Slag-based Geopolymer Research Articles

The Effect of Si/Al Ratio to Compressive Strength and Water Absorption of Ferronickel Slag-based Geopolymer

Geopolymer material is inorganic polymers that are generally synthesized from aluminosilicate materials, such as ferronickel slag. In this study, synthesis of geopolymer material using NaOH 7 molar and Na2SiO3 solutions with different Si/Al ratio to make paste. Paste is molded in a metal mold with dimensions of 5x5x5 cm3, then released from the mold and heated in an oven at 80 °C for 24 hours. The specimens that have been heated further left at room temperature for 28 days and then tested for compressive strengthand water absorption. The results indicate a trend compressive strength increases and water absorption decreases with increasing the Si/Al ratio. The optimum condition is obtained when Si/Al ratio is 3.5.

Experimental study on fly ash and lead smelter slag-based geopolymer concrete columns

Geopolymer concretes have emerged as novel engineering materials with the potential to significantly reduce the environmental footprint of concrete manufacture and utilise high volume of industrial waste materials. Although significant experimental research has focused on the development of geopolymer mix design, there is far less information available regarding the performance of geopolymer concretes at a member level. This has implications in transferring geopolymer concretes from a laboratory material to a material in which can be specified in practice. This paper addresses the application of geopolymer concrete at a member level through an experimental investigation on the behaviour of fly ash/granulated lead smelter slag (GLSS)-based geopolymer concrete columns and beams tested under concentric and eccentric loading. Slenderness effect of the geopolymer concrete columns is investigated and axial load-moment interaction envelopes are generated experimentally. The analytical interaction diagrams are compared to those calculated using classical methods for normal reinforced concrete beams and columns. The results of the comparison show that the analytical interaction diagrams overestimated the test results due to variation in material properties. Nevertheless, the results reveal that fly ash/GLSS-based geopolymer concrete exhibits similar structural behaviour to ordinary Portland cement (OPC) concrete. The results also highlight potential issues with the scaling of ambient-cured geopolymer concrete to the structural level.

Development of Ultrafine Slag-Based Geopolymer Mortar for Use as Repairing Mortar

AbstractGeopolymer has earned a significant position in the construction industry. A number of researchers have attempted to use it as a concrete-repairing material. To enrich the literature with r...

Influence of Blended Activator on Microstructure, Crystal Phase and Physical Properties of Spent Catalyst Slag-Based Geopolymer

Influence of Blended Activator on Microstructure, Crystal Phase and Physical Properties of Spent Catalyst Slag-Based Geopolymer

A new graphene/geopolymer nanocomposite for degradation of dye wastewater

ABSTRACTA novel graphene/geopolymer nanocomposite was firstly synthesized by using two-dimension graphene (GR) and alkali-activated granulated blast furnace slag-based geopolymer (ASG), and used to degrade simulation dye effluents. Diffuse reflectance UV–Vis spectrum indicated that the maximum absorption wavelength of the nanocomposite (GR/ASG) is red-shift to the visible region. The pore diameter distribution results of the GR/ASG1 sample showed that at least 89.59% of pore volume centralized on the region of 2–50 nm. The photocatalytic degradation efficiencies of samples for methyl violet dye is in the order of GR/ASG1 > GR/ASG2 > ASG under the irradiation of UV. The GR/ASG1 photocatalyst exhibited the highest degradation efficiency and approached to 91.16% for 110 min. The photocatalytic degradation reaction belongs to the second-order reaction kinetics.

Immobilization of chromite ore processing residue with alkali-activated blast furnace slag-based geopolymer

Chromite ore processing residue (COPR) is an industrial waste produced in the chromic salts production process and contains a small portion of leached Cr(VI), which is highly toxic and is listed as a hazardous waste. The immobilization of COPR using a blast furnace slag-based geopolymer has been investigated in this study. The optimum parameters for preparing the blast furnace slag-based geopolymer using an orthogonal experiment were obtained. COPR was used to replace the amount of blast furnace slag for the preparation of the geopolymer. The COPR-bearing blast furnace slag-based geopolymer has potential application as a construction material and for geological disposal. The combined effect of physical fixation, adsorption and ion exchange in the geopolymeric and CSH (calcium silicate hydrate) gel is considered to be the main mechanism, and the reduction of S2− in the blast furnace slag played a significant role in the solidification of the COPR.

