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With a lack of standard lateritic soil for use in road construction, suitable economical and sustainable soil-stabilization techniques are in demand. This study aimed to examine flue gas desulfurization (FGD) gypsum, a by-product of coal power plants, for use in soil–cement stabilization, specifically for ability to strengthen poor high-clay, lateritic soil but with a lower cement content. A series of compaction tests and unconfined compressive strength (UCS) tests were performed in conjunction with scanning electron microscope (SEM) analyses. Therefore, the strength development and the role of FGD gypsum in the soil–cement–FGD gypsum mixtures with varying cement and FGD gypsum contents were characterized in this study. The study results showed that adding FGD gypsum can enhance the strength of the stabilized substandard lateritic soil. Extra FGD gypsum added to the cement hydration system provided more sulfate ions, leading to the formation of ettringite and monosulfate, which are the hardening cementitious products from the cement hydration reaction. Both products contributed to the strength gain of the soil–cement–FGD gypsum material. However, the strength can be reduced when too much FGD gypsum is added because the undissolved gypsum has a weak structure. Examinations of FGD gypsum in the soil–cement–FGD gypsum mixtures by SEM confirmed that adding FGD gypsum can reduce the cement content in a soil–cement mix to achieve a given UCS value. [ABSTRACT FROM AUTHOR]

The alkali-silica reaction (ASR) is an important consideration in ensuring the long-term durability of concrete materials, especially for those containing reactive aggregates. Although fly ash (FA) has proven to be useful in preventing ASR expansion, the filler effect and the effect of FA fineness on ASR expansion are not well defined in the present literature. Hence, this study aimed to examine the effects of the filler and fineness of FA on ASR mortar expansion. FAs with two different finenesses were used to substitute ordinary Portland cement (OPC) at 20% by weight of binder. River sand (RS) with the same fineness as the FA was also used to replace OPC at the same rate as FA. The replacement of OPC with RS (an inert material) was carried out to observe the filler effect of FA on ASR. The results showed that FA and RS provided lower ASR expansions compared with the control mortar. Fine and coarse fly ashes in this study had almost the same effectiveness in mitigating the ASR expansion of the mortars. For the filler effect, smaller particles of RS had more influence on the ASR reduction than RS with coarser particles. A significant mitigation of the ASR expansion was obtained by decreasing the OPC content in the mortar mixture through its partial substitution with FA and RS. [ABSTRACT FROM AUTHOR]

This research initially investigates the mechanical behavior of fresh and used ballast grain assemblies through a combination of laboratory experiments and discrete element modeling (DEM). The extended Los Angeles abrasion (LAA) test generated the used ballast grains defined at a fouling index (FI) of 40%, while fresh ballast grains serve as the reference material. Morphological analysis of angularity properties of fresh and used ballast grains was employed in producing 2D polygonal shapes implemented in a discrete element code. Numerical simulations using the contact dynamics method examined the bi-axial compression of the 2D-equivalent fresh and used ballast grain assemblies under varying confining pressures. Results show that both fresh and used ballast grain packings exhibit similar stress-strain curves, with fresh ballast packing displaying slightly higher shear strength (5%) at the residual state. Fresh ballast packing is denser than the used one at the peak shear state, while residual states show nearly identical volume fractions. Microscale analysis of contact and force networks reveals that the used ballast assembly is more anisotropic in contact at peak stress. At the same time, both packings exhibit similar contact anisotropy at the residual state. Fresh ballast packing exhibits higher force anisotropy, particularly in frictional forces, explaining the excess shear stress observed at the residual state. These findings suggest that used ballast grains mobilize local friction less efficiently than fresh ballast grains, potentially impacting the lateral strength properties of ballasted tracks. This study provides valuable insights into the behavior of used and fresh ballast grains, serving as a foundation for further investigations. • FI 40% categorization via extended LAA testing reshapes ballast grain characterization. • DEM simulations unveil contact dynamics, providing insights into bi-axial compression & shear strength nuances. • Microscopic analysis reveals anisotropic behavior in used ballast, exposing frictional forces impacting lateral strength. • Stress-strain curves show consistent behavior; fresh ballast exhibits a subtle 5% shear strength boost at the residual state. • The study lays crucial groundwork, offering insights into fresh & used ballast behavior, guiding future research. [ABSTRACT FROM AUTHOR]

