Ratio Of Slag Research Articles

The Influence of Lime Variations on the Unconfined Compressive Strength of Inorganic Clay Soil Stabilized with a Combination of Nickel Slag and Aluminum Hydroxide

Soil stabilization is a ground improvement technique aimed at enhancing the strength and bearing capacity of soil, particularly in road construction projects. The combination of multiple stabilization materials allows for achieving better improvements in soil bearing capacity. The use of industrial waste materials offers an eco-friendly solution while repurposing materials that are typically discarded. This study focuses on the engineering application of adding limestone as a natural pozzolanic material. The research involves laboratory testing to measure the unconfined compressive strength (UCS) of stabilized clay soil samples. The addition of stabilization materials is based on weight ratios, where the ratio of nickel slag to aluminum hydroxide is 1,5, and limestone is added in varying proportions of 2%, 4%, and 6%. The curing of the test specimens is carried out over periods of 3, 7, 14, and 28 days to examine the influence of curing time on the improvement of soil UCS values. The results indicate that the addition of nickel slag and aluminum hydroxide significantly enhances the soil’s UCS. Furthermore, variations in limestone content show that increasing its concentration up to 6% yields optimal results in improving soil strength. This study concludes that the combination of waste materials and limestone can effectively enhance the mechanical characteristics of soil, providing a sustainable and environmentally friendly solution for soil stabilization in various infrastructure projects.

Experimental Study of Alkali-Excited Steel Slag–Granulated Blast Furnace Slag–Cement-Based Grouting Material Based on Response Surface Methodology

This study aims to refine the ratio of alkali-activated steel slag (SS) to granulated blast furnace slag (GBFS)–cement-based grouting materials, with the dual objectives of cost reduction and performance enhancement. By employing single-factor experiments and response surface methodology (RSM), we have pinpointed the critical factors that influence the slurry’s performance and developed a regression model to assess the impact of these factors and their interplay. Our findings indicate that the compressive strength initially increases with higher SS content but subsequently declines. Additionally, an increase in alkali content and activator modulus is beneficial for strength improvement. However, beyond an alkali content of 8%, the 28-day strength is observed to decrease. Through meticulous model analysis, we have determined the optimal ratio to be 7.07% SS content, 7.82% alkali content, and an activator modulus of 1.8. The material’s performance at this ratio satisfies construction specifications. This research not only offers a cost-effective and high-performance grouting solution for geotechnical applications but also pioneers a novel approach to the resourceful utilization of solid waste materials, such as SS.

Thermodynamic Simulation and Laboratory-Scale Experiments of Tin Smelting at Al2O3 Saturation.

A significant issue encountered in smelting operations is the corrosion of refractory materials that come into direct contact with the molten slag. Magnesia-based refractories are commonly used in nonferrous smelting operations. On the other hand, alumina-based refractories emerge as a possible alternative, particularly when dealing with the unpredictable slag compositions, owing to alumina's amphoteric characteristic. Nevertheless, prolonged interaction with aggressive slag can lead to substantial degradation of the refractory material. The research on the use of alumina-based refractories in tin smelting is not well known. Hence, this paper focuses on slag-refractory interaction in the tin smelting process at Al2O3 saturation. A series of thermodynamic simulations and laboratory-scale experiments were conducted. The software FactSage 8.2 was employed to simulate the solubility of Al2O3 in slag and the ratio of Sn content in slag to Sn content in metal under the conditions relevant to tin concentrate smelting and tin slag reduction stages. The experiments utilized synthetic slag composed of SnO-FeO x -CaO-SiO2-Al2O3, conducted in a vertical tube furnace at a temperature of 1300 °C for 2 h. The experimental parameters that were varied were the Fe/SiO2 ratio in slag (0.3-1.6), CaO/SiO2 ratio in slag (0.3-1.6), and Sn content in slag (3-20%). The simulation results revealed that the solubility of Al2O3 during the tin concentrate smelting and tin slag reduction stages was significantly influenced by temperature, Fe/SiO2, and CaO/SiO2, whereas the ratio of the Sn content in slag to the Sn content in the metal appeared to be independent of these variables, being primarily influenced by the oxidation condition. Experimental results at 1300 °C showed that varying Fe/SiO2 within the range of 0.3-1.6 led to an initial increase in Al2O3 solubility in slag at lower Fe/SiO2 ratios, followed by a decrease in Al2O3 solubility in slag at higher Fe/SiO2 ratios. A similar trend was observed with variations in CaO/SiO2 within the same range, accompanied by the formation of new solid phases, such as hercynite spinel at lower CaO/SiO2 ratios and melilite at higher CaO/SiO2 ratios. Moreover, under constant CaO/SiO2 and Fe/SiO2 ratios of 0.3, reducing the Sn content in the slag was found to increase the solubility of Al2O3 due to the creation of a more aggressive slag toward Al2O3 solid.

