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The challenges of handling user-hostile alkaline solutions in the conventional alkali-activated binders (AAB) have initiated the development of “just add water” or one-part solid-based AAB systems. This paper aims to present a preliminary investigation on the development of one-part ambient-cured alkali-activated binders produced by synthesising high-calcium fly ash (HCFA) and ground granulated blast furnace slag (GGBS) using sodium metasilicate anhydrous. Three test series were conducted in this study to investigate the effects of GGBS/binder, activator/binder and water/binder ratios on the fresh and hardened properties of the one-part synthesis AAB system. It was found that the SiO2/Al2O3 molar ratio plays an important role in the attainment of compressive strength and limits the amounts of solid activators effective in contributing to the alkali-activation reaction process. The optimum SiO2/Al2O3 molar ratio was found between 3.20 and 3.30. The test results revealed that the optimum proportion between HCFA and GGBS was discovered at a GGBS/binder ratio of 0.50. The optimum activator/binder ratio was between 0.08 and 0.12, and it is recommended that the water/binder ratio should not exceed 0.50. This study demonstrated the potential of the one-part synthesis method in the production of alkali-activated binder for practical structural applications.

A new environmentally friendly cemented oil shale residue–steel slag–ground granulated blast furnace slag backfill (COSGB) was prepared using oil shale residue (OSR), steel slag (SS) and ground granulated blast furnace slag (GGBS) as constituent materials. Based on univariate analysis and the Box–Behnken design (BBD) response surface method, the three responses of the 28 days unconfined compressive strength (UCS), slump and cost were used to optimize the mix ratio. Using a combination of scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP), the reaction products, microscopic morphology and pore structure of the specimens with the optimal mix ratio at different curing ages were analyzed. The influence of heavy metal ions from the raw materials and the COSGB mixtures on the groundwater environment was studied by leaching tests. The research demonstrates that the optimal mix ratio is GGBS mixing amount 4.85%, mass ratio of SS to OSR 0.82, and solid mass concentration 67.69%. At shorter curing age, the hydration products are mainly calcium alumino silicate hydrate (C-A-S-H) and calcium silicate hydrate (C-S-H) gels. With the increase of curing age, ettringite (AFt) and C-S-H gels become the main source of the UCS. Meanwhile, the porosity of the filler decreases continuously. The leaching concentration of heavy metal ions from the COSGB mixtures is all lower than the leaching concentration of raw materials and meet the requirements of the Chinese groundwater quality standard (GB/T 14848-2017). Therefore, this new COSGB cannot pollute the groundwater environment and meets backfill requirements. The proposed technology is a reliable and environmentally friendly alternative for recycling OSR and SS while simultaneously supporting cemented paste backfill (CPB).

Ferronickel slag and ground granulated blast-furnace slag (GGBFS) are solid waste by-products from the metallurgical industry. When incorporated into concrete, they help promote resource utilization, reduce hydration heat, and lower both solid waste emissions and the carbon footprint. To facilitate the application of ferronickel slag–GGBFS concrete in 3D printing, this study examines how aggregate size and nozzle diameter affect its performance. The investigation involves in situ printing, rheological characterization, mechanical testing, and scanning electron microscopy (SEM) analysis. Results indicate that excessively large average aggregate size negatively impacts the smooth extrusion of concrete strips, resulting in a cross-sectional width that exceeds the preset dimension. Excessively small average aggregate size results in insufficient yield stress, leading to a narrow cross-section of the extruded strip that fails to meet printing specifications. The extrusion performance is closely related to both the average aggregate size and nozzle diameter, which can significantly influence the normal extrusion stability and print quality of 3D printed concrete strips. The thixotropic performance improves with an increase in the aggregate size. Both compressive and flexural strengths improve with increasing aggregate size but decrease with an increase in the printing nozzle size. Anisotropy in mechanical behavior decreases progressively as both parameters mentioned increase. By examining the cracks and pores at the interlayer interface, this study elucidates the influence mechanism of aggregate size as well as printing nozzle parameters on the mechanical properties of 3D printed ferronickel slag–GGBFS concrete. This study also recommends the following ranges. When the maximum aggregate size exceeds 50% of the nozzle diameter, smooth extrusion is not achievable. If it falls between 30% and 50%, extrusion is possible but shaping remains unstable. When it is below 30%, both stable extrusion and good shaping can be achieved.

