Experimental Observation of Microstructural Behavior of Concrete

Abstract

An experiment was conducted to observe the real distribution of local microstrains at different orientations in the layers of mortar that separate aggregates in concrete material. The relationship between the microstrains at different locations with different orientations and the macroscopic strain tensor was also investigated. Other microstructural features such as the normal microstress-microstrain relation and the crack patterns were observed. Five specimens were tested under uniaxial compressive loading. Three specimens had 5-mm-thick mortar layers between the hard inclusions, and the other two specimens had 10 mm layers. The aggregate were simulated by rounded granite cylinders embedded in mortar. Both mechanical and strain gauges were used to measure the local microstrain. A testing machine with very high stiffness was used. Although the strains at the microlevel are highly scattered and irregular, the average microstrain in all mortar layers in the same direction, but at different locations, can be considered as the resolved components of the macroscopic strain tensor.