Mitigation of Alkali-Silica Reactivity in New Mexico

Abstract

The research experiments reported were conducted at the Materials Research Center, ATR Institute, University of New Mexico, at the request of the Research Bureau, New Mexico State Highway and Transportation Department (NMSHTD). The purpose was to determine the amount of additives required for mitigation of alkali-silica reactivity (ASR) based on screening tests. Fly ash additives routinely used in New Mexico and a new material—lithium nitrate—proposed by the Strategic Highway Research Program were evaluated. The work was motivated by continuous problems with early deterioration of concrete structures due to alkali-silica reactivity. The work was based on the use of acceptance criteria established by NMSHTD for expansion due to ASR, as measured in screening tests. Recommendations resulting from this research do not consider all aspects of the behavior of concrete mixtures and structures. The additive recommendations are based on reduction in mortar-bar expansion during accelerated tests.

Alkali-Silica Reaction Mitigation: State-of-the-Art

“…see PCA IS413, 1997). Similar significant reductions in expansion were found by Barringer (2000) and McKeen et al (1998) using 24% to 27% Class F fly ash cement replacement and reactive New Mexico aggregates. Several other reports confirm the effectiveness of Class F fly ash in ASR mitigation at replacement levels usually between 15% and 45% (ACI 232.2R, 1996;Langley, 2000;Rogers et al, 2000;Fournier, 1999), although levels below 25% may not be effective unless low-lime fly ash is used with 10% or less CaO (Malhotra et al, 1994;Rogers et al, 2000;Glauz et al, 1996).…”

“…A recent study conducted for the NMSHTD (McKeen et al, 1998) concluded that 25% to 27% Class F fly ash replacement was sufficient for most of the reactive aggregates studied. Class C fly ash and blends of Class F and Class C did not provide enough expansion reduction.…”

“…Lithium salts can be added to the concrete mix to counter the reactivity of the aggregates (Durand, 2000;Lane, 2000b;Stokes et al, 2000a;Thomas et al, 2000;Thompson, 2000;McKeen et al, 1998). Lithium can reduce the concrete expansion but the amount of lithium compound needed can be high and varies depending on the aggregate (Durand, 2000;.…”

Mechanisms of Alkali-Silica Reaction in Alkali-Activated High-Volume Fly Ash Mortars

“…The possible mechanisms for the low evidence of ASR degradation in alkali-activated fly ash concrete may be attributed to the low calcium level in the system Williamson and Juenger 2016). In fact, fly ash has been well acknowledged for effective ASR mitigation in OPC concrete (Hobbs 1988;Lane and Ozyildirim 1995;McKeen et al 2000;Pepper and Mather 1959;Rajabipour et al 2015). The fly ash dosage necessary to mitigate ASR in OPC system ranges approximately from about 15% to 40%, depending on the fly ash composition and aggregate reactivity (Malvar and Lenke 2006;Wright et al 2014).…”

Experimental study and empirical modeling of lithium nitrate for alkali-silica reactivity

“…Among the lithium admixtures utilized in concrete, lithium nitrate is the most commonly used, because it is safe, environmentally benign, and easy to handle [30,46,1,12]. Lithium nitrate salt does not increase the pH of pore solution [24,44,12,32,13], and it has no significant effect on concrete properties [24,31,5].…”