Applicability of the Accelerated Mortar Bar Test for Alkali-Silica Reactivity of Recycled Concrete Aggregates

Abstract

Using recycled concrete aggregate (RCA) as a replacement for natural aggregate in new concrete is a promising way to increase the overall sustainability of new concrete. This has been hindered, however, by a general perception that RCA is a sub-standard material because of the lack of technical guidance, specifically related to long-term durability, on incorporating RCA into new concrete. The goal of this research was to determine whether current testing methods (namely, ASTM C1260) for assessing natural aggregate susceptibility to alkali-silica reactivity could be used to assess the potential reactivity of concrete incorporating RCA. Seven different RCA sources were investigated. It was determined that ASTM C1260 was effective in detecting reactivity, but expansion varied based on RCA processing. Depending on the aggregate type and the extent of processing, up to a 100 % increase in expansion was observed. Replicate testing was performed at four university laboratories to evaluate the repeatability and consistency of results. The authors recommend modifications to the mixing and aggregate preparation procedures when testing the reactivity of RCA using ASTM C1260.

A Review on Alkali-Silica Reaction Evolution in Recycled Aggregate Concrete

“…Adams et al [ 68 ] considered that aggregate washing, used in NA AMBT and CPT tests, can reduce adhered cement paste in the RA, promote the hydration of anhydrous cement particles in RA, and/or leach calcium or alkalis from aggregates and adhered paste. The authors proposed limited washing at time intervals for each of the size fractions.…”

“…Adams et al [ 68 ] also modified the mixing process because of the water absorption of RA. First they immersed the RA in water for 30 min and reached 85% of RA saturation.…”

Durability Assessment of Recycled Concrete Aggregates for Use in New Concrete Phase II

“…The gradation of aggregate required for use in the ASTM C1567 test may be too small for this test method to work. Previous work has shown that the amount of crushing performed on an RCA can affect its reactivity (Shehata, Christidis et al, 2010;Adams, Ideker et al, 2012). This was attributed to the amount of adhered mortar on the aggregate (Shehata, Christidis et al, 2010;Adams, Ideker et al, 2012), which is reduced as the level of crushing is increased (Nagataki, Gokce et al, 2004).…”

“…Research into the mechanical properties of concrete containing RCA has shown that, by limiting the amount of RCA used as replacement material in a given mixture and through proper design of a concrete mixture, similar or better concrete than that which is made with natural aggregates can be produced (SagoeCrentsil, Brown et al, 2001;Fathifazl, Abbas et al, 2009;Kou, Poon et al, 2011). RCA that is produced from parent concrete that has shown deterioration due to ASR has shown to be reactive when incorporated into new concrete (Gress, 2000;Shayan and Xu, 2003;Scott and Gress, 2004;Li and Gress, 2006;Gress, Snyder et al, 2009;Shehata, Christidis et al, 2010;Adams, Ideker et al, 2012). ASR is one of the most prevalent causes of premature concrete deterioration.…”

“…It has also been determined that the ASTM C1260/C1567 AMBT is an effective way to detect alkali-silica reactivity (ASR) in RCA (Shehata, Christidis et al, 2010;Adams, Ideker et al, 2012). Previous work has shown, however, that SCM are not as effective at mitigating ASR in concrete made with RCA compared to concrete made with natural aggregates (Shehata, Christidis et al, 2010).…”