Evaluation of Concrete Compressive Strength Prediction Using the Maturity Method Incorporating Various Curing Temperatures and Binder Compositions.

This study aims to systematically analyze the effects of different curing temperatures, unit binder content, and the mixture ratios of ground granulated blast-furnace slag and fly ash based on ordinary Portland cement in binders on the development of concrete compressive strength. Particularly, the study evaluates strength characteristics by calculating the maturity equivalent to 28 days of curing at 20 °C. A model based on the relationship between maturity and strength was applied to predict the compressive strength, and the experimental data were analyzed to derive strength coefficients for each variable. The results showed that at a low temperature of 5 °C, the actual strength was lower than the predicted strength, leading to higher error rates. In contrast, at temperatures of 20 °C and 40 °C, the coefficient of determination (R2 > 0.90) for the predictive equation was high, and the error rates were reduced to within 10%. The study demonstrates that by combining the maturity method with the strength-maturity relationship, the concrete compressive strength can be effectively predicted under specific curing and binder design conditions.

Experimental of verification of alternative hydraulic binders flexural and compressive strength

The paper deals with the investigation of alternative binders, namely the two available samples N6 and N7 with comparison from the reference sample CEM I 42.5R. Both testing binders are provided by company Destro. It is a product that contains different ratios of fly ash and slag. By examining the properties, the mix was compared in different proportions and subsequently tested for flexural strength and compressive strength. The results showed the effect of curing time and cement to binder ratio after 28 and 84 days.

A novel neutralization process for improving dehydration performance of industrial by-product gypsum

By-product gypsum, produced through the traditional neutralization precipitation method for treating industrial acidic wastewater, is difficult to recycle due to its high moisture content. In this study, we proposed a novel neutralization process i.e. the two-stage neutralization method. By-product gypsum was used as an alkaline neutralizer and recycled as seed crystals for the first time. The original by-product gypsum has the poor dehydration performance due to its small particle size and the presence of colloids on its surface. After adding the by-product gypsum to the acidic wastewater, the ratio of CaO/SO3 in the system descended and colloids were dissociated. On the one hand, the alkaline component of the incomplete reaction continues to play a neutralizing role. On the other hand, CaSO4·2H2O particles act as seed crystals, promoting rapid growth of new crystals along their surface, which effectively improved crystallization performance and dehydration performance of the neutralization slag (outward discharge of slag). Compared with the original method, the wet weight of the neutralization slag is decreased from 186.0 g/L to 88.8 g/L, and the water cut is declined from 64.5 % to 34.1 %. The utilization ratio of the carbide slag augmented from 63.0 % to 99.47 %.

