Optical microstructure study on strength of concrete

Abstract

This research present an overview on the optical microstructural features in concrete. Microstructure can be observed by using a range of microscopy methods. In this research, the USB Digital Microscope with magnification power up to x800 was chosen to study the microstructural features in concrete since it is a non-destructive methods which provides larger field of views and observable specimens’ coloured images. The concrete specimens with the manipulation of water/cement ratio 0.3-0.7 (increment of 0.1) in the mix design were used to study the optical microstructural features in concrete and to validate the existence of an interfacial transition zone (ITZ) in concrete. USB Digital Microscope is used to analyze the formation mechanism of microstructure in concrete where the optical microstructural images were analyzed via respective curing periods on 1, 7, 28 and 56 days. This research also extend the scope of study towards the optical microstructural features in composite concrete (fly ash, fiberglass and natural coir fibers as the inclusions) to evaluate it optical microstructural features toward the strength development in concrete. From the experimental results, it observed that normal concrete is consisted of three distinct phases, which are the aggregates, cement, and the interfacial transition phase (ITZ). The ITZ is existed in the concretes for w/c ratio range from 0.3-0.7 and it is detectable by using the optical microscopy. For the formation mechanism of the microstructures in concrete, the results shown that the development of the thickness of interfacial transition zone was the thinnest for normal concrete with water/cement ratio of 0.3 and it has achieved the highest compressive strength. As evaluated across the normal and composites concrete, 2% of fiberglass reinforced concrete achieved the highest compressive strength during the curing ages of 28 days since it induced modification in the microstructures of the concrete to more dense packing.