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Title: Screening Method for Very-Low-Strength Concrete

Author(s): Maisha Maliha, Tomoya Nishiwaki, and A. F. M. S. Amin

Publication: Materials Journal

Volume: 119

Issue: 6

Appears on pages(s): 165-174

Keywords: brick aggregates; groove width (GW); low-strength concrete (LSC); nondestructive test (NDT); rebound hammer (RH); rebound quotient (Q); scratching test (ST)

DOI: 10.14359/51737190

Date: 11/1/2022

A screening method is developed by predicting the strength of very- low-strength (<9 MPa) concrete by the use of the rebound quotient and groove width from two low-energy, direction-independent non-destructive test methods (NDTs)—that is, a Type L rebound hammer and a scratching test—for brick and stone aggregate concrete. It is statistically demonstrated that low-strength concrete (LSC) exhibits a smaller standard deviation because of the low strength of the mortar phase, which ensures reliable LSC screening with any of the aforementioned methods. However, for higher-strength (>9 MPa) concrete classes, due to the increase in standard devi- ation, the simultaneous use of the two methods is proposed with a conservative approach to estimate the in-place concrete strength during “rapid visual screening” of buildings. Normal distribution curves classify the concrete compressive strength considering NDT boundary values with information on occurrence probability. Field test results are verified with laboratory-based correlations within acceptable statistical significance.