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15 pages, 4116 KiB

Open AccessArticle

Performance of Eco-Friendly Zero-Cement Particle Board under Harsh Environment

by Arman Hatami Shirkouh, Farshad Meftahi, Ahmed Soliman, Stéphane Godbout and Joahnn Palacios

Appl. Sci. 2024, 14(7), 3118; https://doi.org/10.3390/app14073118 - 08 Apr 2024

Viewed by 559

The increasing scarcity of virgin natural resources and the need for sustainable waste management in densely populated urban areas have heightened the importance of developing new recycling technologies. One promising approach involves recycling agricultural waste in construction applications and transforming it into secondary [...] Read more.

The increasing scarcity of virgin natural resources and the need for sustainable waste management in densely populated urban areas have heightened the importance of developing new recycling technologies. One promising approach involves recycling agricultural waste in construction applications and transforming it into secondary products. This is anticipated to reduce the demand for new resources and lower the environmental impact, aligning with industrial ecology principles. Combined with a low carbon emission binder (i.e., alkali-activated), utilizing agro-waste to produce zero-cement particle boards is a promising method for green construction. Traditionally, particle boards are engineered from wood or agricultural waste products that are pressed and bonded with a binder, such as cement or synthetic resins. However, alternative binders replace cement in zero-cement particle boards to address environmental concerns, such as the carbon dioxide emissions associated with cement production. This study investigated the effects of accelerated aging on the performance of alkali-activated agro-waste particle boards. Accelerated aging conditions simulate natural aging phenomena. Repeated wetting–drying and freezing–thawing cycles increased water absorption and thickness swelling and reduced flexural strength. The thermal performance of the alkali-activated particle boards did not exhibit significant changes. Hence, it was confirmed that agro-waste has a high potential for utilization in producing particle boards provided that the working environment is carefully selected to optimize performance. Full article

(This article belongs to the Special Issue Alkali-Activated Materials: Advances and Novel Applications)

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20 pages, 4274 KiB

Open AccessArticle

Alkali-Activated Copper Slag with Carbon Reinforcement: Effects of Metakaolinite, OPC and Surfactants

by Patrick Ninla Lemougna, Guillermo Meza Hernandez, Nicole Dilissen, Felicite Kingne, Jun Gu and Hubert Rahier

Appl. Sci. 2024, 14(5), 2081; https://doi.org/10.3390/app14052081 - 01 Mar 2024

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Abstract

Copper slag is an industrial residue with a large unutilized fraction. This study presents the development of alkali-activated composites from a copper slag named Koranel^®. The effects of metakaolinite, ordinary Portland cement (OPC) and surfactants were investigated. The reactivity of Koranel [...] Read more.

Copper slag is an industrial residue with a large unutilized fraction. This study presents the development of alkali-activated composites from a copper slag named Koranel^®. The effects of metakaolinite, ordinary Portland cement (OPC) and surfactants were investigated. The reactivity of Koranel with potassium silicate solutions with molar ratio R = SiO₂/K₂O varying from 1 to 2.75, with 0.25 intervals, was investigated using isothermal calorimetry. The reactivity was relatively low at 20 °C; the reaction started after a few hours with a low silica modulus, to several weeks with the highest silica modulus. The substitution of Koranel by OPC (5 wt.%) or by metakaolinite (10–20 wt.%), both led to higher reaction heat and rate; meanwhile, the addition of 2 wt.% polyethylene glycol/2-methyl 2,4 pentanediol delayed the reaction time in the system containing metakaolinite. Raising the curing temperature from 20 °C to 80 °C shortened the setting time of the low reactive systems, from several days to almost instantaneous, opening perspectives for their application in the production of prepreg composite materials. The use of carbon fabric as reinforcement in the alkali-activated matrix led to composite materials with flexural strength reaching 88 MPa and elastic modulus of about 19 GPa—interesting for engineering applications such as high-strength lightweight panels. Full article

(This article belongs to the Special Issue Alkali-Activated Materials: Advances and Novel Applications)

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22 pages, 7154 KiB

Open AccessArticle

Reduction in Drying Shrinkage and Efflorescence of Recycled Brick and Concrete Fine Powder–Slag-Based Geopolymer

by Xiaoming Liu, Erping Liu and Yongtong Fu

Appl. Sci. 2023, 13(5), 2997; https://doi.org/10.3390/app13052997 - 26 Feb 2023

Cited by 5 | Viewed by 1595

Abstract

It is an effective method to prepare geopolymer with recycled brick and concrete fine powder (RP) and slag as main materials for the resource utilization of construction waste. However, its hydration products have large drying shrinkage and high efflorescence risk under normal curing [...] Read more.

