Alkali-Activated Materials and Geopolymer: a Review of Common Precursors and Activators Addressing Circular Economy
05 Jun 2021-pp 1-32
TL;DR: In this paper, the authors reviewed different types, mechanisms, and result of mechanical and durability properties of alkali-activated materials and geopolymer reported in literature and discussed future projections of waste materials that have cementitious properties and can replace ordinary Portland cement and be used in alkali activated materials.
Abstract: The vast increase in CO2 and waste generation in recent decades has been a major obstacle to sustainable development and sustainability. In construction industry, the production of ordinary Portland cement is a major greenhouse gas emitter with almost 8% of total CO2 production in the world. To address this, Alkali-activated materials and geopolymer have more recently been introduced as a green and sustainable alternative of ordinary Portland cement with significantly lowered environmental footprints. Their use to replace Portland cement products generally leads to vast energy and virgin materials savings resulting in a sustainable concrete production. In doing so, it reuses the solid waste generated in industrial and manufacturing sectors, which is aligned with circular economy. In turn, it reduces the need for ordinary Portland cement consumption and its subsequent CO2 generation. To provide further insight and address the challenges facing the substitution of ordinary Portland cement, this article reviews different types, mechanisms, and result of mechanical and durability properties of alkali-activated materials and geopolymer reported in literature. Finally, it discusses future projections of waste materials that have cementitious properties and can replace ordinary Portland cement and be used in alkali-activated materials and geopolymer.
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TL;DR: In this paper , a critical literature review of current updates related to the fire performance of RF-reinforced GPC subjected to elevated temperatures and during fires is urgently necessary, conducting critical reviews on the type of RFs, spalling mechanism, physical inspection and properties of the RF-RGPCs.
38 citations
27 May 2021
TL;DR: In this article, the connection of construction sector and circular economy with recycled glass in its center is reviewed, and it is shown that by partially replacing Portland cement or aggregate with recycling glass, on average, up to 19% greenhouse gas and 17% energy consumption reduction as well as major cost savings can be made.
Abstract: As a result of socio-economic growth, major increase in solid waste generation is taking place which can lead to resource depletion and environmental concerns. To address this inefficient cycle of make, use and dispose, the concept of circular economy has recently been proposed that de-linearizes the current relationship between economic growth, environmental degradation and resource consumption thorough its 6Rs (Reuse, Recycle, Redesign, Remanufacture, Reduce, Recover). In the construction sector, currently the production of binding agents and transportation of virgin aggregates is associated with considerable environmental pollution. As a result, major attempts are taking place to substitute such ingredients with more sustainable and potentially cheaper materials. With waste glass having a production of roughly 100 million tons annually, and its low recycling rate of 26%, there is a growing number of studies unlocking its potential as an eco-friendly substitute for Portland cement (with particle size of below $$100\ \upmu \hbox {m}$$
) or fine aggregate (with size of below 4.75 mm) in concrete. As a result, this article intends to review the connection of construction sector and circular economy with recycled glass in its center. Accordingly, by partially replacing cement or aggregate with recycled glass, on average, up to 19% greenhouse gas, and 17% energy consumption reduction as well as major cost savings can be made. Additionally, in technical concrete terms, better fresh properties and fire resistance, as well as lower permeability, and in fine grades, favorable cementitious properties are reported as major benefits of using waste glass as a sustainable construction material.
37 citations
TL;DR: In this paper, the authors provide an updated information on recent advances while stressing the sustainability of lightweight geopolymer materials over ordinary Portland cement products that are vastly in use, including perlite, pumice, shale, ceramsite, and slate sand.
Abstract: Alkali-activated materials and geopolymer are major sustainable alternative binding materials to ordinary Portland cement products with higher thermal resistance and often better durability properties. In lightweight form, they have an unmatched lowered thermal conductivity and insulating properties making them a perfect fit for optimized structural components with highest strength to density ratio and major energy savings in green buildings. For them to produce lightweight materials, generally either certain foaming agent or some types of lightweight aggregates in virgin, expanded, or recycled form are utilized that reduce the overall density through higher overall porosity. In accordance, this review provides an updated information on recent advances while stressing the sustainability of lightweight geopolymer materials over ordinary Portland cement products that are vastly in use. In the end, recent mechanical and durability properties developed and documented are reviewed and provided for future applications. Based on the result of this review, the most common lightweight aggregates used in literature are perlite, pumice, shale, ceramsite, and slate sand, in expanded and porous form, along with recycled thermosetting (e.g., rubber), or thermoplastic (e.g., polyethylene) materials. In foam form, chemical and mechanical foaming are the most commonly used foaming techniques to increase porosity of final materials. The pore mechanism of foam-based geopolymer is found to be different from that of lightweight aggregate-based geopolymer. This variation results in different physico-mechanical and durability properties such as better insulation properties (and lower thermal conductivity) for foam-based versus better mechanical properties for lightweight aggregate-based geopolymer.
