Geopolymer Gel Research Articles

Synthesis of nano-alumina and their effect on structure, mechanical and thermal properties of geopolymer

ABSTRACTThis paper reports on a study of the effects of nano-alumina on the structural, mechanical and thermal properties of geopolymer matrices. Sample composites were produced by mixing metakaolin, an alkaline solution and nano-alumina (1%, 2% and 3%) with a constant L/S ratio 0.55. The resulting products were investigated by XRD, XRF, FTIR, SEM, MIP, TG/DTA and a compressive strength test. The results showed that the insertion of nano-alumina powder improves geopolymer strength. From FTIR and XRD spectra, we found that the structure and geopolymer gel content were enhanced, especially for the optimized proportion of nano alumina (2%), leading to a more homogenous structure, as shown in SEM images. Thus, the density and water absorption of the nano-alumina geopolymer mixture were improved. The introduction of the nano-alumina also had the effect on the thermal properties of the geopolymers, of increasing the weight loss of the composite.

Synthesis of Geopolymer from Blends of Tropical Biomass Ashes

Thermal conversion of biomass to produce energy inevitably generates ash as residual matter. Therefore, sustainable utilization of biomass should also consider reuse measures for the ash. This research examines the conversion of locally available biomass ashes in Indonesia into geopolymer. This is an environmentally more benign alkali-aluminosilicate alternative to the ordinary Portland cement produced by low-temperature reactions between aluminosilicates and concentrated alkali solution. Biomass ash sources in this study are corn stover, coconut shell, and sugarcane bagasse. Biomass ash blends are prepared according to a ternary simplex centroid mixture experiment design. These blends are reacted with activator solutions containing NaOH and Na-silicate and blended with sand aggregate to produce geopolymer mortar specimens. Early compressive strengths of geopolymer mortars range from 7.2 to 10.4 MPa, which surpasses the SNI 15-2049-2004 national standard for Portland cement with low heat of hydration. Statistical analysis of the experimental data indicates that the early strength as a function of biomass ash blend formulation is represented by a quadratic mixture model. Bagasse ash produces the highest strength. The quadratic terms consist of bagasse-corn and bagasse-coconut antagonistic blending terms. Morphology of the geopolymer mortar fracture surface indicates good bonding with the sand aggregate. Extensive acicular crystal growth within the amorphous geopolymer gel phase is observed in lower-strength formulations, which points to the formation of zeolite-like phase in the geopolymerization process. While the correlation of biomass ash type to the structure of the resulting geopolymer is yet to be established, this work has clearly identified the technical feasibility of producing geopolymer with satisfactory strength from tropical biomass ashes.

Facile preparation and hardened properties of porous geopolymer-supported zeolite based on swelled bentonite

Porous geopolymer-supported zeolites (PGZs) were successfully prepared by crystallizing bentonite-amended porous geopolymers, to study their synthesis, pore-forming mechanism, pore structure, and hardened properties. The results revealed that geopolymer gel and montmorillonite layers in porous geopolymers could subdivide and refine capillary voids, thereby forming submicron pores. Further, hydrothermal curing resulted in the formation of a zeolite-based matrix. The pores and the zeolite-based matrix caused a considerable reduction in the thermal conductivity of the PGZ. The PGZ pore volume rose steadily from 0.47 cc/g to 0.80 cc/g with increasing bentonite slurry from 40% to 60%. The contents of the bentonite slurry were added to the geopolymer paste and then crystalized for 24 h at 90 °C, yielding PGZs with a thermal conductivity, compressive strength, and dry density of 0.121–0.167 W/m K, 2.3–8.7 MPa, and 774–930 kg/m3, respectively.

Immobilization forms of ZnO in the solidification/stabilization (S/S) of a zinc mine tailing through geopolymerization

Solidification/stabilization (S/S) of a zinc mine tailing through geopolymerization has been studied. The mechanical property and microstructure of the mine tailings based-geopolymers were investigated through compressive strength measurements, FTIR, NMR and SEM characterizations. The stabilization of zinc in the geopolymers was analyzed through toxicity characteristic leaching procedure (TCLP) and the immobilization forms were characterized through XPS. With the content of metakaolin in raw materials increased from 0 to 50%, the amount of geopolymer gel in the binders and the compressive strength of geopolymer increased. As a ratio of metakaolin to mine tailings of 1:1, the mine tailings promoted the formation of silica-rich gel and the compressive strength of geopolymer was 30.1 MPa which was similar to pure metakaolin-based geopolymer. The immobilization efficiency of Zn in the geopolymers is correlated to their mechanical property. Zinc is immobilized in the geopolymers through physical encapsulation and adsorption of the leached Zn2+ by geopolymer gel.

