Alkali-activated Fly Ash Research Articles

Critical parameters affecting the thermal resistance of alkali-activated aluminosilicate wastes: Current understanding and future directions.

Many research articles and reviews have recognized alkali-activated materials (AAMs) as eco-friendly alternative binders to ordinary Portland cement (OPC) due to their economic andenvironmental advantages. However, few literature surveys reported the physical, mechanical and microstructural changes that occur after the exposure of AAMs to elevated temperatures. Owing to the wide diversity in the properties of aluminosilicates, alkali-activation conditions, and additives, a deep survey is needed to understand how different factors can affect the performance of AAMs under elevated temperatures. Therefore, this review extensively discusses the impact of recent critical parameters, including aluminosilicate compositions, aggregate type and mineral, micro, and nano additives, on the behavior of AAMs under thermal load. It can be concluded that regardless of alkali-activator type and concentration, alkali-activated fly ash shows higher thermal resistance than alkali-activated metakaolin and slag. Moreover, the presence of an adequate amount of calcium can increase the thermal stability of AAMs, while the iron has a varying effect on the thermal resistance of AAMs, either positively or negatively. Compared with all additives and aggregates, using waste glass and lightweight aggregates enhanced the thermal resistance of AAMs. Howerver, some types of aggregate having a binding ability which increase the residual strength after heat exposure. Considering the fineness of materials, evaluating the role of nano and micro materials on the properties of AAMs at high temperatures is reviewed. Based on this survey, several promising topics for future work are suggested.

Freeze-thaw cycle and abrasion resistance of alkali-activated FA and POFA-based mortars: Role of high volume GBFS incorporation

Alkali-activated binders made from various waste products can appreciably reduce the emission of CO2 and enhance the waste recycling efficiency, thus making them viable substitutes to ordinary Portland cement (OPC)-based binders. Waste materials including fly ash (FA), palm oil fuel ash (POFA), and granulated blast furnace slag (GBFS) reveal favorable effects when applied to alkali-activated mortars (AAMs) that are mainly related to the high contents of silica, alumina, and calcium. Therefore, fifteen AAM mixes enclosing FA, POFA with high volume of GBFS were designed. The obtained GBFS/FA/POFA-based AAMs were subjected wet/dry and freeze/thaw cycles. The impact of various GBFS contents on the microstructures, freeze-thaw cycle, abrasion resistance, mechanical and durability features of the proposed AAMs were evaluated. The results showed that presence of Ca can significantly affect the AAMs durability features and long-term performance. The abrasion resistance of the AAMs was decreased with the decrease of CaO contents. Furthermore, the abrasion depth of 70% AAMs (0.8 mm) was lower in comparison to the mix made by replacing 50 wt% of FA with GBFS (1.4 mm). Generally, increase in the GBFS contents from 50 to 70% could largely impact the AAMs properties under aggressive environmental exposure. The expansion and physical impacts during the freezing-thawing cycles was argued to destroy the bonds in C–S–H and paste-aggregates, causing the formation of large cracks. It is asserted that the AAM mixes made from FA, POFA and high volume of GBFS may offer definitive mechanical, durable, and environmental benefits with their enhanced performance under aggressive environments.

Developing interpretable machine learning-Shapley additive explanations model for unconfined compressive strength of cohesive soils stabilized with geopolymer.

This paper seeks to develop an interpretable Machine Learning (ML) model for predicting the unconfined compressive strength (UCS) of cohesive soils stabilized with geopolymer at 28 days. Four models including Random Forest (RF), Artificial Neuron Network (ANN), Extreme Gradient Boosting (XGB), and Gradient Boosting (GB) are built. The database consists of 282 samples collected from the literature with three different types of cohesive soil stabilized with three geopolymer categories including Slag-based geopolymer cement, alkali-activated fly ash geopolymer and slag/fly ash-based geopolymer cement. The optimal model is selected by comparing their performances with each other. The values of hyperparameters are tuned by Particle Swarm Optimization (PSO) algorithm and K-Fold Cross Validation. Statistical indicators show the superior performance of the ANN model with three metrics performance such as coefficient of determination R2 = 0.9808, Root Mean Square Error RMSE = 0.8808 MPa and Mean Absolute Error MAE = 0.6344 MPa. In addition, a sensitivity analysis was performed to determine the influence of different input parameters on the UCS of cohesive soils stabilized with geopolymer. The order of feature effect can be ordered in descending order using the Shapley additive explanations (SHAP) value as follows: Ground granulated blast slag content (GGBFS) > Liquid limit (LL) > Alkali/Binder ratio (A/B) > Molarity (M) > Fly ash content (FA) > Na/Al > Si/Al. The ANN model can obtain the best accuracy using these seven inputs. LL has a negative correlation with the growth of unconfined compressive strength, whereas GGBFS has a positive correlation.

