Geopolymer Research Articles

Characteristic compressive strength of a geo polymer concrete

The principle issue the world confronting today is natural contamination. Because of industrialization, there is tremendous discharge of ozone harming substances (for example CO2) into condition. We can diminish the impact of contamination on the earth by expanding the use of modern results. There comes the idea “GEO POLYMERS CONCERTE”. In this entire cement content is swapped with engineering by products. We are replacing with Ground Granulated Blast-furnace Slag (GGBS), silica flumes & gypsum. Alkaline liquid like NaOH & Na2SiO3 are used for binding of materials. On an experimental basis we selected the proportions 1:1.5:3 and 1:1:2 and we are considering 9 M and 13 M of NaOH and 20% and 40% concentration of Na2SiO3.This examination researches the trademark compressive quality of geopolymer concrete by throwing solid shapes and chambers and discovering the trademark compressive qualities at 28 days utilizing encompassing relieving. We are replacing entire cement content with GGBS (70%) and silica fumes (30%). From the outcomes we see that trademark compressive superiority of Geopolymer dense additions with the development in sodium silicate fixation and most extreme happened at 40% of Na2SiO3 and the announcement “compressive strength of cylinder is 0.8 times the compressive strength of cube” is not valid for geopolymer concrete. We also found that geo-polymerization process is sensitive with temperature.

Fiber-matrix Adhesion on Industrial Geopolymer

Fiber-matrix Adhesion on Industrial Geopolymer

Suitability of metakaolin-based geopolymers for underwater applications

The development and use of geopolymers (GPs) considerably increased in the construction industry. This paper assesses the suitability of metakaolin-based GP mortar and concrete mixtures for underwater applications, including the performance comparison to cementitious (CEM)-based materials. Results showed that the flow times and rheological properties of GP mixtures are significantly higher (i.e., about 2 to 5.5-times) than CEM-based ones. This was mostly related to the high viscosity of the alkaline activator that promotes hydrogen bonding and entanglements between interstitial solution and solid particles. The GP mixtures showed no signs of bleeding and remarkably lower levels of washout loss, reflecting excellent stability as well as superior resistance to dilution, erosion, and washout phenomena upon underwater placement. Their residual compressive, flexural, and pull-off bond strengths varied from 65 to 95% (as opposed to 25–70% for CEM-based materials), revealing the suitability of metakaolin-based GPs for underwater placement.

Evaluation of Strength and Durability of Geo Polymer Concrete

Evaluation of Strength and Durability of Geo Polymer Concrete

Lightweight geopolymers made of mineral wool production waste

Lightweight geopolymers made of mineral wool production waste

Gender Balance in Construction Material Research: The Analysis of Alkali-Activated Materials by a Bibliometric Study Using Scopus Database

Research in alkali activated materials (AAMs) is an innovative and dynamic Material Science topic. This is due to the relevant performances in terms of physico-mechanical properties comparable to traditional construction materials (e.g. ordinary Portland cement). The sustainability of AAMs are often highlighted since they can be developed by using many natural or industrial by-products-based precursors. The leads to challenges with the optimization of AAMs production, due to their different performances, availability, and costs. However, they are flexible and locally adapted materials. The research interest on AAMs has rapidly increased in the early 2000s. In recent years, about 1000 international papers have been published each year. This study aims at assessing the gender balance of this specific research topic to investigate the relevance of women participation. Author lists of the published papers were analyzed throughout SCOPUS database, applying “alkali activated material” and “geopolymers” as keywords in the titles, abstracts, and keywords search. The last 10 years (2009 – 2019) were taken into account. The gender of the most prolific authors was analyzed and a focus of European authors on this topic was considered, as more than 25% of the research in AAMs has been carried out in Europe. The analysis of 5900 papers in the last decade shows that there is currently a shift toward men in the gender balance in this specific research and female authors only covered 22% of the most productive authors worldwide. Considering European authors, a more equal gender distribution is reached, when the first author is considered, with a concentration of women in the range of 36-56%, recorded over 1396 papers.

