The effects of sodium hydroxide (NaOH) concentration on setting time, compressive strength and electrical properties at the frequencies of 100 Hz–10 MHz of high calcium fly ash geopolymer pastes were investigated. Five NaOH concentrations (8, 10, 12, 15 and 18 molar) were studied. The liquid to ash ratio of 0.4, sodium silicate to sodium hydroxide ratio of 0.67 and low temperature curing at 40 °C were selected in making geopolymer pastes. The results showed that NaOH concentration had significant influence on the physical and electrical properties of geopolymer paste. The pastes with high NaOH concentrations showed increased setting time and compressive strength due to a high degree of geopolymerization as a result of the increased leaching of silica and alumina from fly ash. The dielectric constant and conductivity increased with NaOH concentration while tan δ decreased due to an increase in geopolymerization. At the frequency of 103 Hz, the dielectric constants of all pastes were approximately 104 S/cm and decreased with increased frequency. The relaxation peaks of tan δ reduced with an increase in NaOH concentration and ranged between 2.5 and 4.5. The AC conductivity behavior followed the universal power law and the values were in the range of 3.7 × 10−3–1.5 × 10−2 at 105–106 Hz.

Effects of NaOH concentrations on physical and electrical properties of high calcium fly ash geopolymer paste

A comprehensive overview about the influence of different admixtures and additives on the properties of alkali-activated fly ash

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 state-of-the-art review on silico-aluminophosphate (SAP) geopolymers in terms of definition, chemistries involved during geopolymerization, mechanical and durability performance, environmental impacts, and their potentials in applications as compared 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, i.e., calcium-bearing C-(A)-S-H gels co-existed with N-A-S-H gels are dominant in AAS geopolymers, while S-A-P gels enhanced by phosphate-containing crystalline/amorphous phases are the main products in SAP geopolymers. Another advantage of SAP geopolymers is 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.

/pdf/silico-aluminophosphate-and-alkali-aluminosilicate-1iecttlysq.pdf

Silico-aluminophosphate and Alkali-aluminosilicate Geopolymers: A comparative review

Recent developments on inorganic polymers synthesis and applications

Volcanic ashes are pyroclastic materials commonly found in many regions of the world. Many deposits of volcanic ashes are unexploited, despite their potential interest for several engineering applications. The mineralogy and chemical composition of volcanic ashes depend on the type of magma from which they originate. The two common pyroclastic materials of interest for engineering applications are scoria and pumice. These pyroclastic materials are rich natural aluminosilicate geo-resources and their valorization can be of environmental and economic benefit. The current review summarizes the main interesting research outcomes on volcanic ashes in the fields of cements and concretes, geopolymers, ceramics, low grade refractory materials, lunar soil simulants and adsorbents. Factors affecting their suitability for specific applications are screened and possible areas of interest for future research suggested.

Review on the use of volcanic ashes for engineering applications

Accounting for carbon dioxide (CO2) emissions is critical for developing evidence-based action plans for climate change mitigation in cities. The recognition of this, over the past three decades or so, has led to an increasing interest in developing methods for urban CO2 accounting and mapping. This study examines 662 articles published over the past three decades to identify major thematic areas of research on carbon accounting in cities and determine how they are linked. We also examine how the focus and intellectual base of the field have evolved over time (i.e., across three periods, namely, 1988–2006, 2007–2014, and 2015–2021) and identify the significant factors (i.e., authors, institutions, and sources) that have contributed to the evolution of knowledge on urban carbon accounting. For this purpose, we used VOSviewer, a widely-used bibliometric analysis software tool that utilizes network analysis techniques such as term-occurrence, co-citation, and bibliographic coupling. Results show that until 2006, research on this topic was very limited and focused on a few American cities. Between 2007 and 2014, the knowledge base expanded considerably, and airborne measurements and various urban metabolism techniques were used. During this period, different types of carbon footprinting methods, such as production- and consumption-based accounting emerged. Since 2015, the field has grown even more rapidly, with more diverse methods being used to estimate the driving factors of urban CO2 emissions. We posit that assessment reports of the Intergovernmental Panel on Climate Change (IPCC) and international policy documents such as the Agenda 2030, Paris Climate Agreement, and the New Urban Agenda could have contributed to this increased interest in urban carbon accounting. This study can function as a reference for those interested in obtaining information about urban carbon accounting and its evolution. 

Urban carbon accounting: An overview

The invention discloses an organic and inorganic composite insulation material which is a composite material prepared from an organic material as aggregate and an inorganic material as a bonder by stirring in a mixed way, moulding and forming at normal temperature or extruding and forming at high temperature The proportion of the organic material to the inorganic material in parts by weight is (5-25): (75-95) The organic material is polystyrene foam or polyvinyl chloride foam or polyurethane foam The inorganic material is aluminium silicate geological polymer material The organic and inorganic composite insulation material prepared by the invention not only has good thermal insulation performance but also is advantageous for bonding to the inorganic material, such as a wall body and the like and is simple for construction and low in cost; and compared with the traditional organic insulation material, the organic and inorganic composite insulation material has the advantages of high strength, difficult combustion, low water absorption, low deformation, air permeability, light weight and the like

Organic and inorganic composite insulation material

The invention discloses a geopolymer/waste rubber powder compound dry powder material and a preparation method thereof The geopolymer/waste rubber powder compound dry powder material comprises a geopolymer dry powder material consisting of ground blast furnace slag powder body, pulverized fuel ash and solid water glass powder, and waste rubber powder The preparation method comprises the step of compounding the geopolymer dry powder with the waste rubber powder to obtain the geopolymer/waste rubber powder compound dry powder material after uniformly mixing The geopolymer/waste rubber powder compound dry powder material has the advantages that 1, the geopolymer/waste rubber powder compound dry powder material is simple preparation in process, easy to store, low in cost, low in energy consumption and free from pollution; 2, main raw materials comprise industrial residue and reclaimed rubber powder, are wide in sources, low in cost and easy to obtain; 3, the material can be applied to road engineering, constructional engineering, port engineering, military engineering and the like

Geopolymer/waste rubber powder compound dry powder material and preparation method thereof

The invention discloses a preparation method of a NaA zeolite molecular sieve. The method employs a chemically synthesized powder Al2O3-SiO2 and sodium silicate with modulus of 0.7-0.9 as raw materials to prepare a geopolymer, which is directly converted into a NaA zeolite molecular sieve through heat treatment without hydrothermal crystallization. Compared with the prior art, the invention has the following advantages: (1) the method provided by the invention combines with the advantage that preparation of the geopolymer material can employ a plurality of moulding methods, and the shape of the zeolite molecular sieve can be designed according to application requirements, so as to further widen the scope of application of the molecular sieve; and (2) the method provided by the invention does not require hydrothermal crystallization and has simple process.

Preparation method of NaA zeolite molecular sieve

A novel aluminosilicate geopolymer material with low dielectric loss

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