Strength and post-fire performance of fiber-reinforced alkali-activated fly ash concrete containing granite industry waste

The mechanical properties and the post-fire performance of alkali-activated fly ash (AAF) concrete containing granite industry waste (GW) and polypropylene (PP) fibers were investigated to promote the application of environmentally friendly concrete. The recycled GW proportions of 0, 25, and 50% by weight were used in fine aggregates to replace the natural river sand, and the PP fiber contents of 0, 0.5, and 1.0% by volume were added to the concrete mixtures. The mechanical properties investigated included compressive strength, flexural load–deflection response, and toughness. The post-fire performance was evaluated from the residual compressive strength and weight loss, together with the visual inspection and the scanning electron microscopy (SEM) investigation of the specimens after fire exposure. It was found that the inclusion of PP fibers was effective to improve the flexural performance of AAF concrete, with or without the GW. Based on the toughness of AAF concrete, the optimal percentage for the GW replacement was 25%. After exposure to the ISO-834 standard fire, the results showed that the degradation of AAF concrete manifested itself in the inner core in the form of extensive cracking, particularly for the fiber-reinforced concrete containing the GW. The residual compressive strengths of AAF concrete were reduced to a range of only 25–39% after the fire exposure of 30 min.

Influence of Process Variables on Shrinkage in Low-Calcium Fly-Ash Geopolymers

The influence of process variables such as curing temperature and relative humidity (RH) on the shrinkage of alkali-activated fly ash (AAF) is examined in this work. The ambient conditions are varied after an initial accelerated moist curing at high-temperature. An analysis interlinking the effects of curing on AAF strength, shrinkage, reaction product content, and porosity is performed. Strength achieved and the pore structure formed for the different curing conditions depend upon the sodium alumino-silicate (N-A-S-H) gel content formed in the AAF. While water is not directly combined in the formation of N-A-S-H gel, its content is sensitive to the availability of moisture. The moisture loss due to drying during the geopolymerization reduces the N-A-S-H content formed in the AAF. Compared to the continuous moist curing at elevated temperature, there is a decrease in the N-A-S-H content on lowering the temperature or drying produced by the decrease in RH. Reducing temperature and RH following initial accelerated curing has the beneficial effect of reducing the shrinkage compared to drying at a higher temperature. Reduction in the N-A-S-H content due to decrease in temperature after the accelerated curing is more significant than the drying on lowering the RH to 50%. The autogenous shrinkage measured under sealed conditions contributes significantly to the total shrinkage in AAF. The shrinkage in the AAF is significantly lower than a comparable cement paste. While shrinkage is produced by drying, the moisture loss and shrinkage relationship is not unique. The shrinkage produced by moisture loss due to drying is primarily influenced by the pore structure formed in the AAF, which also depends on the N-A-S-H content. The influences of temperature and humidity on the strength, pore structure and shrinkage are determined by the N-A-S-H formed in the AAF.

Expansive Soil Stabilization Using Alkali-Activated Fly Ash

Expansive soil swells with water and shrinks with water loss, causing serious safety problems for construction projects. This study emphasizes alkali-activated binder (NaOH excited fly ash) stabilized expansive soil. We found that swelling decreased with an increase in the amount of NaOH in alkali-activated binder. It was found that the alkali-activated binder stabilized expansive soils (AABS) had higher shear strength than untreated expansive soils (US), manifested by increased cohesion and friction angle. In AABS, the highest cohesion and the highest shear strength were found when the NaOH mass was 6% of the fly ash mass. The strength of AABS was similar to that of US without curing. AABS had higher strength than US after 7 and 14 days of curing. The unconfined compressive strength increased with extension of curing time. Combined with XRD and SEM analysis, it was shown that the mechanism of AABS was the formation of C–S–H and (C,N)–A–S–H and the change in the internal structure of expansive soil. This investigation can solve both the expansive soil problem and provide new concepts for green development.

