Reactive magnesium oxide (MgO) and ground granulated blast furnace slag (GGBS) are cementitious materials introduced into sludge solidification, which not only reutilizes solid waste but also reduces cement consumption. Through the carbonation of reactive MgO and GGBS, the strength of the solidified sludge is further improved and CO2 is stably sequestrated in carbonate minerals. This paper investigates the strength and microstructural development and CO2 uptake of solidified sludge with varying water content, binder content, and ratio of MgO to GGBS. According to unconfined compressive strength (UCS) tests, when the binder content is 20% and the ratio of reactive MgO to GGBS is 2 & ratio;8, the strength of carbonated samples increases the most, which is six times that of the sample without reactive MgO. With binder content, the CO2 uptake of sample increases up to 2.1 g. Scanning electron microscope (SEM), X-ray diffractometer (XRD), and thermogravimetry-differential thermogravimetry analysis (TG-DTG) tests were conducted to systematically elucidate the micromechanism of carbonation of sludge solidified by reactive MgO and GGBS. Various carbonation and hydration products enhance the soil strength through filling pores and integrating fine particles into bulk aggregates. As the ratio of reactive MgO to GGBS increases, dypingite and hydromagnesite were converted into nesquehonite with better morphological integrity, and thus strengthens the soil skeleton. Diverse calcium carbonate polymorphs from carbonated GGBS also promote sludge strength growth and CO2 sequestration. Test results indicate that the addition of reactive MgO further improves the hydration and carbonation properties of GGBS, so the CO2 uptake grows with the ratio of reactive MgO to GGBS. The synergistic effect of reactive MgO and GGBS increases the carbonation performance of the mixed binder, so likewise the compressive strength.

The purpose of this study was to evaluate the sustainability benefits of Class F fly ash (FA), lime sludge (LS), and ground granulated blast furnace slag (GGBS)-based geopolymer-stabilized Edgar plastic kaolin (EPK) clay using the sustainability index (ISus) approach. Geotechnical engineering operations usually precede most infrastructural projects, making pavement construction an integral contributor to various environmental effects, due to the production of enormous quantities of greenhouse gas emissions through soil stabilization activities. To nip these concerns in the bud, effective integration of these environmental implications must be achieved during the geotechnical planning phase. The life cycle assessment (LCA) method was used to assess a wide range of environmental effects of a project, from raw material procurement, manufacturing, transportation, construction, and maintenance to final disposal. It is a well-recognized tool for designing environmentally sustainable projects. Experimental results from the geopolymer-stabilized EPK clay showed a notable improvement in unconfined compressive strength of the geopolymer-stabilized clay with 15% (FA + LS) and 5% (FA + GGBS) contents of up to 697% and 464%, respectively, after 28 days of curing at elevated temperature, 70 degrees C. The sustainability index (ISus) of geopolymer and lime treatment methods was analyzed based on the concept of environmental, resource consumption, and socioeconomic concerns, which quantifies the sustainability through greenhouse gas emission, environmental impacts, and the cost of utilizing FA, LS, and GGBS in soil stabilization compared with traditional lime. LCA was conducted for traditional lime treatment, FA-LS, and FA-GGBS geopolymer-stabilized subgrades to determine the most sustainable treatment method. From the sustainability analysis, using FA, LS, and GGBS as geopolymer stabilizers for kaolin clay reduced the global warming potential by 98.03% and 77.55% over the traditional lime stabilizers at 8% dosage. More importantly, results from the sustainability index (ISus) computations showed that FA-LS (ISus = 12.88) and FA-GGBS (ISus = 29.72) geopolymer treatment methods of EPK clay subgrade soils are more sustainable alternatives compared to the traditional lime (ISus = 48.07) treatment method.

Civil engineering structures made upon expansive soils known in India as Black Cotton (BC) soils are susceptible to structural damages due to their seasonal swell-and-shrink behaviour. This study focuses on assessing the mechanical performance of BC soil stabilised using unconventional binders, specifically Sugarcane Bagasse Ash (SCBA) and Ground Granulated Blast Furnace Slag (GGBS) with different proportions. The experimental evaluation included Compaction tests, Unconfined Compressive Strength (UCS) tests, Triaxial tests, and Atterberg's limits tests. Additionally, mineralogical and morphological studies were carried out using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and chemical analysis using x-ray fluorescence spectroscopy analysis (XRF). The results showed that the mixture containing 21% SCBA and 9% GGBS produced cementitious-siliceous-hydrate (C-S-H) molecule, which improved the strength. Based on the soil-binder percentage ratio obtained from UCS tests, a regression equation was developed to estimate consolidated soil strength. The regression model, exhibiting an impressive R2 value of 93.69%, was analysed within the framework of existing empirical correlations by other researchers. This statistical model, with its good fit, is a useful tool for evaluating the compressive strength of stabilised expansive soil. The findings provide insights into successful stabilisation solutions for expansive soils found locally and globally.