• Using 3D image processing and advanced data analytics to differentiate fresh and used ballast morphological parameters. • A machine learning algorithm was trained to distinguish between fresh and used ballast automatically. • Sphericity and convexity were crucial for differentiating fresh and used ballast, with identified threshold values. This study presents a method that utilizes 3D digital image processing and advanced data analytics to differentiate between fresh and used railway ballast materials. Railway ballast degrades over time, necessitating replacement with fresh material. However, fresh ballast may be scarce in some areas, and replacement costs have risen significantly. Recycling large aggregates from deteriorated ballast offers a solution to reduce track maintenance costs and greenhouse gas emissions, gaining popularity in track maintenance activities. Current ballast recycling practices, however, do not account for the morphological changes in the aggregates and their impact on the ballast's mechanical behavior. A machine learning algorithm is trained to differentiate fresh and used ballast automatically. The study examines the morphological parameters of fresh and used ballast materials using 3D scanning and image analysis techniques. A machine learning algorithm was trained to automatically distinguish between fresh and used ballast. The results reveal that sphericity and convexity were crucial parameters for differentiating fresh and used ballast, with identified threshold values of 0.89 for convexity and 0.8 for sphericity. The insights from this study may assist the decision for ballast recycling, reducing the demand for fresh ballast while maintaining track performance. [ABSTRACT FROM AUTHOR]

• Compact laterite-cement samples were tested under wet-dry cycles of water and sulfate solution. • Strength and durability increased with increases in cement content and hydraton. • Strength and weight loss of sulfate-soaked samples were higher than water-soaked samples. • Equations for cement content estimation for desired strength and durability were established. The designed cement content for laterite soil cement base or subbase for road construction can be estimated from the unconfined compressive strength (UCS) of the compressed cement-stabilized laterite soil sample. However, at the actual construction site, several factors such as sulfate and flood adversely affect the strength and durability of the soil cement. Consequently, the cement content estimation under a normal circumstance may not be sufficient. This research aimed to investigate the effects of wetting and drying cycles (w-d cycles) and sulfate-soaked cycles on the strength and durability of cement-stabilized laterite. The result indicated that the 4 % cement content is suitable for the laterite stabilized cement. After 12 w-d cycles, the strength loss of the sample soils soaked in water and in sulfate were 44 % and 55 % respectively. The durability index (ID) of both sample soils decreased with the increase in the w-d cycles. For soil cement base soaked in water and sulfate, the durability index should be lower than 0.88 or the weight loss should not exceed 12 %. The results also indicated that for practical propose, the normalized strengths under wet and dry cycles were related by a linear relationship for the range of tested cement content, water content, and curing periods. This relationship is very useful for the calculation of the desired strength from the estimated optimal cement content for the soil cement base mainly focusing on the durability against the effects of w-d cycles soaked in water and sulfate at any repeated cycles. [ABSTRACT FROM AUTHOR]

Frictional sleepers have been shown to enhance lateral resistance effectively. However, the current design of the bottom grooves in frictional sleepers lacks standardized specifications, and the fundamental mechanisms responsible for enhancing lateral resistance remain unclear. To explore the underlying mechanisms behind the influence of different bottom groove patterns on lateral resistance, five distinct groove shapes for frictional sleepers were designed, and a series of hybrid discrete element method-finite difference method (DEM-FDM) numerical simulations were conducted by using the single sleeper pull-out test (SSPT) as the basis. The results show that in comparison with the standard sleepers, there exists a considerable variation in the degree of increase in lateral resistance among different types of frictional sleepers, ranging from 35.1% to 80.2%. Specifically, the lateral resistance increases logarithmically as the groove side area increases. The analyses show that the effective contact area (i.e., the contact area between ballast particles and the sleeper's bottom surface) was increased due to the constraint effect of the bottom grooves, simultaneously leading to increasing strength of the horizontal force chains near the grooves. Using discontinuous grooves can diminish the initial interference with the ballasts near the sleepers. Frictional sleepers primarily demonstrate anisotropy in the horizontal plane, which constitutes one of the mesoscale factors contributing to the enhancement of lateral resistance. In addition, the displacement and rotation of particles around the sleepers are constrained, whereas the most significant constraint was observed on the ballast shoulders. It is suggested to apply the frictional sleepers with discontinuous grooves and consider patterns that aim to maximize the groove side area in the design and maintenance of ballasted railway tracks. • Five distinct groove patterns were designed with their lateral resistances quantitatively linked to groove shape and area. • Mesoscopic mechanisms of lateral resistance improvement were revealed from ballast particle movement and contact fabrics. • An optimized groove design approach was proposed for frictional sleepers in ballasted railway track. [ABSTRACT FROM AUTHOR]

