Development in Sustainable Infrastructure—Correlation of Concrete Core Data

Abstract

The most direct and reliable method used to estimate the in-situ compressive strength of the hardened concrete structure is by core sampling and testing. This paper investigates the influence of core diameter and aggregate size on the compressive strength of the core. In this work, concrete mixtures having aggregate sizes (Dmax = 6 mm, 10 mm and 20 mm) and core diameters (ø = 69 mm, 100 mm and 150 mm) were prepared to evaluate the compressive strength of cast cores. Concrete cores having a height to diameter (L/D) ratio of 1.5 were extracted from concrete blocks with the help of core cutting machines and tested to find out the correlation of concrete core data so obtained. Cubes of standard size (150 mm × 150 mm × 150 mm) were also prepared with different maximum aggregate sizes. The compressive strength of core and cube strength was tested after 3, 7 and 28 days. The experimental results of core and cube strength were compared and correlated to each other. This research also derives the relationship between, non-destructive tests (Rebound hammer and UPV) and semi destructive tests (core testing) on concrete elements. All this data is required as the fine aggregates used is manufactured sand and the results obtained are compared with natural sand. It was found that with the increase in the diameter of the core and maximum aggregate size, compressive strength of the core increase. The concrete quality achieved by conducting NDT such as rebound hammer test and UPV test was observed to be very good. The compressive strength of cubes and cores was higher for M-sand compared to that of natural river sand. It can be concluded that concrete produced by using M sand has (15–20%) higher compressive strength compared to natural sand for the same grade of concrete. Overall, it can be concluded that manufactured sand has more advantages over natural sand as the compressive strength achieved is always higher for concrete elements and therefore manufactured sand can be used as an alternative building material to sand.KeywordsCompressive strengthConcrete core diameterRatio of length to diameterAggregate size