Effects of aluminum on the expansion and microstructure of alkali-activated MSWI fly ash-based pastes

Alkaline activation is of great potential in the solidification of municipal solid waste incineration (MSWI) fly ash, but the metallic aluminum in the ash inhibits its application. This work studies the effects of residual metallic aluminum on the expansion and microstructure of alkali-activated MSWI fly ash-based pastes. Based on the results obtained, an optimized preparation process is suggested. Characterizations of the pastes include expansion ratio, morphology (SEM), mechanical strength and microstructure (XRD and FTIR). It is confirmed that MSWI fly ash could be solidified through alkaline activation when using a small amount of coal fly ash to adjust the reactive silica and aluminum ratios. In the optimized preparation, sodium hydroxide was added separately, so that expansion in the pastes was significantly mitigated, the formation of geopolymer gel was improved and the compressive strength of the pastes increased.

Experimental investigation and comparison on structural behaviour of Ferro-Geopolymer concrete and mortar cubes with conventional cubes

Abstract The worldwide utilization of concrete is second just to water. As the interest for concrete as a development material increments, so likewise the interest for Portland cement. The global warming is brought about by the emanation of greenhouse gases, for example, carbon dioxide (CO2), to the climate by human exercises. Among the greenhouse gases, CO2 contributes about 65% of a global warming. The cement industry is considered in charge of a portion of the CO2 emanations, that the production of one ton of Portland cement transmits around one ton of CO2 into the environment. As far as global warming, the geopolymer innovation could altogether decrease the CO2 emanation to the atmosphere brought about by the cement industries. The geopolymer gel binds the loose coarse aggregate, fine aggregate and un-reacted source material to form geopolymer composites. The Portland cement free geopolymer composites have many advantages like less curing time, earlier development of higher mechanical strength, very little drying shrinkage and very low creep, excellent resistance to sulphate attack, good acid resistance and resistance to high temperature. Here the concrete cubes are made by varying the fly-ash content by 500 kg/m3, 450 kg/m3, 400 kg/m3. When the fly ash content is 400 kg/m3 the setting time of the geopolymer concrete is quick and provides good result when compared to the other two contents. The geopolymer with the combination of mesh in different layers such as 1 layer, 2 layer and 3 layers increases the compressive strength of the concrete as well as mortar and the combination of 3 layers in concrete provides maximum results in compression strength.

Enhanced geopolymeric co-disposal efficiency of heavy metals from MSWI fly ash and electrolytic manganese residue using complex alkaline and calcining pre-treatment

The predominant heavy metals in MSWI fly ash and electrolytic manganese residue (EMR) were determined to be Zn, Pb, Cd, and Mn, with lesser amounts of Cu and Cr. The curing efficiency of heavy metals in MSWI fly ash and EMR was improved using complex alkaline activators (NaOH and KOH), base addition (calcium hydroxide and complex Portland cement), and EMR calcining (at 800 °C for 3 h) based on a geopolymeric system. The best formulation of the geopolymeric system was composed of 75 wt% MSWI fly ash and 25 wt% EMR with a KOH/NaOH (1:1) complex solution (7.5 M OH−)/solid of 0.5. Calcium ions were dissolved aluminosilicate under the strongly basic conditions to form complex products (ternesite) which further improved the strength. The primary curing mechanism of heavy metals (Pb, Zn, Cd, Mn, Cr, and Cu) mainly was primarily influenced by the acid-base buffering capacity of geopolymers, followed by the physical encapsulation of geopolymeric gels.