The effect of type and concentration of activators on flowability and compressive strength of natural pozzolan and slag-based geopolymers

Materials resulting from the alkali activation of GGBF slag show a wide range of workability, compressive strength and permeability. The main objectives of this work are to determine the effects of alkaline solution type and concentration, modulus of sodium silicate, sodium silicate to alkaline solution ratio and natural pozzolan replacement on the workability and mechanical properties of alkali activated GGBF slag. Results reveal that the geopolymer paste specimens containing KOH solution have higher compressive strength when compared with the geopolymer paste specimens containing NaOH solution. The optimum concentration of the alkaline solution is 6–8 molar. It can be concluded that in the presence of 6 and 8 molar alkaline solutions the maximum strength could be reached with 5% and 10% replacement respectively. The optimum range for each factor is suggested based on the different effects of these factors on the compressive strength.

Preparation and properties of geopolymer from blast furnace slag

In this paper, blast furnace slag was investigated as a source of the basic Si–Al ingredient of geopolymer. On the basis of compressive strength, the effects of grinding time on the activity of blast furnace slag and the effects of activator types, compound activator and particle size of blast furnace slag on the compressive strength were studied. The results showed that the optimum parameters were as follows: the grinding time was 12 hours, the granularity of blast furnace slag powders was 0·053–0·075 mm, the incorporation of blast furnace slag was 90 wt-%, the mass ratio of water glass/NaOH was 7:3, the liquid-to-solid mass ratio was 0·25, Additionally, X-ray diffraction, infrared spectroscopy and scanning electron microscope with energy dispersive spectrometer analysis were used to analyse the composition and polymerisation mechanism of the geopolymer. The reaction products of slag-based geopolymer paste was composed of two separate amorphous phases (geopolymeric and CSH gel).

Split tensile strength of slag-based geopolymer composites reinforced with steel fibers: Application of Taguchi method in evaluating the effect of production parameters and their optimum condition

In the present study, split tensile strength of slag based geopolymer composite reinforced with steel fibers has been designed by Taguchi method. In this ceramic matrix composite, furnace metallurgical slag of rockwool acts as an aluminosilicate source. Four main parameters including water curing regime, sodium hydroxide concentration, alkali activator to cement weight ratio and steel fibers weight percent, each at three different levels, were considered for examination. A total number of 9 experiments were performed according to L9 array which was proposed by the Taguchi method. The obtained results were evaluated by analysis of variance (ANOVA) method to determine the optimum level of each factor. ANOVA revealed that specimen with curing regime of 14 days, sodium hydroxide concentration of 14M, Alkali activator to cement weight ratio of 0.24 and steel fibers with 5wt% was potential of highest strength (8.87±1.71MPa) in considered procedure. Based on achievements, it is possible to produce high strength geopolymer composite reinforced with steel fibers. Also, it was shown that split tensile strength of slag based geopolymer composite reinforced with steel fibers could be suitably designed by the Taguchi method.

The fresh and engineering properties of alkali activated slag as a function of fly ash replacement and alkali concentration

Geopolymers are novel, environmentally friendly and economical materials. These materials are produced from industrial wastes, such as fly ash and slag. The geopolymer material used in this study is made from recycled materials, including fly ash and slag, and aqueous solution of NaOH and silicate. All of the specimens are produced using a fixed liquid-to-solid ratio (L/S=0.5), different ratios of fly ash and slag (fly ash replaces slag by 0%, 20%, 40%, and 60%) and various alkaline solutions (0.5%, 1% and 1.5%). The engineering properties of slump, flow, slump flow, flow time, setting time, compressive strength, ultrasonic pulse velocity and anti-sulfate attack are tested at different curing ages 1, 3, 7 and 28days.The findings show that when the replacement of fly ash is fixed, the slump value, flow value and slump flow increase with the alkalinity of the solutions. The slump value (98mm) before replacement with 1.5% alkaline solutions 1.5% is increased by approximately 20mm compared with different replacements of fly ash. Before the addition of any additive with a slow setting effect, the setting time can be shortened by reducing the alkaline solutions. When the alkaline solution increases from 0.5% to 1.0% or 1.5%, the compressive strength quickly develops. The ultrasonic pulse velocity increases with the addition of alkaline solutions. When alkaline activator 0.5% compared to 1.5% of an alkaline activator sulfate, they get more weight loss. The result shows more alkaline activator, less porosity, higher strength, durability relatively is better. These results are expected to upgrade the technical level of slag-based geopolymer with fly ash to further develop Taiwan’s energy saving, carbon reduction and environmentally friendly recycled admixtures.