This paper aims to develop measures to minimize the early-age fatigue damage of prematurely opened cement-treated bases (CTBs) due to repetitive heavy traffic loading. The four-point bending test was used in this study to characterize the early-age fatigue performance as well as the flexural properties of two different locally sourced granular materials stabilized with 3% general purpose (GP) cement. All the flexural tests were executed under stress-controlled mode. The fatigue test results evinced the existence of an endurance limit in cemented granular materials (CGMs) even at 7 days curing age. A stress-based fatigue performance model was developed for predicting the early-age fatigue performance of CGMs in service. In addition, the 7-day fatigue test data from this study were validated using existing CGM fatigue models. The numerical results obtained from the CIRCLY program indicated that the level of interaction between the axles of an axle configuration decreases with decreasing CTB layer thickness, resulting in increased pavement fatigue damage. It was also found that the asphalt cover over CTB required to prevent the occurrence of initial fatigue damage to the CTB decreases with increasing CTB modulus, subgrade strength, and CTB layer thickness. The limitations and simplifications in current pavement design and testing methods are also critically discussed and addressed on the basis of the results of this study. [ABSTRACT FROM AUTHOR]

Calcium carbide residue (CCR) is a waste obtained from the production of acetylene gas by the hydration reaction of calcium carbide. This residue is generated in large quantities annually and requires appropriate disposal. The main composition of the residue is calcium hydroxide (Ca(OH) 2). Ca(OH) 2 can react with CO 2 gas and form CaCO 3 particles. This process is well known but not very attractive since Ca(OH) 2 is obtained from limestone using an energy-intensive thermal conversion process. This paper examined the synthesis of CaCO 3 from CCR solutions by capturing CO 2 with the aid of triethanolamine (TEA) solutions at doses of 0, 5, 10 and 20% w/w. The precipitated CaCO 3 was characterized, and the application of CaCO 3 as a filler in epoxy resin was tested. The results showed that the precipitated CaCO 3 was mainly calcite, with a 76.6% yield. Cubic calcite was primarily obtained in TEA solutions, whereas small and agglomerated spherical vaterite and cubic calcite particles were formed in non-TEA solutions. The CaCO 3 -filled epoxy composites showed higher compressive strength than the neat resin. However, the transparency of specimen plates was reduced. These results can serve as guidelines for the application of CCR slurry filtrate obtained from the sedimentation ponds of acetylene plants and help to reduce the amount of wastewater that needs to be treated. CO 2 gas from industrial flue gas combined with TEA solution could be applied to precipitate CaCO 3 for carbon-neutral manufacturing. • CaCO 3 was synthesized from CCR solutions by capturing CO 2 /triethanolamine. • Precipitated CaCO 3 was mainly cubic calcite with 76.6% yield. • Compressive strength of CaCO 3 -filled epoxy composites was improved. • Transparency of CaCO 3 -filled specimen plates was reduced to translucent object. [ABSTRACT FROM AUTHOR]

