Performance of alkali-activated mortars for the repair and strengthening of OPC concrete

Pacheco-Torgal, F.; Aguiar, José; Ding, Yining; Tahri, W.; Baklouti, Samir

doi:10.1533/9781782422884.4.627

Cited by 12 publications

(4 citation statements)

References 27 publications

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“…The first could be a result of accelerated hydration of cement matrix, causing irregular adhesion with the shell material. The second reason is expected to be due to higher shrinkage stresses, normally experienced in rapid hardening cements, that induce micro-crack formations leading to weaker interface bonds [20][21][22][23][24].…”

Section: Hardened Propertiesmentioning

confidence: 99%

Self-Waterproofing Performance of Repair Mortars With Inorganic Healing Agents

2023

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In Europe, about 55% of concrete bridges are about 50 years old and require non-structural rapid repair strategies to reinstate the aesthetic and durability performances. Existing strategies focus primarily on superficial restoration that continues to demonstrate premature deterioration due to inevitable micro-crack formations that further propagate to macro-cracks leading to the ingress of moisture along with harmful ions. In this study, the benefits of self-healing technology to control moisture ingress at the microscale were investigated. For this, tailored microcapsule with inorganic healing agent, specifically, commercially available water-repellent agent (SIKAGARD 705L) was added to mortar with two types of commonly used binders namely CEMI 52.5N and CEMI 52.5R. The compatibility assessment in terms of capsule integration, fresh and hardened properties was done. The baseline healing efficiency of the mortars without any healing additions was obtained to understand the autogenous healing capacity of the reference mortars. Subsequently, the reference mortar mixes were compared with mixes containing varying fractions of microcapsules (3, 5, and 10%) for autonomous healing efficiency with capillary absorption as the main durability function. The healing efficiency was further investigated for two different crack mouth widths (<250 μm and >350 μm); representative of non-structural residual crack widths. In mortars with microcapsules, a maximum reduction of sorptivity coefficients up to 82% and 78% with CEMI 52.5N and CEMI 52.5R mortars, respectively, for specimens cracked after 7 days of curing was observed. Subsequently, a synergetic effect of autogenous healing action and autonomous water-repellent action for durability recovery was identified and proved useful for repair mortar applications. The healing agent investigated, capsule content, and healing environment considered in the current study lay a foundation for further optimisation to improve the performance and to suit different applications.

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Section: Hardened Propertiesmentioning

confidence: 99%

Self-Waterproofing Performance of Repair Mortars With Inorganic Healing Agents

2023

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“…These tests are common for OPC steel fibre-reinforced concretes but are seldom used for characterizing the fracture behaviour of AAM. Steel fibre-reinforced AAMs prove to be alternatives to steel fibre-reinforced OPC in fields like repair tasks, underground engineering or pre-cast elements [9,10]. It is thus important to investigate the failure mechanisms of steel fibre-reinforced AAM regarding:…”

Section: Introductionmentioning

confidence: 99%

Application of Steel Fibres in Alkali-Activated Mortars

Hüsken

Wagner

Gluth

et al. 2020

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Alkali-activated materials are ideal for the repair of concrete structures in harsh environmental conditions due to their high durability in chemically aggressive environments. However, slag-based mortars, in particular, are prone to shrinkage and associated cracks. In this respect, the application of steel fibres is one solution to reduce the formation of shrinkage induced cracks and to improve post cracking behaviour of these mortars. This study investigated the influence of two different types of steel fibres on the tensile properties of two alkali-activated mortars. Direct tensile tests and single fibre pull-outs were performed to analyse the determining failure modes both on macro and micro scale. Mechanical testing was accompanied by non-destructive testing methods such as digital image correlation and acoustic emission for a detailed analysis of the fracture process.

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“…These materials show a high long-term durability even under acid and alkali attack and at elevated temperatures [5]. Emerging solutions for concrete protection based on alkali-activated materials, here referred to as geopolymers, show rapid setting and hardening, excellent bond strength and durability, low chloride permeability and high freeze-thaw and chloride resistances [5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23]. Geopolymers also possess an electrolytic conductivity, which can allow them to be simultaneously used as skin-sensors for structural health monitoring [24,25,26,27,28].…”

Section: Introductionmentioning

confidence: 99%

Ambient Cured Fly Ash Geopolymer Coatings for Concrete

et al. 2019

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The reinforced concrete structures that support transport, energy and urban networks in developed countries are over half a century old, and are facing widespread deterioration. Geopolymers are an affordable class of materials that have promising applications in concrete structure coating, rehabilitation and sensing, due to their high chloride, sulphate, fire and freeze-thaw resistances and electrolytic conductivity. Work to date has, however, mainly focused on geopolymers that require curing at elevated temperatures, and this limits their ease of use in the field, particularly in cooler climates. Here, we outline a design process for fabricating ambient-cured fly ash geopolymer coatings for concrete substrates. Our technique is distinct from previous work as it requires no additional manufacturing steps or additives, both of which can bear significant costs. Our coatings were tested at varying humidities, and the impacts of mixing and application methods on coating integrity were compared using a combination of calorimetry, x-ray diffraction and image-processing techniques. This work could allow geopolymer coatings to become a more ubiquitous technique for updating ageing concrete infrastructure so that it can meet modern expectations of safety, and shifting requirements due to climate change.

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Performance of alkali-activated mortars for the repair and strengthening of OPC concrete

Cited by 12 publications

References 27 publications

Self-Waterproofing Performance of Repair Mortars With Inorganic Healing Agents

Self-Waterproofing Performance of Repair Mortars With Inorganic Healing Agents

Application of Steel Fibres in Alkali-Activated Mortars

Ambient Cured Fly Ash Geopolymer Coatings for Concrete

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