plastic cracking of concrete. The main driving mechanisms of plastic cracking have been found to be settlement of solid particles, bleeding, evaporation, capillary action, as well as surface finishing. These, in comb...
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