The use of crushed recycled glass for alkali activated fly ash based geopolymer concrete and prediction of its capacity

The influence of waste glass aggregate (WGA) with fly ash in certain proportions was studied by different amounts of molarity and WGA proportion on geopolymer concrete (GPC). For this aim, the molarity values of the NaoH concentration consumed in this investigation were determined as 11, 13 and 16. At the end of the examinations, workability, setting time, compression strength (CS) test, splitting tensile (ST) tests and flexural strength (FS) tests are performed. The conclusions demonstrated that the slump values increased as the molarity increased and waste glass (WG) percentages decreased. While concerning CS, ST and FS examinations, as the proportion in the combination was increased, these test results tend to decrease correspondingly. While the proportion of molarity of NaOH proportion was altered from 11 to 13 and 13 to 16, these test results tend to increase. This examination study demonstrates that glass aggregate had also a slight adverse influence on capacity and workability. Moreover, the use of 10% glass aggregate with NaOH molarity of 16 is suggested to gain the optimum sustainable GPC considering both fresh and hardening properties as the combined influence of WGA and NaOH molarity. Furthermore, in this examination, the offered strength models are established and related to those built on several standard codes. More importantly is that an equation is derived to predict the compressive strength of the geopolymer mixture utilized in this study. Additionally, scanning electron microscopy (SEM) analysis was achieved on the example parts attained from GPC examples formed with WGA.

High-temperature performance of alkali-activated binders of fly ash and calcium aluminate

This paper studied the effect of elevated temperatures on the compressive strength of alkali-activated fly ash (so-called geopolymer) with the addition of calcium aluminate cement (CAC). In the elevated temperature tests (600 and 800 °C), the unstressed test method was adopted. Taguchi analysis was used to study the effect of three parameters (considered in mix design) on the hot strength. These parameters include the replacement ratio of fly ash by CAC, molarity of sodium hydroxide solution, and alkaline solution to fly ash ratio. The first parameter was found to be the most influential factor. XRD, TG/DSC and SEM techniques were then carried out to investigate the effects of the CAC content on the high-temperature performance of the geopolymer. The phase transformation taking place during the heat exposure was found to affect the compressive strength in the hot state directly. The retained strength of the optimal geopolymer mortar at 600 °C was around 2.5 times higher than that of ordinary Portland cement mortars with a similar original strength level.

Analysis of reaction degree and factors of alkali-activated fly ash/slag

The dissolution rates of alkali-activated fly ash (FA) and alkali-activated slag in hydrochloric acid (HCl) with various pH values were investigated. The geopolymerisation reaction degree of alkali-activated FA/slag (AAFS) can be determined based on the content of hydrochloric-acid-insoluble matter, so X-ray fluorescence, X-ray diffraction and Fourier-transformed infrared spectroscopy were used to analyse the hydrochloric-acid-insoluble matter of the alkali-activated FA and alkali-activated slag. Acid dissolution tests on the AAFS showed that the addition of slag increased the geopolymerisation degree of FA in most cases. For a certain slag content, the reaction degree of FA decreased with an increase in the modulus of the activator and increased with an increase in the liquid/solid ratio. An increase in activator concentration had a greater effect when the slag content was low. At low activator concentrations, the reaction degree of FA increased with an increase in slag content. The slag content corresponding to the highest reaction degree of the FA gradually reduced with an increase in activator concentration.

Effect of superabsorbent polymer and polypropylene fiber on mechanical performances of alkali-activated high-calcium fly ash mortar under ambient and elevated temperatures

This study investigated the mechanical properties of alkali-activated fly ash (AAF) mortars containing superabsorbent polymers (SAPs) and polypropylene (PP) fibers before and after exposure to elevated temperatures. AAF mortars were synthesized using sodium silicate and high-calcium fly ash as the solid activator and aluminosilicate source, respectively. This procedure classified the binder as a one-part AAF mortar. The mechanical properties of the AAF mortar, including compressive and flexural strengths, were investigated considering eight mixes with varying SAP contents (0%, 0.5%, 1%, and 2% by weight of binder) and fiber contents (0 and 0.2% by volume). Moreover, physical properties including the permeability and sorptivity were examined, and physiochemical analysis was performed to evaluate the behavior of AAF mortar at room temperature, 300, 500, and 700 °C. The results show that the compressive strength of specimens at room temperature slightly decreased owing to the increased macroporosity caused by SAPs through pre-swelling, while the flexural strength was maintained via an internal curing effect. The PP fibers significantly enhanced the flexural capacity of the cement mortar, while the compressive strength initially decreased at 28 d and later exhibited a negligible effect at 90 d. The specimens produced using SAPs were effective in preserving the residual compressive and flexural strengths compared with those without SAPs after exposure to 300 °C. Meanwhile, the residual strength of PP fiber specimens diminished after elevated temperature exposure because the melted fiber led to the excessive formation of cavities.

