Lightweight Geopolymer Research Articles

Effect of air agent on mechanical properties and microstructure of lightweight geopolymer concrete under high temperature

Recent innovations in the field of concrete have contributed to the development of lightweight geopolymer concrete (LGC), which can be produced by adding an air agent. This study investigates the possibility of producing an air agent from the powder slag of ferrosilicon (FSS), an industrial waste. A class F fly ash (FA) was used for GC synthesis, and aluminium powder (AP) and FSS were added as air agents for LGC synthesis. The performance of FSS and AP as an air agents was compared by studying the properties of LGC produced under the same conditions. Air agents with 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% and 1.0% mass of FA were adopted to produce LGC. Thirteen mixtures were prepared to evaluate unit weight, the fresh and mechanical properties and the microstructure of LGC with PA and FSS air agents. Influence of high temperature of 200–800 °C for 2hrs on LGC was also investigated. The results show the possibility of using FSS waste powder as an air agent in LGC production. In terms of workability and unit weight, FSS was better compared to AP at the same percentage addition. The slump flow and unit weight, were 548 mm, 1830 kg/m3, and 569 mm and 1740 kg/m3, while compressive strength was 24.7 and 21.8 MPa for LGC containing 1% AP and 1% FSS, respectively.

Mechanical and Thermal Properties of Geopolymer Foams (GFs) Doped with By-Products of the Secondary Aluminum Industry.

The article deals with the investigation of geopolymer foams (GFs) synthesized using by-products coming from the (i) screening-, (iv) pyrolysis-, (iii) dust abatement- and (iv) fusion-processes of the secondary aluminum industry. Based on principles of the circular economy to produce new technological materials, the experimental study involves industrial by-products management through the recovery, chemical neutralization, and incorporation of these relatively hazardous waste into the GFs. The geopolymeric matrix, consisting of metakaolin (MK) and silica sand (SA) with a 1:1 wt.% ratio, and chopped carbon fibers (CFs, 1 wt.% MK), was doped with the addition of different aluminum-rich industrial by-products with a percentage from 1 to 10 wt.% MK. The gas (mainly hydrogen) produced during the chemical neutralization of the by-products represents the foaming agents trapped in the geopolymeric structure. Several experimental tests were carried out to characterize the mechanical (flexural, compressive, and Charpy impact strengths) and thermal properties (thermal conductivity, and diffusivity, and specific heat) of the GFs. Results identify GFs with good mechanical and thermal insulation properties, encouraging future researchers to find the best combination (for types and proportions) of the different by-products of the secondary aluminum industry to produce lightweight geopolymer foams. The reuse of these industrial by-products, which according to European Regulations cannot be disposed of in the landfill, also brings together environmental sustainability and safe management of hazardous material in workplaces addressed to the development of new materials.

Characterization of mechanically activated fly ash-based lightweight geopolymer composite prepared with ultrahigh expanded perlite content

This study focused on the optimization of the production conditions of an ultrahigh expanded perlite lightweight aggregate-filled fly ash-based geopolymer composite and the determination of its product properties. The geopolymer matrix was synthetized using mechanically activated fly ash and an alkaline solution. In a systematic series of experiments, the effect of expanded perlite (EP) content, the compaction pressure and the compaction time on the mechanical properties of the lightweight composite were investigated. In the case of the optimal production conditions, the composites were characterized in terms of physico-mechanical properties, water absorption and microstructure. The composites produced under optimal conditions had an average uniaxial compressive strength of 246 kPa and density of 534 kg/m3 at 80% by volume EP content, and 264 kPa and 221 kg/m3 at 95% by volume EP content. Both the FT-IR spectroscopy and scanning electron microscopy results proved the formation of main geopolymerization reaction products in the matrix of the composite, as well its reaction with the lightweight aggregate.

Low-Density Geopolymer Composites for the Construction Industry.