It is an effective method to prepare geopolymer with recycled brick and concrete fine powder (RP) and slag as main materials for the resource utilization of construction waste. However, its hydration products have large drying shrinkage and high efflorescence risk under normal curing conditions. Until now, the durability of recycled brick and concrete fine powder–slag-based geopolymer (RPSG) has not been well documented, such as drying shrinkage and efflorescence. In this study, the effects of slag content, alkali equivalent and modulus on the durability properties of RPSG were evaluated. The results show: (1) Slag can significantly reduce the drying shrinkage and efflorescence of RPSG. (2) The potential for the efflorescence of RPSG increases with increasing alkali equivalent. The drying shrinkage of RPSG increases with the increase of alkali equivalent in the case of a low alkali equivalent (6 wt.% in this paper) and decreases with the increase of alkali equivalent in the case of a high alkali equivalent. (3) The drying shrinkage of RPSG increases with increasing modulus. In contrast, the degree of efflorescence decreases with increasing modulus. In this study, RP-S45-M1.3N6 (slag content: 45 wt.%; alkali equivalent: 6 wt.%; modulus: 1.3) is the best proportional design for RPSG with excellent durability. Compared to RP-S0-M1.3N6, the drying shrinkage of RP-S45-M1.3N6 is reduced by 76.32%, the capillary porosity is reduced by 60.9%, the visual efflorescence is significantly alleviated, and the early pH value is reduced by approximately 2.0. This paper systematically analyzed the drying shrinkage pattern and the efflorescence pattern of RPSG, which has a positive significance for promoting the recycling of RP from construction waste. Full article

(This article belongs to the Special Issue Alkali-Activated Materials: Advances and Novel Applications)

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13 pages, 3748 KiB

Open AccessArticle

Self-Healing Glass/Metakaolin-Based Geopolymer Composite Exposed to Molten Sodium Chloride and Potassium Chloride

by Patrick F. Keane, Rhys Jacob, Martin Belusko and Frank Bruno

Appl. Sci. 2023, 13(4), 2615; https://doi.org/10.3390/app13042615 - 17 Feb 2023

Cited by 3 | Viewed by 1545

Abstract

Geopolymers (GP) are a class of X-ray amorphous, nanoporous, nanoparticulate materials that can be mixed, poured, and cured under ambient conditions. Typically, geopolymers are made using a Group 1 (G1) alkali activator such as sodium or potassium metasilicate and an aluminosilicate precursor. An [...] Read more.

Geopolymers (GP) are a class of X-ray amorphous, nanoporous, nanoparticulate materials that can be mixed, poured, and cured under ambient conditions. Typically, geopolymers are made using a Group 1 (G1) alkali activator such as sodium or potassium metasilicate and an aluminosilicate precursor. An analogous material to GPs is ordinary Portland cement because of the similarities in processing, however, the resulting microstructure is more similar to that of a glass. Geopolymers are more thermally stable than OPC and can therefore be used in a variety of thermal energy storage systems, as energy storage is an increasing global concern. In this study, potassium metakaolin-based geopolymer composites containing glass particles and alumina platelets were manufactured, heated in air, and exposed to molten sodium chloride or potassium chloride under an air atmosphere. Results showed the formation of an amorphous self-healing geopolymer composite (ASH-G) that could contain molten G1 chlorides for over 200 h without signs of macro or microscopic chemical degradation. The filling of cracks by glass particles in the composite after heating to 850 °C makes this material self-healing. It was found that the morphology of ASH-G composites was more affected by temperature and duration than contact with corrosive molten chlorides in air. Future works include investigating the effect of molten salt on mechanical properties during initial heating, after prolonged heating, and the material compatibility with other molten Group 1 chloride eutectics. Full article

(This article belongs to the Special Issue Alkali-Activated Materials: Advances and Novel Applications)

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19 pages, 1792 KiB

Open AccessFeature PaperArticle

An Investigation on the Synthesis of Alkali Activated Materials from Thermally Modified Clays

by Guilherme Ascensão, Enrico Bernardo and Victor M. Ferreira

Appl. Sci. 2022, 12(18), 9085; https://doi.org/10.3390/app12189085 - 09 Sep 2022

Viewed by 1256

Abstract

The sustainability and economic competitiveness of alkali activation technology greatly depends on expanding the raw materials database with locally available resources. Therefore, a notable trend has been witnessed toward the exploitation of common clays as alternatives to well-established solid aluminosilicate precursors due to [...] Read more.