Incorporation of strontium and calcium in geopolymer gels

Radioactive waste streams containing 90Sr, from nuclear power generation and environmental cleanup operations, are often immobilised in cements to limit radionuclide leaching. Due to poor compatibility of certain wastes with Portland cement, alternatives such as alkali aluminosilicate ‘geopolymers’ are being investigated. Here, we show that the disordered geopolymers ((N,K)-A-S-H gels) formed by alkali-activation of metakaolin can readily accommodate the alkaline earth cations Sr2+ and Ca2+ into their aluminosilicate framework structure. The main reaction product identified in gels cured at both 20 °C and 80 °C is a fully polymerised Al-rich (N,K)-A-S-H gel comprising Al and Si in tetrahedral coordination, with Si in Q4(4Al) and Q4(3Al) sites, and Na+ and K+ balancing the negative charge resulting from Al3+ in tetrahedral coordination. Faujasite-Na and partially Sr-substituted zeolite Na-A form within the gels cured at 80 °C. Incorporation of Sr2+ or Ca2+ displaces some Na+ and K+ from the charge-balancing sites, with a slight decrease in the Si/Al ratio of the (N,K)-A-S-H gel. Ca2+ and Sr2+ induce essentially the same structural changes in the gels. This is important for understanding the mechanism of incorporation of Sr2+ and Ca2+ in geopolymer cements, and suggests that geopolymer gels are excellent candidates for immobilisation of radioactive waste containing 90Sr.

Realistic atomic structure of fly ash-based geopolymer gels: Insights from molecular dynamics simulations

Geopolymers, synthesized through alkaline activation of aluminosilicates, have emerged as a sustainable alternative for traditional ordinary Portland cement. In spite of the satisfactory mechanical performance and sustainability-related benefits, the large scale acceptance of geopolymers in the construction industry is still limited due to poor understanding of the composition-property relationships. Molecular simulation is a powerful tool to develop such relationships, provided that the adopted molecular structure represents the experimental data effectively. Toward this end, this paper presents a new molecular structure of sodium aluminosilicate hydrate geopolymer gels, inspired from the traditional calcium silicate hydrates gel. In contrast to the existing model—where water is uniformly distributed in the structure—we present a layered-but-disordered structure. This new structure incorporates water in the interlayer space of the aluminosilicate network. The structural features of the new proposed molecular structure are evaluated in terms of both short- and medium-range order features such as pair distribution functions, bond angle distributions, and structure factor. The structural features of the newly proposed molecular structure with interlayer water show better correlation with the experimental observations as compared to the existing traditional structure signifying an increased plausibility of the proposed structure. The proposed structure can be adopted as a starting point toward the realistic multiscale simulation-based design and development of geopolymers.

Studying different silica sources for preparation of alternative waterglass used in preparation of binary geopolymer binders from metakaolin/boiler slag

The production of geopolymeric binders based on metakaolin (MK), coal boiler slag (BS) and alternative silica sources (rice husk ash (RHA) and silica fume (SF)) to produce potassium waterglass was successfully carried out. The binders were characterized microstructurally and mechanically at different ages. Monitoring of the reactions of the cements was carried out by techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA/DTG). The results show that byproducts such as BS and RHA can be used with MK as starting materials for the preparation of geopolymer binders. The using of by-product rich on silica produces materials with microstructures similar to those traditionally obtained with commercial potassium silicate (PS). Regarding SF-based binders, the strength declines over time, with late-age instability. The most stable or homogeneous binders over time are those based on RHA. The MK/BS30 binder exhibits good mechanical performance 42.1, 51.04 and 48.3 MPa at 7, 180 and 360 days respectively. The MK/BS30 binder shows a high degree of geopolymerization, a more homogeneous and enhanced connectivity between the grains and geopolymer gel and likewise, a lower content of MK unreacted. In general, the results indicate that geopolymers manufactured with RHA could replace materials produced with commercial silicates.

Mix composition and characterisation of one-part geopolymers with different activators

To improve the commercial viability of geopolymers, there is a need to develop one-part geopolymer mixes. In this research, 100% fly ash or a mixture of fly ash and slag was employed as the precursor. Meanwhile, the highly corrosive alkali solutions used as activators in conventional geopolymers were replaced by different solid activators (in powder form), such as sodium silicate, calcium hydroxide, sodium oxide, lithium hydroxide, potassium carbonate or their combinations. The mixes were subjected to both ambient and heat curing to check the influence of curing conditions. Effects of type/combination of the solid activators on the workability, early and final strength, hardened density and microstructure of these one-part geopolymer mixes were examined. The incorporation of slag in the binder increased the early and final strength of mixes but reduced the workability. Furthermore, the type/combination of solid alkaline activators affects the microstructure of the geopolymer gels and subsequently impacts the mechanical properties. Among the investigated ambient cured geopolymers, a relatively high compressive strength of 38 MPa at 28 days was obtained when the geopolymer precursor was composed of 50 wt% fly ash and 50 wt% slag activated by a combination of sodium silicate, calcium hydroxide and lithium hydroxide.