Enhancing Mechanical Properties of Expansive Soil Through BOF Slag Stabilization: A Sustainable Alternative to Conventional Methods

This study investigates the stabilization of expansive soil using basic oxygen furnace (BOF) slag, an eco-friendly steel by-product, as an alternative to conventional stabilizers like ordinary Portland cement. By evaluating varying concentrations of BOF slag and lime as an activator, the research aims to improve the soil’s mechanical properties, addressing issues like low bearing capacity and high shrink–swell potential. Bentonite clay was treated with different BOF slag ratios (10%, 20%, and 30%) and activated with lime (1%, 3%, and 5%). After mixing and compaction, samples were cured and tested for unconfined compressive strength (UCS), shear wave velocity (BE), and free swell. Microscopic analyses (SEM) provided insight into structural changes post-stabilization, revealing improved properties with increased BOF and lime concentrations. Notably, stabilization with 30% BOF slag and 5% lime achieves a compressive strength of 810 kPa, meeting the minimum subgrade soil stabilization requirement (700 kPa) set by the Federal Highway Administration. This research underscores the potential of BOF slag as a sustainable and practical material for bentonite clay stabilization, offering a promising solution for enhancing soil properties while contributing to environmental sustainability through industrial by-product repurposing.

Design and microstructural analysis of the mixture proportion of alkali-activated fly ash-slag composite cementitious material

Abstract To explore the resource utilization of fly ash, slag, and coal gangue, the composition of hydration products and strength characteristics of fly ash-slag composite cementitious material (FSGF) were studied with NaOH as an alkali activator. First, response surface analysis was used to determine factors influencing the optimal NaOH content, basalt fiber dosage, and length to obtain the complete mix ratio of the composite cementitious material. Microscopic techniques such as XRD, FTIR, TG-DSC, and SEM were employed to analyze the crystal structure, thermal properties, and micro-morphology of the composite cementitious material, and to investigate the mechanism of NaOH-activated fly ash-slag cementitious material. The results indicated that the sensitivity of each factor affecting the mechanical properties of the composite cementitious material followed this sequence: NaOH content > basalt fiber length > basalt fiber dosage, with varying degrees of interaction among them. When the mass ratio of fly ash, slag, and coal gangue was 5:1:4, with 3% NaOH by weight, 2% basalt fiber dosage, and a fiber length of 3 mm, the optimal mix was achieved. The composite material achieved a compressive strength of 8.97 MPa after 28 days of standard curing at room temperature. NaOH, as an alkali activator, provided the strong alkaline environment required for the initial hydration of fly ash-slag composite cementitious materials, promoting the hydration of slag and fly ash. The hydration products in the fly ash-slag composite system were unevenly distributed, primarily consisting of gels like C-S-H, C-A-H, and C-A-S-H. NaOH was highly effective as an alkali activator in the fly ash-slag system.

Facile construction of superhydrophobic porous red mud/slag-based geopolymer for thermal insulation and oil/water separation

Red mud (RM) is difficult to be comprehensively utilized and has a serious impact on the environment due to the high alkalinity, low activity, and high content of harmful substances. In this study, porous RM-based geopolymers (PRGMs) with high porosity ratio (76.83%) and compressive strength (1.16 MPa) were prepared by controlling the ratio of slag and RM (60%) and curing temperature (70 °C) and adding a mechanical foaming agent (MFA: 12%). The flux of the PRGMs was as high as 10180.33 L·m-2·h-1 at a thickness of 3 mm. The equilibrium cold surface temperature was reduced from 175.6 to 131.7 °C compared to a structure without MFA. In addition, a superhydrophobic PRGMs (SPRGMs) was successfully modified by chemical vapor deposition using water and polymethylhydrosiloxane at 120 °C for 3 h. It had excellent superhydrophobic properties (159.04°) and low thermal conductivity (0.1922 W·m⁻1·K⁻1). The contact angle of the SPRGMs was still >150° even after treatment under real simulation conditions including acid/alkali/salt solution contact/immersion, variable temperature (-20 to 450 °C for 2 h), ultraviolet aging (60 h), and physical abrasion (10 cycles). The SPRGMs achieved 100% desorption of light/heavy oils with excellent and stable cycling performances. The contact angle was still larger than 151° after 10 cycles. Furthermore, the SPRGMs are effective for a continuous treatment of oil/water emulsions and mixtures by gravity, which provides a new concept for the development of thermal insulation building materials, large-scale treatment of RM, and industrial treatment of oil/water pollution.

