Influence of alkali activator type and proportion on strength performance of calcined clay geopolymer mortar

Bature, A.S.; Khorami, Morteza; Ganjian, Eshmaiel; Tyrer, Mark

doi:10.1016/j.conbuildmat.2020.120446

Cited by 32 publications

(9 citation statements)

References 36 publications

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“…The diffractograms of the GP-S group mortars in Figure 7 show the spectra with crystalline peaks that correspond to the same atomic ordering of quartz and anatase observed in the XRD of metakaolinite, as similarly observed in the studies of Azevedo et al [ 45 ] and Bature et al [ 46 ]. These phases do not contribute to the formation of polymer chains.…”

Section: Resultssupporting

confidence: 74%

“…The formation of a new phase, zeolite A, was observed, which, according to Longhi et al [ 27 ] and Wan et al [ 47 ], in geopolymers is relatively common in a matrix of metakaolinite activated with hydroxides due to the pseudozeolytic structure. The zeolitic phase was also observed in the studies of Bature et al [ 46 ] in the manufacture of a NaOH-activated mortar. In zeolites, porosity may contribute to decreased strength due to its microporous crystalline structure [ 48 , 49 ], as observed in the compressive strength test.…”

Section: Resultssupporting

confidence: 61%

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Study of Metakaolinite Geopolymeric Mortar with Plastic Waste Replacing the Sand: Effects on the Mechanical Properties, Microstructure, and Efflorescence

et al. 2022

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In this study, the production of a mortar was proposed in which plastic waste replaced sand by 0%, 50%, and 100% in order to create a sustainable alternative for construction. The performance of the mortars was tested with two types of activators, one with NaOH, as a simple activator, and the other with NaOH and Na2SiO3, as a compound activator. The effects of the LDPE plastic bag waste and the activators on compressive strength, porosity, microstructure analysis, and efflorescence formation were correlated and discussed. The results showed that the replacement of sand with plastic waste at 50% and 100% proportionally reduced the compressive strength due to the increase in porosity caused by the waste, especially in the group of mortars with the simple activator, and included the formation of efflorescence. On the other hand, the compound activator increased the packing of the particles in the mortar, as observed in the images of the microstructure. This reduced porosity inhibited efflorescence and resulted in higher resistances that reached a maximum value of 22.68 MPa at 28 days in the group of 50% mortars with the compound activator. Therefore, the study showed that there is potential for the replacement of sand with plastic waste for the production of mortars, which can be considered a more sustainable building material.

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Section: Resultssupporting

confidence: 74%

Section: Resultssupporting

confidence: 61%

Study of Metakaolinite Geopolymeric Mortar with Plastic Waste Replacing the Sand: Effects on the Mechanical Properties, Microstructure, and Efflorescence

et al. 2022

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“…As more oligomers are formed, further geopolycondensation reactions occur and polymerize into ionic clusters, which eventually harden into a three-dimensional network-like structure and improve the mechanical properties of the geopolymers [28]. The sodium silicate solution generally acts as a binder in the geopolymerization reaction, and with the increase in the mass ratio of Na 2 SiO 3 /NaOH, the specimen reaches the maximum flexural strength when there is a sufficient amount of alkali activator, but with the increase in the mass ratio, excess silicate will precipitate, which is not conducive to the dissolution of the silicon-aluminum raw material and destroys the geopolymerization reaction, resulting in a decrease in strength [29]. Moreover, if the mass ratio of alkali activator to metakaolin is too large, it will adversely affect the flexural strength of the geopolymer.…”

Section: Analysis Of Influencing Factorsmentioning

confidence: 99%

Mechanical Properties and Microstructural Characterization of Metakaolin Geopolymers Based on Orthogonal Tests