• Hemp fibers improved both flexibility and impact resistance of the composites. • Waxy substances on the surface of hemp fibers were washed out with NaOH reagent. • Alkalinity in geopolymer acted as a (self)pre-treatment reagent for hemp fibers. • Self-treatment process can shorten the preparation process of hemp fibers. • Self-treatment process could be applied to any natural fibers in geopolymers. The novelty and the aim of this research is to investigate the feasibility of the self-treatment process, which is governed by various levels of alkalinity, i.e., sodium hydroxide (NaOH) solution in the geopolymer system, for natural fibers, and the effect of such treatment on the properties of hemp-geopolymer composites. A digital microscope is used to examine the contact angle (CA). Fourier Transform Infrared (FT-IR) spectrometer, Scanning Electron Microscope (SEM), X-Ray diffractometer (XRD) are used to examine changes in surface functional groups, bonding, micrographs and structural formation of the resulted hemp-based geopolymer products. The results showed that the alkalinity in the geopolymer alternatively acted as an alkaline treatment reagent for the reinforced hemp fibers, which evidently provided effectively self-treatment, indicating by the FT-IR and contact angle analysis. The compressive strength of the composites was slightly dropped as the binder was replaced by the hemp fibers, while the flexural strength and impact resistance were improved by the additional adhesion between the natural fibers and cement matrix. The self-treatment approach could also shorten the preparation process of any natural fibers in geopolymers, allowing both cost-effectiveness in practical usages and in-field applications. [ABSTRACT FROM AUTHOR]

Raw water is a significant resource for industrial water usage, but this water is not directly suitable for use due to the presence of contaminants. Therefore, pre-treatment is essential. The treatment generates water treatment residue (WTR) which consists of silt, clay and undesirable components. Most WTR is conventionally disposed of in landfill. In addition, the presence of iron (Fe) and manganese (Mn) in groundwater can result in a reddish-brown color and undesirable taste and odour. A number of expensive and complex technologies are being used for the removal of such iron and manganese. Due to the high Al 2 O 3 and SiO 2 content in WTR, therefore, this research proposes the use of WTR as the source material for geopolymer production for Fe/Mn removal. With the availability of free alkali in the geopolymer framework, the OH−-releasing behavior of the WTR-based geopolymer was investigated by the precipitation of Fe(II) ion. The WTR-based geopolymer was calcined at 400 °C and 600 °C to obtain a strong geopolymer matrix with the ability to remove Fe/Mn ions. The results show that the WTR-based geopolymer has the potential to remove Fe from Fe-contaminated water. Hydroxide ions are released from the geopolymer and form an Fe(OH) 3 precipitate. Geopolymer with a calcination temperature of 400 °C provides total removal of the Fe after 24 h of immersion. In addition, the existence of Fe(OH) 3 helps to coprecipitate the Mn(OH) 2 in the Fe/Mn solution leading to a significant reduction of Mn from the solution. The pH value and retention time play an important role in the final metal concentration. The final pH of the solution is close to 8.5, which is the recommended value for boiler water. This method offers an alternative use of WTR in making a porous geopolymer for groundwater Fe/Mn removal using a simple method. [Display omitted] • Water treatment residue (WTR) from raw water treatment was utilized in this study. • WTR-geopolymer was produced for iron removal in groundwater. • OH− ion from WTR-geopolymer was released for the precipitation of Fe(II). • WTR had the potential for Mn/Fe removal from aqueous solutions. [ABSTRACT FROM AUTHOR]

• CR was used as CaO source to produce low-CaO FA-based AAM cured at ambient temperature. • Effects of NaOH and ratios of FA to CR on strength and shrinkage of AAM were investigated. • Shrinkage of AAM increased with the increased NaOH and decreased with the increased CR. • AAM made from FA-CR and cured at ambient temperature had compressive strengths up to 60.2 MPa. • Reaction products C–S–H, C–A–S–H, and N–A–S–H were detected by XRD analysis. In this study, the effects of sodium hydroxide (NaOH) concentrations, ratios of low-calcium fly ash (FA) to calcium carbide residue (CR), and adding 5% of Portland cement on compressive strength and autogenous shrinkage of alkali-activated mortar made from FA-CR mixtures were investigated and verified by examining the microstructure and morphology of alkali-activated paste. Both FA and CR were improved by grinding a finer powder. The alkali activators were a NaOH solution and a liquid sodium silicate at a constant ratio of 2:1. The results indicated that the utilization of CR partially substituted in FA and activated with a higher NaOH concentration significantly improved the compressive strength of alkali-activated mortars. The autogenous shrinkage of alkali-activated mortars increased with the increased NaOH concentration and decreased significantly when the CR partially replaced in FA. An alkali-activated mortar made from an FA-CR mixture (without cement) achieved compressive strengths up to 60.2 MPa and had an autogenous shrinkage of less than 100 × 10−6 mm/mm. Moreover, the XRD patterns of alkali-activated pastes showed that the reaction products of C–S–H, C–A–S–H, and N–A–S–H were related to the dense structure and the Si, Al, Ca, and Na detected in SEM/EDS results. [ABSTRACT FROM AUTHOR]