Chemical activation and curing regime of geopolymer concretes

The effects of curing type, binary blends of chemical activators and addition of binder admixtures on the hardening properties of slag-based geopolymer concretes were investigated. Setting and hardening properties of different geopolymer mixtures were determined to assess the efficiency of polymerisation. Experimental investigations showed improved mechanical properties of geopolymer concretes with the adoption of steam curing and lower binder-to-aggregate ratio. Further, the addition of admixtures such as sodium sulfate and calcium nitrate to the slag binder exhibited higher compressive strengths. Furthermore, similar improved mechanical properties such as flexural and elastic modulus was observed with the addition of admixtures in slag activation. The reaction potential of alkali activator and admixtures dosage during slag activation was found to be dependent on high-temperature curing effects.

Research on Sodium Polyacrylate and its Effects on Mechanical Properties of Slag-Based Geopolymer

This report mainly studied the influence of dosage of the sodium polyacrylate on mechanical properties of slag-based geopolymer, and secondary studied the effects on mechanical properties of polyacrylic acid. The analyzing results indicate that compare to the polyacrylic acid, sodium polyacrylate has obvious effects on mechanical properties of slag-based geopolymer. And it’s mainly reflects on the nature of the 28 d, it’s early effects is not obvious. The mechanical properties of slag-based geopolymer doesn’t change with the dosage of sodium polyacrylate increase linearly, but overall mechanics properties is significantly superior to the blank sample.

Quantification of chloride diffusion in fly ash–slag-based geopolymers by X-ray fluorescence (XRF)

Chloride diffusion in cementitious materials is one of the key factors affecting the durability performance of concretes. This paper reports an investigation on the quantification of chloride diffusion in fly ash–slag-based geopolymer pastes. X-ray fluorescence (XRF) technique was used to determine the chemical compositions of the samples after short-term ponding test (contact with the 3% NaCl solution for 72h). The effect of the coexistence of Al-substituted calcium silicate hydrate (C-A-S-H) gel and aluminosilicate geopolymeric gel on the ingress of chloride was evaluated. The results showed that incorporation of slag as a secondary precursor in fly ash-based geopolymers led to the refinement of the pore structure, reducing both sorptivity of the pastes and the ingress of chloride ions. More compact C-A-S-H gel formed in geopolymer pastes with partial slag substitution led to lower permeability compared with the porous aluminosilicate gel that formed in the full fly ash-based geopolymer paste, contributing to the slower transportation of chloride in the fly ash–slag blended geopolymer pastes. The fly ash–slag-based geopolymer paste with 50% of slag performed better than the Portland cement paste in terms of resistance to chloride ingress.

Characterization of natural pozzolan-based geopolymeric binders

Properties and characteristics of fly ash- or slag-based geopolymers have been extensively explored but comparatively less information is available for natural pozzolan-based geopolymers. The present work focuses on microstructural characteristics of natural pozzolan-based geopolymers activated by sodium hydroxide and a mixture of sodium hydroxide and sodium silicate. Synchrotron XRD and SEM-EDS studies combined with compressive strength tests successfully demonstrate the feasibility of the use of natural pozzolan for sustainable construction material. It is concluded that the geopolymers have sufficient strength as structural materials and matrices contain C–S–H like crystal as well as zeolites of hydroxysodalite and zeolite Y. Two zeolites of hydroxysodalite and zeolite Y are found as the main activation products in sodium hydroxide activation. Substitution with sodium silicate solution yields higher compressive strength and a denser microstructure with dominant activation products of C–S–H like crystal, zeolite Y, and phillipsite. It has been proposed that the crystal size of the activation products ranges from 10nm to 1μm. Different microstructural characteristics found herein provide a valuable information to develop natural pozzolan-based sustainable structural materials with improved properties.

Research on Alkali-Activator and its Effects on Mechanical Properties of Slag-Based Geopolymer at early Age

This report studied the influence of effects such as type, modulus, dosage of the alkali-activator on mechanical properties of slag-based geopolymer. The analyzing results indicate that compare to the Na2SiO3, K2SiO3has significant activate effects on slag-based geopolymer. The modulus and dosage have obvious significance on early compression strength of slag-based geopolymer. With the increase of modulus, its early compression strength has apparent increase. With the increase of dosage, its early compression strength increase firstly and then decrease. When the dosage is 12%, the compression strength of the material is highest. The change of modulus and dosage of the alkali-activator has little influence on flexural strength of slag-based geopolymer. With the increase of dosage, its ratio of flexural to compressive strength has a downward trend. And the material brittleness addition.

