Geopolymer Foams Research Articles

Improving thermal insulation and thermal resistance properties of laterite‐based geopolymer foams by direct foaming

AbstractThis work aims to synthesize new foaming laterite geopolymer foam using laterite, sodium silicate solution, sand, and aluminium powder. The porosity rapidly increased with the addition of the foaming agent. The foam matrix had thermal conductivity values of 0.10 W/m K with 0.7% of Al powder and 0.64 W/m K with 0% of Al powder. For fire resistance, samples exposed to high temperatures (200°C and 500°C) showed increased flexural strength, linear shrinkage at 500°C, and a decrease at 900°C due to structural weakening under high thermal pressure and the appearance of new phases such as nepheline and akermanite in X‐ray diffraction analysis. The results also showed that a 30% increase in fine aggregate content increased the strength of the foam matrix, with flexural strength ranging from 5 to 9.1 MPa after 28 days of ambient curing. These laterite geopolymer foams have shown promising thermal insulation and mechanical qualities that are appropriate for building applications.

Energy-Efficient Geopolymer Composites Containing Phase-Change Materials-Comparison of Different Contents and Types.

The purpose of this study was to analyze the effects of phase-change components on the properties of geopolymer foams. Geopolymer foams are lightweight foamed geopolymers that are characterized by a high degree of porosity. Phase change materials, on the other hand, are compounds that, when added to a material, allow it to absorb, store, and then release large amounts of energy. Three types of PCMs, i.e., MikroCaps, GR42, and PX25, were introduced at 15% by weight. Geopolymer materials were produced based on silica fly ash, and hydrogen peroxide H2O2 was used to foam the geopolymer structure. The PCM geopolymer composites were cured at 60 °C. The produced materials were tested for physical, chemical, and thermal properties. The tests included oxide and mineral composition analysis of the base material, PCM particle size analysis, apparent density and porosity tests on the foams, water leachability tests, thermal tests (λ, Cv, Cp, α), and structural and textural analysis. The most relevant tests to confirm the performance of the phase-change materials were thermal tests. With the introduction of PCMs, volumetric heat capacity increased by as much as 41% and specific heat by 45%, and thermal diffusivity decreased by 23%. The results confirm the great potential of geopolymer composites as modern insulation materials for buildings and structures.

A review on serviceability of foam concrete

In the face of the present global warming crisis, building energy conservation and emissions reduction have gained increasing attention. In the sustainable development of buildings, foam concrete has become increasingly popular in the construction industry due to its excellent thermal insulation, sound insulation and fire resistance. Foam concrete employed in buildingand construction (used as either a structural or non-structural member) must meet certain serviceability criteria. This paper reviews the serviceability of ordinary Portland cement (OPC) foam concrete, geopolymer foam concrete (GFC), sulphoaluminate cement (SAC) foam concrete, magnesium phosphate cement (MPC) foam concrete and limestone calcined clay cement (LC3) foam concrete, to include drying shrinkage, creep, thermal conductivity, water absorption and acoustic properties. Subsequently, it is proposed to change the initial curing conditions to reduce drying shrinkage, add glass fiber and basalt fiber to improve creep performance, increase heat flow direction resistance and extend the thermal conduction path to reduce thermal conductivity, control slump flow to regulate water absorption, and combine sound absorbing foam concrete with sound reflecting materials to achieve a comfortable and low noise living environment. Finally, ideas and suggestions for future work are proposed.

Insulating Innovative Geopolymer Foams with Natural Fibers and Phase-Change Materials-A Review of Solutions and Research Results.

Geopolymers are synthesized using anthropogenic raw materials and waste from the energy industry. Their preparation necessitates an alkaline activator, which facilitates the dissolution of raw materials and their subsequent binding. At present, geopolymers are considered a promising material with the potential to replace conventional cement-based products. This research investigates foamed geopolymer materials based on fly ash, natural fibers, and phase-change materials. The study utilized three distinct types of fibers and two phase-change materials manufactured by Rubitherm Technologies GmbH of Germany. This paper presents the results of the thermal conductivity coefficient and specific heat tests on the finished foams. Additionally, compressive strength tests were conducted on the samples after 28 days. Natural fibers decreased the insulation parameter by 12%, while PCM enhanced it by up to 6%. The addition of fibers increased the compressive strength by nearly 30%, whereas PCM reduced this by as little as 14%. Natural fibers and phase-change materials had an increased heat capacity by up to 35%. The results demonstrated the material's potential in various industrial sectors, with the primary areas of application being building materials and insulations. The findings illustrate the significant potential of these composites as energetically and environmentally sustainable materials.