• The mixture of FA and CR was used as a binder in alkali activated CLSM. • Properties of lightweight alkali activated CLSM containing EPS beads are studied. • Lightweight alkali activated CLSM had UCS of 1,500–3,000 kPa. • UCS of lightweight alkali activated CLSM rapidly increased in the first 12 h. • Density of lightweight alkali activated CLSM is ranged from 750 to 900 kg/m3. This research aims to use of alkali activated binder containing expanded polystyrene (EPS) beads for producing lightweight controlled low strength materials (CLSM). Sodium hydroxide (NH) solution and sodium silicate (NS) were used as alkali activators. NH concentration was set as a constant of 6 Molar. The mixture of fly ash (FA) and calcium carbide residue (CR) at a ratio of 75:25 by weight was used as a binder. EPS beads was used as a lightweight aggregate and the binder to EPS beads ratio was varied from 1:2.50 to 1:3.00 by volume. Workability in terms of flow was controlled between 200 and 300 mm. The compressive strength at 6 h up to 28 d and water absorption of lightweight alkali activated CLSM were determined. In addition, XRD and SEM of lightweight alkali activated CLSM were also investigated. The results revealed that the compressive strengths of lightweight alkali activated CLSM rapidly increased in the first 12 h, which were from 451 kPa to 731 kPa. The ratio of binder to EPS beads at 1:2.50 by volume was the optimum ratio and the ratio of NH:NS at 1:0.4 gave the highest compressive strength of lightweight alkali activated CLSM. Lightweight alkali activated CLSM obtained from this study had the compressive strength of 1,500–3,000 kPa and the density of 750–900 kg/m3 at 28 d, which can be used as structural backlinking. [ABSTRACT FROM AUTHOR]

Spatial susceptible landslide prediction is the one of the most challenging research areas which essentially concerns the safety of inhabitants. The novel geographic information web (GIW) application is proposed for dynamically predicting landslide risk in Chiang Rai, Thailand. The automated GIW system is coordinated between machine learning technologies, web technologies, and application programming interfaces (APIs). The new bidirectional long short-term memory (Bi-LSTM) algorithm is presented to forecast landslides. The proposed algorithm consists of 3 major steps, the first of which is the construction of a landslide dataset by using Quantum GIS (QGIS). The second step is to generate the landslide-risk model based on machine learning approaches. Finally, the automated landslide-risk visualization illustrates the likelihood of landslide via Google Maps on the website. Four static factors are considered for landslide-risk prediction, namely, land cover, soil properties, elevation and slope, and a single dynamic factor i.e., precipitation. Data are collected to construct a geospatial landslide database which comprises three historical landslide locations—Phu Chifa at Thoeng District, Ban Pha Duea at Mae Salong Nai, and Mai Salong Nok in Mae Fa Luang District, Chiang Rai, Thailand. Data collection is achieved using QGIS software to interpolate contour, elevation, slope degree and land cover from the Google satellite images, aerial and site survey photographs while the physiographic and rock type are on-site surveyed by experts. The state-of-the-art machine learning models have been trained i.e., linear regression (LR), artificial neural network (ANN), LSTM, and Bi-LSTM. Ablation studies have been conducted to determine the optimal parameters setting for each model. An enhancement method based on two-stage classifications has been presented to improve the landslide prediction of LSTM and Bi-LSTM models. The landslide-risk prediction performances of these models are subsequently evaluated using real-time dataset and it is shown that Bi-LSTM with Random Forest (Bi-LSTM-RF) yields the best prediction performance. Bi-LSTM-RF model has improved the landslide-risk predicting performance over LR, ANNs, LSTM, and Bi-LSTM in terms of the area under the receiver characteristic operator (AUC) scores by 0.42, 0.27, 0.46, and 0.47, respectively. Finally, an automated web GIS has been developed and it consists of software components including the trained models, rainfall API, Google API, and geodatabase. All components have been interfaced together via JavaScript and Node.js tool. [ABSTRACT FROM AUTHOR]

