Abstract
Test resuls of two different non-destructive test methods, the ultrasonic pulse velocity and Schmidt hammer, were used in conjuction with concrete mix proportions and density, to develop mathematical relationships using multiple linear regressions to obtain a first stage estimate of concrete compressive strength. These regressions covered both wet and air-dry concrete conditions. In each part of the work, a total number of 103 different mixes were tested at ages ranging between 7–90 days.
Second stage (more accurate) concrete strength estimates are then obtained by linear correlation between the first estimates of concrete strength from the first part of the work and actual strengths obtained from limited number of cores cut from the structure itself.
This procedure was tested on two separate building cases and was found to yield good predicted values with standard errors of estimate of 2.95. MPa for a concrete with range of strength of (15.7–33.8) MPa for the first case study, and a standard error of only 0.91 MPa for a concrete with range of strength of (12.5–23) MPa for the second case study.
Résumé
Deux méthodes d'essais non-destructifs différentes, la vitesse vibration des ultrasons et le scléromètre de Schmidt, ont été utilisés pour diverses formules et masses volumiques de béton.
Les résultats ont permis de développer un modèle mathématique de prévision de la résistance en compression. Ce modèle couvre les cas de conservation du béton en atmosphère humide et sèche. Dans chaque cas, il a été utilisé 103 mélanges, pour des essais réalisés à un âge allant de 7 à 90 jours.
Dans une deuxième étape, une estimation plus précise des résistances du béton a été réalisée par corrélation linéaire entre les valeurs de résistance obtenues dans la première partie, et les valeurs réelles déterminées sur quelques échantillons prélevés par carrotage sur l'ouvrage.
Cette procédure a été appliquée avec succès aux cas de deux ouvrages: écart-type de 2,95 MPa pour une résistance de 15,7 à 33,8 MPa (premier cas)—écart-type de 0,91 MPa pour un béton d'une résistance de 12,5 à 23 MPa (deuxième cas).
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Kheder, G.F. A two stage procedure for assessment of in situ concrete strength using combined non-destructive testing. Mat. Struct. 32, 410–417 (1999). https://doi.org/10.1007/BF02482712
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DOI: https://doi.org/10.1007/BF02482712