Use of small diameter cores in evaluation of in-situ concrete strength in Eastern Saudi Arabia

Abstract

Deterioration of concrete structures in the Arabian Gulf region is the major problem facing the construction industry in this region. Assessment of concrete structures is important necessity to evaluate the safety of these existing structures. To determine various physical and chemical characteristics of the concrete, core specimens must be retrieved from the structure. Determining the concrete quality along with compressive strength of structure using cores is considered the best technique at present. A review of the literature indicates that as the sample size increases, greater costs are incurred, and, more significantly, the risk of unduly weakening the structure increases. Though large specimens will ensure a reasonable ratio of specimen size to maximum aggregate size, it is impracticable to obtain such cores. Consequently, small cores may have to be adopted.

This research work is aimed to obviate the need of larger diameter cores and to make viable small diameter cores. To achieve this objective, 50 mm diameter cores were used to estimate the "standard" cylinder strength. The compressive strength of cast cylinder was statistically correlated with the 50 mm diameter core strength. The effect of the mixture design variables such as aggregate type maximum aggregate size, blended cements, water-cement ratio and age, was investigated. Results of the present investigation indicated that a linear model can be best used to estimate the in-situ concrete strength using the 50 mm diameter core strength. Moreover, a conversion factor was proposed to convert the 75 mm diameter core strngth into 75 mm diameter cylinder strength.