Effect of GBFS ratio and recycled steel tire wire on the mechanical and microstructural properties of geopolymer concrete under ambient and oven curing conditions

In this study, the effects of waste steel wire ratios, granulated blast furnace slag (GBFS) ratios, and different curing methods on geopolymer concrete (GPC) were investigated. For this purpose, 12 mixtures were produced and eight of them were cured under ambient conditions and the remaining four were cured in an oven. Steel wire ratios and GBFS ratios were added to GPC as 0–1–2–3 % and 0–10–20 % by volume and weight, respectively. As a result of the mixtures, cubes, cylinders, and beams were obtained and these elements were subjected to compression, tensile, and flexural tests. As a result of the tests, the compressive strengths of the specimens were obtained as 8.5 %, 19.7 %, and 24.9 % for ambient curing and 10.4 %, 23.2 %, and 32.2 % for oven curing, respectively, as the steel wire fiber increased from 0 % to 3 %. The maximum compressive strength of the oven-cured specimen with 3 % steel wire fiber was measured as 42.56 MPa. The tensile strength of GPC also increased as the steel wire increased. The highest tensile strength was obtained with 3 % steel wire. In addition, oven curing conditions increased the tensile strength more than ambient curing. The flexural strength (FS) increased by 21.3 %, 29.4 %, and 33.8 % with increasing steel wire ratios of 1 %, 2 %, and 3 %, respectively. The FS was further increased by oven curing conditions and the maximum FS was achieved with 3 % steel wire. In ambient curing conditions, a successful geopolymerization was achieved due to the high calcium content in the samples containing 20 % GBFS. This allowed to obtain similar strengths between ambient curing and oven curing. Although the oven curing values were higher, similar results were obtained for the samples cured in an ambient containing 20 % GBFS. As a result of the study, mixtures containing 3 % steel wire and 20 % GBFS provided sufficient strength without oven curing and increased the usability of GPC under ambient conditions.

Strength formation mechanism and composition design of fly-ash and carbide-slag-stabilized mine solid waste road base

To achieve effective utilization of large-scale solid waste, this study prepared subgrade materials using mine waste, fly ash, and carbide slag as raw materials. The effects of the basic structure and composition ratio of the three raw materials on the performance of the subgrade materials were investigated. The mechanisms and strength enhancement effects of fly ash, carbide slag, and fly ash–carbide slag composite-stabilized mine solid waste were analyzed. The optimal mixing ratio of the subgrade materials was determined. When the mass ratio of carbide slag to fly ash was 1:4 and the total addition amount was 20%, the subgrade material had an optimal moisture content of 16.8%, maximum dry density of 1.70 g/cm3, and 90-day compressive strength of 8.51 MPa. This fully solid waste inorganic binder-stabilized subgrade material can effectively utilize large quantities of solid waste and meet the performance requirements of subgrade materials, thereby providing a good technical solution for large-scale solid waste disposal.

A Robust Static Model of Basic Oxygen Furnace for Analyzing Emerging Steelmaking Scenarios

A robust static model, which incorporates emerging steelmaking scenarios in terms of solid charge mix with the given hot metal in basic oxygen furnace process, is developed. It employs mass and enthalpy balances to comprehend nonequilibrium conditions, considering four key empirical parameters: iron loss, post‐combustion ratio, heat loss, and undissolved lime content in slag, which are fine‐tuned using plant data through a multivariate approach, ensuring the reliability. The model is validated in a basic oxygen furnace (BOF) shop using data from over 4000 heats, achieving a strike rate of ≈77% for input lime prediction within ±1 ton and ≈80% for input oxygen prediction within ±600 Nm3. Model implementation in BOF shop provides valuable guidance to the operators, resulting in the reduction of average oxygen and lime consumption by 139 Nm3 and 652 kg heat−1, respectively. The model also enables the determination of the maximum scrap utilization of ≈16% for 0.8% silicon and ≈14% for 0.6% silicon in hot metal, respectively. The model aids in calculating the maximum tap temperature for varying hot metal silicon and iron ore addition. Overall, the model optimizes primary steelmaking, enhancing efficiency, reducing resource consumption, and offering insights into alternative iron sources like direct reduced iron.

