Fly Ash Based Geopolymer Cement Research Articles

Sodium Silicate from Rice Husk Ash and Their Effects as Geopolymer Cement.

Sodium silicate is a commonly used activator in geopolymer that is produced commercially. In this study, rice husk ash (RHA) from agricultural waste was used to synthesize sodium silicate as an activator for geopolymer cement. This white ash was applied for producing sodium silicate with different molarities (8, 10, and 12) and then used to synthesize fly ash-based geopolymer cement. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) were applied to investigate the micro-characteristics of the geopolymerization products. Bulk density, water absorption, compressive strength, flexural strength, and fracture toughness were carried out to measure and evaluate the geopolymers with sodium silicate. The combination of 10 M NaOH with sodium silicate increased the compressive strength by 16.21% and the flexural strength and fracture toughness by 81.6%. However, sodium silicate combined with 12 M NaOH decreased compressive strengths by 13.23% and flexural strength and fracture toughness by 61.94%. The lowest water absorption value of 12.3% was obtained in a geopolymer paste using sodium silicate combined with 10 M NaOH, and the largest was 13.3% for sodium silicate combined with 8 M NaOH. The microstructure analysis showed the hydrated calcium alumina silicate gel (C–A–S–H) and the SEM image also revealed a compact geopolymer matrix. Thus, it can be concluded that sodium silicate from rice husk ash can be utilized as an activator or reactive material to produce geopolymer cement with a good geopolymer network.

Lignosulfonate as a retarder in geopolymer cement for oil well cementing: Effect on compressive strength

Replacement of Portland cement with eco-friendly cementitious materials may reduce carbon dioxide emission and unfavourable chemical reactions between cement and carbon dioxide, which, in oil well cementing, negatively affect downhole cement integrity. Geopolymer cement is an alternative cementitious material, and therefore, its formulation for oil well cementing has to be studied. In oil well cementing, setting time of the cement has to be considered and, a retarder, such as lignosulfonate, can be added to lengthen the setting time. However, addition of lignosulfonate may negatively affect compressive strength. The present study investigates the effect of lignosulfonate, with varying concentrations of between 0.2 and 0.5% by weight of fly ash, on the compressive strength of fly ash-based geopolymer cement cube samples, with exposure to curing conditions of 3,000 psi and 100 °C for 8 and 24 h. Compressive strengths of samples cured for 8 h indicate that lignosulfonate increased early strength by 39 to 100%, while, even though compressive strengths of samples cured for 24 h reduced by 9 to 28%, their values still exceed 2,000 psi, hence suggesting that lignosulfonate can be employed as a retarder in geopolymer cement for oil well cementing.

Microstructural properties and compressive strength of fly ash-based geopolymer cement immersed in CO2-saturated brine at elevated temperatures

Microstructural properties and compressive strength of fly ash-based geopolymer cement immersed in CO2-saturated brine at elevated temperatures

Influence of Sodium Hydroxide Grade on the Strength of Fly Ash-Based Geopolymer Cement

Portland cement (OPC) is one of the primary contributors accounted for climate change as a massive amount of Carbon dioxide is emitted to the atmosphere during its production processes. Geopolymer cement (GP), a green construction material, is therefore promoted to be an alternative cementitious binder to replace the consumption of that OPC. GP can be synthesized by mixing pozzolanic wastes (e.g., fly ash or slag) with alkaline solutions (e.g., NaOH and Na2SiO3). The mechanical properties of the geopolymer have been confirmed to be similar to or even better than OPC in the same testing conditions. However, the researches on GP have been mostly carrying out in just a laboratory scale, thus, the Laboratory grade of alkaline activators was commonly used. To make GP more realistic in practical works, the Industrial grade of alkaline activators was hence introduced. The results show that the usage of Industrial grade activators not only provides excellent mechanical properties to GP but also reduces its unit price to less than 20 percent of the conventional GP (GP with Laboratory-grade activator). By this approach, the confidence of expanding this green construction material, from Laboratory scale to In-field applications, is considerably increased.

