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UHPC overlay as sustainable solution to preserve old concrete structures
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: 0000-0001-8039-692x
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: MATEC Web of Conferences: International Conference on Concrete Repair, Rehabilitation and Retrofitting (ICCRRR 2022) / [ed] M.G. Alexander; H. Beushausen; F. Dehn; J. Ndawula; P. Moyo, EDP Sciences, 2022, article id 04014Conference paper, Published paper (Refereed)
Abstract [en]

Concrete structures exposed to harsh environments, especially including bridges, harbor structures are often suffered from durability problems. Typical external signs include surface deterioration, cracking caused by for example sulphate attack, frost action or reinforcement corrosion. All are strongly linked to the porous microstructure of the binder matrix and chemical decomposition of certain phases. Full replacement of deteriorated concrete structures is costly and can be troublesome for their users. The increasing demand to reduce the carbon footprint and to prolong the service life of concrete structures adds yet another argument to restore the existing structures. One alternative is to use very dense Ultra-High-Performance concrete (UHPC) as an external protective coating. The goal of this study was to determine the interfacial bonding characteristics between a damaged normal concrete (NC) and the applied thin layer of the UHPC. To curb the CO2 emission, UHPC is produced by substituting 50 wt% of Portland cement with a fine limestone powder. Fresh and hardened properties, shrinkage and frost durability have been evaluated. Mechanical properties were determined on a full-scale hybrid element using ultrasonic pulse velocity (UPV) and bond test (pull-off test). The results showed a significant increase of mechanical properties. Despite the applied thin layer of UHPC and volumetric restrain from the substrate normal concrete (NC) only limited surface shrinkage cracks were observed. The bond test and UPV showed good excellent values.

Place, publisher, year, edition, pages
EDP Sciences, 2022. article id 04014
Series
MATEC Web of Conferences, E-ISSN 2261-236X ; 364
Keywords [en]
Ultra-high-performance concrete (UHPC), Normal concrete (NC), Shrinkage, Frost durability, Ultrasonic pulse velocity (UPV), Bond test (pull-off)
National Category
Other Materials Engineering
Research subject
Building Materials
Identifiers
URN: urn:nbn:se:ltu:diva-93396DOI: 10.1051/matecconf/202236404014OAI: oai:DiVA.org:ltu-93396DiVA, id: diva2:1700562
Conference
International Conference on Concrete Repair, Rehabilitation and Retrofitting (ICCRRR 2022), Cape Town, South Africa, October 3-5, 2022
Funder
Swedish Transport AdministrationVinnovaAvailable from: 2022-10-03 Created: 2022-10-03 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, AnkitRajczakowska, MagdalenaCwirzen, Andrzej

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