The article presents preliminary results in studying reinforced and light-weight geopolymers, which can be employed in buildings, especially for walling. Such materials are very promising for the construction industry having great potential due to their favorable properties such as high mechanical strengths, low thermal conductivity, and low density. Moreover, they also exhibit several advantages from an economic and ecological point of view. The present study exanimated the use of specific fillers for the metakaolin-based light-weight geopolymers, emphasizing the above-mentioned physical properties. This research also investigated the electromagnetic shielding ability of the carbon grid built into the light-weight geopolymer structure. According to the study, the most suitable materials to be used as fillers are polystyrenes, along with hollow ceramic microsphere and Liapor. The polystyrene geopolymer (GPP) achieves five times lower thermal conductivity compared to cement concretes, which means five times lower heat loss by conduction. Furthermore, GPP is 28% lighter than the standard geopolymer composite. Although the achieved flexural strength of GPP is high enough, the compressive strength of GPP is only 12 MPa. This can be seen as a compromise of using polystyrene as a filler. At the same time, the results indicate that Liapor and hollow ceramic microsphere are also suitable fillers. They led to better mechanical strengths of geopolymer composites but also heavier and higher thermal conductivity compared to GPP. The results further show that the carbon grid not only enhances the mechanical performances of the geopolymer composites but also reduces the electromagnetic field. Carbon grids with grid sizes of 10 mm × 15 mm and 21 mm × 21 mm can reduce around 60% of the Wi-Fi emissions when 2 m away from the signal transmitter. Moreover, the Wi-Fi emission was blocked when the signal transmitter was at a distance of 6 m.

Physical and mechanical properties of C class fly ash based lightweight geopolymer mortar produced with expanded vermiculite aggregate

This study presents the physical and the mechanical properties of C class fly ash (FA) based lightweight geopolymer mortars produced with expanded vermiculite (EV) aggregate. The FA was activated with NaOH containing 12%, 14% and 16% sodium by weight. The volumetric ratios of EV/FA in the samples were chosen as 2,4 and 6 in the study. The liquid/solid ratio 0.23, 0.26 and 0.29. Lightweight geopolymer mortar (LGM) samples were produced by mixing FA, EV, NaOH and water in a mixer. The samples placed in molds were exposed to activation temperature of 100°C for 24 hours in the oven. The samples taken out of the oven were demoulded and kept in air curing for 28 days at 20°C±2°C room temperature. After curing, unit weight, apparent porosity, water absorption ratio, ultrasonic pulse velocity (UPV), flexural strength and compressive strength tests were performed on the samples. In addition, the thermal conductivity coefficients of the samples were determined. As a result of the experiment, a compressive strength varying between 0.59 MPa and 3.81 MPa was obtained in lightweight geopolymers samples with a unit weight between 906 kg/m3 and 1477 kg/m3. Expanded vermiculite showed a good performance on thermal conductivity of LGMs and a decrease in thermal conductivity up to the 0.094 W/mK was observed.

Geopolymer as the future oil-well cement: A review

The petroleum and cement manufacturing industries have been accused of contributing substantial quantities of carbon dioxide (CO 2 ) into the atmosphere. Additionally, Portland cement systems suffer carbonation and degradation in high saline and acidic environments. Geopolymer, a much cleaner cementitious binder, synthesized through the reaction of aluminosilicate materials and alkaline solution has been a leading alternative to ordinary Portland cement (OPC). The feasibility of using geopolymer in oil-well cementing is still being explored. The objective of this review study is to provide a single document that summarizes the findings from these studies. In general, researchers have explored geopolymer application in aggressive environments and well plug and abandonment operations, the effect of temperature, and its compatibility with drilling fluid. Compared to OPC systems, geopolymer is more resistant to acidic environments, performs better in high saline conditions, and is highly compatible with drilling mud. The geopolymer being a green technology coupled with its optimized properties implies that it is the future of oil-well cement. For further studies, we suggest in-depth characterization of lightweight geopolymers. • The state of research on the application of geopolymer for oil well cementing has been explored. • Geopolymer overcomes many of the issues faced with ordinary Portland cement (OPC). • Geopolymer would be an excellent alternative to OPC-based systems.