New selective dissolution process to quantify reaction extent and product stability in metakaolin-based geopolymers

A selective dissolution process is developed that can quantify the amount of soluble material, geopolymer gel and remnant unreacted precursor in metakaolin-based geopolymer systems and determine the nanostructural features of the raw materials and geopolymer gel components. The susceptibility of alkalis leachability from the alkaline aluminosilicate hydrate-type gel (N-A-S-H) produced during the geopolymerization is not fully understood. This phenomenon led to deleterious processes from a microstructural, aesthetic and performance point of view. Geopolymers were synthesised using different contents and types of alkalis (M/Al = 0.50–0.83, where M represents Na or K), different contents of soluble silica in the activator (expressed as SiO2/M2O ratio of 1.0, 0.5 and 0.0), and curing temperatures (25 and 50 °C). The selective dissolution process is based on neutral dissolution at pH 7 to extract the soluble materials and acid dissolution using a strong acid at pH 0 to dissolve the geopolymer gel, which provides for the first time a method to quantify the (i) soluble material, (ii) geopolymer gel and (iii) unreacted material in geopolymers. The soluble material provides a reliable indication of the materials that can be removed from the geopolymers in a neutral pH environment and hence the potential for leaching and efflorescence, which is useful for durability prediction and service life. Quantification of remnant unreacted metakaolin determines the reactivity of the precursor and assesses the suitability of different synthesis conditions for varied applications. This work therefore provides a novel and widely applicable approach to determine the susceptibility of geopolymer materials to leaching.

Reaction mechanisms of calcined kaolin processing waste-based geopolymers in the presence of low alkali activator solution

The massive amount of kaolin processing waste was daily formed. To reduce the amount of their waste deposited in landfills and to increase the value- adding of recyclable waste, this work interested to use as raw materials in the preparation of geopolymer. This paper studied the reaction mechanisms of calcined kaolin processing waste-based geopolymers in the presence of low alkali activator solution by the pressing method. The reaction mechanisms of geopolymer were measured as a function of NaOH concentration by DSC, XRD, and FTIR analysis. Furthermore, the effects of NaOH concentration and curing time on the mechanical properties and microstructure of calcined kaolin processing waste-based geopolymer were investigated. The DSC, XRD, and FTIR results indicated that the geopolymerization reaction increased with higher NaOH concentrations. Forming the geopolymer by the pressing method led to the particles being close together in a compact matrix. Subsequently, their surfaces were dissolved with NaOH solution, inducing the geopolymerization reaction. This reaction and continuous reaction resulted in the compressive strength and microstructure of the geopolymer. The compressive strengths of the geopolymer synthesized with NaOH concentration of 10 M (curing time of 7 days) and a curing time of 28 days were 26.98 MPa and 28.55 MPa, respectively, which were approximately 22.58% and 52.35% higher compared to the geopolymer synthesized with NaOH concentration of 4 M and a curing time of 1 day. The SEM micrographs of the geopolymer samples displayed more geopolymeric gel and denser matrices with increases in NaOH concentration and curing time. The nitrogen adsorption and pore volume decreased with increases in NaOH concentration and curing time. Synthesis of geopolymers using kaolin processing waste as a raw material is a value- adding and environmentally friendly process.

Does synthesized C-S-H seed promote nucleation in alkali activated fly ash-slag geopolymer binder?

