Properties and Performance of Alkali Activated Concretes

A special issue of Buildings (ISSN 2075-5309). This special issue belongs to the section "Building Materials, and Repair & Renovation".

Deadline for manuscript submissions: closed (15 July 2023) | Viewed by 5027

Special Issue Editor

School of Natural and Build Environment, Queens University of Belfast, Belfast, UK
Interests: cement; concrete; sustainable and costefficient construction material; alkali activated concretes
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Alkali-activated concretes (AACs) have attracted considerable attention as a class of cement-free concretes with properties comparable to the well-known traditional Portland cement concrete (PCC). One of the important priorities in the world today is the reduction of net carbon emissions to zero by 2050, and AAC can play a significant role by reducing the carbon emissions of concrete structures. This can be promising when all the AAC mechanical and durability properties are well known and have proven their appropriate performance in various applications of the building industry.

The aim of this Special Issue on AACs’ mechanical and durability properties is to provide a comprehensive overview of all aspects related to the application of this type of concrete in the building industry, including the mechanical properties and performance of AACs in different aggressive environments. This review also explores the current problems hindering the universal acceptance and large-scale application of AACs. This Special Issue will bring together high-quality research articles on the different aspects of AACs, including their current status and remaining challenges.

Dr. Dali Bondar
Guest Editor

Manuscript Submission Information

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Keywords

  • Alkali-activated concretes
  • AACs mechanical properties
  • Shrinkage
  • Durability
  • Waste materials
  • Recycled materials
  • AACs in Chloride environment
  • AACs in Sulfate environment
  • AACs fire resistance
  • AACs performance
  • Life cycle

Published Papers (2 papers)

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Research

12 pages, 3442 KiB  
Article
Investigation of Mineral Admixtures on Mechanical Properties of Alkali-Activated Recycled Concrete Powders Cement
by Xin Wang, Yurong Yan, Xiaofang Tong and Yongfan Gong
Buildings 2022, 12(8), 1234; https://doi.org/10.3390/buildings12081234 - 13 Aug 2022
Cited by 11 | Viewed by 1517
Abstract
Recycled concrete powders (RCPs) are collected during the treatment of recycled aggregates using devices that suction dust. However, RCPs have not been effectively utilized as mineral admixtures in concrete due to their low activity and high capacity for water absorption. In this study, [...] Read more.
Recycled concrete powders (RCPs) are collected during the treatment of recycled aggregates using devices that suction dust. However, RCPs have not been effectively utilized as mineral admixtures in concrete due to their low activity and high capacity for water absorption. In this study, alkali-activated recycled concrete powders cement (AARCPC) was prepared using chemical activation, and then the composition, fluidity, setting time, strength and micro-structure of hydration products in AARCPC were studied. We found that the addition of mineral admixtures significantly improved the strength of hardened paste at various ages, and that the effect of slag powders on the mechanical properties was significantly better than that of fly ash. Replacing AARCPC with 50% slag caused the 28 d and 90 d compressive strength of pastes to reach 79.5 and 84.4 MPa, respectively. The optimal ratio of the various minerals that make up AARCPC was 60% recycled concrete powder, 20% slag powder and 20% fly ash. In particular, hydration with fly ash and slag of AARCPC promotes better fluidity and compactness. AARCPC showed higher strength and has the potential to replace Portland cement and be applied to concrete. Full article
(This article belongs to the Special Issue Properties and Performance of Alkali Activated Concretes)
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22 pages, 4950 KiB  
Article
External Sulphate Attack on Alkali-Activated Slag and Slag/Fly Ash Concrete
by Dali Bondar and Sreejith Nanukuttan
Buildings 2022, 12(2), 94; https://doi.org/10.3390/buildings12020094 - 20 Jan 2022
Cited by 5 | Viewed by 2774
Abstract
Two types of alkali-activated material (AAM) concretes were exposed to various sulphate bearing-solutions for over two years. Physical changes to the concrete specimen and chemical changes in the exposure liquid were studied in an attempt to understand how sulphate attack occurs in such [...] Read more.
Two types of alkali-activated material (AAM) concretes were exposed to various sulphate bearing-solutions for over two years. Physical changes to the concrete specimen and chemical changes in the exposure liquid were studied in an attempt to understand how sulphate attack occurs in such binders and the role the mix variables play in offering resistance against such attack. The mix variables of alkali-activated slag concrete (AASC) included water-to-binder ratio, percentage of alkali, and the SiO2/Na2O ratio (silica modulus, Ms); for alkali-activated slag/fly ash (AA-S/F) concrete, the mix variables included slag/fly ash ratio and the SiO2/Na2O ratio. The exposure solutions included water, magnesium sulphate (5%), sodium sulphate (5%), calcium sulphate (0.2%), and two concentrations of sulphuric acid solutions, pH 3 and pH 1. The physical changes studied were length and mass change, visual appearance, and change in compressive strength. The exposure liquids were analysed for change in pH and ionic composition. Findings show that the AA-S/F blend performs better than AASC in sulphate environments, based on strength and change in length. Exposure to water resulted in the most expansion/shrinkage in all mixes studied. An empirical model was proposed for predicting the change in compressive strength for AAS&AA-S/F concretes based on mass gain. Further, a simple performance criterion was put forward for mixes in sulphate environments based on mass gain. Full article
(This article belongs to the Special Issue Properties and Performance of Alkali Activated Concretes)
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