Effectiveness of sealers in counteracting alkali-silica reaction in highway median barriers exposed to wetting and drying, freezing and thawing, and deicing salt

Abstract

This study follows another experimental study where different types of sealers were applied on plain and air-entrained large concrete cylinders made with high-alkali contents and highly alkali–silica reactive limestone aggregates. The main objective was to determine the effectiveness of these sealers in counteracting concrete expansion and surface deterioration due to alkali–silica reaction under various exposure conditions. This study indicated that all three sealers tested, the silane-, oligosiloxane-, and polysiloxane-based sealers, could stop concrete expansion due to ASR and even produced contraction, even for concrete cylinders subjected to wetting and drying, freezing and thawing, and sodium chloride solutions. In 1991, the same silane, oligosiloxane, and polysiloxane were applied on sections of median barriers showing various degrees of deterioration due to ASR. These sections were subjected to wetting and drying, freezing and thawing, and, during winter, to deicing salt. The silane was also applied on other sections of the same barriers in 1994. Observations and measurements over 10 years indicate that the aesthetic appearance of these median barriers, particularly those sealed with the silane, was greatly improved, while internal humidity was significantly reduced, and concrete expansion as well, when not arrested. The period of time during which the above three sealers were capable to stop ASR expansion varies with the sealer used and the degree of concrete deterioration at the time of sealing. For instance, the silane, which was the best among all products tested, caused concrete contraction for at least 6 years in median barriers that were severely affected by ASR, and likely for more than 10 years in moderately affected barriers. The overall results confirm the conclusions obtained previously in the laboratory: a good sealer such as the silane tested may greatly improve the aesthetic appearance and stop the expansion of non-massive ASR-affected concrete members, at least up to about 300 mm in thickness, and subjected to wetting and drying, freezing and thawing, and salt water. However, the poor result obtained in the field with another silane-based sealer indicates that a sealer cannot be selected based on its composition only.Key words: alkali–silica reaction, concrete; cracking, expansion, internal humidity, median barrier, sealer, silane, siloxane.

Effectiveness of Silane to Mitigate Alkali-Silica Reaction in a Historical Bridge

“…Concrete expansion due to ASR will only occur when the internal relative humidity of the concrete is greater than 80 percent [3,4].…”

“…In a study performed on highway median barriers with ASR [3], it was found that the silane-sealed concrete sections reached a much lower relative humidity than the unsealed sections. It was further concluded that silane greatly improved the aesthetics of the barriers for the 10-year study, and the silane was able to stop concrete expansion due to ASR and even caused contraction for at least six years [3].…”

Alkali–Silica Reactions: Literature Review on the Influence of Moisture and Temperature and the Knowledge Gap

“…This could have been due to the duration of the wetting cycle. As a result, such a phenomenon could influence the available moisture in concrete for the ASR [ 15 , 78 ].…”

“…In existing structures already affected by ASR, there is no known method to halt the reaction. Common mitigation measures include controlling moisture availability through the application of coatings/sealers [ 15 , 16 ], the impregnation of lithium, the release of stresses through slot cutting, and external restraint by post-tensioning [ 17 ]. However, new cracks have been reported to appear years after the application of such techniques [ 18 , 19 ].…”

Structural Performance of Nuclear Power Plant Concrete Structures Affected by Alkali-Silica Reaction (ASR) Task 2: Assessing Bond and Anchorage of Reinforcing Bars in ASR-Affected Concrete

“…ASR in concrete structures was first identified by Stanton (1940), and considerable research on this topic has been conducted to date, including investigation of the in-situ mechanical properties of reactive mixtures in service (e.g., Clark, 1989;McLeish, 1990;Deschenes et al, 2009;Smaoui et al, 2006), methods to manage the effects of ASR in existing structures (e.g., Fournier et al,2004;Fournier et al, 2010;Charlwood et al, 2012;Bérubé et al, 2002a;Bérubé et al, 2002b;Drimalas et al, 2012) methods to prevent ASR in new structures (e.g., McCoy and Caldwell, 1951;Jensen et al, 1984;Pleau et al, 1989;Lane and Ozyildirim, 1995;Lane and Ozyildirim, 1999;Mather, 1999;Folliard et al, 2006;Bektas et al, 2006;Carles-Gibergues et al, 2008;Thomas et al, 2008;Thomas et al, 2012c;Thomas et al, 2012d) and methods for simulating the effects of ASR on structural components and structures (e.g., Bažant and Steffens 2000;Ulm et al, 2000;Bangert et al, 2004;Saouma and Perotti, 2006;Pesavento et al, 2012;Saouma, 2014) Of particular importance for the present study are investigations into the structural performance of flexural members, specifically those which studied the bond between ASR-affected concrete and deformed bar reinforcement.…”