Assessment of Strength Development at Hardened Stage on High-Strength Concrete Using NDT

Taegyu Lee,Jaehyun Lee,Hyeonggil Choi

doi:10.3390/app10186261

Abstract

This study proposes model formulae for predicting the strength of concrete by analyzing the relationships between the results of nondestructive testing (NDT) methods and the compressive strength of concrete specimens at the hardened stage. Further, NDT of concrete molds and mock-up specimens was conducted using NDT methods (rebound hammer, ultrasonic pulse velocity). The water/cement (W/C) ratios were set to 0.48, 0.41, and 0.33 to achieve concrete strengths within the compressive strength range of 24–60 MPa. The evaluation parameters included the fresh concrete properties, compressive strength (mold and core), temperature history, maturity, rebound value, and ultrasonic pulse velocity. Evaluation results indicated that the reliability of existing models, based on the rebound and ultrasonic pulse velocity, is significantly low on high-strength concrete of 40 MPa or higher, and cannot satisfy the ±20% error range. Consequently, this study proposes a regression equation of the concrete strength based on the experimental rebound and ultrasonic pulse velocity values in a 24–60 MPa range, which offers satisfactory reliability.

Highlights

The use of concrete facilitates the construction of buildings and structures that can withstand high compressive loads
WC 41 concrete specimens, the rebound values increased by less than 10 as the age increased; 41 concrete specimens, the values rebound values increased by aless than 10 the ageafter increased; the rebound of all specimens showed tendency to as converge
Discussion on Regression Equation of Concrete Strength Based on nondestructive testing (NDT)

Summary

Introduction

The use of concrete facilitates the construction of buildings and structures that can withstand high compressive loads. During construction, various quality issues may arise, owing to factors such as temperature variation, poor compaction, and careless construction. In consideration of such problems, researchers have generally recommended measuring the compressive strength of concrete by conducting destructive tests on the concrete cores that have been extracted from structures for a more precise diagnosis [7,8,9]. The extraction of concrete cores is a useful approach for accurately estimating the compressive strength; this approach may lead to problems such as structural instability and the subsequent repair method

Methods

Results

Discussion

Conclusion