Understanding the effects of nucleation seeds on reaction kinetics and microstructures of alkali activated binders (AABs) is important since it will help us control both early-age and long-term properties. For example, in the calcium-containing AABs, calcium silicate hydrate/calcium aluminosilicate hydrate (C-S-H/C-A-S-H) seeds have been proposed by others to act as nucleation sites to promote formation of geopolymer gel. In this study, we examined the nucleation effects by adding synthesized C-S-H and C-A-S-H seeds into class F fly ash-slag mixes activated both by potassium hydroxide and by potassium silicate solutions. From both calorimetry and ultrasonic wave reflection tests, we found seeding to accelerate reaction of the hydroxide activated binder but decelerate that of the silicate activated binder. Based on further chemical treatments and Fourier-transform infrared spectroscopic characterization, we found the acceleration in the hydroxide binder was due to enhanced formation of C-S-H/C-A-S-H, while the deceleration in the silicate binder was due to decreased formation of K-A-S-H gel despite the enhanced formation of C-S-H/C-A-S-H. Additionally, in both types of binders, we found dissolution of fly ash precursor was enhanced. Evidence in this study suggests that C-S-H seeds act as nucleation sites for further precipitation of C-S-H/C-A-S-H but not for formation of geopolymer gel.

Fly ash based geopolymer stabilisation of silty clay/blast furnace slag for subgrade applications

The mechanical and microstructural properties of problematic silty clay (SC) stabilised with fly ash (FA) based geopolymer and blast furnace slag (BFS) replacement are presented in this research. The influence factors evaluated included FA:BFS replacement ratio, NaOH concentration, and curing temperature. A series of geotechnical laboratory tests and microstructural analyses were also undertaken. The strength of the stabilised material was found to be governed by interparticle forces, mainly from the contribution of the chemical bonding strength. The results indicated that the unconfined compression strength (UCS) values of FA based geopolymers stabilised with SC/BFS blends increased with increasing NaOH concentration, at the various FA:BFS replacement ratios when cured at various temperatures (25, 50 and 80°C). The high concentration of NaOH could dissolve FA particles to leach silica and alumina which reacted with NaOH to produce a geopolymerization (N-A-S-H gel) process, which resulted in high UCS results. The decrease in FA:BFS ratio however reduced the specific area of particles to be welded by FA geopolymerization products and reduces the geopolymer gel due to the reduction in quantity of FA precursor. As such, the interparticle forces increased as the FA:BFS reduced up to the optimum value and then decreased as the FA:BFS reduced. The optimal FA:BFS ratio was found to be 20:10. An elevated curing temperature accelerated the geopolymerization reaction, leading to the higher UCS at higher temperature. The use of waste by-products BFS and FA to stabilise problematic soil in civil engineering applications will contribute to a significant reduction in construction costs and the sustainable development of the project life cycles.

Interfacial chemistry of a fly ash geopolymer and aggregates

The environmental and accessibility concerns associated with the increasing use of river sand in construction have diverted the attention of scientists to alternative materials. Waste glass has been widely investigated as a replacement for sand in geopolymer concretes, and the chemical and mechanical properties of the resulting materials are investigated. Since glass is rich in amorphous silica, it is believed that the surface of glass aggregates can take part in the reaction and make a stronger geopolymer matrix compared to that of sand aggregates. An improvement of 30% in compressive strength was obtained by replacing sand aggregates with glass aggregates. While the mechanical properties support interfacial reaction with glass aggregates, the nature of the chemical bonding structure at the interface has not been revealed. In this research, synchrotron Fourier transform infrared (SR-FTIR) microspectroscopy has been used for the first time to map the distribution of the chemical bonding structures at the geopolymer interface with aggregates. While in-situ FTIR shows the development of geopolymer gel over time, SR-FTIR results show clear differences in gel chemistry around the glass compared to the sand. The study reveals that there is a relatively higher degree of silica-rich gels close to the sand aggregates and a higher extent of geopolymeric gels around glass aggregates. The alkaline content of glass makes the area surrounding the glass aggregates more suitable for maintaining monomeric silica. These small silica species help to develop a higher degree of geopolymer networks in the vicinity of the glass aggregates compared to the sand. This level of visibility is very useful for understanding the behaviour of geopolymer concretes, which is critically important for nano-engineering of materials towards a desirable distribution of the binding gels.

Self-supporting zeolites by Geopolymer Gel Conversion (GGC)

Abstract Many industrial applications need supporting or shaping powdery zeolites. Since geopolymers can be considered the amorphous counterpart or precursors of crystalline zeolites, it is possible to promote zeolite crystallization inside the geopolymeric matrix by tuning pH, temperature and time of the geopolymerization reaction. In this paper, combining zeolite crystallization with a foaming process initiated by silicon, a multifunctional self-supporting zeolitic material has been obtained with pores ranging from the micro to the macro range. Geopolymerization and crystallization have been realized simultaneously curing the samples at specific temperature and humidity conditions. Every specimen obtained at curing time higher than two days, regardless relative humidity and silicon content, contained zeolite A [LTA] and X [FAU] as the only crystalline phases. Finally, the porosity generated by the foaming process promotes the zeolite nucleation mainly on the surfaces of the pores, whereas the struts remain amorphous.

