Cold weather concreting admixtures

Nmai, Charles K.

doi:10.1016/s0958-9465(97)00063-2

Cited by 71 publications

(32 citation statements)

References 3 publications

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“…During cold-weather concreting, to prevent the initial frost damage, it is necessary to control the temperature until the concrete strength reaches 5 N/mm 2 of the heat curing, using a temporary enclosure and heater [ 1 , 2 , 3 , 4 , 5 , 6 ]. On the other hand, under a very low temperature or worse conditions—such as a steep incline, narrow space, or windstorm—anti-freezing agents are used to prevent the initial frost damage and secure the initial strength by sheet curing.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Mechanical and Shrinkage Behavior of Lowered Temperatures Cementitious Mortars Mixed with Nitrite–Nitrate Based Accelerator

et al. 2020

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Recently, calcium nitrite (Ca(NO2)2) and calcium nitrate (Ca(NO3)2) have been increasingly used as the main components of salt- and alkali-free anti-freezing agents, for promoting concrete hydration in cold-weather concreting. With an increase in the amount of nitrite-based accelerator, the hydration of C3A, C3S, and βC2S in the cement is accelerated, thereby improving its early strength and effectively preventing the initial frost damage. Meanwhile, with an increase in the amount of nitrite-based accelerator, the expansion and shrinkage of the concrete—and, therefore, the crack occurrence—are expected to increase. In this study, various experiments were conducted on shrinkage, crack initiation, and the development of mortar containing a considerable amount of a nitrite-based accelerator. The result confirmed that, as the amount of nitrite-based accelerator was increased, the shrinkage was increased, and cracking in early age was more likely to occur, compared to the cases without the addition of this accelerator.

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Section: Introductionmentioning

confidence: 99%

Evaluation of Mechanical and Shrinkage Behavior of Lowered Temperatures Cementitious Mortars Mixed with Nitrite–Nitrate Based Accelerator

et al. 2020

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“…Calcium Chloride 1951Chloride , 1952Chloride , 1958Chloride , 1970Chloride , 1976Chloride , 1990Chloride , 1995Chloride , 1998Chloride , 2007Chloride , 2008Chloride , 2013 Sodium Chloride 1976Chloride , 1990Chloride , 1998 Calcium Nitrate 1991Nitrate , 1999Nitrate , 2003Nitrate , 2013Nitrate , 2015Nitrate , 2016Nitrate , 2018 Calcium Nitrite 1989Nitrite , 1991Nitrite , 1995Nitrite , 1996Nitrite , 1998Nitrite , 2007Nitrite , 2013] Magnesium chloride 2008 [32] Less Therefore, most concrete guidelines recommend the application of special preventive measures when the air temperature drops below 5 • C or when it is colder than 10 • C for at least 12 h during the day [7,10,12,13]. Typically, these steps include heating the mixing water or aggregates, covering with isolative blankets or adding heating systems to the formworks [14].…”

Section: Admixture Years Referencementioning

confidence: 99%

“…Another possibility is the optimization of the concrete mix by the rapid hardening of Portland cement and various types of chemical admixtures, which has the potential to develop higher hydration heats and lower the freezing point of water [1,15,16]. Apparently, this procedure simplifies concrete production in moderately cold climatic conditions without the need of any internal or external heating, isolative covers or tents [7,9,[17][18][19]. However, to prevent early permanent damage, the concrete should reach a critical compressive strength of 3.5 MPa before or during exposure to frost conditions [13,20].…”

Section: Admixture Years Referencementioning

confidence: 99%

“…Furthermore, the combinations of calcium chloride and sodium chloride (3% + 7%), (10% + 5%) and (15% + 7%) enabled concrete works at −10 • C by developing a compressive strength of 32 MPa, 17 MPa, and 16 MPa, respectively, after 28 days. The results indicate that the application of higher dosages than the optimum percentage of CaCl 2 led to a decrease in the compressive strength due to combined effects of expansive crack formation and increased permeability [1,7,28]. Similarly, concentrated magnesium chloride or calcium chloride caused the formation of expansive oxychloride compounds and subsequent cracking of the binder matrix with a reduction in the compressive strength by 30-50% [32].…”

