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Influence of Tropical Environment conditions and materials on plastic shrinkage cracking of concrete

NRC Grant:  14-125

Dr. H.P. Sooriyaarachchi
Dept. of Civil & Environmental Engineering
Faculty of Engineering
University of Ruhuna
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Area of Research:Civil Engineering
Status:Ongoing

 

objectives

 a) Collect data at different environmental conditions and other variable persisted during concrete placement to evaluate the accuracy between the onset plastic shrinkage cracking of concrete and the current ACI305 relationship based on evaporation related environmental conditions and the “Combination formulae” incorporating radiation energy with the ACI305 relationship.

b) Incorporate bleeding rate of the mix in terms of mixing variables (say in terms of water content or water/cement ratio) to establish mix dependent threshold limit for plastic shrinkage cracking. 

c) Study the influence of factors unrelated to environmental conditioning like slab thickness, aggregate proportioning, fines content and cement type on the plastic shrinkage cracking of concrete.       

d)Develop method of predicting plastic shrinkage of concrete coupling both the environmental factors influencing the evaporation of concrete and other factors identified and quantified under this research work.

e)Influence different mitigatory measures to reduce plastic shrinkage cracking of concrete.

overview

Plastic shrinkage cracking of concrete is a phenomenon of concrete cracking during the early stages of concrete cast. Although, shrinkage cracks rarely threaten structural integrity, increase in the number and intensity of plastic shrinkage cracking has created serviceability and durability issues in concrete structures and has made lot of confusions between supply chain of materials and specially cement producers, contractors and clients.  Increase in the plastic shrinkage cracking is in recent times is often attributed to the increase in use of different cement types, pozzolanic compounds and the use of alternative aggregate type for concrete works. Due to its non penetrative and hire line nature made remedying plastic shrinkage cracks often difficult and prevention is considered more appropriate way forward. Use of external environmental conditions along in the consideration of plastic shrinkage cracking potential is the main problem for the use of current guideline to avoid plastic shrinkage cracking of a fresh concrete cast. Under this study it is expected to couple other variable like bleeding of concrete, mixing variable, thickness of the cast and construction variables along with external environmental conditions and establish a new frame work beyond the existing hydrological framework to calculate plastic shrinkage cracking potential of concrete. Development of the proposed frame work is expected to provide more realistic estimates for plastic shrinkage cracking potential and therefore benefit the construction industry to mitigate/eliminate plastic shrinkage cracking of concrete.