Early age concrete cracking

Chiew, Siew Chin (2005). Early age concrete cracking B.Sc Thesis, School of Engineering, The University of Queensland.

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Author Chiew, Siew Chin
Thesis Title Early age concrete cracking
School, Centre or Institute School of Engineering
Institution The University of Queensland
Publication date 2005
Thesis type B.Sc Thesis
Supervisor Dr Peter Morris
Total pages 30
Language eng
Subjects 0905 Civil Engineering
Formatted abstract
Plastic shrinkage is the shrinkage of freshly placed concrete that takes place during the time when the concrete is plastic. The duration is usually short, first starting after the water sheen disappears from the concrete surface and ending shortly thereafter, when the concrete sets. When concrete is placed, the aggregate and cement start to settle and water rises or bleeds to the surface. Plastic shrinkage and cracking are likely to occur if the rate of evaporation exceeds the rate at which bleeding water rises to the surface. Suction of water from concrete by the sub-base or formwork materials or due to the internal consumption of water during hydration can aggravate the effects of surface evaporation. At this stage, since the surface of the concrete has attained some initial rigidity, it cannot accommodate plastic shrinkage by plastic flow. Thus, plastic shrinkage cracks may develop. The need for an energy failure criterion for the design of concrete structures seems to be obvious on the physical ground that the growth of any crack requires the consumption of a certain amount of ene rgy. The objective of this research is to study the early age of plastic concrete: mechanisms of formation and propagation of plastic shrinkage cracks and preventive/ corrective measures. Experimental load-deformation data for plastic concrete of ages up to 8 hours are collected. Our specimens are made up of 3 mixes of 32Mpa-80mm slump & 3mixes of 50Mpa-65mm slump. The data collected was analysed using fracture mechanics approaches with the aim of developing a model of plastic cracking in early age concrete. Understanding of the mechanisms of formation of plastic shrinkage cracks is essential to measure the preventive and corrective method and this can bring about significant economic benefits, achieve uniform safety margins over a wide range of sizes, and improve structural reliability.
Keyword Concrete -- Cracking
Additional Notes Civil Engineering CIVL4560 project thesis, October 2005, call number THE19000 disk 1

Document type: Thesis
Collection: UQ Theses (non-RHD) - UQ staff and students only
Citation counts: Google Scholar Search Google Scholar
Created: Thu, 11 Apr 2013, 12:23:49 EST by Mr Yun Xiao on behalf of Scholarly Communication and Digitisation Service