Influence of Calcium Nitrite on the Hydration of High Volume Slag Cement

Sakai, Etsuo; Ueda, Y.; Aikawa, Yoshihiro; Nito, Nobukazu

doi:10.14250/cement.71.62

Cited by 6 publications

(5 citation statements)

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“…At the curing age of 1 h, AFt (2θ deg 9.2°, 16.1°, 23.2°) and gypsum (2θ deg 11.6°, 20.7°) peaks are visible for all specimens. In the case of the CN4 and CN8 specimens, nitrite-AFm (2θ deg 11.0° to 11.2°, 23.5° to 23.7°) peaks are also visible along with AFt [16,17,18]. In this regard, Balonis confirmed the generation of AFt and nitrite-AFm via the ion exchange reactions of SO 4 − and 2NO 2 − of AFm through the reaction experiment involving synthetic AFm and calcium nitrite [11,14].…”

Section: Results and Analysismentioning

confidence: 99%

Investigation of the Relationship between Compressive Strength and Hydrate Formation Behavior of Low-Temperature Cured Cement upon Addition of a Nitrite-Based Accelerator

et al. 2019

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When concrete is used for construction in cold-temperature regions, cold-resistant accelerators based on calcium nitrite (Ca(NO2)2) and calcium nitrate (Ca(NO3)2) are added to prevent early freezing damage. Although cold-resistant accelerators increase the early compressive strength and prevent early freezing damage by promoting cement hydration, the strength enhancement effect owing to the formation of such hydrates has not been evaluated quantitatively thus far. This study covers various types of analysis to understand the relationship between cement hydrate formation behavior and strength development upon the addition of varying amounts of nitrite-based accelerator. We find that the early compressive strength is enhanced by the addition of nitrite-based accelerator via the promotion of the relative production of monosulfate and C-S-H in the early age. However, the development of compressive strength decreases with an increase in the curing age. Furthermore, we find that the promotion of hydration reactions at an early age with the addition of nitrite-based accelerator can affect the formation ratio of each hydrate at a late age. We believe our findings can significantly contribute to developments in concrete application and allied fields.

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Section: Results and Analysismentioning

confidence: 99%

Investigation of the Relationship between Compressive Strength and Hydrate Formation Behavior of Low-Temperature Cured Cement upon Addition of a Nitrite-Based Accelerator

et al. 2019

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“…Compared with N, the compressive strength tended to increase as the amount of antifreezing agent added increased. From the internal temperature history in Figure 5 , when adding the antifreezing agent instead of N, AFt and AFm (NO 2 − or NO 3 − ) are generated by the temperature rise caused by the dissolution of C 3 A at the first peak immediately after kneading due to the hydration reaction of OPC, and CH and C-S-H are generated by the temperature rise [ 22 , 23 , 24 , 29 ] caused by the dissolution of C 3 S and βC 2 S, which are considered to be the second peak. Additionally, it is presumed that Al 2 O 3 contained in the expansion material (3CaO, 3Al 2 O 3 , and CaSO 4 ) used in this study was also hydrated by the addition of an antifreezing agent, and the AFt production rate increased [ 14 , 22 , 23 , 24 , 26 , 30 ].…”

Section: Resultsmentioning

confidence: 99%

“…However, as the amount of antifreezing agent added increases, the potential for chemical shrinkage of the cement matrix increases. Therefore, reports state that there is a growing concern about the occurrence of shrinkage cracks [ 24 ]. According to the “Basics of Cement-based Repair and Reinforcement Materials” of the Japan Cement Association, repair work is conducted with the objective of “restoring the mechanical performance of safety or usability to the extent that the structure possessed at the time of construction” [ 4 ].…”