Effect of pre-treatment of flax tows on mechanical properties and microstructure of natural fiber reinforced geopolymer composites

In this work we studied the effect of pre-treatment of low-grade flax product (flax tows, FTs) by cleaning it mechanically from shives and weeds, followed by mercerization with a 5% aqueous NaOH solution and ultrasonic (US) treatment (22 kHz, 500 W) in alkaline medium, on the mechanical properties and microstructure of fly ash-based geopolymer (GP) composites. A series of three-point bending flexural tests was conducted on several types of GP/FTs composites while ATR-FTIR spectroscopy, scanning electron microscopy, and confocal laser scanning microscopy were applied to evaluate morphological and chemical characteristics of FTs and their interface strength with GP matrix. It is shown that combined treatment with alkali and high-intensity ultrasound is an effective way to process and modify the surface of FTs fibers for reinforcing “green” geopolymer composites, providing the best technical and economic effects.

Bond strength between concrete substrate and metakaolin geopolymer repair mortars at ambient and elevated temperatures

Ordinary Portland cement (OPC) is commonly adopted as an effective binder in the production of concrete and cementitious mortars. The metakaolin (MK) based geopolymer (GP) binder offers a sustainable alternative to the OPC due to its essential environmental and technical benefits in reducing the carbon footprint. In the present study, two conventional and six GP repair mortars were used. Three GP mortars were plain (without fibers), and the remaining three were produced by mixing Polyvinyl-alcohol (PVA) fibers. The GP mixes were produced by varying sand content, alkaline solids to MK, and sodium silicate to NaOH ratios, resulting in different molar ratios. The test specimens were prepared by overlaying a 5 mm thick layer of repair mortar on a concrete substrate for conducting pull-off strength tests. This research was undertaken to investigate the effect of exposure to elevated temperatures on the performance of bond strength of GP mortar used as a repair material. The test specimens were subjected to ambient temperature and elevated temperatures of 200 and 400 °C for a duration of 3 h before conducting pull-off tests. The test results revealed that the selected GP mixes could be a promising alternative repair material for structures due to their good bond strength performance. The addition of fibers in stable mixes of GP mortars enhanced the bond strength at ambient as well as when exposed to 200 °C, through crack control mechanism.

Correction to: Utilization of geopolymer cements as supercapacitors: influence of the hardeners on their properties

Correction to: Utilization of geopolymer cements as supercapacitors: influence of the hardeners on their properties

Influences of characteristics of the alkaline activator on the compressive strength and microstructure of the fly ash-based geopolymer pastes

Influences of characteristics of the alkaline activator on the compressive strength and microstructure of the fly ash-based geopolymer pastes

Chemical evaluation of immobilization of wastes containing Pb, Cd, Cu and Zn in alkali-activated materials: A critical review

• Insoluble M(OH) 2 , MCO 3 , MSiO 3 , MO and MS (M = Pb, Cd, Cu and Zn) exist in geopolymer. • M(OH) 2 could be transformed within geopolymer into soluble M(OH) 3 − and M(OH) 4 − . • Metal species have water solubilities that are lower than the accepted limits. • Metal sulfides are the most resistance to leaching from geopolymer. • Pb-O, Cu-O and Si-O bonds have similar ionic character. Alkali activated materials, known as geopolymers (GPs), have been shown to be potential hosts for immobilization of heavy metal wastes. Upon incorporation of heavy metals into the GP matrix, metal hydroxides, carbonates, silicates, oxides and sulfides are expected to be formed. Since experimental study of these species is very difficult, the present work is devoted to use the available thermodynamic data to calculate the solubility of metal species in leaching solutions. Metal hydroxides of Pb, Cd, Cu and Zn have water-solubility (0.034, 1.4, 0.011 and 0.13 mg/L, respectively) lower than the recommended limits (5, 1, 15, 100 mg/L, respectively), however at pH 6, the solubility is much higher (43.3, 5.38 × 10 6 , 27.96 and 2.09 × 10 4 mg/L, respectively). Thermodynamic calculations show that metal hydroxides (M(OH) 2 ) have high solubility in 6.0 M NaOH (7.2 × 10 3 , 15, 2.9 × 10 3 , 9.8 × 10 4 mgL, respectively) as oxoanionic species (M(OH) 3 − and M(OH) 4 2- ) which could not be stabilized by attachment to the negatively charged Al of GP matrix. Physical encapsulation of heavy metal species is an irrefutable mechanism. The water solubility of Cd species follows the order: CdS (10 × 10 -9 ) < CdSiO 3 (0.0683) < CdCO 3 (0.11) < Cd(OH) 2 (2.0 mg/L), which suggests that the availability of small amounts of sulfide and increasing the dose of sodium silicate have positive effect on immobilization of Cd. Future work must focus on the role of following factors on immobilization efficiency: the nature and dose alkaline activator, the stage at which the waste is introduced in GP and the effect of small amounts of sulfide and calcium.