Mechanical behaviors of metakaolin-based foamed geopolymer (MKFG) under dynamics loading

In this study, metakaolin-based foam geopolymer (MKFG) with densities of 400 kg/m3, 600 kg/m3, and 800 kg/m3 were prepared. The effect of weak links on the dynamic mechanical behavior, damage morphology, and energy absorption capacity (SEAp) of the MKFG was studied by X-CT analysis, Split Hopkinson Pressure Bar (SHPB) test, and fractal analysis. The results show that the connected porosity of MKFG rises with decreasing density. The sensitivity of the damage level to strain rate decreases with elevated connected porosity, which is because the stress concentrations caused by weak links. The amplifying effect of strain rate on the dynamic compressive strength of MKFG diminishes as the connected porosity increases. The sensitivity of SEAp to the damage level rises with a decrease in the connected porosity. Finally, the simulation results corroborate that the distribution of connected pores has a significant influence on the damage process of the MKFG.

A way to macroporous and alveolar geopolymer foams elaboration: Influence of operating parameters on porosity characteristics

Alveolar cellular foams are widely used in a wide range of applications, from aeronautics and filtration systems to chemical and transformation processes. Their porous characteristics make them a prime candidate for reactions, radiative transfer and flow. Geopolymeric foams, which have their origins in civil engineering, are materials with promising potential in terms of mechanical, thermal and acoustic resistance. As they are mainly used in civil engineering, the structures currently being developed are mainly closed-pore matrices. However, if they are to invert the field of photocatalytic oxidation processes, solar collectors or concentrated solar power plants, the supports need to develop a high exchange surface area. Metal alveolar foams have been identified as ideal but very costly supports. Geopolymeric foams could meet these requirements, but their surface areas are currently too limited for photoreactors. In this study, it is proposed to develop and optimize the operating conditions for geopolymer foam synthesis in order to impart macroporous properties and an interconnected alveolar structure. Based on two well-established synthesis methods (direct foaming and replication), operating conditions such as foaming agent and surfactant content, and drying and calcination conditions, are studied. Geopolymer foams are produced with different macroporous characteristics. We aim to define the synthesis conditions required to produce interconnected macroporous alveolar foams with milimetric pores. In civil engineering, these materials have the advantage of being easy to design, use and shape according to the application.

Effect of Triterpenoid Saponins as Foaming Agent on Mechanical Properties of Geopolymer Foam Concrete.

Geopolymer foam concrete (GFC), an emerging thermal insulation material known for its environmentally friendly and low-carbon attributes, has gained prominence for its use in bolstering building energy efficiency. A critical challenge in GFC production is foam destabilization by the alkaline environment in which foam is supersaturated with salt. In this study, GFC was prepared by using triterpene saponin (TS), sodium dodecyl sulphate (SDS), and cetyltrimethylammonium bromide (CTAB) as blowing agents, with fly ash as the precursor and calcium carbide slag (CA) combined with Glauber's salt (GS, Na2SO4 ≥ 99%) as the activator. The effect of GFC on mechanical properties was analyzed by examining its fluidity, pore structure, dry density, and compressive strength. The results show that TS has a stable liquid film capable of adapting to the adverse effects of salt supersaturation and alkaline environments. TS is highly stable in the GFC matrix, and so the corresponding pore size is small, and the connectivity is low in the hardened GFC. In addition, the hydration products of GFC exhibit different morphologies depending on the surfactant used. TS has better water retention due to hydrogen bonding, which facilitates the hydration process.

