Geopolymer, green alkali activated cementitious material: Synthesis, applications and challenges

Wu, Yunhai; Lu, Bowen; Bai, Tao; Wang, Hao; Du, Feipeng; Zhang, Yunfei; Cai, Lu; Jiang, Can; Wang, Wenjun

doi:10.1016/j.conbuildmat.2019.07.112

Cited by 261 publications

(93 citation statements)

References 190 publications

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“…Geopolymers, known as a synthetic inorganic polymer, are produced by the alkali activation of a variety of aluminosilicates, such as metakaolin (MK), fly ash (FA), rice husk ash (RHA), red mud (RM), and so on [1,2]. Due to its high mechanical properties, corrosion resistance, durability, especially desirable performance under high temperature, wide source of raw materials, and low energy consumption, geopolymers has become an increasingly popular research area in recent years [3][4][5].…”

Section: Introductionmentioning

confidence: 99%

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Thermal and Mechanical Properties of Geopolymers Exposed to High Temperature: A Literature Review

Dai

Wang

2020

Advances in Civil Engineering

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Geopolymers are prepared by alkali solution-activated natural minerals or industrial waste materials, which have been widely used as new sustainable building and construction materials for their excellent thermal and mechanical properties. The thermal and mechanical properties of geopolymers at high temperature have attracted great attention from many researchers. However, there are few systematic works concerning these two issues. Therefore, this work reviewed the thermal and mechanical behaviors of geopolymers at high temperature. Firstly, the thermal properties of geopolymers in terms of mass loss, thermal expansion, and thermal conductivity after high temperature were explained. Secondly, the mechanical properties of residual compressive strength and stress-strain relationship of fly ash geopolymers and metakaolin geopolymers after high temperature were analyzed. Finally, the microstructure and mineralogical characteristics of geopolymers upon heating were interpreted according to the changes of microstructures and compositions. The results show that the thermal properties of geopolymers are superior to cement concrete. The geopolymers possess few mass loss and a low expansion ratio and thermal conductivity at high temperature. The thermal and mechanical properties of the geopolymers are usually closely related to the raw materials and the constituents of the geopolymers. Preparation and testing conditions can affect the mechanical properties of the geopolymers. The stress-strain curves of geopolymer are changed by the composition of geopolymers and the high temperature. The silicon-type fillers not only improve the thermal expansion of the geopolymers but also enhance mechanical properties of the geopolymers. But, they do not contribute to reducing the thermal conductivity. the different raw materials, aluminosilicate precursor and reinforcement materials, result in different geopolymer damage during the heating. However, phase transitions can occur during the process of heating regardless of the raw materials. The additional performance enhancements can be achieved by optimizing the paste formulation, adjusting the inner structure, changing the alkali type, and incorporating reinforcements.

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Section: Introductionmentioning

confidence: 99%

“…(1) To analyze thermal properties in terms of mass loss, thermal deformation, and thermal conductivity of geopolymers exposed to high temperature. (2) To analyze mechanical properties in terms of residual compressive strength and stress-strain relationship of geopolymers exposed to high temperature.…”

Section: Introductionmentioning

confidence: 99%

Thermal and Mechanical Properties of Geopolymers Exposed to High Temperature: A Literature Review

Dai

Wang

2020

Advances in Civil Engineering

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“…The problem is also the significant energy consumption and greenhouse gas emission associating the cement production processes. It is estimated that the whole process of producing 1 ton of cement consumes about 3.2 GJ of energy and generates nearly 810 kg of carbon dioxide (CO 2 ), 1.0 kg of sulfur dioxide (SO 2 ), and 2.0 kg of nitrogen oxides (NO x ) [ 1 ]. Therefore, the development of sustainable bonding materials is important.…”

Section: Introductionmentioning

confidence: 99%

“…Geopolymer materials are gaining ground due to their excellent properties and sustainable. The greatest advantages of geopolymers are strong bonding and good durability, high-temperature resistance, low permeability, great chemical corrosion resistance, and environmental friendliness [ 1 ]. Potential fields of application of geopolymer materials include geopolymer concrete, precast construction elements, materials on pavement, repair materials, protective coatings, immobilization of toxic metals, nuclear waste management, and three-dimensional printing materials [ 7 , 8 , 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Changes in the Microstructure of Geopolymer Mortar after Exposure to High Temperatures

