| The objective of this research is to develop a laboratory methodology that would enable us to detect the first fracture in concrete, and to determine the strength properties at the point of first fracture using rigorous interpretation methods.;In this research, the Superpave IDT test and interpretation methods, developed by Roque and Buttlar (1994), were used to determine first fracture, and tensile strength properties at first fracture. Acoustic Emission (AE) was used to evaluate the first fracture identification for concrete with Superpave IDT test method. Then the recommended procedure was developed for detecting first fracture and determining tensile fracture properties in concrete, followed by the evaluation of the procedure for various concrete curing conditions and material modifications. The two curing conditions used are Oven Dry (OD) and Room Conditions (RC) while the two modified concrete materials are fly ash and metakaolin-fly ash concrete.;The Superpave IDT test was also evaluated for its potential of identifying the onset of microdamage in concrete. The microdamage is the point at which the bulk properties start being negatively affected by microcracking, which manifests as the decrease of Young's modulus and the deformation ratio (V/H).;The methodology developed by Roque and Buttlar (1994) for the Superpave IDT test has been proven to be able to identify first fracture and determine the strength properties at the first fracture in concrete. The potential of Superpave IDT test for identifying the onset of microdamage has also been confirmed and supported by the testing results. The effects of OD curing conditions have been captured by the significant decrease of the mechanical parameters at the microdamage and first fracture of the OD cured concrete of all types. It was also found that the point at which microdamage initiates starts at a lower tensile stress level in modified concrete as compared to that in regular concrete.;In summary, the Superpave IDT test is able to determine the strength properties of concrete at the first fracture, and potentially those at the onset of microdamage. |
