Abstract
As the size of modern infrastructure increases, novelties related to mass concrete mixtures including supplementary cementitious materials (SCMs) become critical. The effects of binary and ternary cement replacement mixtures including metakaolin, silica fume, ground calcium carbonate, granulated blast furnace slag, and fly ash on the rate and amount of heat generated in concrete mixtures are investigated. Twenty three binary and ternary mixtures with a water-to-cementitious binder ratio of 0.43 are evaluated. Between 15% and 45% cement replacement by weight is considered. Results indicate that binary mixtures containing metakaolin or silica fume offer no advantage in reducing the amount of heat but increase compressive strength by 20%. On contrary, ternary mixtures, including two pozzolanic materials, provide 15% reduction in the amount of heat evolution without compromising strength. This reduction is observed regardless of alumina (Al) or silica (Si) content in pozzolanic materials when 45% cement is replaced with a combination of slag and metakaolin, or slag and silica fume. Furthermore, the effect of increased calcium (Ca) content is investigated. It is concluded that ternary mixtures with decreased Ca/(Al+Si) ratio reduce internal temperature in mass concrete structures and are less likely to be exposed to the threshold temperature for delayed ettringite formation.
Highlights
It is shown that GCC15 is more effective in reducing the heat of hydration in binary mixtures compared to MK15 and SF15 mixtures
The effects of binary and ternary mixtures, including metakaolin, silica fume, ground calcium carbonate (GCC), and slag, on the heat of hydration are investigated in this study
Binary replacement mixtures containing a pozzolanic material such as metakaolin (15%) or silica fume (15%) offer no significant advantage in reducing the heat of hydration, the compressive strength increases by more than 20% on 28th day
Summary
The ettringite formed during the initial stages of hydration is decomposed in the event of elevated temperatures and may reform after the paste is already hardened It usually occurs when the temperature exceeds 70 ◦C and causes expansion and cracking in concrete due to its large volume [2]. An internal temperature rise in concrete structures can lead to DEF, undesirable thermal stresses, cracking, deleterious chemical reactions, or reduction in long-term strength [3]. Active cooling such as pre-cooling or post-cooling using pipe cooling systems [4] provides additional benefits in conjunction with the material development in controlling the temperature in mass concrete structures
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