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The Influence of Foaming Agent Towards Metakaolin Based Alkali Activated Materials Properties and Cu2+ Adsorption

Ibrahim Masdiyana, Ibrahim Wan Mastura Wan, Abdullah Mohd Mustafa Al Bakri, Mahamud L. H., Tajuddin Muhammad Noorfadzlin Najmi, Yahya Nur Faezah

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 3

1077--1086

EN

The performance of adsorbent synthesized by alkali activation of aluminosilicate precursor metakaolin with sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) as well as the foaming agent was studied for copper ions adsorption from aqueous solution. This paper investigated the effect of adding hydrogen peroxide (H2O2) and aluminium powder as foaming agents to an alkali activated materials slurry. The experimental range included 0.50 wt%, 0.75 wt%, and 1.00 wt% hydrogen peroxide and 0.02 wt%, 0.04 wt%, and 0.06 wt% aluminium powder. A control sample without a foaming agent was also created for comparison. The specific surface area, water absorption, density, compressive strength and microstructure of metakaolin based alkali activated materials were evaluated. The adsorption capability of Cu2+ with addition of hydrogen peroxide and aluminium powder was then tested. Results indicate hydrogen peroxide addition had superior pore size distribution and homogeneous porosity than aluminium powder, implying improved copper ion elimination. Cu2+ adsorption capability reached 98% with 0.75 wt% hydrogen peroxide and 24.6076 m2/g surface area. The results demonstrating that low cost metakaolin-based AAMs are the most effective adsorbent for removing copper ions.

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Valorization of a steel industrial co-product for the development of alkali-activated materials : effect of curing environments

Sarri Arezki, Oualit Mehena, Kennouche Salim

Advances in Materials Science

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2023

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Vol. 23, nr 2(76)

45--63

EN

While natural resources are becoming scarce and climate change is accelerating, the recovery and recycling of wastes and by-products is an effective way to deal with the economic and ecological constraints of recent decades. The valorization of industrial by-products in civil engineering is a common practice either by their incorporation during the manufacture of Portland cements or as a partial replacement of cement during the production of concrete. The present work aims to develop waste-based alkali-activated materials WAAMs intended for civil engineering applications as a potential alternative to cement-based materials. A steel industrial by-product called commonly granulated blast furnace slag GBFS was used alone as a solid CaO-rich precursor; two alkaline activators such us sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) were used separately for the production of two-part alkali-activated materials. Besides the microstructure analysis of the hardened samples, the influence of activator/precursor mass ratio, NaOH molarity, and two curing environments (Room temperature and 60°C) on the compressive strength, water accessible porosity, mass loss, and drying shrinkage were assessed. The results showed that a high Liquid/Solid ratio leads to a decrease in the compressive strength of the samples, while high NaOH molarity significantly improves the mechanical properties by reducing the porosity of the specimens. Moreover, alkaline silicate activator provides higher compressive strengths compared to the alkaline hydroxide activator, especially when the samples were cured at room temperature where a maximum 28days-compressive strength value of 105.28 MPa was achieved. For the samples activated using sodium hydroxide solution, the results revealed that their curing at 60°C promotes obtaining high initial-compressive strengths (7 days) before decreasing subsequently as a function of the curing time. As an indication, at high alkaline concentration (NaOH = 9M), a mechanical strength decline of 21% was recorded between a curing time of 7 to 28 days. Moreover, curing at 60°C induced high porosity, significant mass loss and high drying shrinkage. SEM analysis highlighted a dense, homogeneous microstructure without apparent defects, in particular for the samples where the alkali silicate activator was used.

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Delayed setting time for alkali-activated slag composites using activator containing SiO2 and Na2O

Hung Chi-Che, Lin Wei-Ting, Yeih Wei-Chung, Chang Jiang-Jhy

Materials Science Poland

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2021

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Vol. 39, No. 4

570--579

EN

This study examines the influence of SiO2 and Na2O mix proportions on the properties of alkali-activated slag (AAS) pastes. In order to solve the rapid setting problem associated with AAS, phosphoric or silicic acid is commonly added to the alkaline activator. The retarding effect of these additions suggests a close relationship between pH and setting time. In this study, AAS pastes with various SiO2 and Na2O dosages were analyzed. Regression analysis was carried out using pH value and setting time to identify the main parameters affecting the setting time. Results showed that the alkali modulus (i.e., the weight ratio of SiO2 over Na2O) is correlated with the pH value. Specifically, the initial and final setting times were significantly reduced under lower SiO2 and Na2O dosages. Therefore, a higher alkali modulus prolonged the setting time.

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Feasibility of alkali-activated mining waste foamed materials incorporating expanded granulated cork

Beghoura I., Castro-Gomes J., Ihsan H., Estrada N.

Mining Science

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2017

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Vol. 24

7--28

EN

Different combinations of mining waste mud, grounded waste glass, Portland cement, metakaolin and expanded cork were mixed together with alkaline activators (sodium silicate and sodium hydroxide solution) and as well aluminum powder or hydrogen peroxide to produce foamed lightweight materials. The size of the mineral materials is under 500 µm and expanded cork particles size is between 2 to 4 mm. The expanded cork added to the mixes changed between 10 to 40% volume of total solids. The influence of expanded cork on compressive strength was investigated. Precursors and activators were mixed together to produce a homogeneous mixture, which was placed into a cubic mold (40 x 40 x 40 mm3), and cured at a temperature of 60°C, for 24 hours. After curing process, samples without foaming agents achieved the maximum compressive strength of 14.7 and 19.5 MPa for 7 and 28 days respectively. The porosity was observed by the naked eye of large voids in a range of 4 mm in size. Microstructure analyses were carried on by SEM. Samples made with aluminum powder showed higher volume increase about 358% compared with samples made with hydrogen peroxide that presented a 141% volume increase. This preliminary study shows the feasibility to produce new improved lightweight foamed alkali activated materials incorporating expanded cork with potential applications in artistic, architectural, and historical heritage restoration.

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A review on mineral waste for chemical-activated binders: mineralogical and chemical characteristics

Sedira N., Castro-Gomes J., Kastiukas G., Zhou X., Vargas A.

Mining Science

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2017

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Vol. 24

29--58

EN

This review discusses the potential of alkali-activated materials obtained from mineral waste. A brief historical background on alkali-activated materials is presented. Recent advances in the development of binders obtained from mineral wastes and alkali-activated solutions are described. The scope of this state of the art review is to identify current knowledge in support that mineral waste can be used for the production of alkali-activated binders. In addition, this review identifies the chemical activators that can be effectively utilized for such purposes in the age when wastes are still viewed by industry as dis-posable. Some mineral wastes which are discussed can be viewed as a new resource for recycling and recovery which will offer important economic and social benefits.