Influence of foaming additives on the porous structure and properties of lightweight geopolymers based on ash–slag waste

Lightweight geopolymer is a promising thermal insulation material that conserves energy used for heating and cooling buildings. This study investigates foaming agents that influence the porous structure and properties of geopolymer foams based on ash–slag waste from thermal power plant using a 12 M sodium hydroxide solution, waterglass, and foaming agents (30 % hydrogen peroxide solution, aluminum, silicon, and zinc powders). The study demonstrates the feasibility of foaming geopolymers by water evaporation without foaming additives, where the best density of 949 kg/m3 and compressive strength of 4.2 MPa were achieved in samples foamed by microwave radiation, but such properties cannot attribute geopolymers as lightweight. Foaming with H2O2 is hard to synchronize with geopolymerization reactions. Aluminum and silicon powders lead to rapid reactions in alkaline conditions, resulting in uneven pore sizes. Zinc powder was the most effective foaming agent, producing materials with a density of 331 kg/m3 and compressive strength of 1.17 MPa, and it also integrates into the geopolymer gel structure. The foaming process should occur at room temperature. Elevated temperatures increase curing rates and result in incomplete geopolymerization, preventing uniform pore formation. Synthesized geopolymers are suitable for building insulation, basements, underground pipelines, and utility networks.

Experimental investigation on the anti-detonation performance of composite structure containing foam geopolymer backfill material

The compression and energy absorption properties of foam geopolymers increase stress wave attenuation under explosion impacts, reducing the vibration effect on the structure. Explosion tests were conducted using several composite structure models, including a concrete lining structure (CLS) without foam geopolymer and six foam geopolymer composite structures (FGCS) with different backfill parameters, to study the dynamic response and wave dissipation mechanisms of FGCS under explosive loading. Pressure, strain, and vibration responses at different locations were synchronously tested. The damage modes and dynamic responses of different models were compared, and how wave elimination and energy absorption efficiencies were affected by foam geopolymer backfill parameters was analyzed. The results showed that the foam geopolymer absorbed and dissipated the impact energy through continuous compressive deformation under high strain rates and dynamic loading, reducing the strain in the liner structure by 52% and increasing the pressure attenuation rate by 28%. Additionally, the foam geopolymer backfill reduced structural vibration and liner deformation, with the FGCS structure showing 35% less displacement and 70% less acceleration compared to the CLS. The FGCS model with thicker, less dense foam geopolymer backfill, having more pores and higher porosity, demonstrated better compression and energy absorption under dynamic impact, increasing stress wave attenuation efficiency. By analyzing the stress wave propagation and the compression characteristics of the porous medium, it was concluded that the stress transfer ratio of FGCS-ρ-579 was 77% lower than that of CLS, and the transmitted wave energy was 90% lower. The results of this study provide a scientific basis for optimizing underground composite structure interlayer parameters.

Design and characterization of geopolymer foams reinforced with Miscanthus x giganteus fibres

This paper presents the results of the optimisation and characterization of Miscanthus fibre reinforced geopolymer foams based on fly ash and represents an important step forward in the development of a sustainable and environmentally friendly insulation material. Miscanthus belongs to a promising group of renewable raw materials with favourable thermal insulation properties. Design of experiment (DoE) were used to optimize the thermal conductivity and compressive strength of Miscanthus x giganteus reinforced geopolymer foams. In addition, the samples was analyzed using X-ray diffraction (XRD), Field emission scanning electron microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FTIR). Mixtures with a low thermal conductivity of 0.056 W (m K)−1 and a porosity of 79 vol% achieved a compressive strength of only 0.02 MPa. In comparison, mixtures with a thermal conductivity of 0.087 W (m K)−1 and a porosity of 58 vol% achieved a compressive strength of 0.45 MPa. Based on the determined parameters especially due to the low compressive strength, an application as cavity insulation or insulation between rafters is possible.