Freeze-thaw durability of red mud slurry-class F fly ash-based geopolymer: Effect of curing conditions

Abstract Freeze-thaw (F-T) durability of geopolymers synthesized from the mixture of red mud slurry-Class F fly ash (RMSFFA) was investigated in this study, with an emphasis on the influence of curing conditions (i.e., curing time and curing temperature). F-T durability was evaluated on the basis of the sustained mechanical strength of RMSFFA geopolymer specimens after subjected to 50F-T conditioning cycles. The change in their chemical bonding, mineralogy, and pore characteristics at various F-T conditioning cycles was examined with Fourier transform infrared spectroscopy, X-ray diffractometer, and Brunauer–Emmett–Teller testing, respectively, to reveal the underlying processes during F-T conditioning. The results of both mechanical strength and microstructural characterization indicate that curing conditions influence F-T resistance of RMSFFA geopolymer samples through affecting their strength development. For 14-day cured RMSFFA samples at 50 °C, they experienced further geopolymerization at the early stage of F-T conditioning but the partial dissolution of geopolymer gel at the later stage of F-T conditioning. For 28-day cured samples at 50 °C, only the partial dissolution of geopolymer gel was likely to occur during the F-T conditioning because the strength development was likely to complete prior to the conditioning.

Geopolymer Synthesis Using Garnet Tailings from Molybdenum Mines

Garnet tailings obtained in large quantities from molybdenum ore beneficiation are regarded as industrial waste, which not only occupies large areas of land but also causes environmental issues and ecological fines. Preparing garnet tailings based geopolymers (GTGs) is one of the efficient methods to recycle and utilize garnet mine tailings. In this work, geopolymers were synthesized using garnet tailing (GT) and metakaolin (MK) as the main precursors and sodium silicate as the alkali-activation agent. The effect of MK and alkali activator dosage, as well as curing temperature on the compression strength of GTGs were analyzed in detail. Results showed that the maximum strength (46 MPa, 3 days) was reached at a 20 wt % MK dosage with 35% sodium silicate addition cured at room temperature. The microstructure and phase composition of GTGs were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR), which confirmed the formation of an amorphous geopolymer gel. Lastly, it can be concluded that the garnet tailing is a promising material for geopolymer production, as an alternative for its utilization.

Creep and Drying Shrinkage of Different Fly Ash-Based Geopolymers

Fly ash geopolymer concrete is a sustainable green construction material that has outstanding mechanical performance and is a low-energy material with a low carbon footprint. In this study, a detailed investigation of the long-term creep and drying shrinkage of three different 100% fly ash geopolymer concretes was carried out up to 1 year of age. Two geopolymers, produced from Gladstone and Pt. Augusta fly ashes, achieved approximately 700 microstrain at the end of 1 year-equivalent to the total creep strain displayed by portland cement (PC) concrete. Moreover, both geopolymer concretes displayed a lower creep coefficient than PC concrete. Hence, AS 3600 or the CEB-FIP model could be conservatively used to predict creep coefficient for two geopolymers. However, the Tarong fly ash geopolymer concrete differed significantly from the other geopolymers and achieved approximately 1900 microstrain after 1 year. The drying shrinkage of Gladstone and Pt. Augusta geopolymer concretes at 1 year are 175 and 190 microstrain, respectively, while Tarong geopolymer and PC concrete achieved 615 and 475 microstrain, respectively. All the fly ash geopolymer concrete showed lower drying shrinkage than the maximum permitted value recommended by AS3600. Incorporation of calcium-aluminasilicate-hydrate (C-A-S-H) gel with the sodium-alumina-silicatehydrate (N-A-S-H) geopolymeric gel was seen to positively affect the packing density of the gel phase. The degree of uniformity and compactness of aluminosilicate gel matrix together with the macroporosity in the 50 nm to 1 µm range was identified as determining the long-term creep and drying shrinkage of the 100% low-calcium fly ash geopolymer concrete.