Response surface optimization of geopolymer mix parameters in terms of key engineering properties

The main aim of the current study is to search the impact of variable matrix phase features on fly ash based lightweight geopolymer mortars (LWGM). Another scope of the study is to obtain performance oriented optimum mixture proportions through response surface method (RSM). In order to have low unit weight for LWGMs, pumice aggregate was utilized as a part of the aggregate. The investigated engineering properties are water absorption, drying shrinkage and thermal conductivity. By performing optimization analysis, it was aimed to obtain the best numerical models representing the experimental results depending on the input variables. The decrease of liquid (alkali activators) to powder (fly ash) ratio, Na2SiO3 solution to NaOH solution ratio and increase of sodium hydroxide molarity led to improvement of compressive strength. Dry thermal conductivity values in dry state were observed to be less than those of saturated ones. Moreover, the higher sodium hydroxide molarity and lower Na2SiO3 solution to NaOH solution ratios, and liquid to powder ratios resulted in further shrinkage reduction. Depending on the goals of maximum compressive strength, minimum water absorption, and drying shrinkage, optimum values for molarity, SS/SH, and l/p factors were determined as 14 M, 1.586, and 0.45, respectively.

Development of New Material for Geopolymer Lightweight Cellular Concrete and its Cementing Mechanism

Development of New Material for Geopolymer Lightweight Cellular Concrete and its Cementing Mechanism

Evaluation of mix ratios of light weight concrete using geopolymer as binder

Concrete, an old material which is changing its nature rapidly based on supplementary materials used in it. Geopolymer concrete is a sustainable material developed by replacing 100% flyash of cement. To activate the stable flyash particles in concrete, alkaline solutions are added in place of water. Foam is one of the additional materials added in concrete to obtain light weight. These additional materials will affect the mix proportions directly. Light weight Geopolymer Concrete (LWGC) is the combination of two techniques which doesn’t have similarity in single prospect, so the mix design methods for nominal concrete and light weight concrete alone will not be useful to develop LWGC. This paper will discuss the mix proportions of light weight geopolymer concrete with different materials and different variables viz: foam volume, mass ratio, Solution to binder ratio and density based on available codes of practices and literature. The results indicated 0.6 solution to binder ratio is suitable for 8 M LWGC with good workability and compressive strength.

Strength performance of alkali activated structural lightweight geopolymer concrete exposed to acid

This study investigates the performance of structural lightweight geopolymer concrete (SLWGC) exposed to chemical attack. The objective of this study is validation the ability of using light weight geopolymer concrete for structural purpose under hard conditions. The alkali activator was produced using sodium silicate, sodium hydroxide and water. Flay ash and slage as waste materials were replaced by 90% of ordinary Portland cement to produce the geopolymer concrete. Also, ordinary cement concrete produced to comparison. Three types of lightweight aggregate were used instead of normal aggregate represented by pumice stone, expanded clay and construction waste clay brick to produce SLWGC. The unit weight of produced SLWGC were in the range (1800–2100) kg/m3. Normal weight geopolymer concrete and SLWGC were produced simultaneously to compare their performance each with other. The geopolymer concrete mixes treated by heat curing at 65 °C for 24 h after removing the molds. The specimens of all mixes exposed to sulfuric acid with concentration 5% and 10% for 8 weeks. The investigated mechanical properties represented by compressive strength and flexural tensile strength. The results indicate that the geopolymer concrete exhibit better resistance for acid attack compared to OPC concrete where the strength deterioration for SLWGC lower than ORC light weight concrete after exposed to acid, crushed clay bricks exhibit superior mechanical and durability performance compared to other LWA. Finally, the results proved the ability of producing light weight geopolymer concert for structural purposed with acceptable performance of strength and durability under hard chemical conditions.

