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Grout-Concrete Interface Bond Performance: Effect of Interface Moisture on the Tensile Bond Strength and Grout Microstructure

Published

Author(s)

Igor de la Varga, Jose Munoz, Dale P. Bentz, Paul E. Stutzman, Benjamin Graybeal

Abstract

Bond between two cementitious materials is crucial in applications such as repairs, overlays, and connections of prefabricated bridge elements (PBEs), to name just a few. It is the latter that has special interest to the authors of this paper. After performing a dimensional stability study on grout-like materials commonly used as connections between PBEs, it was observed that the so-called ‘non-shrink' cementitious grouts showed a considerable amount of early-age shrinkage. This might have negative effects on the integrity of the structure, due not only to the grout material's early degradation, but also to a possible loss of bond between the grout and the prefabricated concrete element. Many are the factors that affect the bond strength between two cementitious materials (e.g, grout-concrete), the presence of moisture at the existing concrete substrate surface being one of them. In this regard, pre-moistening the concrete substrate surface prior to the application of the grout material is sometimes recommended for bond enhancement. This topic has been the focus of numerous research studies in the past; however there is sometimes controversy among practitioners on the real benefits that this practice might provide. This paper evaluates the tensile bond performance of two non-shrink cementitious grouts to a concrete substrate, and how the supply of moisture at the grout-concrete interface affects the bond strength. "Pull-off" bond results show increased tensile bond strength when the concrete surface is pre-moistened. Reasons to explain the observed increased bond strength are given after a careful microstructural analysis of the grout-concrete interface. Interfaces where extra moisture is provided show reduced porosity on the grout side of the interface, which is thought to directly contribute to the increased tensile bond strength.
Citation
Construction and Building Materials
Volume
170

Keywords

Cementitious grout, Interface moisture, Porosity, Tensile bond strength.

Citation

de la Varga, I. , Munoz, J. , Bentz, D. , Stutzman, P. and Graybeal, B. (2018), Grout-Concrete Interface Bond Performance: Effect of Interface Moisture on the Tensile Bond Strength and Grout Microstructure, Construction and Building Materials, [online], https://doi.org/10.1016/j.conbuildmat.2018.03.076, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=922420 (Accessed August 11, 2022)
Created March 7, 2018, Updated October 12, 2021