Synthesis of water treatment sludge ash-based geopolymers in an Amazonian context
- Authors: Santos, Gessica , Melo Filho, Joao , Pinheiro, Mauricio , Manzato, Lizandro
- Date: 2019
- Type: Text , Journal article
- Relation: Journal of Environmental Management Vol. 249, no. (Nov 2019), p. 8
- Full Text: false
- Reviewed:
- Description: Water treatment plants (WTP) in the City of Manaus, Brazil, generate tons of sludge daily, which are then disposed of in landfills and main watercourses, particularly two important Amazonian Rivers: the blackwater Negro River and the pale sandy-colored water Solimoes River. Because WTP-based sludges are rich in silicon and aluminum, they have been employed in the synthesis of geopolymers - alkaline activated inorganic polymers consisting of silicate and aluminosilicate chains. This paper reports the results of a geopolymeric synthesis process in which calcined sludge was explored as a source of silica and alumina. In this research, a laboratory testing program was developed to characterize the waste material generated from a water treatment plant in Manaus, whose intake water is influenced by the above referred rivers. Sample preparation involved kiln drying at 110 degrees C for 8 h, grinding in ball mill for 2 h, and calcination at 750 degrees C for 6 h. The calcined sludge was used as precursor, and potassium hydroxide added as activating alkali. Two geopolymers, one from each sludge source, were prepared following identical procedures. The chemical, compositional, morphological, thermal and mechanical properties of the fresh and hardened geopolymers were characterized. The geopolymers reached uniaxial compressive strengths of over 50 MPa at 28 days. Calcination conveyed more refined properties to the sludge-based geopolymers, akin to metakaolin-based geopolymers. The results presented herein support the technical feasibility of geopolymer synthesis in the lab scale.
Temperature and duration impact on the strength development of geopolymerized granulated blast furnace slag for usage as a construction material
- Authors: Arulrajah, Arul , Maghool, Farshid , Yaghoubi, Mohammadjavad , Phetchuay, Chayakrit , Horpibulsuk, Suksun
- Date: 2021
- Type: Text , Journal article
- Relation: Journal of Materials in Civil Engineering Vol. 33, no. 2 (2021), p.
- Full Text: false
- Reviewed:
- Description: Through the process of extracting iron from iron ore, a by-product is generated known as granulated blast furnace slag (GBFS). Traditional stabilization methods such as cement stabilization are not entirely sustainable options. This research investigates the engineering properties of geopolymer-stabilized GBFS and their viability for usage as a construction material. A combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) was used as the liquid alkaline activator (L) along with low-carbon pozzolanic binders, namely, fly ash (FA) and slag (S). The L was prepared with a Na2SiO3:NaOH ratio of 70 30 and binders were added up to 30%. The effect of different curing regimes on the strength of geopolymerized GBFS was evaluated using scanning electron microscopy (SEM) and unconfined compressive strength (UCS) tests. The effect of both the temperature and duration of curing had a vital role in the strength development of the mixtures. The test results indicated that the combination of FA+S as a geopolymer binder could perform better than FA or S alone. With the lowest UCS value of 7.8 MPa and highest value of 43 MPa, all the geopolymer-stabilized GBFS were found to be suitable for a variety of civil and construction applications. © 2020 American Society of Civil Engineers.