Behaviour of Fly Ash based Geopolymer Concrete using Nano-Material

In the Construction sector the need of cement is expanding step by step for fulfilling the need of improvement of foundation developments. The creation of Ordinary Portland concrete emanates the enormous amount of CO2 into the climate. Hence, it is basic to discover choices to make the solid eco - neighborly. Low calcium fly ash based geopolymer cement is a substitute choice for bond based cement. It is an inorganic alumina-silicate compound, blended from fly ash remains. The exploratory work on Geopolymer cement is to assess the impact of different parameters influencing its compressive quality and usefulness of cement so as to improve its general execution was extended. Basic arrangement utilized for present examination is mix of sodium hydroxide and sodium silicate. By applying the Nano Technology, expansion of Nano silica is to improve the quality of cement. The essential distinction between geo-polymer cement and Portland bond cement is the binding property. The silicon and aluminum oxides in the low-calcium fly slag responds with the soluble fluid to frame the geo-polymer concrete that ties the free coarse aggregate, fine aggregate, and other un-responded materials together to shape the geo-polymer concrete. As on account of Portland bond concrete, the coarse and fine totals possess around 75 to 80% of the mass of geo-polymer concrete. The impact of totals, for example, reviewing, precision and quality, are viewed as equivalent to on account of Portland bond concrete. Along these lines, this segment of geo-polymer solid blends can be structured utilizing the instruments as of now accessible bond for Portland concrete. The principle goal of this exploration work is to break down the carbon dioxide free cementitious material with its quality, functionality properties and their impacts on Geopolymer concrete for maintainable improvement.

Comparison between reactive MgO- and Na2SO4-activated low-calcium fly ash-solidified soils dredged from East Lake, China

A novel approach to mitigate the environmental concerns associated with cement industry is to replace Portland cement with low carbon alternative materials such as fly ash-based geopolymer cement. Hence, reactive MgO-activated low-calcium Class F fly ash was employed in comparison to Na2SO4-activated fly ash to stabilize a lacustrine soil reused potentially in soft coastal reclamation projects and as reinforced aggregates for anti-corrosion in marine engineering. The microstructural and strength properties were investigated with series of tests including X-ray diffraction (XRD), thermogravimetry/differential thermogravimetry (TG/DTG), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and unconfined compressive strength (UCS). The results demonstrate that the main hydration products in reactive MgO- and Na2SO4-fly ash-solidified soils are, respectively, magnesium silicate hydrate (M-S-H) gel and sodium aluminosilicate hydrate (N-A-S-H) gel. This finding is reconfirmed by the weight loss of solidified samples at 40–200 °C, which is correspondingly attributed to the dehydration of magnesium silicate hydrate (M-S-H) gel and sodium aluminosilicate hydrate (N-A-S-H) gel. The morphology and bonding ability of hydration products affects the microstructure and long-term strength of solidified soils. The microstructural change identified from SEM images coincides well with the quantitative evolution of pore structure. The pores with radius of 0.01–1 µm, i.e., micropore and mesopore, are supposed to be the dominant pores in reactive MgO- and Na2SO4-activated fly ash-solidified soils. The comparison of UCS indicates reactive MgO-activated low-Ca fly ash behaves much superior to Na2SO4-activated fly ash in enhancing the long-term compressive strength of soils. This study provides insight into the promising potential of low-Ca fly ash activated by immerging material – reactive MgO to replace cement in soil improvement.

