Assessment of in-situ compressive strength of concrete with brick chips by capo test

Abstract

This thesis presents a comparative study on concrete made from different types of aggregate, including machine-crushed brick and stone chips. Concrete mixtures with 20MPa, 25MPa, and 30MPa target strengthswere prepared using the mix design method suggested in ACI211.1-91. Cylinder and concrete block specimens were prepared from these concrete mixtures. Using these samples, the compressive strength of concrete was measured by the CAPO (Cut and Pull Out ) test, Core test, and cylinder test for concrete at ages of 14,28,56, and 90 days. The strength of concrete in structure is often different than the strength of control specimens. To measure in situ strength of concreteseveral techniques have been developed. Pullout testing of concrete is one suchtechnique,which is divided into two basic categories; the first has an insert cast into the concrete (LOK-TEST), and the other has an insert fixed into a hole drilled into the hardened concrete (CAPO-TEST). This study aims to verify the accuracy and reliability of the CAPO-test method in estimating the compressive strength of concrete made with commonly used local material (brick chips) for different target strengthsatdifferent ages.The study has developed the necessary correlation between CAPO force, standard cylinder strength and core test results. The study showsa significant linear correlation between compressive strength and the pullout force. Based on regression analysis of test results compressive strength of core and cylinder specimens were correlated with CAPOforce. A linear relationship exists between the compressive strength of the cylinder and CAPO force, and also in the core and CAPO force. The correlation coefficient R2is 0.84 and 0.99 respectively. Ithas been found that the variation of estimated compressive strengths by the CAPO tests is within the limit of 5 ~ 17 % of the cylinder strength and 0~ 6 % of the corestrength for the brick-made concrete. Hence, the CAPO test can be used for measuring the in-situ compressive strength of concrete made with brick chips.