Experimental Investigation of Some Strength Parameter Correlation in Blended Cement Concrete

Abstract

Sri Lanka has adopted Eurocodes for structural designs. Accordingly, the design of concrete structures should adhere to EN1992 (Eurocode 2). The strength parameters of concrete essential for designs are classified in Eurocode 2 based on the compressive strength of concrete. Most of the other relevant strength parameters are derived using correlations with compressive strength. These correlations based on past empirical test results would typically be valid for concrete made using ordinary Portland cement (OPC). Recently there has been a tendency to use blended cements for concrete. To develop economical and safe designs in such cases the correlations among strength parameters used in EN 1992 should be verified as being applicable to blended cement concrete too. The study presented here was aimed at investigating the applicability of EN 1992 correlation between compressive strength and split cylinder tensile strength to blended cement concretes. Test specimens of concrete made using a blended cement – Portland Composite Cement (PCC) – were cast, cured, and tested under standard conditions for their compressive strength and split cylinder tensile strength. These tests were repeated for greater reliability. For comparison, similar tests were performed on concrete made using OPC also. The measured compressive strengths were used to produce estimated values of corresponding tensile strengths following the EN1992 correlations. Comparisons were made, in graphical form, between the measured tensile strengths and the estimated tensile strengths. Separately for each cement type. They revealed that the test results for OPC concrete, as expected, aligned with EN1992 correlations with a significant margin of safety while those related to blended cement, though complying with EN1992 correlations, provided only a narrow margin of safety. This indicates a need for a higher level of quality assurance for blended cement concrete. As these observations are based on a limited number of tests it is recommended to conduct further comprehensive studies.