Dudek

Sitarz

2020

Materials

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The inorganic structure formed at the stage of setting of the geopolymer binder ensures high durability of the material under high-temperature conditions. However, changes in the microstructure of the material are observed. The purpose of the study was to analyze changes in the structure of geopolymer mortar after exposure to high temperatures T = 200, 400, 600, 800, and 1000 °C. Mortars with a binder based solely on fly ash (FA) and mixed in the 1:1 ratio with a binder containing fly ash and ground granulated blast-furnace slag (GGBFS) were tested. The descriptions of their microstructures were prepared based on digital microscope observations, scanning electron microscope (SEM) observations, EDS (energy dispersive spectroscopy) analysis, and mercury intrusion porosimetry (MIP) porosity test results. Changes in the material due to high temperature were observed. The differences in the microstructure of the samples are also visible in the materials that were not exposed to temperature, which was influenced by the composition of the materials. Porosity increases with increasing annealing temperature. The distribution of individual pores also changes. In both materials, the proportion of pores larger than 1000 nm increases with the temperature increase. Moreover, the number of cracks and their width also increases, reaching 20 µm in the case of GGBFS. Furthermore, the color of geopolymers has changed. The obtained results extend the current state of knowledge in the field of changes in the microstructure of geopolymers subjected to high temperature.

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“…It revealed the dense microstructure of AAM coating and interfacial bonding zone, which led to the high adhesive strength of coating due to the typical AAM C-A-S-H/A-S-H gels chemically bonded into the cement mortar substrate. However, lots of smashed fragments presented in sample #1 ( Figure 5A) after being split, which resulted from typical brittle behavior with low ductility and low fracture toughness [31]. In addition, visible cracks were gradually showing on the coating surface during curing period, which extremely affected the adhesive behavior (discussed in Section 2.3).…”

Section: Mechanical Strengthmentioning

confidence: 99%

One-Part Plastic Formable Inorganic Coating Obtain from Alkali-Activated Slag /Starch(CMS) Hybrid Composites

Qin

Lin

et al. 2020

Molecules

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Coating technology can be applied to decorate building constructions. Alkali-activated materials (AAM) are promising green and durable inorganic binders which show potential for development as innovative coating. In the paper, the possibility of using AAM composited with starch (CMS) as a novel plastic formable inorganic coating for decorating in building was investigated. The rheological properties, including plastic viscosity, yield stress, and thixotropy were considered to be critical properties to obtain the working requirements. Four different mixtures were systematically investigated to obtain the optimum formulation, and then were used to study their hardened properties, such as mechanical strengths (compressive, flexural, and adhesive strength), drying shrinkage, cracking behavior, and microstructure. Study results found that CMS could quickly and efficiently be hydrolyzed in an alkaline solution to produce organic plastic gel which filled in AAM paste, leading to the significant improvement of coating consistency, plastic viscosity, and thixotropy. The optimum coating composited with 15.40 wt% CMS shows a relatively stable rheological development, the setting time sufficient at higher than 4 h. Furthermore, CMS shows a significant positive effect on the cracking and shrinkage control due to padding effect and water retention of CMS, which results in no visible cracks on the coating surface. Although the mechanical strength development is relatively lower than that of plain AAM, its value, adhesive strength 2.11 MPa, compressive strength 55.09 MPa, and flexural strength 8.06 MPa highly meet the requirements of a relevant standard.

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Geopolymer, green alkali activated cementitious material: Synthesis, applications and challenges

Cited by 261 publications

References 190 publications

Thermal and Mechanical Properties of Geopolymers Exposed to High Temperature: A Literature Review

Thermal and Mechanical Properties of Geopolymers Exposed to High Temperature: A Literature Review

Analysis of Changes in the Microstructure of Geopolymer Mortar after Exposure to High Temperatures

One-Part Plastic Formable Inorganic Coating Obtain from Alkali-Activated Slag /Starch(CMS) Hybrid Composites

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