Utilisation of alkaline activated industrial by-products in deep soil mixing
- Authors: Yaghoubi, Mohammadjavad , Arulrajah, Ar , Disfani, Mahdi , Horpibulsuk, Suksun , Bo, Myint , Leong, Melvyn
- Date: 2017
- Type: Text , Conference paper
- Relation: Seventh International Conference on Geotechnique, Construction Materials and Environment, Nov. 21-24, 2017, ISBN: C3051, Mie, Japan p. 96-101
- Full Text:
- Reviewed:
- Description: The use of deep soil mixing (DSM) technique in deep ground improvement projects has increased over the past decade due to being more cost-effective and easier to implement compared to other techniques such as piling, for structures subject to low to medium loads. Currently, Portland cement, lime and their combination are being used as the most common binders in DSM. However, due to the economic and concerning environmental disadvantages of using these binders, there is a need for new environmentally friendly cementing materials. This research attempts to find a way to use stockpiles of industrial by-products, such as fly ash (FA) and slag (S), as new green binders; consequently, reducing the carbon footprint in ground improvement projects. Different contents of FA and S, activated by liquid alkaline activator (L), were added to a soft marine soil to evaluate the changes in its behaviour as well as its microstructure. In addition, mixtures with cement (C), lime (Li) and their combination were prepared and tested for comparison. Binders were added at contents of 10, 20 and 30%, by dry soil mass, and samples were cured for 7 days. The results revealed that these new binders significantly increased the strength and stiffness of the soft soil, and they can be a suitable replacement for C and Li. The optimum mixture was found to be CIS+5% FA+15% S, within the range of binder, L and water content studied in this research. Moreover, recycling FA and S would substantially limit the expansion of landfill sites.
Review and experimental investigation of retarder for alkali-activated cement
- Authors: Holschemacher, Klaus , Tekle, Biruk
- Date: 2023
- Type: Text , Book chapter
- Relation: Proceedings of the 75th RILEM Annual Week 2021: Advances in Sustainable Construction Materials and Structures p. 614-625
- Full Text: false
- Reviewed:
- Description: Alkali-activated cement (AAC) cured at ambient temperature conditions have a wider application area compared to heat cured AAC. High calcium precursor materials such as ground granulated blast furnace slag (GGBS) are commonly used to achieve ambient curing behavior. However, the GGBS results in a short setting time. Hence setting adjustment is critical in such AAC systems. This paper reviews state-of-the-art in the area of retarders for AAC systems. The most promising prospective retarders such as zinc salts, borax, sucrose, and phosphates are investigated. The retarder’s effect is dependent on the precursor materials and alkaline activators used. Consequently, in the review, these are identified for each retarder discussed. Some of the retarders were then tested in AAC with a blended precursor system containing fly ash (FA) and GGBS activated with sodium hydroxide and sodium silicate. The results showed that each borax percentage, with respect to the total solid binder, increases the setting time by about 50% of the mix without borax. Sucrose, sodium acetate, acetic, and phosphoric acids have no significant effect on the investigated AAC’s setting time. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.
Freeze–thaw resistance and sorptivity of fine-grained alkali-activated cement concrete
- Authors: Tekle, Biruk , Ly, Tran , Hertwig, Ludwig , Holschemacher, Klaus
- Date: 2023
- Type: Text , Journal article
- Relation: Structural Concrete Vol. 24, no. 3 (2023), p. 4286-4296
- Full Text:
- Reviewed:
- Description: The paper investigates the freeze–thaw resistance and sorptivity behavior of fine-grained alkali-activated concrete cured at ambient temperature. A blended binder system containing fly ash, ground granulated blast furnace slag, and silica fume was used. A combination of sodium hydroxide and sodium silicate was used as an activator. The freeze–thaw resistance was evaluated based on mass loss (scaling), and the extent of internal damage was assessed by testing the ultrasonic time at different cycles. Initial and secondary sorptivity coefficients were calculated based on the cumulative water absorption values at different time intervals. Alkali content, sodium silicate to sodium hydroxide ratio, and water to binder ratio were investigated. The experimental results showed that water to binder ratio is the most significant parameter for the scaling; higher ratios result in higher scaling. In terms of internal damage, alkali content is the most significant. The increase of alkali increased the amount of internal damage in the concrete. The initial sorptivity coefficient increased with the water and alkali content and decreased with the silicate content. The secondary sorptivity coefficient showed no significant change with the investigated parameters. © 2022 The Authors. Structural Concrete published by John Wiley & Sons Ltd on behalf of International Federation for Structural Concrete.