Autoclave products of two kinds of typical alkali reactive rocks in alkaline solutions

Surface alteration of typical rocks with alkali-silica reactivity and alkali-carbonate reactivity, i.e. Spratt(SL) limestone and Pittsburg dolomitic(PL) limestone, were studied by XRD and SEM/EDS after autoclaved in 1.8 mol/L KOH, NaOH and LiOH solutions at 150°C for 150 h. The results indicate that: (1) Both rocks suffer the strongest attack in NaOH solution and the weakest attack in LiOH solution. (2) For the products of both rocks autoclaved in different alkali media, the crystalline degree, morphology and distribution are quite different. Sheet-like tobermorite and poor crystalline or amorphous Na-Ca-Si gel products are mainly formed in NaOH solution. Well-formed crystalline products are formed on rock surfaces in KOH and LiOH solutions. (3) In addition to dedolomitization in PL limestone in KOH, NaOH and LiOH solutions, cryptocrystalline quartz in the rock is also involved in reaction and forms typical alkali-silica product in NaOH and KOH solutions, but forms lithium silicate (Li₂SiO₃) in LiOH solution. (4) In addition to massive alkali-silica product formed in SL limestone autoclaved in different alkaline solutions, a small amount of dolomite existing in the limestone can also simultaneously dedolomitize in alkali solution. (5) ASR and ACR might coexist in some limestone aggregates, although the contributions from ASR and ACR might be different.