Utilisation of FeNi-Slag for the Production of Inorganic Polymeric Materials for Construction or for Passive Fire Protection

This paper deals with the utilisation of ferronickel slag for the production of inorganic polymeric materials, with advanced mechanical or thermal properties, intended either for construction or for passive fire protection respectively. Initially, the development of Fe–Ni slag-based geopolymers, achieving high compressive strength and low water absorption, is described, and the produced materials are compared with some common construction and building materials. Secondly, the development of two fire resistant geopolymer materials is described. Their mechanical strength and thermal conductivity were measured, and the materials were tested for their resistance under high temperatures according to a standardized fire resistance test, by employing two different thermal loading curves. The fire resistant geopolymers were shown to comply with the test criteria concerning the temperature in the unexposed face of the specimen, the structural integrity and the concrete protection from mechanical damages. They also achieved similar or even better mechanical strength and thermal conductivity compared with the commercially available fire resistant materials.

The Role of Fly Ash in the Granulated Blast Furnace Slag-Based Geopolymer

Inorganic polymers using slag as cementitious materials have the advantage of a short setting time, high early strength, but the sensitivity of the reaction rate to temperature and the likelihood to subsequently crack, which leads to reduction of strength, limit its application. This article, by configuring different proportion of fly ash and slag, studied its dry shrinkage with the different kinds of activator, the effects of fly ash on the hydration heat release curves, differences of setting time and strength with different configuration, and then explored the effect of fly-ash in inorganic polymer. Experiments had shown that through rational configuration, the addition of fly ash can effectively reduce the rate of heat release and the amount of heat, meanwhile can solve the problem about short setting time of alkali-activated cementitious materials without reducing its strength.

Study on Sulfate-Attack of Slag-Based Geopolymer Concrete

Geopolymer has been attracted world attention as a potentially revolutionary material that is one of the ideal substitutes of portland cement. Fundamental studies on geopolymer are increasing rapidly because of its potential commercial applications. However, little work has been done on its erosion resistance of sulfate. In this paper, slag and metakaolin as source materials, different modules of water-glass as activator were used to prepare slag-based geopolymer which was then prepared to make slag-based geopolymer concrete. Linear expansion rate and mass loss of concrete were used as indicators to explore different erosion rules of slag-based geopolymer concrete which was long-term immersed in the 5% ( by mass ) Na2SO4 solution. Comparative experiments were also done between slag-based geopolymer concrete and ordinary cement concrete. The results showed that geopolymer concrete had excellent sulfate resistance performance, linear expansion rate and mass loss rate of geopolymer were 0.024% and 0.58% respectively at the soaking age of 49d as the water glass modulus was 1.4 and the water-glass content was 4%. It was also found that the anti-sulfate ability of geopolymer concrete is much better than that of ordinary concrete with the same strength grade.

Microstructure of Alkali-Activated Granulated Blast Furnace Slag-Based Geopolymer

The microstructure of alkali-activated granulated blast furnace slag-based geopolymer was studied by means of field emission scanning electron microscope (FESEM) coupled with energy dispersive X-ray analysis (EDXA). FESEM images showed that the geopolymer material has worm-like microstructure in the nanoscale with an average particle size of 20 nm. EDXA results demonstrated that the Na-based and Ca-based geopolymers were produced via the disintegration of amorphous phases and some minerals in GBFS and polycondensation reaction of oxygen-silicon and oxygen-aluminum tetrahedrons under alkaline condition.

Effect of Curing System on Mechanical Property of Slag-Based Geopolymer

Geopolymer has been gradually attracting world attention as a potentially revolutionary material that is one of the ideal substitutes of Portland cement, and fundamental studies on geopolymer are increased rapidly because of its potential commercial applications. However, little work has been done in the field of curing system of geopolymer. In this paper, influence of curing temperature, curing time and curing humidity on the mechanical properties of slag-based geopolymer was studied by using the compressive strength as benchmark parameter. Results have shown that the early age compressive strength of geopolymer increased and the long-term compressive strength decreased at first and then increased as the curing temperature increased, 80°C was the best curing temperature. With prolonging the curing time, it was found that the compressive strength of early age of geopolymer reached the maximum ( 116.3 MPa for 1d, 97.5 MPa for 3d) as the curing time was 12h, and that of 28d geopolymer was 91.3 MPa as the curing time was 10h. It was also found that the compressive strength of geopolymer reduced evidently as the humidity increased.