Impact of wet supercritical CO2 injection on fly ash geopolymer cement under elevated temperatures for well cement applications

An alternative cement system created through geopolymerization of fly ash offers favorable properties such as able to resist acidic fluids and possess high compressive strength. However, the application of fly ash geopolymer as wellbore cement under carbon dioxide (CO2) environment at elevated temperature is not well recorded in the literature. This paper characterizes the fly ash-based geopolymer cement and experimentally investigates its mechanical and microstructure changes after exposed to CO2 under elevated temperature. Microstructure identification on the altered cement paste was conducted by the analysis of XRD and SEM. In this study, fly ash-based alkali-activated cement was made using 8 molal sodium hydroxide and sodium silicate as alkali activators. The results found that crystal-like shape identified as calcium carbonate was formed at the surface of spherical fly ash particle after carbonation formation. The strength of geopolymer cement was found not to be decreased although carbonation process was occurred. Microstructure analysis revealed that zeolite was formed during CO2 acid exposure for geopolymer cement which contributes to the strength development.

Fly ash Class C based geopolymer for oil well cementing

For many years Portland cement has been used in oil well cementing. Even though Portland cement has been used for many years, it has several drawbacks, including operational failures and severe environmental impacts. Fly ash based geopolymer cement has been recently investigated as a low-cost, environmentally friendly alternative to Portland cement. This research develops a novel formulation of Class C fly ash based geopolymer and investigates its applicability as an alternative to Portland cement in hydrocarbon well cementing. Twenty-four variations of fly ash Class C based geopolymers were prepared, and by comparing several of their properties using API standard tests, the most favorable geopolymer formulation was determined. The effect of varying the ratios of alkaline activator to fly ash, sodium silicate to sodium hydroxide, and sodium hydroxide concentration was investigated. The selection of the formulation was based on four different tests, including rheology, density, compressive strength, and fluid loss test. Then, a comparison between the selected mix design and Portland cement was conducted using the same tests, in addition to stability tests (sedimentation test and free fluid test). Based on our results, geopolymer was found to have superior rheological and mechanical properties compared to the Portland cement. The geopolymer design, which had lower fluid loss, 93 ml after 30 min, sufficient compressive strength, 1195 psi in 24 h, and an acceptable density, 14.7 lb/gal, and viscosity, 50 cp, was further compared to the Portland cement. The higher mechanical strength of geopolymer using fly ash Class C compared to Portland cement is very promising for achieving long-term wellbore integrity goals and meeting regulatory criteria for zonal isolation.

Influence of some additives on the properties of fly ash based geopolymer cement mortars

In order to minimize CO2 emission due to manufacture of Portland cement, researches have been focused on alternative construction materials such as geopolymer cement. Geopolymer cement is made from waste materials such as fly ash by alkali-activation. This paper reports the properties of fly ash based geopolymer mortars activated by sodium hydroxide/potassium hydroxide and sodium silicate/lithium silicate. Alccofine powder, aluminum powder and calcined clay were added during geopolymerization. Curing was done at 80 °C. Compressive strength of geopolymer mortar was found maximum in the presence of potassium hydroxide–lithium silicate—5% alccofine powder—10% calcined clay. Durability of cubes in sulphuric acid was studied. Fire resistant properties of some of the mortars at 600, 800 and 1000 °C were also studied.

Influence of sulfuric and hydrochloric acid on the resistance of geopolymer cement with nano-silica additive for oil well cement application

PurposeThe purpose of this paper is to investigate the resistivity of geopolymer cement with nano-silica additive toward acid exposure for oil well cement application.Design/methodology/approachAn experimental study was conducted to assess the acid resistance of fly ash-based geopolymer cement with nano-silica additive at a concentration of 0 and 1 wt.% to understand its effect on the strength and microstructural development. Geopolymer cement of Class C fly ash and API Class G cement were used. The alkaline activator was prepared by mixing the proportion of sodium hydroxide (NaOH) solutions of 8 M and sodium silicate (Na2SiO3) using ratio of 1:2.5 by weight. After casting, the specimens were subjected to elevated curing condition at 3,500 psi and 130°C for 24 h. Durability of cement samples was assessed by immersing them in 15 wt.% of hydrochloric acid and 15 wt.% sulfuric acid for a period of 14 days. Evaluation of its resistance in terms of compressive strength and microstructural behavior were carried out by using ELE ADR 3000 and SEM, respectively.FindingsThe paper shows that geopolymer cement with 1 wt.% addition of nano-silica were highly resistant to sulfuric and hydrochloric acid. The strength increase was contributed by the densification of the microstructure with the addition of nano-silica.Originality/valueThis paper investigates the mechanical property and microstructure behavior of emerging geopolymer cement due to hydrochloric and sulfuric acids exposure. The results provide potential application of fly ash-based geopolymer cement as oil well cementing.