The sustainability and economic competitiveness of alkali activation technology greatly depends on expanding the raw materials database with locally available resources. Therefore, a notable trend has been witnessed toward the exploitation of common clays as alternatives to well-established solid aluminosilicate precursors due to their availability and wide geographical distribution. However, common clays are complex and dedicated research is needed to tailor synthesis procedures and mix designs for different clay resources. This paper describes the outcomes of a study conducted to investigate the influence of several synthesis parameters (solid-to-liquid ratio, NaOH molarity, Si availability, and curing conditions) on the properties of alkali activated binders produced from different thermally modified clays. Optimal synthesis conditions for benchmark metakaolin systems have been identified and binders were produced with progressive dosages of metakaolin replacement by common local clays. Fundamental physical and mechanical properties such as apparent density, open porosity, water absorption, and compressive strength were examined at different curing ages, and X-ray diffraction (XRD) was used to provide complementary mineralogical insights. By combining the effects of the parameters studied, mortar specimens were produced with the developed binders, reaching compressive strength values exceeding 28.2 ± 0.1 MPa, a bulk density as low as 1.78 ± 0.0 g/cm³, and open porosity and water absorption values lower than 15% and 8%, respectively. These properties are comparable to those of conventional hydraulic products, which presents them as interesting candidates for construction. Ultimately, this work aims to contribute with valuable insights toward the valorization of a large group of unexploited clay precursors by demonstrating the feasibility of producing technologically competitive alkali activated materials with little or no use of the prime precursors, thus adding to the extant knowledge and contributing to future scientific and industrial developments in this field. Full article

(This article belongs to the Special Issue Alkali-Activated Materials: Advances and Novel Applications)

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16 pages, 3631 KiB

Open AccessArticle

High-Temperature Behavior of CaO-FeO_x-Al₂O₃-SiO₂-Rich Alkali Activated Materials

by Guilherme Ascensão, Flora Faleschini, Maurizio Marchi, Monica Segata, Jorn Van De Sande, Hubert Rahier, Enrico Bernardo and Yiannis Pontikes

Appl. Sci. 2022, 12(5), 2572; https://doi.org/10.3390/app12052572 - 01 Mar 2022

Cited by 9 | Viewed by 1787

Abstract

Alkali-activated materials (AAMs) provide an opportunity to up-cycle several residues into added-value materials. Although generally praised for their performance under thermal loads, the thermal behavior of AAMs is dictated by a multitude of factors and the performance of CaO-FeO_x-rich systems may [...] Read more.

Alkali-activated materials (AAMs) provide an opportunity to up-cycle several residues into added-value materials. Although generally praised for their performance under thermal loads, the thermal behavior of AAMs is dictated by a multitude of factors and the performance of CaO-FeO_x-rich systems may differ from geopolymers. Therefore, this work ascertains the high‑temperature resistance of CaO‑FeO_x-Al₂O₃-SiO₂-rich AAMs. Mortars were exposed to different heating rates (≤10 °C/min) and temperatures (≤1100 °C), and volume and mass loss, apparent density, compressive strength (CS), mineralogical composition, and morphology were evaluated. At low heating rates, the main effects noted were densification and a gradual lightening of color as the temperature rose. CS underwent an abrupt decline at 750 °C and recovered at higher temperatures, reaching a maximum value of 184 ± 13 MPa at 1100 °C. With an increased heating rate to 10 °C/min, the strength loss at 750 °C persisted, but maximum CS was halved when firing at 900 °C. At 1100 °C, a significant reduction of CS was observed, but all samples maintained their integrity. Except for 1100 °C at 10 °C/min, all sintered-AAMs presented residual CS above 40 MPa. These results demonstrate that CaO-FeO_x-Al₂O₃-SiO₂-rich AAMs present interesting thermal behavior and can be potentially used to produce glass-ceramics or refractory materials from secondary resources. Full article

(This article belongs to the Special Issue Alkali-Activated Materials: Advances and Novel Applications)

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21 pages, 7252 KiB

Open AccessArticle

Effect of Elastomeric Expandable Additive on Compressive Strength and Linear Expansion of Fly-Ash-Based Strength-Enhanced Geopolymer Cement for Shrinkage-Resistant Oil-Well Cementing

by Siti Humairah Abd Rahman, Syed Ahmad Farhan, Yon Azwa Sazali, Luqmanul Hakim Shafiee, Nadzhratul Husna, Afif Izwan Abd Hamid, Nasir Shafiq, Nurul Nazmin Zulkarnain and Mohd Firdaus Habarudin