Stabilization of Aeolian Sand for Pavement Subbase Applications Using Alkali-Activated Fly Ash and Slag

Using local materials to construct building elements as well as transport road facilities, including highways, intercity roads, and roads, in remote areas is a top topic of scholarly research all over the world. The main reason for that is the fact that these kinds of materials not only ease the intensity of material transportation but are also cost-efficient. In desert areas, aeolian sand is a commonly used local material and it has been investigated in unbound and cement-stabilized pavement base/subbase applications. However, the production of cement is associated with a high carbon footprint, leading this research to seek alternative low-carbon binders. This research investigated the strength properties and the carbon footprint of fly ash (FA) and a ground-granulated blast-furnace slag (S)-based geopolymer-stabilized aeolian sand. Setting time, compressive strength, California bearing ratio (CBR), and temperature shrinkage measurements of the stabilized aeolian sand were carried out in this research. The maximum strength of the stabilized aeolian sand was found at the optimal ratio of Si/Al ratio of 2.5 and Na/Al ratio of 1.0. The compressive strength increased as the geopolymer stabilizer content increased. A stabilizer content ranging between 8% and 20% is recommended in practice. The carbon footprint of the geopolymer-stabilized aeolian sand was lower than that of cement-stabilized aeolian sand. This tendency became more evident in the samples with higher strength, indicating the effectiveness of geopolymer as an alternative green soil stabilizer to traditional Portland cement.

Alkali-activated fly ash foam concrete with Yellow River silt: Physico-mechanical and structural properties

Developing innovative techniques to elevate the utilization efficiency of the Yellow River silt (YRS) is very important for the protection of the Yellow River in China. In this study, an approach to use the YRS in the fabrication of alkali-activated fly ash (AAFA) foam concrete was first attempted, and YRS was used as a kind of supplementary binder material. The effects of silt dosage and alkali content on the fluidity, water absorption, compressive strength, drying shrinkage and thermal conductivity of as-fabricated foam concrete with YRS were examined. Besides, the characteristic of pore structure and microstructures of foam concrete were characterized. The results show that the incorporation of YRS significantly affects the physico-mechanical properties of the AAFA foam concrete. With the increase of YRS dosage, the fluidity of fresh foam concrete and the dry density, mechanical properties, thermal conductivity and drying shrinkage of hardened foam concrete is reduced. However, the water absorption and pore structure of foam concrete is improved. In addition, the change of Ca(OH)2 content has a great influence on the physico-mechanical and structural properties of AAFA foam concrete. With the increase of Ca(OH)2 dosage, the dry density and thermal conductivity of AAFA foam concrete is increased obviously. Furthermore, the main hydration product of the AAFA foam concrete with YRS is C-S-H gels. The overall findings demonstrate the feasibility of using YRS as dependable and cost-effective building materials in the preparation of AAFA foam concrete.

Relationship between macro-properties and amorphous gel of FA-based AAMs with different curing conditions after elevated temperature

This study investigated the effect of curing conditions (40 °C, 60 °C, and 80 °C curing temperature, 3 h, 5 h, and 8 h curing time) on the macro-properties (compressive strength, surface properties, and length change) of alkali-activated fly ash materials (FA-based AAM) at elevated temperatures (300 °C, 600 °C, 800 °C, and 1000 °C). The microstructure properties of samples before/after high-temperature treatment were studied by the FTIR, XRD, XRD- Rietveld, SEM-EDS, and 29Si NMR experiments. The results show that the compressive strength of samples shows a decreasing trend beyond elevated 600 °C. A similar phenomenon was found in the surface and length properties. Unlike samples with lower curing temperatures (40 °C) exit the lower residual mechanical properties beyond 600 °C, samples with higher curing temperatures have stable performance in the compressive strength, surface properties, and length change. And high curing temperature is favorable for the formation of amorphous gels with a Si-rich phase in FA-based AAM. Lower diffusion coefficient of water and high skeleton stability were obtained in the higher Si/Al ratio of N-A-S-H amorphous gel decreasing the evaporative rate of water to exacerbate the damage of microstructure at a low elevated temperature, while increasing the stability at high temperature.