Expansive soils swell when wet and shrink when dry, causing differential settlements that can lead to structural failures in roads and buildings. In cases where these soils cannot be avoided, improving their stability is essential. This study investigates the use of two binders, ground granulated blast-furnace slag (GGBS) and bagasse ash (BA), byproducts of steel and sugarcane processing, respectively, to reduce soil swelling and enhance stability by assessing the mechanical behavior of reinforced expansive soil. To evaluate the behavior of reinforced expansive soils, tests such as Atterberg limits, compaction, swelling potential, and direct shear were conducted. Results indicated that as reinforcement levels increased to an optimal threshold (3 % GGBS and 12 % BA), the optimum moisture content rose, while maximum dry unit weight generally decreased. A 15 % increase in moisture content and a 3.16 % decrease in maximum dry unit weight were observed with reinforcement. Cohesion decreased by 27 % in soaked conditions and 31 % in unsoaked, while the angle of internal friction rose by 106 % and 111 %, respectively, at the maximum reinforcement threshold. These additives also improved shear strength, reduced swelling potential, and lowered plasticity index, shifting the soil behavior from clay-like to silty. The results show that bagasse ash and GGBS effectively enhance soil properties and provide a sustainable solution for soil stabilization in construction.

Sensitive marine clays (SMCs) often pose considerable problems in the construction of embankments for transportation structures. In this study, extensive mechanical, microstructural, and monitoring experiments were carried out to evaluate the evolution of mechanical properties of SMCs stabilized via Deep Mixing Method. The results indicate that unconfined compressive strength and secant modulus increase with curing time. A significant improvement in mechanical properties is observed at early ages. Higher binder contents produce higher mechanical properties after same curing period. However, excess binder content does not provide significant improvement effects. The addition of ground granulated blast furnace slag (GGBFS) results in higher mechanical properties after long-term curing, and the enhancing degree is more evident with a higher proportion of GGBFS. But the situations are reversed at young age due to the retarding effect of GGBFS. These observations are also supported by results of physical properties, mercury instruction porosimetry, suction monitoring, and X-ray diffraction analyses. In addition, predictive models are established based on elastic-plastic theory and binder hydration model. The developed models are implemented in COMSOL Multiphysics and validated against experimental results. A good agreement is observed between experimental and predicted results which confirms the ability of developed models to predict the mechanical characteristics.

Over the last 20 years, the development of electrically conductive composites for removing snow and ice from transportation infrastructure has received exceptional traction. However, these composites need to exhibit stable electrical conductivity and high mechanical properties to be sustainable and cost-effective. Towards this goal, the article investigates the roles of ground granulated blast furnace slag (BFS) and copper slag (CS) content, in addition to hooked-end steel fiber length, on the electrical properties of eco-friendly ultra-high performance hybrid fiber-reinforced self-compacting concrete (HFR-SCC) for the first time in the literature. For this purpose, sixteen eco-friendly electrically conductive ultra-high-performance HFR-SCC were designed based on the variable parameters of four different BFS/total binder ratios (20, 40, 60, and 80 %), a CS/total fine aggregate ratio of 50 %, and two different hooked-end fiber lengths (30 and 60 mm), while all mixes used 1.75 % by volume fraction of steel fibers. After determining the workability properties (slump-flow and T500 values) of all mixes, compressive strength and electrical resistivity/conductivity tests of 90-day specimens were conducted. Additionally, environmental and economic evaluations of all mixes in terms of sustainability were performed in order to clarify the effects of the variable parameters. Taking into account the experimental results obtained, it was observed that all electrically conductive ultra-high performance HFR-SCC mixes demonstrated satisfactory workability properties, while the compressive strength values reached to impressive values of 127 MPa. The optimum BFS/total binder ratio was identified to be 40 % for higher compressive strength and conductivity of ultra-high performance HFR-SCC specimens. On the other hand, the addition of CS to the mixes resulted in an increase of almost 9 % in compressive strength compared to one without CS, while at the same time, a significant increase of approximately 363 % was observed in the electrical conductivity values of the specimens. As for the influence of different lengths of hooked steel fibers, the use of 30 mm length hooked-end steel fibers in HFR-SCC mixes performed better in terms of compressive strength, whereas 60 mm fibers performed better regarding electrical conductivity. In conclusion, this experimental work has evidenced that it is possible to develop an ecofriendly and sustainable electrically conductive ultra-high performance cementitious composite (the optimal mix compressive strength and electrical resistivity values were 127 MPa and 2242 Omega.cm, respectively) by using waste from different industries such as iron and copper. Thus, it will provide important insights for the design and application of future electrically conductive concretes, which can be an important alternative in efficient active deicing and snow-melting applications.