Engineering performance of sustainable geopolymer foamed and non-foamed concretes

This study investigates the effect of using palm oil fuel ash (POFA) as a partial replacement for fly ash (FA) in lightweight geopolymer foamed concrete and geopolymer mortar. Three different proportions of POFA contents of 10%, 20%, and 30% with a target fresh density of about 1300 ± 50 kg/m3, were used. The development of compressive strength and splitting tensile strength were investigated over a 28-day curing period. Transport properties, in terms of water absorption, porosity, and sorptivity, were also investigated. Microstructural characteristics through XRD, SEM and EDX were also investigated and reported. The results found that the compressive strength of geopolymer foamed concrete, with up to 30% POFA, was higher than the control; however, for the POFA-based geopolymer mortar, the compressive strength reduced with increasing POFA content. The highest compressive strength of 6.1 MPa was recorded in the geopolymer foamed concrete with 20% POFA, whereas the control mix of geopolymer mortar produced 36.6 MPa. The geopolymer foamed concrete achieved 70% of its 28-day compressive strength within 3 days. The oven-dry density of the geopolymer foamed concrete ranged from 1193-1344 kg/m3. The ultrasonic pulse velocity (UPV) value was 1.5 km/s for the geopolymer foamed concrete while the geopolymer mortar had the range of 2.2–2.4 km/s. In general, the transport properties were mostly dependent on the oven-dry density of the geopolymer foamed concrete. The POFA content of 20% was found to provide the required silica and alumina to produce geopolymerization gel. Further, the SEM images showed unreacted FA particles that led to an increase in the voids. Furthermore, the XRD patterns showed the addition of foam affected the intensity of the peaks.

Mechanical behavior of fiber reinforced slag-based geopolymer mortars incorporating artificial lightweight aggregate exposed to elevated temperatures

The present research investigates the effects of artificial lightweight aggregate (ALWA) and polyvinyl alcohol (PVA) fiber utilization on the mechanical performance of slag-based lightweight geopolymer mortar (LGPM) specimens cured at ambient temperature. Also, the influence of elevated temperature (250 °C and 500 °C) on the resulting performance of LGPM samples was studied. For the production of LGPM specimens, 60% and 80% ALWA were utilized as a partial replacement of river sand. The slag-based LGPM samples were activated by a mixture of sodium silicate and 12 M sodium hydroxide solutions. The fresh and hardened state properties of LGPM specimens with and without fibers were assessed by workability, density, compressive strength, uniaxial tensile strength, and flexural strength tests. Also, the micro-scale variations were evaluated by scanning electron microscopy (SEM). The findings revealed that the incorporation of ALWA reduced the workability, density, and compressive strength of the LGPM, and the reductions in all these properties were more with 1% PVA inclusions. Meanwhile, inclusions of 1% PVA fibers significantly enhanced the uniaxial tensile and flexural behaviors of LGPM. After exposure to 250 °C, all mechanical strengths were improved due to the further geopolymerization, while mechanical strength reductions were observed at 500 °C due to the vapor impact and difference in thermal expansion. The uniaxial tensile strength of fiber-reinforced LGPM samples was improved from 1.47 MPa to 2.16 MPa at 250 °C, while uniaxial tensile strength reduced at 500 °C, and the samples exhibited a brittle failure mode due to the melting of PVA fibers. The results pointed out that tensile and flexural properties of LGPM significantly enhanced with ALWA and 1% PVA fiber utilization.

Mechanical performance and durability of geopolymer lightweight rubber concrete

This research focuses on producing and testing a type of geopolymer concrete as an alternative to the conventional Portland cement concrete. The proposed concrete incorporates lightweight expanded clay aggregate (LECA) and rubber from car tyre waste which results in the production of a new concrete: “geopolymer LECA-Rubcrete”. A total of ten geopolymer concrete mixes were produced using rubber and LECA as partial replacements of fine and coarse aggregates, respectively. Variables such as the ratio of geopolymer binders, LECA pre-treatment, concrete curing method, and mixing procedures were examined. Physical, mechanical, and durability tests were conducted including workability, compressive strength, drying shrinkage, water absorption, surface abrasion, and carbonation. This research aimed to provide the necessary information needed to develop lightweight geopolymer Rubcrete structures to reduce carbon emissions and move a step closer towards a greener future. The results indicated that lightweight geopolymer Rubcrete is a suitable alternative to lightweight conventional concrete with similar or better durability properties. The workability increased by 9% and 20% when using rubber and LECA, respectively; however, the compressive strength decreased by 32% and 67%, respectively. Using 25% slag to 75% fly-ash decreased the workability by 44% and increased the strength by 47%. Specimens cured in the ambient condition showed less strength compared to those cured in water. Heat + water curing showed less strength in all mixes, except in mixes with no lightweight materials and with high fly-ash content, which showed 16–21% strength increase. Of the tested mixes, geopolymer LECA-Rubcrete mix that has high slag content showed comparable or better performance than that showed by Portland cement LECA-Rubcrete mix in all measured characteristics.