Carbonation resistance of fly ash/slag based engineering geopolymer composites

Engineering geopolymer composites (EGC) are promising environmentally friendly building materials with excellent mechanical properties. However, the durability of EGC is compromised by gradual carbonation from atmospheric exposure. For the first time, this study provided an insight of the carbonation of EGC by comprehensively investigating the effect of mix design, such as fly ash/ground granulated blast furnace slag ratio (FA/GGBS ratio), alkali content, water/binder ratio (W/B ratio) and polyethylene (PE) fibre content, on its carbonation resistance. Our results showed the components in EGC affected the carbonation through the alternation of microstructures. An increase of FA content and W/B ratio significantly increased the carbonation depth by 206.6 % and 116.3 % respectively due to the increased porosity and transition pore fraction, resulting in more than 30 % reduction in tensile strength and 15 % reduction in compressive strength. However, increased alkali and fibre content prevent carbonation with around 60 % and 26 % decrease of the carbonation depth, leading to a less loss of the mechanical properties. Furthermore, we tested the pH values of the EGC along the carbonation depth, proposing a novel approach to assess the carbonation degree by dividing the area into completely carbonated area (pH around 9.21–10.44) and non-carbonated area (pH around 12.58–13.37). These findings provide insights for mitigating carbonation effects in EGC and facilitate the widespread use of this sustainable material in construction applications, ensuring long-term durability and reliability.

Experimental Study on Optimization of Consolidation Parameters of Silty Clay Based on Response Surface Methodology: A Case Study on the Protection and Restoration of the Ming and Qing Dynasty Hangzhou Seawall Site

The preservation of the ancient seawall site is a focal point and challenge in the protection of historical relics along Hangzhou’s Grand Canal in China. This endeavor holds significant historical and contemporary value in uncovering and perpetuating Hangzhou’s cultural heritage. Researchers investigating the Linping section of the seawall site aimed to address soil site deterioration by selecting environmentally friendly alkali-activated slag cementitious materials and applying the response surface method (RSM) to conduct solidification experiments on the seawall soil. Researchers used the results of unconfined compressive strength tests and microscopic electron microscopy analysis, considering the comprehensive performance of soil solidification mechanisms and mechanical properties, to establish a least-squares regression fitting model to optimize the solidification material process parameters. The experimental results indicate that the optimal mass ratio of lime, gypsum, and slag for achieving the best solidification process parameters for the seawall soil, with a 28-day curing period, is 1:1.9:6.2. This ratio was subsequently applied to the restoration and reconstruction of the seawall site, with parts of the restored seawall exhibited in a museum to promote the sustainable conservation of urban cultural heritage. This study provides theoretical support and practical guidance for the protection and restoration of soil sites.

Properties and hydration mechanism of slow-setting and expansive cement based on CFB ash and slag

Aiming at the problems of long construction time and easy shrinkage cracking of pavement base, the slow-setting and expansive cement (SEC) was prepared using circulating fluidized bed ash and slag (CFBA and CFBS), S95 ground granulated blast furnace slag (GGBFS), and silica fume (SF) as supplementary cementitious material in this paper. By adjusting the content of supplementary cementitious material, the ratio of ash and slag, the performance of SEC was evaluated by the indexes of water consumption of standard consistency, setting time, flexural and compressive strength. The hydration products of mortar samples and the influence mechanism were studied by means of XRD, TG-DTG, FTIR, and SEM-EDS. The results showed that when the SF content was 6 %, the compressive strength of the mortar specimens reached its maximum (35.19 MPa) at 28 days, which increased by 23.04 % compared to the control group. Meanwhile, the free calcium oxide and gypsum in CFBA reacted under alkaline conditions to form ettringite (AFt) and C-S-H gel, which caused the volume expansion of cement and led to a decrease in shrinkage within the cement system. SEC has higher mechanical properties and much smaller shrinkage cracks than ordinary cement. Therefore, replacing part of the cement by solid waste such as CFBS to prepare SEC to compensate for the shrinkage of the pavement base is an effective way to reduce pavement cracking.