Appl. Sci. 2022, 12(4), 1897; https://doi.org/10.3390/app12041897 - 11 Feb 2022

Cited by 5 | Viewed by 2262

Abstract

The present study aimed to investigate the effect of an expandable additive on the compressive strength and linear expansion of geopolymer cement, which is an alternative to ordinary Portland cement, for oil-well cementing. Fly-ash-based geopolymer cement samples, with the addition of slag cement [...] Read more.

The present study aimed to investigate the effect of an expandable additive on the compressive strength and linear expansion of geopolymer cement, which is an alternative to ordinary Portland cement, for oil-well cementing. Fly-ash-based geopolymer cement samples, with the addition of slag cement as a strength enhancer, were prepared by using an elastomeric expandable additive (R-additive), which consists of styrene–butadiene rubber with a specific gravity of 0.945, at concentrations of 10%, 15%, 20% and 25% by weight of the solid blend, and cured in a water bath at 60 °C and atmospheric pressure, and a curing chamber at 90 °C and 3000 psi, or approximately 20.68 MPa. Mixability, amount of free water and slurry density were studied, and the effects of the concentration of R-additive on the compressive strength (F) and linear expansion (∆l/l₀) of the samples were analyzed. When cured at 60 °C and atmospheric pressure, the highest F of 15.01 MPa was obtained when the concentration of R-additive was 10%, while the highest ∆l/l₀ of 0.9985% was obtained when the concentration of R-additive was 25%. An increase in the curing temperature and pressure to 90 °C and 3000 psi (≈20.68 MPa) resulted in the reduction of F from 15.01 to 14.62 MPa and from 10.33 to 9.61 MPa, and the increase in ∆l/l₀ from 0.52% to 0.63%, and from 0.99% to 1.32%, when the concentrations of R-additive were 10% and 25%, respectively. The findings suggest that the formulations adopted, which contain R-additive at concentrations ranging from 10% to 25%, fulfilled the requirements of the oil and gas industry. Full article

(This article belongs to the Special Issue Alkali-Activated Materials: Advances and Novel Applications)

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18 pages, 3124 KiB

Open AccessFeature PaperArticle

Performance Enhancement of Alkali-Activated Electric Arc Furnace Slag Mortars through an Accelerated CO₂ Curing Process

by Dany Kassim, Ghandy Lamaa, Rui Vasco Silva and Jorge de Brito

Appl. Sci. 2022, 12(3), 1662; https://doi.org/10.3390/app12031662 - 05 Feb 2022

Cited by 10 | Viewed by 3639

Abstract

The use of electric arc furnace slag (EAFS) as sole precursor to produce alkali-activated mortars has been experimentally investigated. EAFS, a by-product of the steel recycling industry, is a coarse material with unevenly distributed and size-extensive particles. Milling of EAFS was required to [...] Read more.

The use of electric arc furnace slag (EAFS) as sole precursor to produce alkali-activated mortars has been experimentally investigated. EAFS, a by-product of the steel recycling industry, is a coarse material with unevenly distributed and size-extensive particles. Milling of EAFS was required to achieve a cement-like sized powder before it could be used as precursor. Different combinations of sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) were used, by varying the Na₂O/binder concentration (4%, 6%, 8%, 10%, 12%) and SiO₂/Na₂O ratio (0, 0.5, 1.0, 1.5, 2.0, 2.5) to maximize the mechanical performance. The alkaline solutions were prepared 24 h prior to mixing to unify temperatures for all mixes. The results showed that the SiO₂/Na₂O ratio and strength development are directly proportional. The maximum 28-day compressive strength obtained, after being subjected to an initial 24 h thermal curing at 80 °C, was 9.1 MPa in mixes with 4% Na₂O/binder and 2.5 SiO₂/Na₂O. However, after an additional 28 days of accelerated carbonation, the maximum compressive strength (i.e., 31 MPa compared to 3.9 MPa in uncarbonated mixes, corresponding to an 800% increase) was obtained in mixes with 12% and 1.0 for Na₂O/binder and SiO₂/Na₂O, respectively, thus showing an alteration in the optimal alkaline activator contents. Full article

(This article belongs to the Special Issue Alkali-Activated Materials: Advances and Novel Applications)

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