Shrinkage in concrete structures can lead to cracking and increased deflections among other effects. In South Africa, drying shrinkage potential of concrete under ordinary environmental exposure condition is tested according to the methods outlined in codes such as SANS 6085:2006b, ASTM C 157M-08, BS EN 12390-16:2019 and AS 1012.13-1992. The SABS Method 1085:2021 is also used when testing for accelerated shrinkage. Using test results from the two approaches above, the aim of the study is to enable practitioners interpret results and be able to choose appropriate test methods from the same. Three concrete mixes with water/binder ratios of 0.45, 0.55 and 0.65 were cast in the laboratory. One set of samples was cured for 3 days, while the other was cured for 10 days before testing commenced. The mixes were tested for shrinkage according to SANS 6085:2006b and SABS Method 1085:2021. From test results, cumulative shrinkage strains increase with time while the rate of shrinkage is higher at early ages. A higher temperature increases the rate of early age shrinkage, although it reduces ultimate shrinkage. On average, shrinkage reduced by 40% when the SABS Method 1085:2021 was used. While the study adds to the database of shrinkage measurements, more robust and analytical studies are necessary to predict the shrinkage potential of concrete accurately and quickly.

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Evaluating Temperature Effects on Concrete Shrinkage Using South African Test Methods

  • Nicholas M. Kizito,
  • Sivuyile Q. Mkalali,
  • Philemon Arito

摘要

Shrinkage in concrete structures can lead to cracking and increased deflections among other effects. In South Africa, drying shrinkage potential of concrete under ordinary environmental exposure condition is tested according to the methods outlined in codes such as SANS 6085:2006b, ASTM C 157M-08, BS EN 12390-16:2019 and AS 1012.13-1992. The SABS Method 1085:2021 is also used when testing for accelerated shrinkage. Using test results from the two approaches above, the aim of the study is to enable practitioners interpret results and be able to choose appropriate test methods from the same. Three concrete mixes with water/binder ratios of 0.45, 0.55 and 0.65 were cast in the laboratory. One set of samples was cured for 3 days, while the other was cured for 10 days before testing commenced. The mixes were tested for shrinkage according to SANS 6085:2006b and SABS Method 1085:2021. From test results, cumulative shrinkage strains increase with time while the rate of shrinkage is higher at early ages. A higher temperature increases the rate of early age shrinkage, although it reduces ultimate shrinkage. On average, shrinkage reduced by 40% when the SABS Method 1085:2021 was used. While the study adds to the database of shrinkage measurements, more robust and analytical studies are necessary to predict the shrinkage potential of concrete accurately and quickly.