A multifunctional barium-modified geopolymer foam for the efficient and flexible treatment of high-sulfate coal mine drainage

Adsorption is a low-energy and easy-to-perform technique that can directly remove pollutants from water. However, owing to material limitations in terms of the adsorption capacity, efficiency, cost, and pollutant type, the application of this method is challenging in high-sulfate coal mine drainage (CMD) purification. Based on a coal mine in Erdos (China) with high-sulfate CMD, a multifunctional Ba-modified geopolymer foam (Ba/GPF) adsorbent was developed, and its ion adsorption efficiency was verified, along with its application performance in a practical situation. The excellent pore structure of Ba/GPF adsorbent allowed the dynamic removal of SO42− (>86%), Ca2+ and Mg2+ (>99%), Na+ (>50%), K+ (>77%), TDS (>60%), and suspended solids (>97%) from actual CMD. Furthermore, the addition of Na2CO3 combined with ultrasonic and acid treatment effectively removed the BaSO4 crystals to recover the regeneration capacity of Ba/GPF. Importantly, the adsorption capacity decreased by only 25.9% after 8 regeneration cycles. Subsequently, Ba/GPF was applied on a small scale to an actual coal mine, and its effectiveness was verified. This adsorbent can therefore be considered applicable in energy-free working conditions, such as those found in underground producing mine goafs. Overall, the Ba/GPF shows promising potential for the efficient and flexible treatment of high-sulfate wastewater.

Optimisation in Water Absorption of Low Molarity Seawater and Zeolite Based Geopolymer Foam Reinforced with Nanocellulose

The aim of this study is to optimize the composition of geopolymer foam that leads to the highest water absorption. This study utilized Response Surface Methodology (RSM) to analyze the relationship between factors Seawater/Potassium Silicate (SW/KSil), Potassium Hydroxide/Potassium Chloride (KOH/KCl), Sodium Lauryl Ether Sulfate/Benzalkonium Chloride (SLES/BAC) and Hydrogen Peroxide/Nanocellulose (H2O2/NC) and its response, water absorption. The concentration of the alkaline solution is maintained at a low level of Molar Ratio (MR) 2.01-2.53 and 0.320 M to 1.620 M. It was found that all factors are significant with ρ-value < 0.05 except for KOH/KCl. The highest water absorption by geopolymer measured is 35%, in the middle range of all factors. Simple water immersion of 30 days shows no significant physical changes on the geopolymer, proving its rigidity under water.

Optimizing the photocatalytic properties of macroporous geopolymer foam: Influence of SILAR-technique synthesis conditions

Macroporous cross-linked materials such as 3D honeycomb foams are used as substrates for heterogeneous photocatalysis. They offer a number of interesting properties. They are highly open-porosity substrates, guaranteeing optimum mass and radiation transfer, making them ideal for photo-conversion applications such as photo-oxidation or photo-reduction, which take place in photo-reactors for pollutant degradation or solar fuel production. Many cross-linked supports such as polymeric and metallic foams studied in the literature have revealed photocatalytic capacities similar to those obtained for the catalyst nanoparticle suspensions used as a reference. To reduce the production costs of this type of material, geopolymers, widely used in civil engineering, offer a wide range of properties suitable for shaping cellular foams. In addition to their low cost and mechanical properties, it is also possible to impart porous properties and modulate their characteristics according to the synthesis operating conditions so as to elaborate macroporous cellular foams. In this study, we propose to investigate the photocatalytic properties of honeycomb geopolymer foams coated with a catalyst: ZnO. To achieve ZnO deposition, the SILAR technique was applied by modifying the key synthesis operating conditions, i.e. precursor concentration and the number of quenching cycles applied. The results obtained make it possible to define the optimum operating conditions (pH, temperature) and, above all, the number of cycles and precursor concentration required to obtain the best photocatalytic efficiency. These innovative and promising materials, little studied in the literature, are prime candidates for solar photo-conversion applications.

Monitoring the Geopolymerization Reaction of Geopolymer Foams Using 29Si and 27Al MAS NMR

This study aims to investigate the geopolymerization reaction of geopolymer foams produced with three different foaming agents: aluminum powder, zinc powder, and hydrogen peroxide. The geopolymerization reaction of geopolymer foam was monitored using the 27Al and 29Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy technique. 27Al MAS-NMR was used to monitor the reaction at an early stage, while 29Si and 27Al MAS-NMR analyses were employed at specific time intervals of 3, 6, 10, 15, and 28 days to examine the changes that occurred in the formed gel over time. We discussed in detail how the type of foaming agent used and the duration of the reaction both influence the quantity of gel formed and the amount of remnant fly ash. Our findings indicate that the type of foaming agent used affects the formation and structure of the gel, with aluminum powder leading to the highest gel formation. Additionally, the duration of the reaction plays a significant role in determining the quantity of remnant fly ash, with longer reaction times resulting in decreased fly ash content. This study sheds light on the relevance of understanding the role of foaming agents in the geopolymerization reactions of geopolymer foams and the influence of reaction time on the formed gel properties.