Investigation on utilization and microstructure of fine iron tailing slag in road subbase construction

The iron tailing slag is solid waste produced during the iron ore refining process and is considered a potential hydraulic material that can be used in road construction. This study focused on fine iron tailing from a location in Hebei, China, to prepare road subbase specimen with a high proportion of fine iron tailing. The research investigated the effects of raw material ratios and additives on the 7-day unconfined compressive strength and elastic modulus of the specimens, as well as their mechanisms of action. A series of single-factor experiments were conducted using a controlled variable approach, including the mass ratio of slag to fly ash (SFR), cement content, and calcium oxide content. It was found that under the conditions of an SFR of 6:1, a calcium oxide content of 4 %, a cement content of 5 %, and a water-resistant base stabilizer additive of 0.02 %, the eco-friendly road subbase specimen achieved a 7-day unconfined compressive strength of 1.97 MPa and an elastic modulus of 286 MPa, demonstrating good mechanical properties. Additionally, a linear relationship was observed between the cement content and the 7-day unconfined compressive strength of the specimen: Rc = 0.253w + 0.793. Using characterization techniques such as X-ray Fluorescence Spectroscopy (XRF), X-Ray diffraction (XRD), Scanning Electron Microscope & Energy Dispersive Spectroscopy (SEM-EDS), and Fourier Transform Infrared Spectroscopy (FTIR), a dense structure was observed in the slag-based road subbase specimen, composed of needle-rod hydrated calcium silicate (C-S-H) gel, hydrated calcium aluminate (C-A-H), hydrated calcium silicoaluminate (C-A-S-H), flake-like hydrated magnesium silicate (M-S-H) gel, and a system containing a large amount of Forsterite. Finally, the study examined the impact mechanisms of five additives—Na2CO3, Na2O·2SiO2, triethanolamine (C6H15NO3), CaSO4, and a water-resistant base stabilizer—on the compressive strength and elastic modulus of the slag road base specimen. It was concluded that the water-resistant base stabilizer significantly improved strength and reduced water absorption. The road subbase specimen can be used by simply mixing at room temperature and pressure, offering broad prospects for industrial application. This technology provides a paradigm for the comprehensive utilization of fine iron tailing and the preparation of new road subbase materials.

Rheology and buildability of sustainable 3D printed magnesium potassium phosphate cement composites incorporating MgO-SiO2-K2HPO4

MKPCs with unique advantage of superior strength, excellent durability and high thixotropy provides alternative binder for 3D printing. The acid-base reaction between dead burnt MgO and K2HPO4 is intense and the retarding effect is limited in practical cases. This paper presents the investigation of MKPCs incorporating MgO-SiO2-K2HPO4 binders prepared with dead burnt MgO, soluble phosphate (K2HPO4•3 H2O) and silica fume (SF). The effects of magnesium-to-phosphate (M/P) mass ratio, SF and slag ratios on rheological properties and the printability were tailored and setting time reached to 50 min by increasing the alkaline environment of the solution. In addition, the pozzolanic activity of SF and slag were synergistically motivated and thus promoted the precipitation of K-struvite, MgSiO3 and C-(A)-S-H hydrates. Two-stage Athix values were calculated to describe the structuration rate. It is confirmed excellent thixotropy was dominated by early-age physical re-flocculation and later-age cement hydration. Although the structure deformation increased significantly as SF content increased, the beneficial effect of SF content on the increase of strength is significantly important than that of adverse effect on the buildability. Slag powder and fine aggregate were incorporated to make the binders more “printable”. A cylinder with 16 layers on optimum mixture was printed without deformation.

