Effect of sulfate on cement mortars containing Li2SO4, LiNO3, Li2CO3 and LiBr

Abstract

The purpose of this study is to explore the influence of sulfate on the fresh and hardened mortars containing lithium additives added with the aim to prevent alkali-silica reaction (ASR). Four different types of lithium additives (Li2SO4, LiNO3, Li2CO3 and LiBr) were added to the cement at the ratios of 0.5%, 1%, 1.5%, and 2% by mass in order to produce mortar specimens. Influence of sulfate on the specimens was then investigated. Used in order to keep the expansion under control, expansion characteristics and mechanical properties of Li2SO4, LiNO3, Li2CO3 and LiBr were defined. Initial setting and final setting tests were conducted on the cement pastes as per the provisions of TS EN 196-3 standard. Flexure and compressive tests were conducted in accordance with TS 196-1 in order to identify the mechanical properties of cement mortars. Prisms of 25 x 25 x 285 mm in dimension were produced as per ASTM C 1012-95 in order to measure the length change of the cement bars and results were analyzed. The results showed that Li2CO3 among the other lithium additives was effective in shortening the initial setting and final setting times, while LiNO3 and LiBr additives gave the best results in terms of strength and length change when tested for 1% additive ratio by mass. The highest length change was observed for the specimens with Li2CO3 cured both in water and sulfate solution. The lowest length change was observed for the specimens with LiNO3 cured both in water and sulfate solution. 1% LiNO3 additive gave the best results under sulfate effect for all test days. The length change of cement mortar with 1% LiNO3 additive was decreased by 53%, 25%, and 41% under sulfate effect for the 90th, 180th, and 360th day, respectively. It is believed that the use of LiNO3 and LiBr additives at the ratio of 1% by mass will reduce the unfavorable influence of sulfate. Li2CO3 and LiSO4 should not be used because they have negative effects on mechanical properties and length changes. (C) 2017 Elsevier Ltd. All rights reserved.