The Influence of the Addition of Basalt Powder on the Properties of Foamed Geopolymers.

Geopolymers are binder materials that are produced by a chemical reaction between silica or aluminum compounds with an alkaline activating solution. Foamed geopolymer materials are increasingly being cited as a viable alternative to popular organic insulation materials. Since the foaming process of geopolymers is difficult to control, and any achievements in improving the performance of such materials are extremely beneficial, this paper presents the effect of the addition of basalt powder on the properties of foamed geopolymers. This paper presents the results of physicochemical studies of fly ash and basalt, as well as mechanical properties, thermal properties, and structure analysis of the finished foams. The scope of the tests included density tests, compressive strength tests, tests of the thermal conductivity coefficient using a plating apparatus, as well as microstructure tests through observations using light and scanning microscopy. Ground basalt was introduced in amounts ranging from 0 to 20% by mass. It was observed that the addition of basalt powder contributes to a reduction in and spheroidization of pores, which directly affect the density and pore morphology of the materials tested. The highest density of 357.3 kg/m3 was characterized by samples with a 5 wt.% basalt powder addition. Their density was 14% higher than the reference sample without basalt powder addition. Samples with 20 wt.% basalt addition had the lowest density, and the density averaged 307.4 kg/m3. Additionally, for the sample containing 5 wt.% basalt powder, the compressive strength exceeded 1.4 MPa, and the thermal conductivity coefficient was 0.1108 W/m × K. The effect of basalt powder in geopolymer foams can vary depending on many factors, such as its chemical composition, grain size, content, and physical properties. The addition of basalt above 10% causes a decrease in the significant properties of the geopolymer.

An innovative intelligent design method of alkali-activated foamed geopolymer: Mixture optimization and performance prediction

The complex design parameters and lack of standard mix design methods generate a difficulty in the high efficiently preparation of alkali-activated foamed geopolymer (AAFG). Therefore, this paper proposes an innovative intelligent design method of AAFG based on machine learning (ML) and Metaheuristic Optimization Algorithms (MOA). The effects of twelve factors on drying density (DD) and compressive strength (CS) of AAFG are revealed. The DD and CS predictive models of AAFG with high accuracy (R2 = 0.96 and 0.84) and strong generalization are trained through Random Forest (RF). The enlargements of proportions of granulated blast furnace slag (GBFS) and metakaolin (MK) in precursors can improve the CS but are not conducive to reduction of DD. Higher proportion of fly ash (FA) in precursors can efficiently reduce DD but can weaken the CS. Higher or lower Na2O content, silicate modulus (Ms) and water to binder (W/B) can reduce DD and CS with the optimal foaming conditions of 20 %, 1.0 and 0.75. More additions of foaming agents and foam stabilizers can reduce DD, while the CS has a remarkable degradation. Higher or lower foaming temperature (FT) is both not beneficial for the reduction of DD and enhancement of CS with the optimal FT of 60 °C. The intelligent design system of AAFG developed by RF and Slime Mould Algorithm (SMA) has easy operability, high efficiency, and good stability. The optimal preparation parameters can be efficiently acquired and the corresponding performances can be quickly and accurately predicted.