Evaluation of the formation of andraditeand carbonates of calcium in the synthesis of a geopolymer from white slag

En este artículo se evalúa la influencia de la andradita en la resistencia mecánica de un geopolímero sintetizado a partir de escoria blanca de horno convertidor y escoria negra de horno eléctrico. Como activadores se utilizó hidróxido de sodio 12 M y silicato de sodio 5 M. El hidróxido de sodio se mantuvo constante en 5% y en 15% en silicato de sodio. Se añadió material cerámico en proporciones del 5%,10%, 15% y 20%. El curado de la pasta se hizo a temperatura ambiente durante 24 horas. El tamaño de partículas de la escoria blanca y del material cerámico fue de 150 μm. Se utilizó XDR y MEB para analizar los posibles mecanismos de formación de la andradita y del carbonato de calcio. Se fallaron las muestras en la maquina universal de ensayos. Se determinó la influencia de los compuestos químicos formados en la resistencia a la compresión. Los resultados indican que las condiciones propuestas son adecuadas para la formación estructuras cristalinas propias de los materiales geopoliméricos

Water permeability of geopolymers emulsified with oil

Recently, geopolymer (GP) cements have proven adequate to immobilize oil emulsions as GEOIL composites. When used for radioactive waste storage, the vicinity of GEOIL with Portland Cement (PC) concretes may induce leaching by the PC pore water. This research identifies the preferential water flow pathways, and quantifies the water permeability of hardened GEOIL mortars using a typical PC pore water. Two alkali-activated GP cements are used, either made of 100% metakaolin (MK) or of 80%MK-20% slag, for oil proportions of 0, 20, 40 or 60%vol.For the identification of the preferential water flow pathways, two water flow scenarii are investigated numerically. Either water flows through the oil emulsion (Scenario 1) or water flows through the GP cement mortar pores (Scenario 2). The 3D structure of the oil emulsion is quantified by X Ray micro-computed tomography (X Ray micro-CT), and the pore structure of GP cement mortars is identified by image analysis. Fluid pathways are predicted for both scenarii by 3D numerical simulations. Secondly, water permeability experiments are conducted on GEOIL mortars. Water permeability Kwater of highly alkaline PC water is deduced over several weeks. The results validate Scenario 2; for 20 or 40%vol oil, water flows preferentially through the GP cement mortar pores (at a permeability below 10−18 m2), instead of through the percolating oil emulsion.Finally, experiments show that Kwater for the GP cement mortar made of 80%MK-20%GGBFS does not remain stable over time when added with 20%vol oil. Comparatively, for the 100%MK GP cement mortar with 20%vol oil, a stable Kwater is recorded for 40 days. Whatever the oil percentage, the initial Kwater value is identical and smaller than without oil. A dedicated experiment shows that the oil additives (surfactants) are very probably responsible for this behaviour. At 60%vol oil, water and organic matter flow progressively out of the GEOIL composite.

Surface Modification of Cured Inorganic Foams with Cationic Cellulose Nanocrystals and Their Use as Reactive Filter Media for Anionic Dye Removal.

In this work, a surface cationized inorganic–organic hybrid foam was produced from porous geopolymer (GP) and cellulose nanocrystals (CNCs). GPs were synthesized from alkali-activated metakaolin using H2O2 as a blowing agent and hexadecyltrimethylammonium bromide (CTAB) as a surfactant. These highly porous GPs were combined at pH 7.5 with cationic CNCs that had been synthesized from dissolving pulp through periodate oxidation followed by cationization in a deep eutectic solvent. The GP-CNC hybrid foams were employed as reactive filters in the removal of the anionic dye, methyl orange (MO; 5–10 mg/L, pH 7). The effects of a mild acid wash and thermal treatments on the structure, properties, and adsorption capacity of the GPs with CNCs and MO were investigated. The CNCs aligned as films and filaments on the surfaces of the neutralized GPs and the addition of CNCs improved MO removal by up to 84% compared with the reference sample. In addition, CTAB was found to disrupt the attachment of CNCs on the pores and improve adsorption of MO in the GPs with and without CNCs.