Building materials with hydrophobic surfaces can exhibit increased service life by preventing moisture absorption or diffusion through their surfaces. For concrete used in construction, this hydrophobicity can prevent the corrosion of reinforcing steel bars. Geopolymers are a new cement-free binding material that have been extensively studied to replace Portland cement. However, similar to normal concrete, geopolymers are susceptible to the intake of moisture. This paper presents the fabrication of a superhydrophobic and self-cleaning surface on a fly ash geopolymer as a method to prevent moisture intake. A composite coating of polydimethylsiloxane (PDMS) solution containing dispersed polytetrafluoroethylene (PTFE) or calcium stearate (CS) microparticles was applied by dip-coating to form the hydrophobic surface. Additionally, fly ash was incorporated with the PTFE and CS microparticles to increase surface roughness and reduce material cost. The experimental results showed that the coating containing CS microparticles yielded a hydrophobic surface with a contact angle of 140°, while those containing PTFE microparticles provided a superhydrophobic surface with a contact angle of 159°. The incorporation of fly ash resulted in increased surface roughness, leading to a larger contact angle and a smaller sliding angle. A contact angle of 153° with a sliding angle of 8.7° was observed on the PTFE/fly ash-coated surface. The cleaning process was demonstrated with a test whereby dust was removed by water droplets rolling off the surface. The tested coating exhibited self-cleaning and waterproofing properties and could thus improve the sustainability of materials in building construction., (© 2023. The Author(s).)

Geopolymer (GP) was invented to replace concrete, but its heat curing requirement hinders extensive use in real-world construction. Past studies have tested several methods of heat curing. However, the conventional heat curing process (using an oven) is still required for GP to develop good strength on the laboratory scale. This study introduces a new heat curing method for GP based on an electromagnetic field (EMF)generator and a ferromagnetic material. Waste iron powder (WIP) was used as the ferromagnetic material mixed with the fly ash-based GP to generate heat through induction. The sample was cured at 1.18 kW with 150-200 kHz of EMF generator for 15 min. The results showed that 5% of the WIP mixed sample gained compressive and flexural strength at 28 days more than the control (oven-cured). Compressive and flexural strengths of 76.8 MPa and 11.3 MPa were obtained, respectively. In addition, heat induction enhanced the densification and geopolymerization in the GP matrix following SEM and XRD results. This alternative method of heat curing accelerated the formation of the GP matrix, reduced curing time, and increased strength. Moreover, this EMF curing method can save 99.70% of the energy consumed compared to the conventional heat curing method., (© 2022. The Author(s).)

The worldwide demand for roads to serve global economic growth has led to the increasing popularity of road improvement using cement. This, in turn, has led to increased demand for cement and the associated problem of CO 2 emissions. Alkaline-activated materials (AAMs) could be an alternative binder for relatively low strength construction and rehabilitation as a cement replacement material. Compared to other applications, the lower strength requirements of road construction materials could ease any difficulties with AAM production. In this study, crushed rock (CR) was used as a prime raw material. The mechanisms and microstructures of the hardened AAM were investigated along with its mechanical properties. The results showed that CR-based AAM with an optimum mixture of 5 M of NaOH concentration, an SS/SH ratio of 1.00, and a liquid alkaline-to-binder (L/B) ratio of 0.5 could be used for roadway applications. At this ratio, the paste samples cured at room temperature (26 ± 3 °C) had an early compressive strength (3 days-age) of 3.82 MPa, while the paste samples cured at 60 °C had an early compressive strength of 6.45 MPa. The targeted strength results were able to be applied to a cement-treated base (CTB) for pavement and roadway applications (2.1 to 5.5 MPa).

