The main goal of this article was evaluated the compressive strength of concrete by combination method of non-destructive testing using ultrasonic pulse velocity and Schmidt rebound hammer. For the comparison of different method it was molded cylindrical and cubical samples of concrete at the laboratory with different size of aggregate (stone 0, 1 and 2) and water/cement ratio. Rilem [4[4] RILEM TC 43 - CND. Draft recommendation for in situ concrete strength determination by combined non-destructive methods, Journal Materials and Structures, v. 26, n. 15, pp. 43-49, 1993.], Gasparik [5[5] J. GASPARIK, Prove Non distruttive Nell´edilizia, Universitá di Brescia, Itália, 1992.] and Di Leo and Pascale [6[6] LEO, A.DI., PASCALE, G., Prove Non distruttive Sulle Costruzioni in cement armato, convegno sistema qualitá e prove non distruttive per l´affidabilitá e la sicurezza dele struture civili, Bologna, Italy, 1994.] theoretical model were used to preview the compressive strength of concrete. The conclusions of this work were: for concrete with compressive strength above 30 MPa, it was found a higher variability on the ultrasonic pulse velocity, differently that was found for rebound index. The ultrasonic pulse velocity for concrete with aggregate size 0 was higher when compared with concrete with aggregate size 1 and 2. For rebound index, it wasn´t possible to verify the difference between the rebound index and the size of the aggregate. Comparing the experimental and theoretical strengths of nondestructive method, it was observed that the results were below of the unitary line (experimental / theoretical), which confirms that Rilem [4[4] RILEM TC 43 - CND. Draft recommendation for in situ concrete strength determination by combined non-destructive methods, Journal Materials and Structures, v. 26, n. 15, pp. 43-49, 1993.], Gasparik [5[5] J. GASPARIK, Prove Non distruttive Nell´edilizia, Universitá di Brescia, Itália, 1992.] and Di Leo and Pascale [6[6] LEO, A.DI., PASCALE, G., Prove Non distruttive Sulle Costruzioni in cement armato, convegno sistema qualitá e prove non distruttive per l´affidabilitá e la sicurezza dele struture civili, Bologna, Italy, 1994.] are non-reliable models for the prediction of concrete strength.
ultrasound; rebound hammer; combined methods; mechanical strength