Influence of different brine water salinity on mechanical properties of fly ash-based geopolymer cement

PurposeThe purpose of this paper is to investigate the mechanical properties changing of geopolymer cement under different brine salinity.Design/methodology/approachGeopolymer Cement of Class F Fly Ash and Class G Cement slurries were prepared according to API RP 10B. The optimum alkaline activator/cement and water/cement ratio of 0.44 was used for geopolymer and Class G cement samples, respectively. The alkaline activator was prepared by mixing the proportion of Sodium Hydroxide (NaOH) solutions of 8 M and Sodium Silicate (Na2SiO3) using ratio of 1:2.5 by weight. The slurries were cured for 24 hours at 130oC and 3,000 psi in HPHT Curing Chamber followed by coring process. Both cement sample were immersed in brine water salinity up to 28 days with different brine salinity up to 30 per cent of NaCl. The mechanical properties were investigated using OYO Sonic Viewer-SX and Uniaxial Compressive Strength. The surfaces of the cement samples were extracted for Scanning Electron Microscope (SEM) and EDS tests to evaluate the morphology and chemical compositions of the cured samples.FindingsThe paper shows that geopolymer samples experiences strength reduction in brine water but the reduction rate of geopolymer is about half of the Ordinary Portland cement based oil well cement. The finding was also verified by SEM and EDS result.Originality/valueThis paper investigates the mechanical property changes of emerging geopolymer cement due to different water salinity. The results provide potential application of geopolymer cement for oil well cementing.

Microstructure Behavior of Fly Ash-Based Geopolymer Cement Exposed to Acidic Environment for Oil Well Cementing

Acidizing is a widely used technique to stimulate an oil well in order to enhance its production. When portland cement is placed in contact with acid fluids, it will dissolve and, at some time, will be fully degraded because the acids have reacted with calcium silicate hydrate which resulted in the breaking up of the cement intergranular structure. This in turn will give rise to well integrity issue. Instead of introducing a new acid type, which may not be as effective toward reservoir formation, researchers have come up with a new cementing material, namely geopolymer cement. Literature has shown that geopolymer cement is unreactive toward conventional acids. In addition, its strength may be improved by introducing Nano-silica in the admixture. However, the studies were conducted at ambient condition. The objective of this work is to investigate geopolymerization mechanism and microstructure behavior of fly ash-based geopolymer cement with Nano-silica admixture. Two cement slurries, geopolymer and Class G OPC, were prepared in accordance with API RP-10B. The slurries were cured for 24 h at 130 $${^{\circ }}$$ C and 20.69 MPa at the HPHT curing chamber before being exposed to 15 wt% acid solution for 14 days. The reaction mechanism of the cement samples was investigated by using FTIR and XRD analyses. The results were further validated by carrying out SEM and EDS tests to evaluate the microstructure behavior and chemical compositions of the cured samples. Results show that fly ash-based geopolymer cement with 1 wt% of Nano-silica additive was the least affected cement samples after acid treatment as compared to a similar weight of Class G OPC.