The present paper reports the results of experimental investigations performed to examine the feasibility of using fly ash (FA) and ground-granulated blast furnace slag (GGBS) geopolymers as barrier materials for waste containment facilities. The alkaline geopolymer is a blend of FA and GGBS with sodium hydroxide in concentrations varying from 1 to 5. The important properties of most barrier materials include strength and hydraulic conductivity. While FA can develop compressive strength through pozzolanic reactions, polymerized FA develops tensile strength. For the construction of barriers for landfills with higher heights, tensile strength assumes importance. To further improve the strength, FA can be amended with GGBS. Results indicate that the FA-GGBS mixture in the ratio of 40:60, when cured, exhibited higher strength at any molar concentration. Further, the hydraulic conductivity of the material, which is predominant for barriers in waste containment facilities, is studied. To examine the impact of the presence of heavy metals in the leachates, batch adsorption studies were executed on a 40% FA- 60% GGBS mixture. Leachate with nickel and lead were adapted for their retention within the barrier. It has been observed that the geopolymerized FA and GGBS can retain ionic metals. The retention capacity of heavy metals is due to their precipitation in the voids of the barrier material enabling further reduction in the hydraulic conductivity making geopolymer a sustainable barrier material.

This study examined the rheology of slag-based geopolymer concrete (GPC) incorporated with corncob ash (CCA). In an attempt to sustain an effective way of recycling our waste products and remedying land, water and air pollution, the study harnessed both ground granulated blast furnace slag (GGBFS) and corncob ash (CCA) as sustainable binders. In addition, sodium hydroxide (NaOH) solution and sodium silicate gel (Na2SiO3) were used as alkaline liquid. Method of volume by batching was adopted where GGBFS was replaced by CCA in 0, 20, 40, 60, 80, and 100%. The paste normal consistency was used to prepare the specimens for both initial and final setting times of the fresh concrete. However, slump and compacting factor values on the freshly made concrete were determined on both grade 30 MPa and grade 40 MPa concretes using the activation of 12, 14 and 16 molar concentrations of NaOH pellets. The experimental results show that the initial and final setting times increased with increasing CCA content; while the slump, compacting factor tests also increased with increasing CCA content. On the other hand, the workability of GPC reduced with increasing grade of concrete and molarity of NaOH solution. The study finding is beneficial in that fresh concrete remains workable for longer periods, thus resulting in lesser joints. It is also advantageous especially in hot weather conditions.

The study investigated the effects of rest period on the short-term mechanical property of geopolymer concrete (GPC) that could possibly be easy to embrace in the field to achieve an optimum strength performance. The study utilized both corncob ash (CCA) and ground granulated blast furnace slag (GGBFS) as sustainable construction binders with a view to building sustainable infrastructure. Also, sodium silicate gel (Na2SiO3) and sodium hydroxide (NaOH) solution was used as an alkaline activator, and prepared in 14 molar concentration of NaOH pellets using a mix ratio of grade 30 MPa and grade 40 MPa concretes. GGBFS was substituted in 0, 20, 40, 60, 80, and 100% by volume of CCA. The rest periods (RP) for the fresh concrete were selected as 1, 2, 3, 4 and 5 days before being demoulded. Thereafter, the concrete samples were removed from the moulds and cured under ambient conditions for 7, 28, 56 and 90 days. The compressive strength of the hardened concrete samples was then determined. The study findings reveal an optimum strength performance at 4 days rest period for all classes of concrete produced when compared with 1, 2, 3 and 5 days. Thus, this result can be practically employed and incorporated in the design of geopolymer concrete and at the construction site.

