Search

Using waste as a raw material for the synthesis of construction materials is gaining increasing attention due to the declining availability of natural resources. This research seeks to assess the impact of using cellulose acetate microfibers (CAMs) derived from discarded cigarettes as a reinforcement for alkali-activated materials (AAMs). In this context, seven blends were elaborated with the addition of various percentages of CAMs (0%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, and 1.5%) per dry mass of fly ash, and using an alkaline solution composed of Na2SiO3 and 10 M NaOH solution. Then the physico-mechanical, thermal, and environmental properties of these composites were evaluated. The experimental results indicated that the addition of CAMs led to lighter composites, which decreased compressive strength, P-wave velocity, and density, while slightly increasing flexural strength, porosity, and water absorption. Moreover, a slight enhancement in thermal insulation capacity was observed (up to ∼9.28%). The microstructural analyses, encompassing XRD, FT-IR, and SEM/EDX examinations, revealed the formation of geopolymeric gels N-A-S-H and C-A-S-H in all specimens. The Toxicity Characteristic Leaching Procedure indicated that the released contaminants were within the regulatory limits, as well as the binder exhibited a remarkable decrease in carbon dioxide emissions and energy demand by 77.23% and 57.92% in comparison to cement. Thus, the prepared materials are viewed as a more environmentally responsible choice for reducing greenhouse gas emissions while avoiding potential toxicity issues.

This study investigated the carbonaluminate cementitious materials (i.e., sodium aluminate (NaAlO2)-activated limestone pastes) with gradient calcite (CaCO3)/NaAlO2 molar ratios ranging from 1:1 to 6:1 (samples M1 to M6). NaAlO2 dosage affected the reaction process, hydration product, and cementitious property of the formed pastes. The thermonatrite (Na2CO3·H2O) and AH3 phase as hydration products exist in all the samples. Microcrystalline AH3 phase (crystallite size is near 22 nm) held a superior cementitious property, which was evidenced by diffraction spots scattered on concentric rings in transmission electron microscopy (TEM) results. Other hydrates varied with the CaCO3/NaAlO2 ratio. In case of lower CaCO3/NaAlO2 ratio (i.e., M1), NaAlO2 was incompletely consumed. The residual NaAlO2 promoted the formation of cubic-shaped katoite (3CaO·Al2O3·6H2O). Such hydrate barely contributed to the cementitious property of the formed matrix. When the CaCO3/NaAlO2 ratio reached 1.5:1 (e.g., M1.5-M6), NaAlO2 was entirely consumed, and monocarboaluminate (Mc, 3CaO·Al2O3·CaCO3·11H2O) instead of katoite was preferentially generated. The amounts of total hydrates decreased with the increasing CaCO3/NaAlO2 ratio, leading to the degraded properties of formed matrix. Thus, the 28-day compressive strength of M1.5 was the highest among these samples, reaching 35.55 MPa.

The production process of dolomite aggregate yields a huge content of the rejected size, namely dolomite waste. This waste causes many environmental problems including increasing the wastage area, disposal of landfill, and increasing the air pollution. This work pay attention to the sustainable disposal of this waste in the production of an innovative binder using chemical exchange reaction. This work aims to examine the role of metakaolin (MK) and diatomite (DT) in enhancing the physicochemical properties of alkali-activated binder-based dolomite waste (AADW). The DW powder was combined with varying weight percentages of MK and DT. The resultant admixtures were activated via Na2SiO3, followed by curing at room temperature. The fabricated mixtures possess a wide range of compressive strength values, dependent on the contents of the additives (MK and DT). AADW without any additives represents a compressive strength of 34.6 MPa. DT was found to have a minimal effect on early compressive strength but significantly enhanced later strength. In contrast, incorporating MK into the alkali-activated system materially improved the early compressive strength, while it recorded 28-day strengths similar in hardness to the hardened sample with DT. Specifically, AADW-DT10 and AADW-MK10, which contain 10 wt% DT and MK, respectively, exhibited 7- & 28-day compressive strengths of 14.4 MPa & 32.1 MPa and 57 MPa & 56.2 MPa, respectively. Replacing DW with DT reduced drying shrinkage of the resultant hardened alkali-activated materials. However, incorporating MK up to 10 wt% reduced the drying shrinkage of AADW, while the sample with 15 wt% recorded the highest drying shrinkage. Nonetheless, AADW-DT exhibited lower drying shrinkage than that of AADW-MK at all curing ages up to 90 days. Overall, the result indicated that the higher reactivity and high alumina content of MK provide suitable conditions for synthesizing hardened materials with better physical and mechanical properties when compared to AADW-DT.