Effects of wetting and drying on alkalinity and strength of fly ash/slag-activated materials

The alkalinity of alkali-activated materials, so-called geopolymer (GP), is attributed to the alkali activator remained in the pores. For the application of GP in reinforced concrete as binder, it is necessary to investigate the alkalinity change of GP concrete in various environments. In this study, after GP concrete (GPC) and GP mortar (GPM) specimens, which used active fillers of fly ash (FA) and ground granulated blast furnace slag (GGBS), were stored in water, wet-dry repeating, accelerated carbonation (AC), and AC-dry repeating environments for a certain period, we observed the coloring reaction to the spraying phenophthalein indicator, measured pH values in different depths and the compressive strengths, and did micro-structure analysis by SEM. A comparison was also performed between GPM and Portland cement (PC) mortar specimens. It was found that, the alkalinity of GP mortar is much easier to decrease no matter in any of above environments, compared to PC mortar. Heat-cured GP has a higher alkali leaching resistance in the wet-dry repeating environment than ambient air-cured GP. Carbonation only decreases the alkalinity in the outer zone, but drying and wetting redistributes the alkalis and promotes the movement of internal alkalis to the outer zone even to the surface of GP, resulting in an alkalinity drop in both the outer zone and the inner zone. The AC-dry repeating causes a greater alkalinity drop than the wet-dry repeating. The AC results in a faster and greater alkalinity drop in the outer zone, compared to the water immersion. Carbonation and water immersion can raise GP’s strength, but intense drying causes cracks to harm the strength of GP.

On the mechanical performance of K- and Na-based strain-hardening geopolymer composites (SHGC) reinforced with PVA fibers

Strain-hardening cementitious composites (SHCC) are known by their high deformation capacity due to a multiple cracking tolerance under increasing tensile loading. While SHCC have been well investigated, the design of geopolymer (GP) composites in the same context is not sufficiently understood, mainly due to varying precursor materials used in previous studies. In this work, two metakaolin-based GP mixtures were produced, using K and Na as alkali sources. The incorporation of fine-grained sand was extensively investigated to evaluate its compatibility with both strain-hardening geopolymer composites (SHGC) reinforced with short polyvinyl-alcohol (PVA) fibers. Their mechanical properties were analyzed by means of compression, bending, and tension tests. Digital Image Correlation (DIC) was used to evaluate the fracture mechanisms under uniaxial tension. Particle size distribution (PSD), X-ray diffraction (XRD), Thermogravimetric analysis (TGA) and mercury intrusion porosimetry (MIP) were conducted. Additionally, single-fiber pullout tests with subsequent Environmental Scanning Electron Microscopy (ESEM) were carried out. NaGP composites, reinforced with fine-grained sand, yielded improved mechanical responses, reaching a strain capacity of approximately 4.5%, with enhanced multiple cracking, as opposed to the lower performance observed for KGP composites, that did not present a typical strain-hardening curve when in presence of fine-grained sand, but a strain-softening one. When compared to typical SHCC responses, Na-based SHGC showed a mechanically improved multiple cracking behavior, indicating the potential of this material for a wide range of applications, such as dynamic loading and requirements of long-term durability.

Behavior of Geopolymer Concrete by using Steel Fibers

Research for complete OPC free cement is as of recently advancing and there is a need for making elective restricting bosses which are earth neighborly. One such option is seen to be geo polymer which routinely contains fly garbage, sodium silicate, and sodium or potassium hydroxide (NaOH or KOH). Since, many coal based force plants in India have been leaving an immediate consequence of pushed towards cleaner importance age and this may induce absence of fly ash in future. The generation of Ordinary Portland concrete and the use of typical waterway sand are expanded because of the interest of cement in development Industries. The emanation of CO2 increments during the generation of concrete and simultaneously the accessibility of waterway sand is likewise getting costlier and shortage because of illicit digging of stream sand. The primary intension of this exploration paper is to center the eco inviting elective material for the concrete and waterway sand. In the present study an experimental investigation was conducted on fly ash based geo polymer cement is examine the clean and hardened characteristic of geo polymer cement by using steel fibers. The percentage addition of steel fibers are 0.00%, 0.50%, 1.00%, 1.50%, 2.00%. The addition of steel fibers from 0% to 2%, the estimation of droop diminishes the 60 mm to 25 mm with increment in the level of steel standards. The estimation of compaction factor increments from 0.84 to 0.95 for M30 Grade concrete with increment in the level of steel standards from 0% to 2%.

