Evaluation of cement grouts for embedding anchors under water

Abstract

Approximately 110 pull-out tests were conducted on grouted anchors cast in the laboratory to investigate the effects of the rheological and mechanical properties of cement grouts, the initial free drop distance of grout, as well as the age of testing on the behavior of anchorages cast in dry and submerged conditions. The anchors consisted of 19-ram, conventional steel bars with an embedment length fixed at five times the bar diameter. Two different casting procedures corresponding to initial free drop of the grout in water of 20 and 200 mm were investigated. The cement grouts used in this investigation incorporated either a Type 10 or a blended silica fume cement and a fixed water-binder ratio of 0.40. The grouts incorporated various concentrations of a high-range water reducer, a rheology-modifying admixture, and silica fume. The rheology-modifying admixture and high-range water reducer were jointly incorporated to enhance both fluidity and washout resistance.The test results indicate that properly designed grouts can be easily cast into place, and yet be cohesive enough to resist the washout ofcementitious materials. The spread in load-carrying capacity between anchor bars cast in dry versus submerged conditions can decrease when cement grouts having a greater washout resistance level are used which can be secured by incorporating a rheology-modifying admixture and silica fume. The bond strength is shown to increase when incorporating silica fume regardless of the casting condition. RESUME Des essais d'arrachement ont ~t~ r&lis& en laboratoire afin d'&udier l'effet des propriSt& rh&logiques et

Cement-matrix structural nanocomposites

“…The addition of untreated silica fume to concrete increases the shear bond strength between concrete and steel rebar [205][206][207][208][209][210][211]. This effect is mainly due to the reduced porosity and thickness of the transition zone adjacent to the steel, thereby improving the adhesion-type bond at small slip levels [208][209][210][211].…”