Does a High Amount of Unhydrated Portland Cement Ensure an Effective Autogenous Self-Healing of Mortar?

Document identifier: oai:DiVA.org:ltu-76510
Access full text here:10.3390/ma12203298
Keyword: Engineering and Technology, Materials Engineering, Other Materials Engineering, Teknik och teknologier, Materialteknik, Annan materialteknik, Continued hydration, Ultra-high performance concrete, Cracking, Microstructure, Calcite, Byggmaterial, Building Materials
Publication year: 2019
Relevant Sustainable Development Goals (SDGs):
SDG 9 Industry, innovation and infrastructureSDG 3 Good health and wellbeing
The SDG label(s) above have been assigned by OSDG.ai

Abstract:

It is commonly accepted that the autogenous self-healing of concrete is mainly controlled by the hydration of Portland cement and its extent depends on the availability of anhydrous particles. High-performance (HPCs) and ultra-high performance concretes (UHPCs) incorporating very high amounts of cement and having a low water-to-cement ratio reach the hydration degree of only 70–50%. Consequently, the presence of a large amount of unhydrated cement should result in excellent autogenous self-healing. The main aim of this study was to examine whether this commonly accepted hypothesis was correct. The study included tests performed on UHPC and mortars with a low water-to-cement ratio and high cement content. Additionally, aging effects were verified on 12-month-old UHPC samples. Analysis was conducted on the crack surfaces and inside of the cracks. The results strongly indicated that the formation of a dense microstructure and rapidly hydrating, freshly exposed anhydrous cement particles could significantly limit or even hinder the self-healing process. The availability of anhydrous cement appeared not to guarantee development of a highly effective healing process.

Authors

Magdalena Rajczakowska

Luleå tekniska universitet; Byggkonstruktion och brand
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Lennart Nilsson

Luleå tekniska universitet; Institutionen för samhällsbyggnad och naturresurser
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Karin Habermehl-Cwirzen

Luleå tekniska universitet; Byggkonstruktion och brand
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Hans Hedlund

Luleå tekniska universitet; Byggkonstruktion och brand; Skanska, Stockholm, Sweden
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Andrzej Cwirzen

Luleå tekniska universitet; Byggkonstruktion och brand
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