Pull-out Strengths of GFRP-Concrete Bond Exposed to Applied Environmental Conditions

Abstract

This paper presents results of an experimental investigation on the behaviour of bond between external glass fibre reinforced polymer reinforcement and concrete exposed to three different environmental conditions, namely, temperature cycles, wet-dry cycles and outdoor environment separately for extended durations. Single shear tests (pull-out test) were conducted to investigate bond strengths (pull-out strengths) of control (unexposed) and exposed specimens. Effect of the exposure conditions on the compressive strength of concrete were also investigated separately to understand the effect of changing concrete compressive strength on the pull-out strength. Based on the comparison of experimental results of exposed specimens to control specimens in terms of bond strengths, failure modes and strain profiles, the most significant degradation of pull-out strength was observed in specimens exposed to outdoor environment, whereas temperature cycles did not cause any deterioration of strength.

The Use of Destructive and Non-Destructive Testing in Concrete Strength Assessment for a School Building

“…The procedure, reported in [5], is based on a few cores extracted in the structures on point where non-destructive sclerometric and ultrasonic measures are done. The cores are subjected to direct compressive tests.…”

“…The coefficients on the equation (1) have to be determined by the correlation with some destructive tests. As an example, some proposed exponents and coefficients are reported in the literature and summarized in equations (2)(3)(4)(5). The obtained expression of Rc can be used, in the subsequent indirect testing to obtain the desired concrete resistance whether one does not have sufficient core test results [32].…”

“…It has to be stressed that in equations (2-5) dimensional units affect the results and the coefficients order of magnitude; in particular, Rc is the compressive cubic strength of equivalent cube in N/mm 2 , Ir is the rebound index and V is the ultrasonic speed expressed in m/s in expression (2,3,5) while in km/s in expression (4).…”

“…The relation (4) proposed by Gasparik [30] was taken from tests on concretes of usual composition but is not specified by the author; therefore, it is not well establishing the limits of its applicability. The last equation (5) provided by RILEM NDT4 [31] contains no detailed indications on the limits of its applicability. More detailed description of the framework of NDT and DT procedures can be found in [32] and in [10] with reference to concrete cubic strength assessment.…”

“…The most advanced seismic legislations [1,2] have showed interest to the existing buildings indicating that the type, technique and urgency of a possible intervention must be based on a careful evaluation of the structure in question. Therefore, it is needful to define the mechanical characteristics of concrete in situ [3,4,5], and its compressive strength, using not much onerous and invasive tests and methods. Among the methods some indirect testing can be used that are based on overall displacement and strain measures after load bearing tests nowadays such testing can be done with very effective and accurate measure of strain and displacement [6].…”