Abstract
The effectiveness of lithium nitrate as a chemical additive which reduces the negative effects of alkali aggregate reaction was subject to research by scientists in many centres around the world. The literature data on the impact of lithium nitrate on the physical and mechanical properties of cements are rare. Without a precise definition of the impact of lithium nitrate on the cement properties, it is extremely hard to determine its real advantages in practical usage. In this paper, studies were undertaken to assess the impact of LiNO3 on the properties of pastes and mortars with Portland cement. The rate of hydration of the cement with lithium additive was examined by isothermal calorimetry, measurements of setting time and phase composition of cement pastes in the initial stages of hydration. The influence of the admixture on the compressive strength development of mortars after 2, 7 and 28 days of hardening was also researched. Results indicate that lithium nitrate accelerates the early hydration of Portland cement, affecting the precipitation of hydration products. The compressive strength of mortars with lithium admixture decrease after 28 days, although 2 an 7-day strength were greater than the control mortars.
Highlights
The problem of the alkali aggregate reaction was first noticed in the United States of America in the 1940s, when Stanton provided evidence for the existence of internal corrosion processes, leading to concrete expansion and cracking [1]
In 1957 Swenson demonstrated the occurrence of a reaction between alkali and carbonate aggregate, indicating that it is a different type of a reaction between aggregate and sodium and potassium hydroxides than the one discovered by Stanton [2]
As a result of the research programmes conducted later on by the U.S Department of Transportation, Federal Highway Administration Research and Technology, it has been proven that lithium nitrate was used as a compound efficiently limiting internal corrosion of the concrete in airport pavements in Atlanta as well as bridges and highways among others in Mexico, Texas and Pennsylvania [9]
Summary
The problem of the alkali aggregate reaction was first noticed in the United States of America in the 1940s, when Stanton provided evidence for the existence of internal corrosion processes, leading to concrete expansion and cracking [1]. The negative effects of alkali-silica reaction in concrete can be reduce by some supplementary cementing materials which leads to reduction the amount of alkalis available for reaction with aggregate [4,5,6,7].
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