Geopolymer Research Articles

Novel natural rubber composites with geopolymer filler

AbstractThe main objective of this study was to apply geopolymer (GP) particles as novelty fillers in natural rubber (NR) composites with various loadings (0, 10, 20, 30, and 40 phr). Influence of GP particles on cure characteristics, mechanical, dynamic, thermal, and morphological properties of the NR/geopolymer composites was investigated. It was found that incorporation of geopolymer particles significantly affected the cure characteristics and the mechanical properties. That is, faster curing was observed due to acceleration by metal oxide impurities. It was also found that 100% modulus and tensile strength increased with the addition of 10 phr GP. This is attributed to the physical interactions of GP particles with NR molecules. In addition, the Payne effect and improved thermal stability were also observed in the GP‐filled NR composites. It was concluded that 10 phr of GP in NR composites might be suitable for some industrial applications.

Carbonation resistance of fly ash and blast furnace slag based geopolymer concrete

For putting geopolymer (GP) to practical use in reinforced concrete, the carbonation resistance of GP concrete should be clarified. In this study, the carbonation depths of various GP concrete and GP mortar, of which the aluminosilicate materials were fly ash (FA) and ground blast furnace slag (BFS), were measured by the accelerated carbonation test at different elapsed times. The relationship between the carbonation depth and the elapsed time were further examined based on the experimental results and by theoretical analysis. A root function was proposed to describe the carbonation rate of FA&BFS-based GP concrete. Finally, the influencing factors of carbonation resistance of FA&BFS-based GP concrete were discussed through a comparison of carbonation rate coefficients. It is mainly concluded that the carbonation resistance of FA&BFS-based GP concrete cured at room temperature is lower than usual concrete using Ordinary Portland Cement (OPC). The carbonation resistance increases with the increase of BFS ratio in active fillers (AF), NaOH content in active activator solution (AS), and BFS fineness, or with the decrease of AS/AF ratio, and water/AF ratio. Moreover, heat curing and the use of the retarder are benefit to the carbonation resistance of FA&BFS-based GP concrete.

Performance of FRP confined and unconfined geopolymer concrete exposed to sulfate attacks

In this study, the effects of magnesium sulfate on the mechanical performance and the durability of confined and unconfined geopolymer concrete (GPC) specimens were investigated. The carbon and basalt fiber reinforced polymer (FRP) fabrics with 1-layer and 3-layers were used to evaluate the performances of the specimens under static and cyclic loading in the ambient and magnesium sulfate environments. In addition, the use of FRP materials as a rehabilitation technique was also studied. For the geopolymerization process of GPC specimens, the alkaline activator has selected a mixture of sodium silicate solution (Na2SiO3) and sodium hydroxide solution (NaOH) with a ratio (Na2SiO3/NaOH) of 2.5. In addition to GPC specimens, an ordinary concrete (NC) specimens were also produced as a reference specimens and some of the GPC and NC specimens were immersed in 5% magnesium sulfate solutions. The mechanical performance and the durability of the specimens were evaluated by visual appearance, weight change, static and cyclic loading, and failure modes of the specimens under magnesium sulfate and ambient environments. In addition, the microscopic changes of the specimens due to sulfate attack were also assessed by scanning electron microscopy (SEM) to understand the macroscale behavior of the specimens. Results indicated that geopolymer specimens produced with nano-silica and fly ash showed superior performance than the NC specimens in the sulfate environment. In addition, confined specimens with FRP fabrics significantly improved the compressive strength, ductility and durability resistance of the specimens and the improvement was found higher with the increased number of FRP layers. Specimens wrapped with carbon FRP fabrics showed better mechanical performance and durability properties than the specimens wrapped with basalt FRP fabrics. Both FRP materials can be used as a rehabilitation material in the sulfate environment.

Hybrid fuzzy model to predict strength and optimum compositions of natural Alumina-Silica-based geopolymers

This study introduces the supervised committee fuzzy model as a hybrid fuzzy model to predict compressive strength (CS) of geopolymers prepared from alumina-silica products. For this purpose, more than 50 experimental data that evaluated the effect of Al2O3/SiO2, Na2O/Al2O3, Na2O/H2O and Na/[Na+K] on (CS) of geopolymers were collected from the literature. Then, three different Fuzzy Logic (FL) models (Sugeno fuzzy logic (SFL), Mamdani fuzzy logic (MFL), and Larsen fuzzy logic (LFL)) were adopted to overcome the inherent uncertainty of geochemical parameters and to predict CS. After validating the model, it was found that the SFL model is superior to MFL and LFL models, but each of the FL models has advantages to predict CS. Therefore, to achieve the optimal performance, the supervised committee fuzzy logic (SCFL) model was developed as a hybrid method to combine the benefits of individual FL models. The SCFL employs an artificial neural network (ANN) model to re-predict the CS of three FL model predictions. The results also show significant fitting improvement in comparison with individual FL models.

