Evaluation of the potential improvement in the environmental footprint of geopolymers using waste-derived activators

Passuello, Ana; Rodríguez, Erich D.; Hirt, Eduardo; Longhi, Márlon A.; Bernal, Susan A.; Provis, John L.; Kirchheim, Ana Paula

doi:10.1016/j.jclepro.2017.08.007

Cited by 162 publications

(60 citation statements)

References 28 publications

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“…-RHA can offer an alternative to the commercial solution with the potential advantage of lower cost and lower environmental impact, as has been suggested in the literature (Passuello et al, 2017;. Some further economic and environmental analysis, even at a preliminary level, would strengthen the case for converting a waste into an added value product for either local use or for export to provide a valuable income stream.…”

Section: Research Significancementioning

confidence: 92%

“…The process is also expensive due to its energy consumption. The development of alternative activators with reduced CO2 footprint and thus better sustainability credentials when used for geopolymer concrete is therefore much desired and can lead to significant reduction in the global warming potential of alkali activated binders (Passuello et al, 2017;.…”

Section: Introductionmentioning

confidence: 99%

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Use of Vietnamese rice husk ash for the production of sodium silicate as the activator for alkali-activated binders

Tong

Vinai

Soutsos

2018

Journal of Cleaner Production

193

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Geopolymer and Alkali-Activated Binders (AAB) has recently emerged as a new, green material with the potential to replace Portland cement in several applications. They can reduce the CO2 footprint of concrete by up to 80% and this is in addition to being more durable in certain aggressive environments. However, commercial alkaline activators contribute significantly to the cost and CO2 footprint of AAB concrete mixes. This research investigated the production of a low cost, low environmental impact sodium silicate solution (waterglass) from Rice Husk Ash (RHA) and more specifically RHA from Vietnam. A hydrothermal process for the dissolution of RHA in sodium hydroxide solution was developed. Sodium hydroxide solution concentration, process temperature and duration were studied. Optimised procedure parameters were found to be: NaOH concentration 3M, heating temperature 80 ℃ and heating duration 3h. The obtained solution was used for the production of AAB mortar made with a blend of fly ash and ground granulated blast furnace slag. Obtained compressive strength of mortar was in the range of 60 MPa at 28 days, matching the strength obtained from control samples produced with commercially available activators. Microstructural investigation (isothermal calorimetry, infrared spectroscopy, X-ray diffraction and thermogravimetric analysis) on pastes confirmed the equivalence between the solution produced with the optimised method and commercially available options. Cost analysis indicated that the proposed method could allow a reduction of almost 55% of the cost for the activation of AAB. Results from a simplified preliminary environmental analysis suggested increased sustainability of the RHA-derived solution when compared with commercially available waterglass.

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Section: Research Significancementioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Use of Vietnamese rice husk ash for the production of sodium silicate as the activator for alkali-activated binders

Tong

Vinai

Soutsos

2018

Journal of Cleaner Production

193

View full text Add to dashboard Cite

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“…Due to the vast of mineral resource consumptions, intensive energy usage and high carbon emissions companioned with ordinary Portland cement (OPC) production, it is believed that the geopolymer binders should be strongly proposed as green building materials to partially replace cement in future construction applications (Walkley et al, 2017). Usually, the life cycle assessment (LCA) methodology, also known as the "cradle to grave" approach, is internationally normalized to provide quantitative information for the environmental burden of each product manufacture system (ISO, 2006;Passuello et al, 2017). However, the recent findings related to the LCA-based comparison between geopolymer and OPC products showed a wide variation, even some conflicting results, depending on the goal, scope, the needs, and the targeted audience used in LCA analysis (Ouellet-Plamondon and Habert, 2015).…”

Section: Environmental Impact Portland Cement and Geopolymer Bindersmentioning

confidence: 99%

Silico-Aluminophosphate and Alkali-Aluminosilicate Geopolymers: A Comparative Review

