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Effects of sodium nitrate and OPC-GGBS concrete mix composition on phase transition of pore water at subzero temperatures
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.ORCID iD: 0000-0001-5136-9412
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering. Skanska Teknik AB, Skanska Sverige AB, 40518 Göteborg, Sweden.
Fiber and Particle Engineering Research Unit, Faculty of Technology, University of Oulu, P.O. Box 4300, 90014 Oulu, Finland.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.ORCID iD: 0000-0001-6287-2240
2022 (English)In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 327, article id 126901Article in journal (Refereed) Published
Abstract [en]

Lowering the freezing temperature of the mixing water is crucial for concrete works at subzero temperatures. In this study, formation of ice was examined for various pastes and concretes of OPC-GGBS based, while exposed to a constant temperature of −15 °C. Sodium nitrate antifreeze admixture was added as 0, 6, 10, 15, 20, 25, 30 wt% by the total binder amount. The ice formation and its effects on the binder matrix microstructure was studied using differential scanning calorimetry (DSC), ultrasonic pulse velocity (UPV) and Scanning Electron Microscopy – Energy Dispersive Spectrometry (SEM-EDS). Several curing procedures were applied to samples before commencing tests. Results showed that, addition of 25 wt% of the sodium nitrate caused the most extensive delay of the ice growth. Mixes containing less admixture showed an increasing amount of the forming ice which in some cases lead to the development of the false strength. The hydration rate has been the highest for the mix with 25 wt% of the sodium nitrate and tended to be limited at lower additions. The porosity of the hydrated binder matrix tended to be lower for mixes characterized by a lower amount of the forming ice. In general, application of above freezing temperature resulted in resuming of the hydration process that led to densification of the microstructure and strength increase. This trend was more pronounced for mixes having lower amounts of the formed ice.

Place, publisher, year, edition, pages
Elsevier, 2022. Vol. 327, article id 126901
Keywords [en]
Antifreeze admixture (AF), Compressive strength, Differential scanning calorimetry (DSC), Ground Granulated Blast-Furnace Slag (GGBS), Ordinary Portland Cement (OPC), Porosity, SEM-EDS, Temperature, UPV
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
URN: urn:nbn:se:ltu:diva-89435DOI: 10.1016/j.conbuildmat.2022.126901ISI: 000770575300003Scopus ID: 2-s2.0-85125521821OAI: oai:DiVA.org:ltu-89435DiVA, id: diva2:1641756
Projects
ARCTIC-ecocrete
Funder
Interreg NordNorrbotten County Council
Note

Validerad;2022;Nivå 2;2022-03-03 (sofila)

Available from: 2022-03-03 Created: 2022-03-03 Last updated: 2024-04-16Bibliographically approved
In thesis
1. Low Portland cement content concretes at freezing and subfreezing temperatures
Open this publication in new window or tab >>Low Portland cement content concretes at freezing and subfreezing temperatures
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Concrete is the most used building material. With the increasing growth of industries and urbanization globally; the demand for concrete is increasing significantly. Ordinary Portland Cement (PC) is the binder used to produce typical concrete. Unfortunately, for every ton of manufactured cement about 0.61-ton CO2 is emitted into the earth’s atmosphere. As a result, several solutions have been implemented to reduce the usage of this material in the production of concrete. This includes its partial or full replacement with supplementary cementitious materials (SCMs) or alternative binders. Some of these combinations could be problematic to be used in cold climates due to a lower developed hydration heat, slower setting, or worse frost durability.

In winter the immediate exposure of fresh concrete to freezing temperatures results in pore ice formation and could delay or completely stop the hydration process. This is commonly prevented by using an additional heating system installed in concrete or the formwork. Unfortunately, usually, it adds complexity, increases the price, and depending on the used power source, could increase the CO2 footprint. Another potentially simpler and more sustainable solution is to modify the concrete itself by adjusting the mix design, by using certain chemical admixtures and special cementitious binders.

This research aimed to better understand how partial replacement of Portland cement with GGBFS and/or CSA cement affects the properties of concretes exposed to freezing and subfreezing temperatures in a fresh state and at a young age. The secondary aim was to evaluate a possible application of UHPC to protect new and existing concrete structures from frost damage.

The research included a literature review of methods used to produce concrete structures at zero and subzero temperatures. A special emphasis was on the application of chemical and mineral admixtures that could eliminate the need to use heat treatments. The output of this analysis enabled to narrow the scope of the research.

The experimental program focused on the optimization, testing, and analysis of mixes containing various combinations of chemical admixtures, CSA cement, and Portland cement. Tests included exposure to freezing and subfreezing temperatures. The aim was to lower the freezing point of water and promote faster hydration and strength gain. Fresh and hardened properties were determined for all produced concretes. The phase transition of pore water into ice, the ice-forming temperature, and their effects on the binder matrix were studied using differential scanning calorimetry (DSC). Other tests included ultrasonic pulse velocity measurements (UPV), bond test (pull-off), scanning electron microscope (SEM) for analysis of the microstructure and phase composition, frost durability evaluation with Båras test, semi-adiabatic calorimetry to study hydration processes, compressive strength measurements.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2024
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Building Technologies Composite Science and Engineering
Research subject
Building Materials
Identifiers
urn:nbn:se:ltu:diva-105133 (URN)978-91-8048-540-1 (ISBN)978-91-8048-541-8 (ISBN)
Public defence
2024-06-18, F1031, Luleå University of Technology, Luleå, 10:00 (English)
Opponent
Supervisors
Funder
InterregVinnovaSvenska Byggbranschens Utvecklingsfond (SBUF)Swedish Transport AdministrationSwedish Energy Agency
Available from: 2024-04-17 Created: 2024-04-16 Last updated: 2024-05-28Bibliographically approved

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Kothari, AnkitHedlund, HansCwirzen, Andrzej

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