Influence of Na/Al Ratio and Curing Temperature of Geopolymers on Efflorescence Reduction

Influence of Na/Al Ratio and Curing Temperature of Geopolymers on Efflorescence Reduction

Experimental Study on Shrinkage Behavior of Geopolymer Mortar

Experimental Study on Shrinkage Behavior of Geopolymer Mortar

Technological Properties of Moulding Sands with Geopolymer Binder for Aluminium Casting

Technological Properties of Moulding Sands with Geopolymer Binder for Aluminium Casting

Immobilization of toxic inorganic anions (Cr2O72-, MnO4- and Fe(CN)63-) in metakaolin based geopolymers: A preliminary study

Geopolymer (GP) consists of polymeric Al and Si tetrahedral network, with alkali metal cation (Na+ or K+) balancing the negative charge of Al tetrahedra. Although immobilization of heavy metal cations, that could balance the negatively charged Al tetrahedra in GP, was extensively studied, this is the first study that deals with immobilization of metal anions (dichromate, permanganate and hexacyanoferrate). GP samples were prepared from metakaolin (MK) as an aluminosilicate material and sodium silicate activator (Si/Al molar ratio 2) in the presence of the three anions. The efficiency of immobilization was studied in terms of % leaching of metal anions using atomic absorption spectrophotometry and in terms of leaching of total metal anions by conductivity measurements. The % leaching was less than 10% when 0.2% (w/w) of metal anion salts were incorporated in the GP. However, the % leaching increased from 10% to 20% with increasing loading of dichromate salt from 0.2% to 1.5% (w/w) which indicates that GP has limited capacity (limited number of pores) for immobilization of metal anions. When silica gel and alumina were employed as additives to MK (changing Si/Al ratio), the leaching of dichromate and total ions increased substantially and the surface of GP becomes more crystalline as indicated by SEM and EDS studies. The present work suggests that the mechanism of heavy metals immobilization by balancing the negatively charged Al tetrahedra of GP is not true.

Superhigh strength of geopolymer with the addition of polyphosphate

Geopolymers (GPs) have an important applications in the construction and medical fields owing to their attractive physical and thermal properties. However, the compressive strength of GP is usually less than 80MPa; therefore, it should be further strengthened to improve the mechanical strength and structural properties of end products. This study presents a facile method to enhance the compressive strength of GP by incorporating aluminum dihydrogen triphosphate (ATP) into the GP matrix during the geopolymerization of metakaolin. The microstructure, thermal properties, and compressive properties of the doped GPs (D-GPs) are investigated. The results show that the ATP is transformed to many granules, bonded and surrounded by GP gel, and the unique microstructure increases the compressive strength of D-GP to 160MPa with an optimum 1.0wt% ATP, which is a 108% increase as compared to pure GP. The superhigh compressive strength of ATP-reinforced GP makes them potential alternatives for existing high-strength cement materials.

Study on the compressive strength of fly ash based geo polymer concrete

Introduction of the alternative materials for complete replacement of cement in ordinary concrete will play an important role to control greenhouse gas and its effect. The 100% replacement of binder with fly ash (in integration with potassium hydroxide (koh) and potassium silicate (k2sio3) solutions) in concrete gives a significant alternative to conventional cement concrete. This paper focuses on the effect of alkaline solutions koh and k2sio3 on strength properties of fly ash based geo polymer concrete (fgpc); compared the strength at different molarities of alkaline activator koh at different curing temperature. Fly ash based geo polymer concrete was produced from low calcium fly ash, triggered by addition of koh and k2sio3 solution and by assimilation of superplasticizer for suitable workability. The molarities of potassium hydroxide as 8m, 10m and 12m molarities were used at various curing temperatures such as 60°c, 70 °c and 80°c. Results showed that for given proportion to get maximum compressive strength the optimum molarity of alkaline solution is 12m and optimum curing temperature is 70 °c.

Alkali Activated Cements Versus Geopolymers

Alkali Activated Cements Versus Geopolymers

The Influence Sugarcane Bagasse Ash and Metakaolin on Mechanical Properties Fly Ash Geopolymer Paste

This paper present an optimization of sugarcane bagasse ash and metakaolin on fly ash geopolymer paste with sea water treatment. Mechanical properties were assessed by compressive strenght test (SNI 03-1974-2011), UPV test (ASTM C597 – 16), and porosity test (ASTM C642-90). Na 2 SiO 3 (Sodium Silicate) and NaOH (Sodium Hydroxide) with concentration of 12 Molar were used as alkali activators with ratio activator of 2,5. Percentage of fly ash and alkali used is 70% and 30%. Compressive strength test was conducted on binder 5cm x 5cm x 5cm with the age of 7, 14, 28 days, while UPV and Porosity test was performed in 28 days. Based on the compressive strength of 7-day-old concrete paste. It was found that the compressive strength of concrete paste used as a control was 21.3 MPa, V1 was 24.7 MPa, and V5 was 22.1 MPa. While at the age of concrete pasta 28 days. It was found that the compressive strength of the control was 49.6 MPa, V1 was 34.1 MPa, and V5 was 39.3 MPa. So it is assumed that those with the greatest compressive strength and the most stable are the controls (100% FA), V1(80% FA : 20% SGBA) and V5 (80% FA : 20% Metakaolin).