Concrete is the primary material use for the construction of many edifices, including buildings, roads, bridges, and dams. Though numerous hundreds of years ago, a few in consequential constructions and several elegantly designed masterpieces have been erected over time all across the planet. With regards to rising development initiatives, namely an intensified effort on high-quality yet economical structures, change has been a constant factor in the concrete sector. This transition has consequently brought with it a multitude of tangible innovation patterns in terms of how it is seen and, more specifically, how it is handled, blended, and so on. In any instance, strength and durability are the primary factors for concrete to be taken into account throughout these progressions. In illumination of this, due to enormous and widespread technological advancements, now have extraordinary varieties of concretes, such as double-blended concrete, It has excelled in enhancing the serviceability of the construction with which it is utilized compared to conventional concrete. This study concentrates on double blended concrete, highlighting its importance, constituent materials, packing techniques, testing procedures, and key components examined for this project.

Geopolymer concrete (GPC) offers a sustainable alternative by eliminating the need for cement, thereby reducing carbon dioxide emissions. Using durable concrete helps prevent the corrosion of reinforcing bars and reduces spalling caused by chemical attacks. This study investigates the impact of adding 5, 10, and 15% silica fumes (SF) on the mechanical and durability properties of GPC cured at 60 °C for 24 h. In the research, concrete specimens were submerged continuously for 62 days in four different chemicals: 6% sodium sulfate, 6% sodium chloride, 2% sulfuric acid, and 2% hydrochloric acid. The study assessed the effects of chemical exposure on concrete properties by examining water absorption, sorptivity, and compressive strength loss in GPC specimens. Maximum compressive strength, split tensile strength, and flexural strength of about 48.35 MPa, 4.91 MPa, and 5.01 MPa are achieved after incorporation of 10% SF in GPC after 28 days of curing. Results indicated that GPC with a significant dosage of SF (10%) improves its mechanical and durability properties. The maximum rebound number and ultrasonic pulse velocity are achieved after 90 days of curing with a 10% dosage of SF. Moreover, an economic analysis was conducted to confirm the economic viability.

Alkali-activated slag is considered as a sustainable construction material due to its environmentally friendly nature. To further promote the sustainable nature of alkali-activated slag, a sodium sulfate activator is suggested to be used since it can be obtained naturally and generates lower greenhouse gas emissions. However, the mixtures activated by sodium sulfate exhibit low early strength and very long setting times. This study investigates the effects of calcium hydroxide (Ca(OH)2) addition on some engineering properties such as rheology, setting time, mechanical properties, porosity, and microstructure of sodium sulfate activated ground granulated blast furnace slag (GGBFS). Furthermore, the changes of chemical groups in reaction products and phase identification have been evaluated by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction. Test results showed that Ca(OH)2 addition can substantially increase the reaction rate and the compressive strength at early ages. In addition, the very long setting times of the sodium sulfate-activated mixtures were shortened by the addition of Ca(OH)2. SEM analysis confirmed that the incorporation of excessive amounts of Ca(OH)2 could lead to a less well-packed microstructure although the reaction degree of GGBFS remained the same at later ages as compared to the sodium sulfate mixture. It was also revealed that in case of the Ca(OH)2 addition into sodium sulfate activator, the main reaction products are chain-structured C-A-S-H gels and ettringite.

The increase in cement production as a result of growing demand in the construction sector means an increase in energy consumption and CO2 emissions. These emissions are estimated at 7% of the global production of CO2. Ultra-high-performance concrete (UHPC) has excellent mechanical and durability characteristics. Nevertheless, it is costly and affects the environment due to its high amount of cement, which may reach 800–1000 kg/m3. In order to reduce the cement content, silica fume (SF) was utilized as a partial alternative to cement in the production of UHPC. Nevertheless, SF is very expensive. Therefore, the researchers investigated the use of supplementary cementitious materials cheaper than SF. Very limited review investigates addressed the impact of such materials on different properties of UHPC in comparison to that of SF. Thus, this study aims to summarize the effectiveness of using some common supplementary cementitious materials, including fly ashes (FA), ground granulated blast furnace slag (GGBS), metakaolin (MK) and rice husk ashes (RHA) in the manufacturing of UHPC, and comparing the performance of each material with that of SF. The comparison among these substances was also discussed. It has been found that RHA is considered a successful alternative to SF to produce UHPC with similar or even higher properties than SF. Moreover, FA, GGBS and MK can be utilized in combination with SF (as a partial substitute of SF) as a result of having less pozzolanic activity than SF.