Experimental research about early age creep of B65 and B85 concrete mixtures

The early age creep behavior of concrete mixtures with characteristic cubic compressive strength of 65 and 85 MPa, indicated as B65 and B85, was investigated. Creep under compression was studied varying the age of the application of the load. B65 concrete was studied under a load corresponding to stress/strength ratio at the age of loading of https://www.w3.org/1998/Math/MathML" display="inline"> 40 % . The measured total strains were lower the earlier the application of the load, while the creep coefficients were higher for earlier loading ages. B85 concrete was also studied under a stress/strength ratio of https://www.w3.org/1998/Math/MathML" display="inline"> 40 % . The conclusions were similar to the ones for B65 concrete. Also a mixture with a https://www.w3.org/1998/Math/MathML" display="inline"> 25 % replacement of the normal weight aggregates with saturated lightweight particles was studied, showing, as far as creep was concerned, almost the same behavior as the mixture with normal density aggregates. For all mixtures, the creep and relaxation coefficients were calculated. A comparison between measured values of creep coefficients and predicted by models found in literature showed discrepancy between the two values.