Mineralized carbon sequestration evaluation of coal-based solid waste consolidated backfill: A novel data-driven approach

The coal mining industry and its byproduct utilization are confronted with challenges such as the accumulation of coal-based solid waste and the emission of CO2, which seriously jeopardize environmental protection. A lucrative way of mitigating these problems is CO2 mineralization storage technology of coal-based solid waste consolidated backfill. Its successful realization stringy depends on the CO2 mineralization sealing stock and requires accurate account of the carbon sequestration rate of cemented backfill. Therefore, this study proposes a novel hybrid intelligent model combining the adaptive enhanced whale optimization algorithm and the support vector regression (A-E-WOA-SVR) to forecast the carbon sequestration performance of cemented backfill. The respective data set of cemented backfill was obtained through laboratory tests under different values of seven factors influencing the carbon sequestration rate, including water–solid ratio, cement ratio, fly ash ratio, slag ratio, curing pressure, curing temperature, and curing time. The results exhibit that the adaptive enhanced whale optimization algorithm can effectively optimize the hyperparameters of the support vector regression. The A-E-WOA-SVR hybrid intelligent model proposed in this paper accurately predicted the carbon sequestration rate of cemented backfill. Coefficient of determination, mean absolute error, root mean square error, and other indices were used to evaluate the performance of the intelligent prediction model. The obtained values of these indices implied small errors. The mean impact value sensitivity analysis revealed that water–solid ratio, cement content, curing pressure, and curing time were the key sensitive factors controlling the carbon sequestration performance of cemented backfill, which should mainly considered in the control of cemented backfill mineralization carbon sequestration performance. The research results provide a theoretical reference which enhance the CO2 mineralization storage performance of coal-based solid waste consolidated backfill.

Image analysis as a geometry- and integrity-independent tool for predicting strength of cemented tailings backfill using slag-based binder

Compressive strength is a crucial indicator for assessing the stability of the cemented tailings backfill (CTB) matrix. The stringent requirements of traditional non-destructive testing (NDT) methods (e.g., ultrasonic pulse velocity and electrical resistivity) regarding the geometry, section flatness, and integrity of the core sample severely limit their use in the in-situ measurement of CTB strength. Therefore, this study proposes a novel NDT technique for assessing the in-situ strength of CTB made from ground granulated blast furnace slag (slag) by means of image analysis. Strength tests and image analysis are carried out in 258 specimens maintained at different solid concentrations (71−79 %), binder contents (6−14 %), activator ratios (from 28:2–20:10) and curing temperatures (5−40℃). In addition, microscopic investigations are carried out to clarify the underlying mechanisms contributing to the macroscopic features. Increasing solid content, desulfurized gypsum to calcium carbide slag (DG/CS) ratio, and curing temperature results in increases in UCS of 87.9−199.9 %, 171.3−421.2 %, and 27.5−173.8 %, respectively. The strength-enhancing effect of increasing the curing temperature diminishes with time, from 173.8 % at 3 days to 27.5 % at 28 days. Strength initially rises and then abruptly decreases as binder content rises. The grayscale value generally has an opposite trend to strength, but the former is less sensitive to changes in influencing factors. An obvious exponential relationship is found between strength and grayscale for all specimens (R2 = 0.92). Compared with traditional NDT methods, the application of image analysis is not restricted to the shape, size, and integrity of CTB and therefore provides a faster, easier, and less costly tool for the quality evaluation of field CTB matrix.

Experimental Study on Chloride Binding of Slag-Blended Portland Cement with Different Slag Ratios

Experimental Study on Chloride Binding of Slag-Blended Portland Cement with Different Slag Ratios