VALIDATION OF THE MODEL CODE 2010 AND EUROCODE CONCRETE SHRINKAGE PREDICTION MODELS

Shrinkage strain is a requirement of the concrete design process that has proven difficult to model. Shrinkage of concrete has a negative effect on its structural performance. In cases where the concrete is restrained, which includes most structures, shrinkage may result in appreciably sized cracks. Such cracks effect the aesthetics of the structure and have negative durability related implications. Although laboratory tests may be undertaken to quantify the shrinkage, this is time consuming. For this reason, empirical code-type prediction models are used to predict shrinkage strain. This paper considers the accuracy of the fib Model Code 2010 (MC2010) [1] and European Standard Eurocode – EC2 (BSI, 2004) [2] shrinkage prediction models. The models were evaluated, when compared with the actual shrinkage strains measured, over a period of approximately six months, on a range of concretes under laboratory-controlled conditions, for six mixes. The six mixes comprised three South African aggregate types (quartzite, granite and andesite) and two water-cement ratios (0.56 and 0.4). Both the MC2010 [1] and Eurocode 2 (EC2) [2] Models generally over-predicted shrinkage strain with age. Furthermore, the EC2 [2] yielded the more accurate predictions of the two models in the initial six days. The MC2010 [1] Model was found to be the least accurate in the case of all six mixes with an overall coefficient of variation (ω_all ) of 70,1%. The EC2 [2] Model was the most accurate model with a ω_all of 63,1%. When considering the mixes on the basis of the included aggregate type, in the case of both models, the predictions were more accurate and the shrinkage was less in the higher strength mix (w/c of 0.4) of each aggregate type.