Behavior of geopolymer concrete under cyclic loading

Much effort has been done on compressive strength of Geo Polymer Concrete (GPC) under monotonic loading to study the mechanical and durability properties. It is also very important to study its behavior when the concrete members are subjected to cyclic loads. In this research, some new concepts of nature of stress-strain curve, envelope curve and common point curve of geopolymer concrete are presented for three different grades of GPC. Investigations related to study of stress-strain characteristics of geopolymer concrete under cyclic loading is focused. The locus of common and stability points was determined from the cyclic stress-strain curve. The identification of these is an important contribution for the design of GPC. Analytical equations were proposed for envelope curve, common point curve and stability point curve. The Proposed curves fit well with experimental test data.

Utilization of Coal Fly Ash and Rice Hull Ash as Geopolymer Matrix-cum-Metal Dopant Applied to Visible-Light-Active Nanotitania Photocatalyst System for Degradation of Dye in Wastewater

Geopolymer (GP) spheres made from coal fly ash (FA) and rice hull ash (RHA) waste products are utilized as both support matrix and dopant applied to titania (TiO2) photocatalyst for organic dye degradation in wastewater. Processing of FA and RHA via suspension-solidification method resulted in GP spheres with nanoporous morphology. The nanocrevices enabled low-energy sol-gel TiO2 coating technique because they served as anchoring sites on the geopolymer surface that favored rigidity and larger surface area. The GP-TiO2 system has been characterized by infrared spectroscopy, X-ray diffraction and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. Diffuse reflectance spectroscopy revealed a narrowing of the GP-TiO2 system optical band gap due to the interaction of metal dopants contained in RHA and FA with TiO2, thus making the GP-TiO2 system a visible-light-active photocatalyst, as confirmed by methylene blue dye degradation measured through UV-Vis spectroscopy.

Adhesion Enhancement of Poly (acrylamide -co- Acrylic Acid)/ Polyethylene Glycol anti-Biofouling Coating using Fly Ash based Geopolymer

Hydrogel has been used as an alternative to replace biocide-based paint in preventing biofouling. However, hydrogel has low adhesion on metallic substrate, hindering its application for coating. Therefore, the aim of this project is to enhance the adhesion strength and anti-biofouling properties of the poly(acrylamide-co-acrylic acid)/polyethylene-glycol hydrogel, poly(AAm-co-AAc/EG) coating via the incorporation of fly ash-based geopolymer that range from 0.5 wt% to 2.5 wt%. The hydrogel coating was synthesised via free radical polymerisation with the aid of N,N-methylenebisacrylamide (MBA) as the crosslinker, and ammonium persulfate (APS) as the initiator. The Fourier transform infrared (FTIR) spectra of the hybrid hydrogel had proved the presence of geopolymer with the availability of significant peaks at 3,294 cm-1 (N-H bond), 2,946 cm-1 (O-H bond), 1,545 cm-1 (C-O-C bond) and 1,113 cm-1 (Si-O-Si or Al-O-Si bond). The average swelling capacity of the hybrid hydrogel coating in distilled water (up to 50,000%) was significantly higher than in artificial seawater (up to 5,000%) due to osmotic pressure difference. The anti-biofouling performance test by using algae (Chlorella vulgaris sp.) suspension showed that the incorporation of 2.0 wt% geopolymer into hybrid hydrogel coating had successfully reduced the algae attachment on the substrate by 92% as compared to the control sample. The adhesion strength of all hydrogel coatings was investigated by using the pull-off adhesion test in accordance to ASTM D4541. The incorporation of 2.0 wt% geopolymer into hydrogel matrices demonstrated an increment of 58% in adhesion strength on steel plate as compared to neat hydrogel. The results showed that geopolymer has the potential to improve the anti-biofouling and adhesion strength of hydrogel coating.