Development and Characterization of Lightweight Geopolymer Composite Reinforced with Hybrid Carbon and Steel Fibers.

The aim of this paper is to analyze the influence of hybrid fiber reinforcement on the properties of a lightweight fly ash-based geopolymer. The matrix includes the ratio of fly ash and microspheres at 1:1. Carbon and steel fibers have been chosen due to their high mechanical properties as reinforcement. Short steel fibers (SFs) and/or carbon fibers (CFs) were used as reinforcement in the following proportions: 2.0% wt. CFs, 1.5% wt. CFs and 0.5% wt. SFs, 1.0% wt. CFs and 1.0% wt. SFs, 0.5% wt. CFs and 1.5% wt. SFs and 2.0% wt. SFs. Hybrid reinforcement of geopolymer composites was used to obtain optimal strength properties, i.e., compressive strength due to steel fiber and bending strength due to carbon fibers. Additionally, reference samples consisting of the geopolymer matrix material itself. After the production of geopolymer composites, their density was examined, and the structure (using scanning electron microscopy) and mechanical properties (i.e., bending and compressive strength) in relation to the type and amount of reinforcement. In addition, to determine the thermal insulation properties of the geopolymer matrix, its thermal conductivity coefficient was determined. The results show that the addition of fiber improved compressive and bending strength. The best compressive strength is obtained for a steel fiber-reinforced composite (2.0% wt.). The best bending strength is obtained for the hybrid reinforced composite: 1.5% wt. CFs and 0.5% wt. SFs. The geopolymer composite is characterized by low thermal conductivity (0.18–0.22 W/m ∙ K) at low density (0.89–0.93 g/cm3).

Synergistic effects of iron (Fe) and biochar on light-weight geopolymers when used in wastewater treatment applications

The conventional geopolymer usually has bad wastewater treatment ability. How to maximum improve the wastewater treatment ability of geopolymer become a hot topic. The synergistic effects of iron (Fe) and biochar on the circulation fluidized bed combustion fly-ash and bottom ash-based geopolymer (BFBAG) in the removal of dyes and toxic heavy metals were investigated. The hydration numerical models of BFBAG and immobilization mechanisms of heavy metals were proposed at first time. The removal efficiency (RE) of geopolymer with and without Fe is 68% and 84%, respectively, and the RE difference of geopolymer with Fe and biochar is 87%. It indicated that Fe and Biochar had synergistic catalytic effects when used in geopolymer for wastewater treatment applications. During the geopolymer production/formation process, whilst Fe enhanced the removal efficiency of the methylene blue dye, Biochar was concurrently instrumental in enhancing the immobilization efficiency and removal of the toxic heavy metals from the wastewater.

Stabilized homogeneous porous structure and pore type effects on the properties of lightweight kaolinite-based geopolymers