Dai

Wang

et al. 2022

Materials

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Metakaolin was used as a raw material for the preparation of geopolymers, where two types of alkali activators (Na2SiO3 + NaOH and Na2SiO3 + NaOH) were used to prepare metakaolin geopolymers at room temperature. The mechanical properties and microstructures of the metakaolin geopolymers were analyzed. A three-factor, four-level orthogonal test was designed to investigate the mechanical properties of the metakaolin geopolymer with different ratios. The compressive and flexural strength of different specimens were tested for 7 and 28 days. Both the Na-based and K-based geopolymers exhibited excellent mechanical properties, but the K-based geopolymer had better mechanical properties. The optimal compressive strength and flexural strength of the K-based geopolymer were 73.93 MPa and 9.37 MPa, respectively. The 28-day optimal compressive strength of the Na-based polymer was 65.79 MPa, and the flexural strength was 8.71 MPa. SEM, XRD, and FTIR analyses showed that the mechanical properties of the geopolymers could be greatly improved by using a higher alkaline solution concentration, proper Na2SiO3/MOH mass ratio, and proper mass ratio of alkali exciter to metakaolin. Amorphous silicoaluminate was more favorable for the dissolution of silicon–alumina raw materials, promoted the formation of an amorphous silicoaluminate gel, and caused the internal structure of the geopolymer to be more compact.

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“…However, the matrix of mortar (1-3NS) exhibits cracks besides some lightly stacked aluminosilicate particles and unreacted material. The presence of residual unreacted particles prevents the development of the network of a uniform geopolymer network [55]. Additionally, the blast furnace slag and corrected recycled sand in the mixture facilitated the formation of an increased amount of C-A-S-H gels [43,44].…”

Section: Microstructure Analysis By Scanning Electron Microscopementioning

confidence: 99%

A Comparative Study of Metakaolin/Slag-Based Geopolymer Mortars Incorporating Natural and Recycled Sands

2022

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Great efforts are being made to minimize the negative impact of the Portland cement industry on the environment by using industrial by-products during the manufacture of clinker or by the partial replacement of cement during the preparation of concrete. However, the carbon footprint remains relatively high in addition to the large consumption of natural resources such as sand and other aggregates. A solution to these problems is to completely replace Portland cement with a new generation of mineral binders, commonly known as geopolymers, which have properties similar to those of Portland cement. These binders can be obtained by the alkali-activation of siliceous or aluminosilicate materials. This study aims to develop pozzolanic type binders at room temperature (20°C) from the alkali-activation of aluminosilicate materials based on metakaolin and blast furnace slag at different percentages. Different activators were employed, including solid (NaOH) and liquid (Na2SiO3.nH2O). The optimal mixtures were used for making mortars based on natural sand (NS) and concrete recycled sand (CRS). A comparative experimental study of the physical, mechanical, and microstructural characteristics of the two types of mortars was conducted. Cement mixtures with a high amount of slag and an association of sodium hydroxide and sodium silicate gave the best physico-mechanical properties. A drop in the compressive strength of mortars prepared with CRS was observed after 365 days, but it was still higher than those with NS. The obtained results show the possibility of designing an eco-friendly CRS-based geopolymer mortar that is more resistant than NS-based mortar with a homogeneous and integrated microstructure. Doi: 10.28991/CEJ-2022-08-08-07 Full Text: PDF

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Influence of alkali activator type and proportion on strength performance of calcined clay geopolymer mortar

Cited by 32 publications

References 36 publications

Study of Metakaolinite Geopolymeric Mortar with Plastic Waste Replacing the Sand: Effects on the Mechanical Properties, Microstructure, and Efflorescence

Study of Metakaolinite Geopolymeric Mortar with Plastic Waste Replacing the Sand: Effects on the Mechanical Properties, Microstructure, and Efflorescence

Mechanical Properties and Microstructural Characterization of Metakaolin Geopolymers Based on Orthogonal Tests

A Comparative Study of Metakaolin/Slag-Based Geopolymer Mortars Incorporating Natural and Recycled Sands

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