Mechanical Strength Property of Concrete at Early Ages as Reflected by Schmidt Rebound Number, Ultrasonic Pulse Velocity, and Ultrasonic Attenuation

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Title: Mechanical Strength Property of Concrete at Early Ages as Reflected by Schmidt Rebound Number, Ultrasonic Pulse Velocity, and Ultrasonic Attenuation

Author(s): G.V Teodoru

Publication: Special Publication

Volume: 95

Issue:

Appears on pages(s): 139-154

Keywords: age-strength relation; coefficient of variation; compressive strength; concretes; curing; impact hammer tests; nondestructive tests; steam curing; ultrasonic tests.

Date: 10/1/1986

Abstract:
The paper presents results concerning the correlations between on the one hand the compressive strength at early ages of hydrothermally treated concrete - steam cured, cured in heating moulds, autoclaved - and that hardened under standard conditions (20° C and 65 % R.H.) and on the other hand the rebound number (R), ultrasonic pulse velocity (V) and ultrasonic pulse attenuation (A). The importance in practice is due to the fact that on European construction sites some building components may be subjected to a hydrothermal treatment while others may not. In such a case, dif-ferent values of the compressive strength of concrete correspond to the same values of the nondestructively measured R, V and A. This leads to the conclusion that, in the absence of information on the conditions of curing and hardening of the concrete under investigation, the results of nondestructive tests can be very misleading. The paper discusses also the influence of concrete age on the coef-ficients of variation of the compressive strength, deduced both in a destructive and nondestructive way. Examples of the practice are used to illustrate the laboratory results.