Problems and normative evaluation of bond-strength tests for coated reinforcement and concrete

Abstract

This paper focuses on the problems of the bond-strength between concrete and reinforcement and defines the basic factors affecting the quality of the bond. Two types of coated concrete reinforcement (the zinc-and epoxy-coated) and methods of testing their bond-strength with concrete are described. The goal of this work is to generalize the results of the bond-strength tests so that they would consider only the influence of the corrosion of the zinc-coated reinforcement in fresh concrete or, in the case of the epoxy-coated reinforcement, its probable constriction during the testing. Based on described standards, it is recommended to use the pull-out test to obtain these generalized results: two Czech standards (Bond-strength test of the reinforcement cast in prisms, Beam-strength test of the reinforcement in cubes) and a RILEM recommendation. Keywords: concrete, corrosion of concrete reinforcement, bond-strength, bond-strength tests, hot-dip galvanized reinforcement, epoxy-coated reinforcement, standardŝ lanek obravnava probleme trdnosti vezi med betonom in armaturo ter dolo~a osnovne faktorje, ki vplivajo na kvaliteto vezi. Opisani sta dve vrsti prekritja armature (prekritje s cinkom in prekritje z epoksi smolo) in kako se preizkusi njihova trdnost vezi z betonom. Cilj tega dela je bil dobiti rezultate preizkusov trdnosti vezi, ki bi upo{tevali samo vpliv korozije pri armaturi, pokriti s cinkom v sve`em betonu ali, v primeru armature, pokrite z epoksi smolo, na njeno zo`enje med preizkusom. Na podlagi opisanih standardov se priporo~a preizkus izpuljenja, da se dobi posplo{ene rezultate: dva~e{ka standarda (Preizkus trdnosti vezi betona ulitega v prizme, Preizkus trdnosti betonske kocke) in RILEM-priporo~ilo. Klju~ne besede: beton, korozija armature v betonu, trdnost vezi, preizkusi trdnosti vezi, vro~e cinkana armatura, armatura z nanosom epoksi smole, standardi

Effects of Bar Reinforcement Arrangement on Deformations and Cracking of Concrete Elements

“…A four point bending test of a concrete beam with a central hinge represents the alternative test setup (RILEM-RC5 1982). Both methods produce quite different results, which complicates assessment of the bond behaviour (Pokorný et al 2015). In the case of the pull-out test, different stress states are characteristic for the concrete and steel: the bar experiences tension, while the concrete is in compression (Ashtiani et al 2013).…”

The impact of produced hydrogen gas and calcium zincate on changes of porous structure of cement paste in the vicinity of hot-dip galvanized steel

“…Vznikající vodík zvyšuje pórovitost ještě tvárného cementového tmelu na fázovém rozhraní a snižuje adhezivní faktor (f ad ) soudržnosti výztuže s betonem [16]. Vliv koroze zinkového povlaku na adhezivní faktor soudržnosti je ovšem složitější.…”

“…Prokazatelně majoritním korozním produktem v tomto prostředí je komplexní zinečnatan vápenatý -resp. nejpřesněji: dihydrát bis(trihydroxozinečnatanu) Nelze předpokládat, že by tato křehká směsná krystalická fáze měla pojivové vlastnosti, a dokázala zajistit dostatečnou soudržnost výztuže s betonem [16], ačkoli výsledky některých prací tomu nasvědčují [18][19][20].…”

Effect of Elevated Temperature on the Bond Strength of Prestressing Reinforcement in UHPC

“…Similar to ribbed reinforcement, the bond strength of prestressing reinforcement with concrete (for prestressed components) is given by the mechanical properties of the concrete (surface roughness of the reinforcement, anchoring length, temperature during loading and other parameters). Reduction of mechanical properties of UHPC due to increasing temperature will have a negative effect on the bond strength of any reinforcement in general [17].…”