2019

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Chemically activated materials (often termed as geopolymer) have received attracting attentions in civil, material and environmental research fields as a toolkit alternative to traditional Portland cement in specific applications. This paper presents a comparative review on silico-aluminophosphate (SAP) geopolymers in terms of definition, chemistries involved during geopolymerization, mechanical performance, durability, environmental impacts, and their potentials in applications relative to conventional alkali-aluminosilicate (AAS) geopolymers. Recommendations for future applications are also highlighted. It is found that S-A-P gels with six-coordinated aluminum environment dominate in SAP geopolymers, while the aluminum in N-A-S-H gels formed in the AAS geopolymers is characterized by four-coordinated features. Besides, the slow performance development of SAP geopolymer matrix under ambient temperature curing can be compensated through incorporating additional countermeasures (e.g., metal sources) which allow the tailored design of such geopolymers for certain in-situ applications. Generally, the calcium-bearing C-(A)-S-H gels co-existing with N-A-S-H gels are dominant in AAS geopolymers, while the S-A-P gels enhanced by phosphate-containing crystalline/amorphous phases are the main products in SAP geopolymers. The SAP geopolymers show their environmental friendliness relative to the AAS geopolymers due to the utilization of phosphate activators that require lower production energy relative to silicate-containing activators. However, the higher cost of phosphate activators may confine the applications of SAP geopolymers in some exquisite or special fields.

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“…The increase in the environmental impact can be related to the composition of the alkali-activator, where soluble silicate (such as sodium silicate) is the highest contributor. More recently, Passuelo et al (2017), using a Brazilian calcined clay as precursor and a rice husk ash as part of the activator, reported that, per unit of compressive strength, the right design of material can provide a 50-75% reduction of CO 2 emissions. These have been one of the main forces driving the current research and industrial development of geopolymers.…”

Section: Introductionmentioning

confidence: 99%

Efflorescence of Alkali-Activated Cements (Geopolymers) and the Impacts on Material Structures: A Critical Analysis

et al. 2019

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Even with the rapid development of the alkali-activated cement (AAC) technology in the past few years, some phenomena still needs to be better understood, that may alter the durability of the material. In many industrial uses and laboratory researches the formation of the salts on the surface alkali-activated type cements was observed, which was identified as efflorescence. This occurs due to the presence of an alkali transported in contact with the humidity and CO 2 environment. It may present externally from the formation of salts on the surface and internally with the carbonation of the alkalis in capillary pores. The effects of efflorescence on the material in use, as well as all factors that can influence its formation are not yet fully understood or reported. The search for papers was conducted using the search words efflorescence and geopolymer/alkali-activated, combined in the electronic data base. Due to the limited quantity of papers published related to efflorescence in geopolymers, the review was complemented using papers that discuss this behavior in Portland cement (PC) and based on the main properties that can influence the formation of efflorescence. In this paper, to understand the nature of efflorescence, upon which proper methods of minimizing of this issue can be based, the following aspects are discussed and reexamined: (1) the development of efflorescence's in PC concrete, (2) the role of alkalis in AACs, (3) efflorescence in AACs, and (4) effect from a physical and microstructural point of view of efflorescence's on the ACCs. This paper highlights that the nature of the pore structure and the design parameters (such as alkali concentration, presence of soluble silicates, and water content in the activator) are the two most important factors that control efflorescence rate and changes in mechanical behavior. However, the stability of the alkalis and their relationship with the formed gel, which are determining factors in the formation of efflorescence, remain not completely understood. In the same way, the effect of efflorescence in tensile strength and shrinkage needs to be evaluated.

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Evaluation of the potential improvement in the environmental footprint of geopolymers using waste-derived activators

Cited by 162 publications

References 28 publications

Use of Vietnamese rice husk ash for the production of sodium silicate as the activator for alkali-activated binders

Use of Vietnamese rice husk ash for the production of sodium silicate as the activator for alkali-activated binders

Silico-Aluminophosphate and Alkali-Aluminosilicate Geopolymers: A Comparative Review

Efflorescence of Alkali-Activated Cements (Geopolymers) and the Impacts on Material Structures: A Critical Analysis

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