Steel slag composite grout (SSCG) was prepared by a large amount of steel slag (SS) to reinforce expressway photovoltaic (PV) slopes and reduce carbon emission. Laboratory tests were conducted to investigate SSCG properties, including flowability, effective water-solid ratio (W/S), stone rate, initial and final setting time, as well as flexural strength (FS), unconfined compressive strength (UCS), FS/UCS ratio and microstructure of SSCG stone body. Ordinary Portland cement (OPC, 42.5) and sulphoaluminate cement (SAC, 42.5) grouts were selected to make contrasts. Based on the performance results, the recommended SSCG composition for engineering application is 40 % SS + 25 % blast furnace slag (BFS) + 20 % silicate cement clinker (CC) + 10 % fly ash (FA) + 5 % flue gas desulfurisation gypsum (FGDG). and the recommended admixture is: 6 % AA + 2 % bentonite + 0.4 % FND-C. With the above SSCG and related grouting techniques for slope soils, the soil cohesion was increased by 7.3–12.2 % and the angle of internal friction was increased by 10.2–19.7 %. To further validate the beneficial effects of SSCG on slope stability and the safe application of PV systems, numerical modelling calculations were conducted based on the soil sample test results. The simulations demonstrated the positive effect of SSCG in enhancing slope stability and facilitating the secure installation of PV systems on expressway slopes. The successful operation of grid-connected PV systems provided compelling evidence for the technical applicability of SSCG and it contributed to the application feasibility of PV systems to expressway slopes. The innovative use of SSCG in this study not only ensures the safety of construction projects but also contributes to environmental sustainability through the application of industrial slags.

In this study, central composite design (CCD) was used to optimize the porosity structure of NaOH-activated volcanic scoria (VSc) and rice husk ash (RHA) composite materials. The synthesis conditions, namely VSc and RHA fractions by mass and NaOH concentration were used as the input (independent) variables and the porosity parameters, iodine index and methylene blue index, as the output variables. The optimum conditions that gave the material, CM, with the highest iodine index and methylene blue index, and hence porosity structure, were attained at 0.67 VSc (2g)/RHA (3g) ratio by mass and 5 M NaOH. The CM and precursors were characterized using FTIR, SEM, pHpzc, Methyl Blue index, and Iodine index. The CM and the precursor VSc were used to sorb crystal violet (CV) dye from synthetic wastewater. The pseudo-second-order kinetic and Langmuir models best-described CV adsorption by both materials. The adsorption mechanism was controlled by Coulombic interactions. At an initial CV concentration of 20–60 mg/L, 0.1g/30 mL adsorbent dosage, and pH of 6 at 25 °C, the CM had a slightly higher (∼1.13 times) adsorption capacity (11.06 mg/g) for the uptake of crystal violet dye than the precursor VSc (9.75 mg/g) consistent with their methylene blue indices. Electrostatic interactions and ion exchange are proposed dominant adsorption mechanisms. The porosity and adsorption performance of the VSc-RHA alkali-activated materials are shown to be strongly and significantly dependent on the RHA fraction and NaOH concentration relative to VSc.