Alkali-activated fly ash cured with pulsed microwave and thermal oven: A comparison of reaction products, microstructure and compressive strength

The reaction products and microstructure of an 8 M NaOH-activated fly ash (AAFA) cured with microwave and thermal oven curing were comparatively investigated. The results show that the formation of an Al-rich N-A-S-H gel with a flaky morphology and crystalline chabazite-Na between fly ash particles were favoured under the microwave curing, whilst a Si-rich N-A-S-H gel with a fibrilllar morphology and crystalline hydroxysodalite on the surface of fly ash particles were dominant under the thermal oven curing. The formation of these unique reaction products and microstructure under the microwave curing is attributed not only to the thermal effect of microwaves which can increase the temperature of AAFA volumetrically, but also to the non-thermal effects of microwaves which can promote the dissolution and diffusion of silica and alumina during the AAFA reaction process. This explains why AAFA can achieve a high early strength within a short period of microwave curing.

Investigation of agro-forestry and construction demolition wastes in alkali-activated fly ash bricks as sustainable building materials

Production of burnt clay bricks, cement and burning of agricultural/forestry wastes are responsible for major greenhouse gases emission. The present work investigate the effect of treated rice straw and forestry leaves in alkali-activated fly ash bricks with construction & demolition wastes for non-load bearing partitions walls at elevated temperature of 800 °C. 1–4 wt% incorporated agro-forestry wastes fly ash bricks with 10 and 20 wt% ground granulated blast slag (GGBFS) addition shows compressive strength ranging from 8 to 15 MPa. The thermal conductivity of the panels with 1–4 wt% agro-forestry addition varies from 0.4 to 0.5 W/m.K. The sound transmission class (STC) of 20 mm thick agro-forestry waste fly ash samples depict moderate sound insulation properties over the range of 24 to 37 dB. The wallette units of burnt clay bricks and agro-forestry based fly ash bricks show load carrying capacity of 360 kN, 273 kN and 195 kN, 110 kN at temperatures of 35 °C and 800 °C respectively. The present study shows a potential green solution toward sustainable building materials in construction sector leading to reduced depletion of fertile soil used in production of burnt clay bricks.

Behaviour of alkali-activated concrete at elevated temperatures: A critical review

Alkali-activated concrete (AAC) is recognised as a novel sustainable construction material to substitute Portland cement concrete with superior thermal and mechanical performance. However, AAC would suffer significant deterioration when subjected to elevated temperatures due to different damage mechanisms, including thermal incompatibility caused by different thermal coefficients between matrix and aggregates, pore pressure build-up and phase transformation. This paper presents a systematic and comprehensive review on the behaviour of different types of AAC such as alkali-activated fly ash, alkali-activated slag, alkali-activated metakaolin and alkali-activated fly ash-slag systems at elevated temperatures in terms of phase stability and microstructural evolution as well as thermal and mechanical performance. The effective strategies for improving the high-temperature resistance of AAC are reviewed and discussed from the perspectives of AAC matrix, aggregates and fibre incorporation, with special focus on how these strategies can tackle different damage mechanisms. This paper summarises the recent advances in the field and identifies the remaining challenges and opportunities for future research.

Chloride transport resistance of alkali-activated concrete exposed to combined chloride, sulfate and carbonation environment

The chloride transportation in alkali-activated fly ash (AAFA), alkali-activated slag (AAS) and alkali-activated fly ash/slag (AAFS) concrete exposed to the environments of single chloride and combined of chloride, sulfate and carbonation were investigated. The iodide migration, chloride diffusion and capillary absorption tests were carried out before and after exposure, as well as the analysis of their microstructure and compositions. It was found that the initial chloride transport of AAFA concrete was the highest but decreased gradually with the increase of exposure period. For AAFA and AAFS specimens with a relatively lower strength, chloride and sulfate salt crystallization led to the surface spalling and strength reduction. The coupling of carbonation would further accelerate the deterioration of AAFA, but the inhibitory effect was acted for AAFS specimen. Although the appearance of AAS specimens had little change under various aggressive environments, carbonation led to the decalcification of C-(A)-SH gels and deterioration of pore structure, both the porosity and the harmful 10–50 nm pores content of the specimens were higher compared with that before exposure, and their chloride transport increased with time. However, the deterioration of AAFS specimens resulted from carbonation was less serious, due to the formation of C-(N)-ASH gels with a higher degree of cross-linking and polymerization, thereby it had the best long term performance under the combined environment of chloride, sulfate and carbonation.

