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Number of results: 4
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Abstract

This study explores the influence of alkali activators on the initiation of polymerization reaction of alumino-silicate minerals present in class-F fly ash material. Different types of fly ash aggregates were produced with silicate rich binders (bentonite and metakaolin) and the effect of alkali activators on the strength gain properties were analyzed. A comprehensive examination on its physical and mechanical properties of the various artificial fly ash aggregates has been carried out systematically. A pelletizer machine was fabricated in this study to produce aggregate pellets from fly ash. The efficiency and strength of pellets was improved by mixing fly ash with different binder materials such as ground granulated blast furnace slag (GGBS), metakaolin and bentonite. Further, the activation of fly ash binders was done using sodium hydroxide for improving its binding properties. Concrete mixes were designed and prepared with the different fly ash based aggregates containing different ingredients. Hardened concrete specimens after sufficient curing was tested for assessing the mechanical properties of different types concrete mixes. Test results indicated that fly ash -GGBS aggregates (30S2‒100) with alkali activator at 10M exhibited highest crushing strength containing of 22.81 MPa. Similarly, the concrete mix with 20% fly ash-GGBS based aggregate reported a highest compressive strength of 31.98 MPa. The fly ash based aggregates containing different binders was found to possess adequate engineering properties which can be suggested for moderate construction works.

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Authors and Affiliations

P. Gomathi
A. Sivakumar
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Abstract

Currently, one of the main challenges of civil engineering and science materials engineers is to develop a sustainable substitute for Ordinary Portland Cement. While the most promising solution is provided by the geopolymerisation technology, most of the studied geopolymers are based on natural raw materials (kaolin). The metakaolin is mainly preferred because of its rapid rate of dissolution in the activator solution, easy control of the Si/Al ratio, and white color. However, its high cost prevents it from being widely used in geopolymer composites or other materials that can become an industrial alternative for Ordinary Portland Cement. Several studies have shown that geopolymers with good performance can also be obtained from secondary raw materials (industrial wastes such as coal ash or slag). This explains why countries with rapidly developing economies are so interested in this technology. These countries have significant amounts of industrial waste and lack a well-developed recycling infrastructure. Therefore, the use of these by-products for geopolymers manufacturing could solve a waste problem while simultaneously lowering virgin raw material consumption. This study evaluates the effect of replacing different amounts of coal ash with sand on the microstructure of sintered geopolymers. Accordingly, scanning electron microscopy and energy dispersive X-ray analysis were involved to highlight the morphological particularities of room-cured and sintered geopolymers.
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Authors and Affiliations

D.D. Burduhos-Nergis
1
ORCID: ORCID
P. Vizureanu
1 2
ORCID: ORCID
D.C. Achitei
1
ORCID: ORCID
A.V. Sandu
1 3
ORCID: ORCID
D.P. Burduhos-Nergis
1
ORCID: ORCID
M.M.A.B. Abdullah
4 5
ORCID: ORCID

  1. Gheorghe Asachi Technical University of Iasi, Faculty of Materials Science and Engineering, D. Mangeron 41, 700050 Iasi, Romania
  2. Technical Sciences Academy of Romania, Dacia Blvd 26, 030167 Bucharest, Romania
  3. Romanian Inventors Forum, St. P. Movila 3, 700089 Iasi, Romania
  4. Centre of Excellence Geopolymer and Green Technology (CEGeoGTech), Universiti Malaysia Perlis (UniMAP), Arau 02600, Perlis, Malaysia
  5. Universiti Malaysia Perlis (UniMAP), Faculty of Chemical Engineering Technology, Arau 02600, Perlis, Malaysia
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Abstract

This paper details the properties, microstructures, and morphologies of the fly ash-based alkali-activated material (AAM), also known as geopolymers, under various steam curing temperatures. The steam curing temperature result in subsequent high strengths relative to average curing temperatures. However, detailed studies involving the use of steam curing for AAM remain scarce. The AAM paste was prepared by mixing fly ash with an alkali activator consisting of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH). The sample was steam cured at 50°C, 60°C, 70°C, and 80°C, and the fresh paste was tested for its setting time. The sample also prepared for compressive strength, density, and water absorption testings. It was observed that the fastest time for the fly ash geopolymer to start hardening was at 80°C at only 10 minutes due to the elevated temperature quickening the hydration of the paste. The compressive strength of the AAM increased with increasing curing time from 3 days to 28 days. The AAM’s highest compressive strength was 61 MPa when the sample was steam cured at 50°C for 28 days. The density of AAM was determined to be ~2122 2187 kg/m3, while its water absorption was ~6.72-8.82%. The phase analyses showed the presence of quartz, srebrodolskite, fayalite, and hematite, which indirectly confirms Fe and Ca’s role in the hydration of AAM. The morphology of AAM steam-cured at 50°C showed small amounts of unreacted fly ash and a denser matrix, which resulted in high compressive strength.
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Authors and Affiliations

Rafiza Abd Razak
1 2
ORCID: ORCID
Sh. Nur Syamimi Sy. Izman
2
ORCID: ORCID
Mohd Mustafa Al Bakri Abdullah
1
ORCID: ORCID
Zarina Yahya
1 2
ORCID: ORCID
Alida Abdullah
1
ORCID: ORCID
Rosnita Mohamed
1
ORCID: ORCID

  1. Universiti Malaysia Perlis, Geopolymer and Green Technology, Center of Excellence (CEGeoGTech), Kangar, Malaysia
  2. Universiti Malaysia Perlis (UniMAP), Faculty of Civil Engineering Technology, Perlis, Malaysia
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Abstract

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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Authors and Affiliations

M. Ibrahim
1 2
ORCID: ORCID
W.M.W. Ibrahim
2 3
ORCID: ORCID
M.M. Al B. Abdullah
1 2
ORCID: ORCID
L.H. Mahamud
1
ORCID: ORCID
M.N.N. Tajuddin
1
ORCID: ORCID
Nur Faezah Yahya
ORCID: ORCID

  1. Universiti Malaysia Perlis (UniMAP), Faculty of Chemical Engineering Technology, Taman Muhibbah, Jejawi, 02600 Arau, Perlis, Malaysia
  2. Universiti Malaysia Perlis (UniMAP), Center of Excellence Geopolymer & Green Technology (CeGeoGTech), 02600, Arau, Perlis, Malaysia
  3. Universiti Malaysia Perlis (UniMAP), Faculty of Mechanical Engineering Technology, 02600, Arau, Perlis, Malaysia

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