Sulfate soils often caused foundation settlement, uneven deformation, and ground cracking. The distribution of sulfate-bearing soil is extensive, and effective stabilization of sulfate-bearing soil could potentially exert a profound influence on environmental protection. Ground granulated blast furnace slag (GGBS)-magnesia (MgO) can be an effective solution to stabilize sulfate soils. Dynamic cyclic loading can be used to simulate moving vehicles applied on subgrade soils, but studies on the dynamic mechanical properties of sulfate-bearing soil under cyclic loading are limited. In this study, GGBS-MgO was used to treat Ca-sulfate soil and Mg-sulfate soil. The swelling of the specimens was analyzed by a three-dimensional swelling test, and the change in compressive strength of the specimens after immersion was analyzed by an unconfined test. The dynamic elastic properties and energy dissipation of GGBS-MgO-stabilized sulfate soils were evaluated using a fatigue test, and the mineralogy and microstructure of the stabilized soils were investigated by X-ray diffraction and scanning electron microscopy. The results showed that the maximum swelling percentage of stabilized Ca-sulfate soil was achieved when the GGBS:MgO ratio was 6:4, resulting in an expansion rate of 14.211%. In contrast, stabilized Mg-sulfate soil exhibited maximum swelling at GGBS:MgO = 9:1, with a swelling percentage of 5.127%. As the GGBS:MgO ratio decreased, the dynamic elastic modulus of stabilized Ca-sulfate soil diminished from 2.8 MPa to 2.69 MPa, and energy dissipation reduced from 0.02 MJ/m3 to 0.019 MJ/m3. Conversely, the dynamic elastic modulus of stabilized Mg-sulfate soil escalated from 2.16 MPa to 6.12 MPa, while energy dissipation decreased from 0.023 MJ/m3 to 0.004 MJ/m3. After soaking, the dynamic elastic modulus of Ca-sulfate soil peaked (4.01 MPa) and energy dissipation was at its lowest (0.012 MJ/m3) at GGBS:MgO = 9:1. However, stabilized Mg-sulfate soil exhibited superior performance at GGBS:MgO = 6:4, with a dynamic elastic modulus of 0.74 MPa and energy dissipation of 0.05 MJ/m3. CSH increased significantly in the Ca-sulfate soil treated with GGBS-MgO. The generation of ettringite increased with the decrease in the GGBS-MgO ratio after immersion. MSH and less CSH were formed in GGBS-MgO-stabilized Mg-sulfate soil compared to Ca-sulfate soils. In summary, the results of this study provide some references for the improvement and application of sulfate soil in the field of road subgrade.

Clay soils, characterized by their cohesiveness and water retention capacity, exhibit low aeration and tend to swell when water is absorbed, leading to subsequent contraction. The moisture content significantly affects the properties of marine clay, resulting in low strength and high compressibility. Traditional stabilizers such as lime and cement have been extensively studied for their ability to enhance the compressive strength, reduce swelling potential, and improve the overall durability of the soil. These stabilizers offer numerous benefits in terms of soil properties and have been extensively researched. However, due to environmental concerned, geopolymer has been explored as an alternative replacement to the traditional stabilizer. In this research, stabilized clay soil using ground granulated blast furnace slag (GGBS) based geopolymer were prepared and tested for the compressive strength and durability characteristic. Different percentages of GGBS (10%, 20% and 30%) were used to stabilize the clay soil with different activator/binder ratio (0.5, 0.75 and 1.0) and initial moisture content (0.75wL, 1.0wL, and 1.25wL). Cement stabilized specimen were also prepared for comparison. Unconfined compression test and wet-dry cycle were performed to evaluate the compressive strength and durability of treated soil. It was found that the strength of treated sample decreased with increment of initial moisture content. Increasing the binder dose was necessary to achieve the strength requirements for high water content soils. Thus, it shows that the use of a GGBS based geopolymer binder for the purpose of stabilizing soft soil is an alternative that is both effective and environmentally friendly.