Influence of Erosion Induced by NaCl on the Mechanical Performances of Alkali-Activated Mineral Admixtures

In this paper, the influence of NaCl freeze-thaw (F-T) cycles and dry-wet (D-W) alternations on the flexural, compressive and bonding strengths of alkali-activated fly ash (FA) and a blast furnace slag powder (BFS) is investigated. The considered NaCl concentration is 3%. The effect of polypropylene fibers on the mechanical strengths is also examined. Scanning electron microscopy (SEM), thermogravimetry (TG) and X-ray diffraction (XRD) are selected to discern the mechanisms underpinning the NaCl-induced erosion. The obtained results indicate that the best results in terms of material resistance are obtained with admixtures containing 60% BFS and 40% FA in terms of mass ratio and 3% polypropylene fibers in terms of volume ratio. The maximum rates of decrease of the flexural, compressive and bonding strengths after 300 NaCl F-T cycles are 21.5%, 20.3% and 22.6%, respectively. The corresponding rates of decrease due to NaCl D-W alternations are 28.1%, 26.1% and 31.5%, respectively. The TG curves show that the alkali-activating activity of BFS is higher than that of FA. Moreover, in the first case, the microstructure of the hydration products is more compact. The results also show that NaCl F-T cycles lead to increasing cracks in the alkali-activated BFS.

Alkali activation of recycled concrete and aluminum salt slag aggregates for semi-rigid column inclusions

Stone columns develop their load-bearing capacity from the circumferential confinement offered by the surrounding soils. In highly plastic soils, the circumferential confinement provided by the surrounding soft soils may not be sufficient to develop the required bearing capacity. Meanwhile, the ground improvement industry has been keen to explore substitution backfill materials due to the depletion of natural aggregate resources typically used to construct stone columns. This research investigated the viability of using recycled concrete aggregate (RCA) and recycled aluminum salt slag (RASS), stabilized with alkali-activated fly ash (FA), slag (S) and a binary precursor (FA + S), as a novel semi-rigid inclusion column system for ground improvement of soft soils. The effect of the RCA/RASS ratios, additive types and dosages along with different curing conditions on the unconfined compressive strength (UCS) of geopolymer-stabilized mixtures, were evaluated. Various reinforcing mechanisms were suggested through the microstructure characterization of the mixtures. In addition, the permanent deformation responses of mixtures under cyclic loading were studied using repeated load triaxial (RLT) tests that simulate the cyclic moving traffic loads imposed on the stone columns system. The results demonstrated that increasing the RASS contents resulted in a subsequent decline in the UCS of the mixtures. Increasing the additive dosages on the other hand, in general led to higher strengths. The effects of both curing duration and temperature were found to play a vital role in the strength development of the mixtures. Furthermore, 100RCA stabilized by as low as 5% alkali-activated FA, S or (FA + S), met the minimum UCS requirement of 1.034 MPa for ground improvement. The highest reduction in permanent strain of 87.3% was recorded for the stabilized 100RCA + 10%(FA + S) mixture compared to the unbound 100RCA (control group). The practical implications of the findings were also discussed in detail throughout the paper.

Durability and mechanical long-term performance of reclaimed asphalt pavement stabilized by alkali-activation

The application of alkali-activated industrial by-products for the stabilization of reclaimed asphalt pavement (RAP), can become a sustainable solution to reduce the carbon footprint of road construction and maintenance activities. Furthermore, this approach can also reduce the increasing depletion of natural resources. Thus, the durability and long-term mechanical performance of RAP stabilized with alkali-activated fly ash were assessed in this study. The alkaline activator was a solution composed of sodium hydroxide and sodium silicate. To this extent, unconfined compressive strength (UCS) and durability tests were conducted in this research. The proposed alkali-activated binder significantly increased the UCS of RAP mixtures, with long-term (365 days) results reaching values up to 32 MPa; fulfilling the strength requirements for cement-stabilized soil mixtures and even stable inorganic binder materials for road base and sub-base layers of pavements. These results indicate that when stabilized with an alkali-activated fly ash binder, RAP presents several applications for road engineering; even when subjected to seasonal variations in humidity and temperature, as shown by the durability tests.