Hydrogen peroxide and metal powders are widely used as foaming agent to prepare lightweight cementitious materials including geopolymers; however, it is difficult to control the generated cell size due to high reactivity of the system. This study aimed to investigate the influences of sodium lauryl ether sulfate (SLES) foaming agent on pore types and properties of lightweight kaolinite-based geopolymers suggested to be used as thermal insulation. The results revealed that the SLES enhanced the porosity, therefore leading to low density, strength, and thermal conductivity. The lightest geopolymer having a bulk density of 0.69 g cm−3 and total porosity of 72.34% was obtained when 15 wt% SLES was employed. It exhibited adequate compressive strength of 4.69 MPa with very low thermal conductivity of 0.197 W m−1 K−1 that suitable for using as thermal insulation. In addition, the open and total porosity of geopolymer increased significantly as the amount of SLES increased, while the closed porosity increased to the maximum value at 10 wt% SLES and decreased afterward. At this condition, a stabilized homogeneous porous structure was obtained. Regression analysis was adopted to study the relationships between the amount of SLES and pore types with properties of the lightweight geopolymers. It was revealed that the amount of SLES exhibited linear relationships with porosities and properties of the lightweight geopolymers. R-squared values indicated that the total porosity had the strongest effect on all properties except for water absorption, which was highly affected by the open pores. The closed pores had the strongest effect on the compressive strength.

Effects of high‐temperature exposure on properties of lightweight geopolymer foams incorporating diatomite powders

AbstractA kind of metakaolin‐based geopolymer foams incorporating diatomite powders (GKGP) with open cellular was presented by addition of diatomite powder via hydrogen peroxide method. Impacts of high‐temperature exposure on the microstructure, pore structure, and mechanical properties of the GKGP samples were investigated. The GKGP foams achieved a typical amorphous phase structure at room temperature. Open porosity of the samples reached approximately 74%. After high‐temperature exposure treatment, the KGP matrix is basically transformed into leucite crystal phase. The compression strength of the leucite foams was also enhanced with increasing temperature to 1200℃ (9.28 MPa). The lightweight foamed GKGP samples with high open porosity might have great potential for membranes and industries, etc.

Effect of elevated temperatures on mechanical properties of lightweight geopolymer concrete

This study aims to examine the effect of high temperatures on lightweight geopolymer concrete (LWGC) and lightweight ordinary concrete (LWOC) made of natural pumice and lightweight expanded clay aggregate (LECA) with the addition of trapped air. To this end, a geopolymer concrete matrix has been synthesized by the alkali-activation of fly ash (FA) and granulated blast furnace slag (GBFS). The geopolymer concrete samples were cured for 24 h at a temperature of 80 °C. To study the properties of fresh concrete, slump and slump flow tests and unit weight were applied. The mechanical properties were also measured by the compressive strength, splitting tensile, flexural strength, and elastic modulus tests. High temperatures of 100 °C, 200 °C, 300 °C, 400 °C, 500 °C, 600 °C, 700 °C, and 800 °C were applied on the geopolymer concrete samples to obtain the residual compressive strength. In general, pumice and LECA can be used as an alternative to the dolomite aggregate to produce LWGC and LWOC. The mixture F-50D50P-A achieved the lowest of unit weight of 1660 kg/m, a slump flow of 555 mm, and compressive strength of 32.9 MPa at 91-days. Lightweight geopolymer concrete containing 50 % fly ash and 50 % GBSF achieved the best compressive strength test results. The results showed a similarity in the behaviour of LWGC with LWOC under the influence of all the variables applied in this study.

Change in compressive strength of lightweight geopolymers after immersion

Change in compressive strength of lightweight geopolymers after immersion

A Study on the Flexural Behaviour of Geopolymer Lightweight Eco-Friendly Concrete Using Coconut Shell as Coarse Aggregate

This paper presents the flexural behaviour of concrete containing ground granulated blast furnace slag (GGBS) as a binder, manufactured sand (M-sand) as a fine aggregate, and coconut shell (CS) and crushed stone aggregate (CSA) as coarse aggregates. Alkaline activator sodium hydroxide with 10 molarity and sodium silicate were used in a weighing proportion of 1 : 2.5 to produce structural grade concrete. Out of 12 beams cast, 6 were used to study geopolymer coconut shell concrete (GPCSC) beam behaviour and 6 were used to study geopolymer conventional concrete (GPCC) beam behaviour. Data presented include cracking behaviour, ultimate moment capacitates, deflection behaviour, ductility ratio, and end rotation of the beam. Laboratory investigations show encouraging results, and it can be summarized that coconut shell has good potential as a coarse aggregate for the production of structural grade geopolymer lightweight coconut shell concrete.