Green liquor dreg (GLD) is a side stream generated by pulp industry. Due to its complex physicochemical nature, it has been reported to be difficult material to utilize. Here, a novel approach towards utilization of moist and dry green liquor dreg as binder and filler in alkali-activated lightweight artificial aggregates was developed. Dried GLD and moist GLD were granulated with blast furnace slag (BFS) and Bioash in different mixtures using alkali activation. The effect of the GLD nature (dried and moist) on strength, microstructure and durability of the lightweight granules were determined and compared. Results show that the method used in homogenizing the moist GLD and other powders was efficient and improved the frost resistance. The reaction product identified in the granule’s includes calcium silicate hydrate, Mg–Al layered double hydroxides, and ettringite. These results demonstrate the potential of GLD as a binder and fillers in cementitious applications.

The disposal of municipal solid waste incineration fly ash (MSWIFA) has become a prominent issue due to high environmental risks. In this study, as a potential aluminosilicate precursor, MSWIFA was further alkali-activated as a sustainable construction material in the form of an alkali-activated MSWIFA-based material (AAFM), with a low leaching level of heavy metals. Various 3D-printed polymeric lattices were designed and inserted into the AAFM to promote its inherent brittleness. A special coating was also considered to enhance the alkali resistance of the PEGT lattices. Through a flexural tension test with a 3D digital image correlation (3D-DIC) technique, the failure patterns and strain distributions of the 3D-printed polymeric lattice-enhanced MSWIFA-based composites were tracked. These polymeric lattice-containing composites indicated the promotion of mechanical performance, i.e., higher flexural strengths and good ductility. The 3D polymeric lattice-enhanced MSWIFA-based composites showed application prospects as sustainable construction materials, gaining both environmental benefits and good mechanical performance.

This study aims to improve the stability of alkali-activated products, such as powdered volcanic scoria and metakaolin, by thermal treatment in addition to their partial replacement with aluminium oxy-hydroxide. To this effect, mixtures obtained from a partial replacement of aluminosilicate sources (volcanic scoria or metakaolin) with respectively 0, 10, 20 or 30 % of mass of aluminium oxy-hydroxide were alkali-activated and stored for 28 days at room temperature in the laboratory. The various specimens obtained were heated at 900–1200 °C and both the alkali-aluminosilicates and the heated products were analysed. It appeared that aluminium oxy-hydroxide improves the stability of heated products. Thus, without replacement, alkali-activated specimens of metakaolin showed cracks at 1100 °C while those of volcanic scoria melted at 1150 °C. Conversely, heated alkali-activated specimens of either volcanic scoria or metakaolin with the replacement showed stability up to 1200 °C and an improvement in the residual compressive strength as from 900 °C. Indeed, at 1150 °C, the metakaolin-based geopolymers or the alkali-activated volcanic scoria with 30 % of mass of the replacement showed residual compressive strength of 76.7 and 35.0 MPa, respectively, due to the sintering and to the formation of new crystalline phases (mullite, corundum, carnegieite and nepheline). Yet, residual compressive strength in the alkali-activated aluminosilicate specimens with replacement that were heated at 1200 °C dropped as a result of the partial dissolution of nepheline and carnegieite which may have generated closed pores within their microstructure. Hence, alkali-activation of volcanic scoria or metakaolin partially replaced with aluminium oxy-hydroxide is a remarkable process to get thermally stable products.

Adsorption is one of the most effective methods for ecotoxic antibiotics removal, while developing high-performance adsorbents with excellent adsorption capacity is indispensable. As the unavoidable by-product of wastewater, sewage sludge has dual properties of pollution and resources. In this study, dyeing sludge waste was converted to biochar by KOH activation and pyrolysis, and used as an efficient adsorbent for aqueous antibiotics removal. The optimized dyeing sludge-derived biochar (KSC-8) has excellent specific surface area (1178.4 m 2 /g) and the adsorption capacity for tetracycline (TC) could reach up to 1081.3 mg/g, which is four and five times higher than those without activation, respectively. The PSO (pseudo-second-order) kinetic model and the Langmuir isotherm model fitted better to the experimental data. The obtained KSC-8 has stabilized adsorption capacity for long-term fixed-bed experiments, and maintained 86.35% TC removal efficiency after five adsorption-regeneration cycles. The adsorption mechanism involves electrostatic attraction, hydrogen bonding, π-π interactions and pore filling. This work is a green and eco-friendly way as converting the waste to treat waste in aiming of simultaneous removal of antibiotics and resource recovery of dyeing sludge., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