Section: Opc-based Concretesmentioning

confidence: 99%

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A Review of the Mechanical Properties and Durability of Ecological Concretes in a Cold Climate in Comparison to Standard Ordinary Portland Cement-Based Concrete

et al. 2020

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Most of the currently used concretes are based on ordinary Portland cement (OPC) which results in a high carbon dioxide footprint and thus has a negative environmental impact. Replacing OPCs, partially or fully by ecological binders, i.e., supplementary cementitious materials (SCMs) or alternative binders, aims to decrease the carbon dioxide footprint. Both solutions introduced a number of technological problems, including their performance, when exposed to low, subfreezing temperatures during casting operations and the hardening stage. This review indicates that the present knowledge enables the production of OPC-based concretes at temperatures as low as −10 °C, without the need of any additional measures such as, e.g., heating. Conversely, composite cements containing SCMs or alkali-activated binders (AACs) showed mixed performances, ranging from inferior to superior in comparison with OPC. Most concretes based on composite cements require pre/post heat curing or only a short exposure to sub-zero temperatures. At the same time, certain alkali-activated systems performed very well even at −20 °C without the need for additional curing. Chemical admixtures developed for OPC do not always perform well in other binder systems. This review showed that there is only a limited knowledge on how chemical admixtures work in ecological concretes at low temperatures and how to accelerate the hydration rate of composite cements containing high amounts of SCMs or AACs, when these are cured at subfreezing temperatures.

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“…Muitas vezes, nessas condições, a falta de cuidados pode causar danos no ciclo operacional das obras, bem como baixa resistência à compressão, baixo módulo de elasticidade, manifestações patológicas irreversíveis, devido aos problemas envolvendo a resistência inicial da matriz [15,40,41]. No entanto, procedimentos podem e devem ser adotados para mitigar os efeitos físicos no início e fim de pega do cimento [42].…”

Section: Introductionunclassified

Impacto nas propriedades mecânicas do concreto curado sob baixas temperaturas

et al. 2019

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RESUMO O processo de cura das matrizes cimentícias é muito importante na determinação das suas propriedades no estado endurecido. Nessas circunstâncias, o concreto pode sofrer sérias avarias quando exposto às severas variações térmicas. As baixas temperaturas de cura em que as matrizes cimentícias são expostas podem influenciar nas propriedades no estado endurecido, principalmente nas idades iniciais, prejudicando os processos de desfôrma e escoramento. Locais de frio intenso devem seguir procedimentos específicos de dosagem e aplicação de uma matriz cimentícia. Sendo assim, essa pesquisa objetivou analisar a influência da temperatura de cura no comportamento mecânico e físico de concretos em diversas temperaturas de cura, tanto nas idades inicias como nas mais avançadas. Observou-se que a diminuição na temperatura de cura proporcionou aumento de resistência em até 26% na idade de 28 dias nos concretos analisados, apesar de que apresentaram desenvolvimento lento das propriedades mecânicas nos 7 dias iniciais. Concretos com maior consumo de cimento apresentaram melhor desempenho nas idades inicias quando submetidos às temperaturas menores que 3 oC. Porém, percebeu-se que a cura em baixas temperaturas é capaz de proporcionar misturas mais íntegras em idades avançadas, visto que atingiram maior velocidade de propagação onda ultrassônica e resistência, pelo fato de ocorrer a hidratação residual do cimento.

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Cold weather concreting admixtures

Cited by 71 publications

References 3 publications

Evaluation of Mechanical and Shrinkage Behavior of Lowered Temperatures Cementitious Mortars Mixed with Nitrite–Nitrate Based Accelerator

Evaluation of Mechanical and Shrinkage Behavior of Lowered Temperatures Cementitious Mortars Mixed with Nitrite–Nitrate Based Accelerator

A Review of the Mechanical Properties and Durability of Ecological Concretes in a Cold Climate in Comparison to Standard Ordinary Portland Cement-Based Concrete

Impacto nas propriedades mecânicas do concreto curado sob baixas temperaturas

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