Impact of electric arc furnace slag on geopolymer composites exposed to sulphate solution

Effect of sulfate solution on the geopolymer formed from electric arc furnace slag (EAF) along with water cooled slag and cement kiln dust was studied. Activation was carried up on usage of 25% CKD as it bears high alkali content that can initiate and propagate the polymerization process. The formed geopolymer products were immersed in 5% MgSO4 solution to determine the stability up on sulfate attack. FTIR, XRD, SEM, compressive strength and water absorption were utilized to examine the resulted geopolymer product under sulfate attack. Results showed that, the compressive strength of geopolymer specimens increase with EAF slag up to 50% then decrease with further slag increase, possessing stability up 12 months and giving an increased compressive strength than the control mix that has not EAFS by 6.53%, 14.72%, 47.44% and -4.89 % after immersing ages of 3 months and 2.26, 14.26, 43.97 and 19.98 % after immersing age of 12 months for replacement by 10, 25, 50 and 75% of EAFS, respectively. Data elucidated a good stability and resistance of mix containing slag substitution by 50 % EAF and 25 % GGBFS and results in further enhancement in both mechanical and microstructural characteristics than the non-immersed samples (28days).

Effects of Different Heavy Metals on Fly Ash-based Geopolymer

Effects of Different Heavy Metals on Fly Ash-based Geopolymer

Effects of relative humidity on the properties of fly ash-based geopolymers

The investigation into geopolymers (GPs) is developing rapidly due to the properties they offer. In spite of this, few researchers have reported on the relative humidity (RH) during the curing process and its impacts on alkali-activated fly ash-based geopolymers. This study investigates the mechanical and microstructural properties of alkali-activated fly ash (FA) based geopolymers cured at various RH ratios at 75°C. Compressive and flexural strength tests were conducted to determine the mechanical properties, and X-ray diffraction (XRD), as well as scanning electron microscopy (SEM) tests were carried out to study the microstructural properties of the mixtures. The study revealed that both compressive and flexural strengths improved when RH was set at 70%. The microstructural analysis indicated a mixture of unreacted fly ash particles, some crystals, and a reacted gel phases as the geopolymerization products.

Experimental Study on Geopolymer Motor with Marble Powder under High Temperature

Experimental Study on Geopolymer Motor with Marble Powder under High Temperature

Feasibility Analysis of use of Bagasse Ash for the Production of Geo Polymer Concrete

Feasibility Analysis of use of Bagasse Ash for the Production of Geo Polymer Concrete

Durability and Pore Structure of Nano-particle-modified Geopolymers of Waste Brick Powder-class C Fly Ash

Durability and Pore Structure of Nano-particle-modified Geopolymers of Waste Brick Powder-class C Fly Ash

Geopolymer matrix for fibre reinforced composites aimed at strengthening masonry structures

The paper presents the assessment of a metakaolin-slag-sodium-silicate GeoPolymer (GP) grout as a matrix for bonding four bidirectional meshes made of basalt, glass, carbon fibres and two unidirectional ultra-high tensile strength steel fabrics to soft mud and strong extruded clay bricks for strengthening purposes. A detailed chemical/physical characterization of the geopolymer is given, evidencing the completion of the geopolymerization reaction and the good stability of the geopolymer to leaching, freeze-thaw cycles and high temperature treatments as well as its adequate mechanical properties. Pull-off tests proved the excellent adhesion strength of the geopolymer grout, also embedding meshes and fabric, to both types of clay bricks.

Efficiency and mechanism of stabilization/solidification of Pb(II), Cd(II), Cu(II), Th(IV) and U(VI) in metakaolin based geopolymers

This work deals with stabilization/solidification of Pb(II), Cd(II), Cu(II), Th(IV) and U(VI) in metakaolin (MK) based geopolymer (GP) prepared using one activator (sodium silicate) or two activators (sodium silicate and sodium hydroxide). Different leaching solutions with varying pH and ionic strength were used: deionized water, 0.1M HCl, 0.1M NaCl, 1.0M NaCl and 0.1M NaOH to evaluate the efficiency of stabilization. Effective stabilization was achieved regardless of using one or two activators. The efficiency of stabilization was found to increase with increasing the ionic size of heavy metal which was explained by ion-pair theory. The leaching of total ions from the GP matrix was studied by conductivity measurements which indicated that heavy metal ions in the GP matrix resulted in reduction of the leaching of the alkali ions. This excluded the mechanism that heavy metal ions can be exchanged with the alkali ions balancing the negatively charged Al tetrahedral in GP. Heavy metals were proposed to form coordination bonds between the nonbridging SiO− and AlO− of GP framework (crosslinkers) leading to more effective stabilization of total ions in the GP matrix. The FTIR study suggested formation of heavy metal hydrates, carbonates and silicates. The XRD patterns revealed an amorphous structure, and the SEM analysis indicated almost condensed homogenous surface of GP.