Controlling efflorescence in geopolymers: A new approach

Simão, Lisandro; Fernandes, E.; Hotza, Dachamir; Ribeiro, M.J.; Montedo, Oscar Rubem Klegues; Raupp-Pereira, F.

doi:10.1016/j.cscm.2021.e00740

Cited by 22 publications

(43 citation statements)

References 40 publications

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“…In OPC-based systems, the efflorescence occurs due to the migration of soluble Ca 2+ ions to the surface and the reaction of such migrated ions with the atmosphere [ 9 ]. In contrast to geopolymer systems, efflorescence forms from the migration of Na + and OH − ions from the pore solution to the outer surface and the final reaction with atmospheric CO 2 and water [ 7 , 9 ]. In practise, the appearance of efflorescence is not aesthetically pleasing and reduces the longevity and strength of building materials [ 52 ].…”

Section: Resultsmentioning

confidence: 99%

“…Researchers estimated that about 4800 metric tons of cement would have been produced across the world by 2030, resulting in enormous energy consumption and carbon dioxide (CO 2 ) gas emissions into the atmosphere during its manufacturing stage, while 2.8 tons of raw materials would have been utilised for every ton of cement production [ 2 , 3 ]. As such, an enormous effort has been made by researchers to explore the possibility of completely phasing out cement by developing an eco-friendly/alternative geopolymer binder for application in concrete [ 4 , 5 , 6 , 7 ].…”

Section: Introductionmentioning

confidence: 99%

“…Geopolymers are inorganic alumino-silicate polymers with a three-dimensional network, which are obtained by the reaction of rich aluminosilicate materials, such as metakaolin, fly ash, Ground Granulated Blast Furnace slag (GGBS), etc., with a highly alkaline aqueous solution [ 7 , 8 ]. This reaction is an alkali activation mechanism where the final products of geopolymerisation are usually influenced by the chemical composition of the alkaline activators and the source aluminosilicate materials that act as a precursor [ 6 ].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Physico-Mechanical Evaluation of Geopolymer Concrete Activated by Sodium Hydroxide and Silica Fume-Synthesised Sodium Silicate Solution

et al. 2023

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Commercial sodium hydroxide (NaOH) and sodium silicate (SS) have remained two of the leading alkaline activators widely used in producing geopolymer concrete, despite some identified negatives regarding their availability and additional CO2 emissions relating to the overall manufacturing process. This study reports the viability of developing geopolymer concrete using a laboratory-synthesised silica fume (SF)-derived SS solution in combination with NaOH at a molarity of 10M as an alternative binary alkali-alkaline activator to Ground Granulated Blast Furnace slag (GGBS). The use of SF in the development of geoolymer activators will pave the way for the quality usage of other high-silica content by-products from nature, industry, and agriculture. In the currently reported proof of concept, four geopolymer concrete batches were produced using different alkaline activator/precursor-A/P ratios (0.5 and 0.9) and SS to NaOH-SS/SH volume ratios (0.8/1.2 and 1.2/0.8), to establish the impact on the engineering performance. Two controls were adopted for ordinary and geopolymer concrete mixes. The engineering performance was assessed using slump and compaction index (CI) tests, while the Unconfined Compressive Strength (UCS) and tensile splitting (TS) tests were measured at different curing ages in accordance with their appropriate standards. The results indicated a reduction in slump values as the A/P ratio decreased, while the CI values showed a reversal of the identified trend in slump. Consequently, mix GC2 attained the highest UCS strength gain (62.6 MPa), displaying the superiority of the alkali activation and polymerisation process over the CSH gel. Furthermore, the impact of A/P variation on the UCS was more pronounced than SS/SH due to its vital contribution to the overall geopolymerisation process.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Physico-Mechanical Evaluation of Geopolymer Concrete Activated by Sodium Hydroxide and Silica Fume-Synthesised Sodium Silicate Solution

et al. 2023

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“…The molar ratio of Na 2 O/Al 2 O 3 is a relevant parameter that should be considered in efflorescence control [ 54 ]. In this research, the increase in the molar ratio Na 2 O/Al 2 O 3 was from 0.45 in group S to 0.72 in group C, which was due to the incorporation of Na 2 O contained in the Na 2 SiO 3 solution.…”

Section: Resultsmentioning

confidence: 99%

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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“…Geopolymers can be considered to be challenging to create, because the manufacturing process includes a corrosive chemical substance that can harm humans, such as sodium hydroxide [13]; there is no standard mix design, and the properties differ significantly depending on the used raw materials (even the chemical composition of fly ash produced by the same manufacturer in different years is quite diverse); a special curing method is needed [14], which require more skilled labors and practice. Also, there are technical problems, such as high thermally induced shrinkage in fly ash based geopolimers [15] and efflorescence, which can reduce the durability of geopolymer due to reduced compressive and tensile strength and aesthetic issues [16]. Undoubtedly, the above-mentioned aspects limit the application and use of geopolymer concrete instead of OPC-based concrete.…”

Section: Introductionmentioning

confidence: 99%

Foamed geopolymers: a review of recent studies

Radina

Sprince

Pakrastins

et al. 2023

J. Phys.: Conf. Ser.

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Undoubtedly, current environmental trends force scientists to search for a way to reduce carbon dioxide emissions in the production process of building materials. Geopolymers have been called as a potential alternative to traditional concrete for decades, allowing us to obtain more sustainable and durable materials with good thermal and reasonable mechanical properties and solve the problems related to waste materials utilization. Despite the great interest of scientists and the many advantages both in the production process of geopolymers and in terms of material properties, this idea looks unattainable in the near future, so it is worth investigating alternative ways of geopolymer applications. Thereby this review paper summarizes the recent progress in the field of foamed geopolymer concrete, focusing on the different preparation methods, material base, as well as information about the obstacles and challenges that hinder the transition of foamed geopolymers from research laboratories to real application in the civil engineering. This report also describes the density, compressive strength, thermal conductivity, pore size and distribution. A random sampling method and descriptive analysis were used in the preparation of a review, taking into account the year of publication, used materials, availability and the number of citations.

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Controlling efflorescence in geopolymers: A new approach

Cited by 22 publications

References 40 publications

Physico-Mechanical Evaluation of Geopolymer Concrete Activated by Sodium Hydroxide and Silica Fume-Synthesised Sodium Silicate Solution

Physico-Mechanical Evaluation of Geopolymer Concrete Activated by Sodium Hydroxide and Silica Fume-Synthesised Sodium Silicate Solution

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

Foamed geopolymers: a review of recent studies

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