Quantitative assessment of alkali silica reaction potential of quartz-rich aggregates: comparison of chemical test and accelerated mortar bar test improved by SEM-PIA

Abstract

The alkali silica reaction (ASR), which originates in highly alkaline conditions in concrete where reactive forms of silica are available, causes serious damage to concrete structures. The ASR potential of various quartz-rich aggregates (pegmatite quartz, quartzite, quartz meta-greywacke, and chert) was quantified using accelerated mortar bar test (AMBT), chemical test (CT), and scanning electron microscopy combined with petrographic image analysis (SEM-PIA). Only two samples (quartz meta-greywacke, and pegmatite quartz) were judged as deleterious according to the CT; the other aggregates were classified as innocuous. AMBT gave different results. Quartz meta-greywacke, chert, and quartzite exceeded the 0.100 % expansion limit after 14 days of testing. Pegmatite quartz indicated a lower value. The results of SEM-PIA confirmed the results of AMBT, indicating the most extensive ASR in those AMBs containing chert and quartz meta-greywacke. Parts of aggregates were leached out and massive deposits of alkali-silica gels were found filling air voids, microcracks, and the aggregate/cement paste interface. The medium or low degree of ASR was confirmed in AMBs containing quartzite or pegmatite quartz, respectively. ASR accentuated pre-existing microcracks and formed new dissolution gaps. In contrast, no correlation was found with the results of CT, which under-evaluated the ASR potential of chert and quartzite and over evaluated the ASR potential of pegmatite quartz. The variable ASR potential of the investigated aggregates was explained by the significant content of poorly crystalline matrix (in chert and quartz meta-greywacke), and by the presence of strained quartz typical with undulose extinction and the origin of quartz subgrains (in quartzite and pegmatite quartz).

Oligomictic alluvial aggregates: petro-mineralogical and geochemical evaluation of sandy gravel formations on the middle course of the Danube (Hungary)

“…8) are micro-cryptocrystalline quartz, strained (deformed, stretched) quartz crystals with strain lamellae, subgraining and/or sutured/interlobate boundaries indicating bulging recrystallization (BLG), subgrain rotation recrystallization (SGR) or grain boundary migration (GBM) (Stipp et al 2002;Krutilová and Přikryl 2017). According to Passchier and Trouw (2005), these microstructural characteristics indicate deformation and recrystallization under middle temperature regimes and (Wigum 1995;Wenk et al 2008;Šachlová et al 2017). In addition, micro-cryptocrystalline quartz or chalcedony/ moganite of siliceous limestone and radiolarite (Fig.…”

“…sandstone-siltstonegreywacke) also requires attention (e.g. Katayama 2004Katayama , 2010aMarinoni et al 2012;Šachlová et al 2017). The potentially ASR reactive forms of silica in subordinate amount (>6%) of volcanic rock fragments are glassy or microcrystalline groundmass (Fig.…”

Application of Image Analysis to Identify Quartz Grains in Heavy Aggregates Susceptible to ASR in Radiation Shielding Concrete

“…Less reactive forms of silica can eventually cause concrete deterioration after 15 or even 25 years after construction. So, the primary factors influencing alkali-silica reactions include the aggregate reactivity, namely the amount and grain size of reactive SiO 2 [ 18 ]…”