High-performance cementitious grout with fly ash for corrosion protection of post-tensioned concrete structures

In order to provide corrosion protection of tendons in post-tensioned (PT) concrete systems, the congested interstitial spaces between the strands and duct are ideally to be filled with cementitious grouts. However, many currently used grouts do not have the desired fluidity and resistance to segregation - leading to formation of voids, frothy grout materials, and premature corrosion of strands. This paper presents a 3-phase study on the development of high-performance, pre-blended grouts. Several grouts were formulated with various proportions of ordinary portland cement (OPC), fly ash and chemical admixtures. The fluidity, bleed (i.e., standard, wick-induced, pressure-induced, and -inclined tube), softgrout, rheological, and shrinkage parameters of the formulated grouts were assessed; based on which a systematic selection of grouts was performed in three phases. Finally, a grout with 52 and 48% of OPC and fly ash, respectively (by volume) and optimal dosages of chemical admixtures was formulated and preblended in an industrial facility. This grout satisfies a set of performance specifications on fluidity, resistance against segregation (say, bleedwater and softgrout formations), and shrinkage. Therefore, the grout is capable of filling the ducts and providing long-term corrosion protection of PT strands. (C) 2021 Elsevier Ltd. All rights reserved.