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Early Age Performance of OPC-GGBFS-Concretes Containing Belite-CSA Cement Cured at Sub-Zero 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.ORCID iD: 0000-0003-0459-7433
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.ORCID iD: 0000-0001-6287-2240
2023 (English)In: Buildings, E-ISSN 2075-5309, Vol. 13, no 9, article id 2374Article in journal (Refereed) Published
Abstract [en]

This study determined how replacing sodium nitrate-based antifreeze admixture (AF) with belite-calcium sulfoaluminate (belite-CSA) cement affects the early age properties of ecological concretes based on ordinary Portland cement (OPC) and ground granulated blast-furnace slag (GGBFS). Concrete specimens were cured at −15 °C and treated in various ways before testing, i.e., no treatment, stored at 20 °C for 12 and 24 h. Generally, the addition of belite-CSA cement shortened the setting time due to the rapid formation of ettringite. The incorporation of 25 wt% of antifreeze admixture (AF) to the OPC-GGBFS concrete cured at −15 °C partially inhibited ice formation and enabled the continuation of hydration processes. This trend was observed for all samples, independent of the applied AF after freezing curing. On the contrary, the addition of 20 wt% of CSA failed to inhibit the ice formation and increased the risk of frost damage for concretes despite the treatment after freezing. These concrete specimens had lower hydration, lower strength, and a more porous binder matrix. The microstructure of the binder matrix was significantly affected by the amount of CSA and extreme negative curing, followed by no notable recovery post-curing at room temperature. Therefore, pre-curing at room temperature for at least 6 h has the potential to avoid frost damage. Concrete containing 25 wt% AF combined with 12 h and 24 h of curing at 20 °C after removal from freezing and prior to testing could enhance the compressive strengths of all concretes. The renewed hydration was indicated as the main influencing factor.

Place, publisher, year, edition, pages
MDPI, 2023. Vol. 13, no 9, article id 2374
Keywords [en]
ordinary Portland cement (OPC), calcium sulfoaluminate cement (CSA), ground granulated blast-furnace slag (GGBFS), hydration, microstructure—SEM, antifreeze admixture (AF), differential scanning calorimetry (DSC), negative temperature, compressive strength, porosity, UPV
National Category
Building Technologies Other Materials Engineering
Research subject
Building Materials
Identifiers
URN: urn:nbn:se:ltu:diva-101403DOI: 10.3390/buildings13092374Scopus ID: 2-s2.0-85172798992OAI: oai:DiVA.org:ltu-101403DiVA, id: diva2:1799262
Funder
Svenska Byggbranschens Utvecklingsfond (SBUF)Rock Engineering Research Foundation (BeFo)
Note

Validerad;2023;Nivå 2;2023-09-25 (hanlid)

Available from: 2023-09-21 Created: 2023-09-21 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, AnkitBuasiri, ThanyaratCwirzen, Andrzej

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