29 citations
TL;DR: In this paper , nano-modified alkali-activated composites (AACs) or geopolymers have attracted attention owing to their excellent performance and modification mechanisms, and the results mostly indicated that while increasing nano-additives proportion to a certain extent improves the mechanical characteristics, including compressive, flexural, tensile, and impact strengths, incorporation beyond that amount deteriorates them.
23 citations
TL;DR: In this article , the most commonly used curing regimes for AAMs are conducted in thermal or ambient temperature environments, adopted in the form of immersion of the AAM in water, ambient and high humidity, sealing, oven and, more recently, microwave curing.
23 citations
References
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TL;DR: A brief history and review of geopolymer technology is presented with the aim of introducing the technology and the vast categories of materials that may be synthesized by alkali activation of aluminosilicates as mentioned in this paper.
Abstract: A brief history and review of geopolymer technology is presented with the aim of introducing the technology and the vast categories of materials that may be synthesized by alkali-activation of aluminosilicates. The fundamental chemical and structural characteristics of geopolymers derived from metakaolin, fly ash and slag are explored in terms of the effects of raw material selection on the properties of geopolymer composites. It is shown that the raw materials and processing conditions are critical in determining the setting behavior, workability and chemical and physical properties of geopolymeric products. The structural and chemical characteristics that are common to all geopolymeric materials are presented, as well as those that are determined by the specific interactions occurring in different systems, providing the ability for tailored design of geopolymers to specific applications in terms of both technical and commercial requirements.
3,302 citations
TL;DR: In this paper, the effect of mineral properties on the compressive strength of the synthesized geopolymer was investigated, and it was shown that a wide range of natural Al-Si minerals could serve as potential source materials for the synthesis of geopolymers.
1,424 citations
TL;DR: In this paper, the authors present the work carried out on the chemical reaction, the source materials, and the factor affecting geopolymerization, and demonstrate that certain mix compositions and reaction conditions such as Al2O3/SiO2, alkali concentration, curing temperature with curing time, water/solid ratio and pH significantly influences the formation and properties of a geopolymers.
Abstract: Geopolymerization is a developing field of research for utilizing solid waste and by-products. It provides a mature and cost-effective solution to many problems where hazardous residue has to be treated and stored under critical environmental conditions. Geopolymer involves the silicates and aluminates of by-products to undergo process of geopolymerization. It is environmentally friendly and need moderate energy to produce. This review presents the work carried out on the chemical reaction, the source materials, and the factor affecting geopolymerization. Literature demonstrates that certain mix compositions and reaction conditions such as Al2O3/SiO2, alkali concentration, curing temperature with curing time, water/solid ratio and pH significantly influences the formation and properties of a geopolymer. It is utilized to manufacture precast structures and non-structural elements, concrete pavements, concrete products and immobilization of toxic metal bearing waste that are resistant to heat and aggressive environment. Geopolymers gain 70% of the final strength in first 3–4 h of curing.
1,078 citations
Book•
02 Apr 2003
TL;DR: Alkali-Activated Cement and Concrete as discussed by the authors is a type of Cementitious Systems that uses Alkaline Activators to activate slag cements and lime-pozzolan cements.
Abstract: Introduction 1. Alkaline Activators 2. Cementing Components 3. Hydration and Microstructure of Alkali-Activated Slag Cement 4. Properties of Alkali-Activated Slag Cement Pastes and Mortars (Under Both Atmospheric Pressure and Autoclave Conditions) 5. Properties of Alkali-Activated Slag Cement Concrete 6. Durability of Alkali-Activated Slag Cement and Concrete 7. Mix Design of Alkali-Activated Slag Cement Concrete 8. Alkali-Activated Portland Cement Based Blended Cement 9. Alkali-Activated Lime-Pozzolan Cement 10. Other Alkali-Activated Cementitious Systems 11. Applications of Alkali-Activated Cement And Concrete 12. Standards and Specifications
1,008 citations
TL;DR: In this article, the degradation of geopolymer materials using a class F fly ash (FA) and alkaline activators when exposed to 5% solutions of acetic and sulfuric acids was studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM).
836 citations