Physico-mechanical, thermal insulation properties, and microstructure of geopolymer foam concrete containing sawdust ash and egg shell

Recently, energy conservation through building thermal insulation has gained significant importance in solving sustainability-related issues. In this context, this study investigates the potential for manufacturing geopolymer foam concrete (GFC) containing eggshell powder (ESP) and sawdust ash (SDA) using aluminium (Al) powder as a foaming agent. The role of Al-powder percentages on the mechanical and thermal properties of GFC was thoroughly investigated. The effect of ESP and SDA incorporation as partial replacements of precursors (from 0 to 20 %) on the thermal properties, durability, and microstructure of GFCs were also discussed. The experimental findings demonstrate that the bulk density and compressive strength of GFC with different Al-powder contents ranged between 1928 and 1798 kg/m3 and 17.45 and 9.37 MPa, respectively. The SEM images and MIP tests show that foams with different numbers of micro- and macropores are formed in GFCs. The ESP-based GFC had an apparent porosity range of 13.09 %–10.29 % and a bulk density range of 1823 to 1713 kg/m3. The SDA-based GFC had an apparent porosity range of 14.21 %–12.96 % and a bulk density range of 1834 to 1807.8 kg/m3. It was found that the 10 % ESP and 5 %, SDA mixtures enhanced the strength by 16.54 % and 4.45 %, respectively, compared to the control mix. The thermal conductivity, thermal diffusivity, and specific heat of 10 % ESP-mixture and 5 % SDA-mixture were 1.237 and 1.167 W/(mK), 0.795 and 0.922 mm2/S, and 1.556 and 1.266 MJ/m3K, respectively. Finally, the residual strength and microstructure investigations demonstrate that ESP-based GFCs have more stability than SDA-based GFCs and the control mix when subjected to elevated temperatures.

Quantitative characterization and control mechanism of pore structure in geopolymer foams with addition of various surfactants

Pore structure control mechanism in geopolymer foams (GPFs) remains qualitatively understood, posing great challenges for GPF applications. In this study, by modelling of various pore structures with regular geometric patterns, total porosity, open porosity, pore size distribution, and pore deformation were quantitatively characterized. Then, we focused on slurry viscosity and surface tension as the two crucial parameters, and investigated their impacts on the evolution of pore structures. It was revealed that viscosity primarily influenced foam deformation and coalescence, ultimately affecting foaming height, sample appearance, and the occurrence of foam collapse. Slurry surface tension predominantly affected pores connectivity, low surface tension corresponded to highly interconnected pores, while higher values favored closed pores. Additionally, a simple prediction model that enables the estimation of pore structures and their distributions based on GPFs visual appearance and height was proposed. At last, the relationships between pore structure and macro-performance were analyzed.

Effect of Precursor Blending Ratio and Rotation Speed of Mechanically Activated Fly Ash on Properties of Geopolymer Foam Concrete

This research used fly ash and slag to create geopolymer foam concrete. They were activated with an alkali, resulting in a chemical reaction that produced a gel that strengthened the concrete’s structural integrity. The experimental approach involved varying the fly ash content in the precursors at incremental percentages (10%, 30%, 50%, 70% and 90%) and subjecting the fly ash to mechanical activation through a planetary ball mill at distinct rotational speeds (380, 400, 420 and 440 rpm). The investigation discerned that the fly ash content and particle structure exert a discernible influence on macroscopic properties, including flowability, air generation height, compressive strength, dry density and microstructural characteristics such as pore distribution and hydration product arrangement in the geopolymer foam concrete. Employing analytical techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM), it was deduced that diminishing the fly ash content correlates with an enhancement in compressive strength. Furthermore, the specific strength of the geopolymer foam concrete reached a peak of 0.041 when the activated fly ash in the planetary ball mill rotated at 420 rpm, manifesting a lightweight and high-strength outcome.

POROUS FLY ASH-BASED GEOPOLYMER USABLE AS AN UNCONVENTIONAL CONSTRUCTION MATERIAL

Geopolymer foam with thermal insulation properties was made by foaming the alumino-silicate mixture composed of fly ash and clay brick waste activated with alkaline activator (water glass and sodium hydroxide in aqueous solution). Other mixture components were expanded perlite as siliceous additive, usual fine aggregate (quartz sand), and less frequently used surfactant (olive oil). The main characteristics of the geopolymer foam were: low density, low thermal conductivity, and relatively high compressive strength. The residual materials contributed to low costs and the complete replacement of ordinary cement led to the significant reduction of CO2 emissions.