Predicting a Mathematical Models of Some Mechanical Properties of Concrete from Non-Destructive Testing

Abstract

Nondestructive tests NDT are considered as a one of the methods of evaluation and quality control of concrete. The fundamental aim of the present study is constructing a mathematical models  to predict some mechanical properties  of concrete from Nondestructive testing, in addition the study of (NSC and HSC) properties (density, compressive strength ,modulus of elasticity and modulus of rupture ) of concrete grade (20-100) MPa) by using NDT methods namely; Schmidt Hammer test (RN )and Ultrasonic Pulse Velocity test ( UPV) with destructive test methods at different four ages (7, 28, 56 and 90) days. This study  used  ready mixes (1:2:4 and 1:1.5:3) and design mixes (C₄₀, C₅₀, C₆₀, C₇₀, C₈₀, C₉₀ and C₁₀₀), in order to find  the relationship between these properties. of concrete with (RN and UPV), and compressive strength  of concrete-combined NDT(RN and UPV) relationship, for all mixes (as freelance and as group). The results of compressive strength for both types of concrete NSC and HSC exhibit an increase with the increase of bulk density and time of curing. Also, the results show a good correlation between compressive strength and (RN) and the relationship between the two is not affected by maximum aggregate size (MAS). Also, a good correlation between compressive strength and Ultrasonic Pulse Velocity (UPV) and The value of UPV in HSC increased 8% from 28 days to 90 days. Also, the results indicated that the percentages of increase in relationship between static modulus of elasticity and compressive strength for 28 days to 90 days are 15% at low strength, 5.6% at high strength and the relationship between static modulus of elasticity and rebound number for 28 days to 90 days is3.3%.The results indicate that the percentage of increase in direct method to surfacing method of UPV for (7, 28, 56 and 90) days is (7%, 5%, 4% and 3.5%) respectively, due to the higher the continuity of hydration of cement.  Also, the pulse velocity of concrete is decreased by increasing the cement paste, especially for concrete with high w/c.

Keywords— Nondestructive tests, Schmidt hammer test(RN), Ultrasonic pulse velocity test  ( UPV) , Density , Compressive strength, modulus of elasticity , modulus of rupture.