One of the most used characterization techniques in the field of alkaline activated cements studies is infrared spectroscopy. Its prominence lies in that it allows characterizing mixtures during the alkaline activation by providing information about the vibrations of the chemical bonds in the molecular units, both of amorphous and crystalline products. This research paper is aimed at examining the influence of the concentration of calcium hydroxide (CH), sodium hydroxide (SH), temperature and curing time on the structure of alkaline activated cements, based on coal fly ash, from the deconvolution of the infrared spectrum between 4000 and 400 cm -1 . 9 mixtures were analyzed by infrared spectroscopy at 3 and 28 days after curing, based on a surface's response experimental design by varying the amount of SH (5.17-10.83 M), CH (2.93-17.07% ash's wt.) and the curing temperature (25, 35 and 45 °C). The results show significant variations in the frequency and area of the deconvolved bands in the functional groups: O-H (2600-3800 cm -1 ), C-O (1580 and 1350 cm -1 ) and T-O (T: Si (Al), 1300-400 cm -1 ). Such variations are due to the reorganization of the forming elements (present in the ash) network and modifiers (present in CH and SH) for the formation of cementing gels C-(A) -S-H (970 cm -1 ) and N-A-S-H (1009 cm -1 )., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Power generation and other industries using solid fossil fuels like coal, lignite, oil shale and peat are responsible for producing large quantities of solid residues that are often chemically reactive and/or unstable and are disposed in holding ponds and deposition sites. Stability and long-term behaviour of such deposits are typically studied in short-term laboratory experiments that cannot describe nor predict long-term changes taking place in these materials. Here, we study long-term (>40 years) transformations, in highly alkaline conditions, of the Ca-rich ash deposit in Estonia composed of oil shale processing residues from the Eesti power plant. Detailed mineralogical, chemical and micromorphological analyses using X-ray diffraction, X-ray fluorescence, 29 Si nuclear magnetic resonance, scanning electron microscopy and other methods were applied in order to identify the composition of the waste with a focus on formation and transformation of semicrystalline phases in the deposit. The results show progressive formation of calcium-silicate-hydrate (C-S-H) type phase at the expense of silicate minerals and amorphous glass phases with increasing depth and age of the sediments, from about 25% in the upper part of the depository to over 60% in the oldest-deepest part. This demonstrates that over time the high alkalinity of the ash is responsible for initiating natural alkali-activation. The formation of C-S-H-type phases increases the mechanical strength of the sediment and ensures long-term stability of waste deposits. These findings may encourage the use of these ashes in binder or other construction material production or as construction aggregates., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In the present work fly-ash based geopolymers with different contents of alkali-activator and water were prepared. Alkali-activation was conducted with sodium hydroxide (NaOH) at the SiO 2 /Na 2 O molar ratio of 3, 4, and 5. Water content was at the ratio of 30, 40, and 50wt% in respect to the weight of the fly ash. Structural and microstructural characterization (FT-IR spectroscopy, 29 Si and 27 Al MAS NMR, X-ray diffraction, SEM) of the specimens as well as compressive strength and apparent density measurements were carried out. The obtained geopolymers are mainly amorphous due to the presence of disordered aluminosilicate phases. However, hydroxysodalite have been identified as a crystalline product of geopolymerization. The major band in the mid-infrared spectra (at about 1000cm -1 ) is related to SiO(Si,Al) asymmetric stretching vibrations and is an indicator of the geopolymeric network formation. Several component bands in this region can be noticed after the decomposition process. Decomposition of band at 1450cm -1 (vibrations of CO bonds in bicarbonate group) has been also conducted. Higher NaOH content favors carbonation, inasmuch as the intensity of the band then increases. Both water and alkaline activator contents have an influence on compressive strength and microstructure of the obtained fly-ash based geopolymers., (Copyright © 2018 Elsevier B.V. All rights reserved.)