Section: Introductionmentioning

confidence: 99%

Effects of Nitrite/Nitrate-Based Accelerators on Strength and Deformation of Cementitious Repair Materials under Low-Temperature Conditions

et al. 2023

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This study aimed to develop a cementitious repair material that can be constructed in cold weather conditions. The addition of nitrite/nitrate-based antifreezing agents has been shown to increase the initial strength of cementitious repair materials in cold weather. However, increasing the amount of these agents may lead to an increase in deformation behavior and shrinkage cracking. In this study, the effects of different types and amounts of nitrite/nitrate-based antifreezing agents on the strength development and deformation behavior of cementitious repair materials under low-temperature conditions were evaluated. As a result, it was found that the addition of a large amount of calcium nitrite can promote hydration and improve the initial strength of the repair material, irrespective of the type of antifreezing agent. However, this also leads to an increase in shrinkage and the concern of shrinkage cracking. Therefore, a repair material that is repairable in winter was developed by balancing the initial strength and deformation behavior through the appropriate selection of antifreezing agents. The developed repair material can be used to repair structures in cold weather conditions, which is of great significance for the construction industry in Hokkaido, Japan.

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“…They would also include nitrite-Aft and nitrate-Aft resulting from nitrite ions (NO 2 − ) and nitrate ions (NO 3 − ). The latter inclusion is caused by CN occupying the areas between the layers of the cement matrix in place of sulfate (SO 4 2− ), nitrite-AFm(Ca 4 Al 2 (NO 2 ) 2 (OH) 12 ·4H 2 O), and nitrate-AFm(Ca 4 Al 2 (NO 3 ) 2 (OH) 12 ·4H 2 O) [13,14,15]. According to previous research, the peak of the formation of nitrite-AFm differs slightly depending on the dryness level, but it typically appears at around 11.04° to 11.23° [14,15].…”

Section: Resultsmentioning

confidence: 99%

Physicochemical Study on the Strength Development Characteristics of Cold Weather Concrete Using a Nitrite–Nitrate Based Accelerator

et al. 2019

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There has recently been an increased use of anti-freezing agents that are primarily composed of salt- and alkali-free calcium nitrite (Ca(NO2)2) and calcium nitrate (Ca(NO3)2) to promote the hydration reaction of concrete in cold weather concreting. Nitrite–nitrate based accelerators accelerate the hydration of C3A and C3S in cement more quickly when their quantities are increased, thereby boosting the concrete’s early strength and effectively preventing early frost damage. However, the connection between the hydrate formation behavior and the strength development characteristic over time has yet to be clearly identified. Therefore, in this study, a wide range of physicochemical reviews were carried out to clarify the relationship between the hydrate formation behavior and the strength development characteristics, both at an early age and at later ages, which results from the addition of nitrite–nitrate based accelerators to concrete in varying amounts. These accelerators also act as anti-freezing agents. The results show that an increased quantity of nitrite–nitrate based accelerators caused an increase in the early strength of the concrete. This was due to the formation of nitrite and nitrate hydrates in large amounts, in addition to ettringite containing SO42, which is generated during the hydration reaction of normal Portland cement at an early age. On the other hand, at later ages, there was a rise in nitrite and nitrate hydrates with needle crystal structures exhibiting brittle fracture behavior. A decrease in C–S–H gel and Ca(OH)2 hydrates, deemed to have caused a decline in strength on Day 3 and thereafter, was also observed.

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Influence of Calcium Nitrite on the Hydration of High Volume Slag Cement

Cited by 6 publications

References 0 publications

Investigation of the Relationship between Compressive Strength and Hydrate Formation Behavior of Low-Temperature Cured Cement upon Addition of a Nitrite-Based Accelerator

Investigation of the Relationship between Compressive Strength and Hydrate Formation Behavior of Low-Temperature Cured Cement upon Addition of a Nitrite-Based Accelerator

Effects of Nitrite/Nitrate-Based Accelerators on Strength and Deformation of Cementitious Repair Materials under Low-Temperature Conditions

Physicochemical Study on the Strength Development Characteristics of Cold Weather Concrete Using a Nitrite–Nitrate Based Accelerator

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