Supplementary cementitious materials have been widely used to reduce the greenhouse gas emissions caused by ordinary Portland cement (OPC), including in the construction of road bases. In addition, the use of OPC in road base stabilization is inefficient due to its moisture sensitivity and lack of flexibility. Therefore, this study investigates the effect of hybrid alkali-activated materials (H-AAM) on flexibility and water prevention when used as binders while proposing a new and sustainable material. A cationic asphalt emulsion (CAE) was applied to increase this cementless material's resistance to moisture damage and flexibility. The physical properties and structural formation of this H-AAM, consisting of fly ash, hydrated lime, and sodium hydroxide, were examined. The results revealed that the addition of CAE decreased the material's mechanical strength due to its hindrance of pozzolanic reactions and alkali activations. This study revealed decreases in the cementitious product's peak in the x-ray diffraction analysis (XRD) tests and the number of tetrahedrons detected in the Fourier transform infrared spectroscopy analysis (FTIR) tests. The scanning electron microscope (SEM) images showed some signs of asphalt films surrounding hybrid alkali-activated particles and even some unreacted FA particles, indicating incomplete chemical reactions in the study material's matrix. However, the H-AAM was still able to meet the minimum road base strength requirement of 1.72 MPa. Furthermore, the toughness and flexibility of the H-AAM were enhanced by CAE. Notably, adding 10% and 20% CAE by weight to the hybrid alkali-activated binder produced a significant advantage in terms of water absorption, which can be explained by its influence on the material's consolidation of its matrices, resulting in significant void reductions. Hence, the outcomes of this study might reveal an opportunity for developing a new stabilizing agent for road bases with water-prevention properties and flexibility that remains faithful to the green construction material concept.

Geopolymer (GP) has been applied as an environmentally-friendly construction material in recent years. Many pozzolanic wastes, such as fly ash (FA) and bottom ash, are commonly used as source materials for synthesizing geopolymer. Nonetheless, many non-pozzolanic wastes are often applied in the field of civil engineering, including waste iron powder (WIP). WIPs are massively produced as by-products from iron and steel industries, and the production rate increases every year. As an iron-based material, WIP has properties of heat induction and restoration, which can enhance the heat curing process of GP. Therefore, this study aimed to utilize WIP in high-calcium FA geopolymer to develop a new type of geopolymer and examine its properties compared to the conventional geopolymer. Scanning electron microscopy and X-ray diffraction were performed on the geopolymers. Mechanical properties, including compressive strength and flexural strength, were also determined. In addition, setting time and temperature monitoring during the heat curing process were carried out. The results indicated that the addition of WIP in FA geopolymer decreased the compressive strength, owing to the formation of tetrahydroxoferrate (II) sodium or Na 2 [Fe(OH) 4 ]. However, a significant increase in the flexural strength of GP with WIP addition was detected. A flexural strength of 8.5 MPa was achieved by a 28-day sample with 20% of WIP addition, nearly three times higher than that of control.

This research evaluated the feasibility of using vetiver plantlets (Vetiveria zizanioides (L.) Nash) on a floating platform with aeration to degrade phenol (500 mg/L) in illegally dumped industrial wastewater (IDIWW). The IDIWW sample was from the most infamous illegal dumping site at Nong Nae subdistrict, Phanom Sarakham district, Chachoengsao province, Thailand. Laboratory results suggested that phenol degradation by vetiver involves two phases: Phase I, phytopolymerization and phyto-oxidation assisted by root-produced peroxide (H 2 O 2 ) and peroxidase (POD), followed by phase II, a combination of phase I with enhanced rhizomicrobial degradation. The first 360-400 h of phenol degradation were dominated by phytopolymerization and phyto-oxidation yielding particulate polyphenols (PPP) or particulate organic matter (POM) as by-products, while phenol decreased to around 145 mg/L. In Phase II, synergistically, rhizomicrobial growth was ∼100-folds greater on the roots of the vetiver plantlets than in the IDIWW and participated in the microbial degradation of phenol at this lower phenol concentration, increasing the phenol degradation rate by more than three folds. This combination of phytochemical and rhizomicrobiological processes eliminated phenol in IDIWW in less than 766 h (32 days), while without the vetiver plantlets, phenol degradation by aerated microbial degradation alone may require 235 days. To our knowledge, this is the first that systematically reveals the complete phenol degradation mechanism by vetiver plantlets in real aerated wastewater.