Additive manufacturing of geopolymer for sustainable built environment

This paper evaluates the potential of fly ash based geopolymer cement for large scale additive manufacturing (AM) of construction elements. Geopolymer is considered as a green construction material and its use in AM may contribute towards sustainable environment since in AM process material is only deposited whereby it is necessary. As part of this research, an industrial robot was employed to print geopolymer mortar in layer-by-layer manner directly from 3D computer-aided design (CAD) model. The characteristic of raw materials and fresh properties were examined by rheology, x-ray diffraction (XRD), and scanning electron microscopy (SEM). Mechanical tests such as compression, flexural and tensile bond strength were conducted on the printed geopolymer in different printing directions and their performance was compared with casted samples. It was found, from the experimental results, that the mechanical properties of 3D printed geopolymer are mostly dependent of loading directions due to anisotropic nature of the printing process and retains intrinsic performance of the material.

Thickening Time Compatibility of Geopolymer Cement for Drilling Application

This paper investigates the composition of geopolymer cement for thickening time under elevated temperature and pressure. Geopolymer based-cement becoming popular in construction industries because of its improved properties either chemically and physically as compared to Ordinary Portland Cement (OPC). At the same time, replacement of OPC with geopolymer cement able to eliminate CO2 emission due to calcination burning process. However, applications of geopolymer cement to oil and gas industry for cementing job are not well recorded. Fly ash based geopolymer cement with different percentages of slag from 0% to 10% were mixed using sodium hydroxide and sodium silicate as alkali activators. Density, fluid loss and compressive strengths were determined. The sample were cured at 3,000 psi and 65°C for 24 hours. Results show that the addition of slag reduces the thickening time from 30 minutes to just only 18 minutes with almost 40% reduction in time. In terms of density and compressive strength, an increment of slag is directly proportional as the value increased from 14.3 ppg to 15.0 ppg for density and 1,120 psi to 2,155 psi for compressive strength. For fluid loss test, increment of slag results in decrement of fluid loss from 0.64 ml to just only 0.38 ml.

Bond Properties of Sand-Coated GFRP Bars with Fly Ash–Based Geopolymer Concrete

AbstractBond behavior is an important subject in the design and performance of reinforced concrete structures. In this research, the bond property between sand-coated glass fiber–reinforced polymer (GFRP) bars, a corrosion-resistant substitute to steel bars, and fly ash–based geopolymer cement (GPC) concrete, a more environmental friendly alternative to ordinary portland cement (OPC) concrete, is investigated. Pullout test specimens containing GFRP bars embedded in GPC and OPC concrete cylinders with 100-mm diameter and 170-mm height were prepared. Three different embedment lengths were tested: three, six, and nine times the bar diameter. Average concrete compressive strengths of approximately 25 and 45 MPa and GFRP bar diameters of 12.7 and 15.9 mm were the other test parameters. For each specimen, the test results include the bond failure mode, the average bond strength, the slip at the loaded and free end, and the bond-slip relationship curves. The test results showed that GFRP-reinforced GPC concrete ...

Development of Fly Ash based Geopolymer behaviour of Fly Cement

Geopolymer is a novel binding material produced from the reaction of fly ash with an alkaline activator liquid; ensure durability and environmental sustainability and is emerging greener alternative to Ordinary Portland cement in the construction field. In this research, the influence of various parameters on the consistency and setting times of low-calcium fly ash-based geopolymer cement under varied heat curing temperature were investigated. Systematic trials were carried to optimise the normal consistency and setting times over a number of parameters. The consistency of the geopolymer cement does not show any variation when mixed with different combinations of alkaline activator solution; whereas the setting times were observed to be dependent on the concentration of NaOh solution, ratio of alkaline activator liquid and variation in temperature. The test results revealed that the normal consistency of the fly ash-based geopolymer paste is found to be at 28% of alkaline activator solution for all the selected mixtures. wherein, increase in concentration of NaOh solution increases setting times; increase in alkaline liquid ratio decreases setting times up to certain limits viz; increase in alkaline liquid ratio from 1.5 to 2.0, decreases setting times; further increase in alkaline liquid ratio from 2.0 to 2.5, increases setting times. The setting times were observed as decreased when the alkaline liquid ratio increased from to 2.5 to 3.0.