The effects of urea on strength gaining of fresh concrete under the cold weather conditions

Demirboğa, Ramazan; Karagöl, Fatma; Polat, Rıza; Kaygusuz, Mehmet Akif

doi:10.1016/j.conbuildmat.2014.04.008

Cited by 84 publications

(25 citation statements)

References 8 publications

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“…are experienced with low temperature, especially negative temperature (<0 ∘ C) during initial hydration stage, cement hydration will be greatly affected [9][10][11]. In this case, the hydrated products, phase conversion, for example, from ettringite (AFt) to monosulfate (AFm), and pores solution will be affected by low temperatures [5,12].…”

Section: Introductionmentioning

confidence: 99%

Portland Cement Hydration Behavior at Low Temperatures: Views from Calculation and Experimental Study

Liu

Jiao

Sha

et al. 2017

Advances in Materials Science and Engineering

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Environmental condition affects the property of construction materials. This study gives an initial understanding of Portland cement hydration under low temperatures from the views of laboratory experiments (including electrical resistivity, degree of hydration (DoH), and maturity) as well as thermodynamic calculation. The hydrates of Portland cement at the given period were detected with X-ray diffraction (XRD), and their microstructure was observed by scanning electron microscope (SEM). Experiment result (i.e., DoH and electrical resistivity) indicated that the hydration of Portland cement was delayed by low temperature without hydration stopping at −5 ∘ C. Based on a basic kinetics model, the thermodynamic calculation predicted that the final hydrate differs in dependence on environmental temperatures. The mechanical behavior trend of Portland cement paste affected by low temperatures potentially is linked to the appearing of aluminate compounds and reduction of portlandite.

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Section: Introductionmentioning

confidence: 99%

Portland Cement Hydration Behavior at Low Temperatures: Views from Calculation and Experimental Study

Liu

Jiao

Sha

et al. 2017

Advances in Materials Science and Engineering

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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]. 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].…”

Section: Admixture Years Referencementioning

confidence: 99%

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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“…Sodium nitrite was added to make it possible for binding material hydrating at negative temperature [22,23]. Compressive and flexural strength of cement mortar were tested and the content of Ca(OH) 2 in hydration product was measured by TG-DSC and heat of hydration and the hydrated rate were measured.…”

Section: Introductionmentioning

confidence: 99%

Hydration of the silica fume-Portland cement binary system at lower temperature

Liu

Yao

Ouyang

et al. 2015

Construction and Building Materials

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The effects of urea on strength gaining of fresh concrete under the cold weather conditions

Cited by 84 publications

References 8 publications

Portland Cement Hydration Behavior at Low Temperatures: Views from Calculation and Experimental Study

Portland Cement Hydration Behavior at Low Temperatures: Views from Calculation and Experimental Study

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

Hydration of the silica fume-Portland cement binary system at lower temperature

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