Incorporation Of Blast Furnace Slag Research Articles

Experimental Investigation of Sustainable Concrete Production using Blast Furnace as A Cement Substitute- A art of Review

The pursuit of sustainable construction practices has led to a growing interest in alternative materials that can reduce the environmental impact of traditional concrete production. This experimental study focuses on the utilization of blast furnace slag as a substitute for cement in concrete, aiming to assess its mechanical properties, environmental impact, and overall sustainability. The primary objectives of this research are threefold. Firstly, the study seeks to evaluate the mechanical properties of concrete by varying the content of blast furnace slag in the mix, with a specific emphasis on strength, durability, and structural performance. This involves conducting a comprehensive analysis of the concrete's compressive strength, flexural strength, and other relevant mechanical characteristics. Secondly, a life cycle assessment (LCA) will be employed to analyze the environmental impact of the concrete mixtures. This assessment will compare carbon dioxide (CO2) emissions, energy consumption, and overall sustainability of the concrete produced with varying percentages of blast furnace slag. The LCA will provide valuable insights into the environmental implications of using slag as a cement substitute, aiding in the identification of eco-friendlier concrete production practices. Lastly, the research aims to assess the environmental impact of blast furnace slag itself when employed as a cement substitute. This involves examining the production, transportation, and incorporation of blast furnace slag into the concrete mix, providing a holistic view of its sustainability across the entire life cycle. The experimental approach involves the meticulous design of concrete mixes with different percentages of cement replaced by blast furnace slag. The varying mix designs will be tested for mechanical properties, and the data obtained will be used to draw correlations between slag content and concrete performance. In summary, this research endeavors to contribute to the body of knowledge surrounding sustainable concrete production by exploring the mechanical, environmental, and sustainability aspects of utilizing blast furnace slag as a cement substitute. The findings of this study are anticipated to provide valuable insights for the construction industry to adopt more environmentally friendly practices while maintaining or enhancing concrete performance.

Effects of UV Radiation on the Carbonation of Cement-Based Materials with Supplementary Cementitious Materials

Solar light with high-energy ultraviolet (UV) radiation acting on the surface of cement-based materials easily changes the properties of cement-based materials by affecting their carbonation reaction. In order to elucidate the difference in the carbonation process under UV radiation in cement-based materials with different supplementary cementitious materials (SCMs), the carbonation depth (apparent pH values), chemical composition (XRD, FTIR, and TG analysis), and mechanical properties (compressive strength and microhardness) of cement-based materials were evaluated. The results revealed that UV radiation acting on the surface of cement-based materials accelerated the carbonation reaction, which enhanced the decrease rate of pH and formation of stable calcite, thereby improving the macromechanical and micromechanical properties of cement-based materials. In addition, the carbonation process under UV radiation differs according to the added SCM. In particular, silica fume substantially increased the carbonation of cement-based materials under UV radiation, resulting in a 53.3% increase in calcium carbonate coverage, a 10.0% increase in compressive strength, and a 20.9% increase in mean microhardness, whereas the incorporation of blast furnace slag resulted in a smaller effect on UV irradiation-induced carbonation. In addition, UV radiation facilitates the crystallographic transformation process of cement-based materials containing metakaolin, resulting in more stable crystals of carbonation products. This study provides a theoretical framework and serves as an important reference for the design of cement-based materials under strong UV radiation for practical engineering applications.

Effect of High Temperature Reconstruction and Modification on Phase Composition and Structure of Steel Slag

This study investigates the pattern of influence of blast furnace slag tempering on the composition and structure of steel slag. The chemical composition, equilibrium phase composition, microscopic morphological characteristics and elemental composition of microscopic regions of steel slag and blast furnace slag modified by high temperature reconstruction were analyzed using X-ray diffractometer (XRD), FactSage7.1 thermodynamic analysis software, mineral phase microscopy and field emission scanning electron microscopy. The results show that blast furnace slag blending can promote the generation of a low melting point phase in the slag, as well as reducing its melting temperature and improving its high temperature kinetic conditions. On the one hand, the incorporation of blast furnace slag was found to promote the generation of C2S in the steel slag and improve its gelling activity. Notably, at 1400 °C, the C2S content (mass fraction) of steel slag modified with 15% high temperature reconstruction reached 39.04%, while that of unmodified steel slag at this temperature was only 16.92%, i.e., only 1/4 of the C2S content in the modified slag. On the other hand, the incorporation of blast furnace slag inhibited the generation of a-C2S-C3P and calcium ferrate minerals, refined the grains of calcium–aluminum yellow feldspar, reduced the alkalinity and promoted the generation of silicate phases with high hydration activity in steel slag.

Chloride-related steel corrosion initiation in cement paste prepared with the incorporation of blast-furnace slag

Steel corrosion caused by chloride penetration is an important problem in construction practices threatening the long-term durability of reinforced concrete structures. In this study, the effects of blast-furnace slag on the passivation and corrosion processes of carbon steel embedded in cement pastes were investigated by electrochemical measurements, and equivalent circuit models were proposed for analysis of the passivation and corrosion processes. The spatial chloride distributions in the cement paste after corrosion initiation were determined distinguishing between amounts of total, free and bound chloride. The values of the open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) measurements indicated that the carbon steel embedded in cement pastes was passivated due to the presence of an alkaline pore solution. However, the formation of passive layers on the surface of carbon steel in the slag-blended cement paste was weakened by the more negative OCP value due to a lower pH value and higher sulphide concentration in the pore solution. Upon initiation of corrosion during the electrical acceleration test, the OCP value dropped to a significantly more negative value whereas the Warburg impedance in the equivalent circuit model sharply decreased. Moreover, the addition of slag decreased the threshold chloride concentration at the steel surface to initiate steel corrosion. On the other hand, the enhanced resistance against chloride penetration and the higher chloride binding capacity resulted in an overall increase of the corrosion resistance of carbon steel in slag-blended cement paste.

THE MULTIFRACTAL PROPERTY OF HETEROGENEOUS MICROSTRUCTURE IN CEMENT PASTE

Highlights (1) Microstructure of cement paste is acquired through computed tomography. (2) Multifractal property of heterogeneous microstructure is examined. (3) Incorporation of blast furnace slag results in a decrease of singularity width. The microstructure of cement paste is highly heterogeneous in nature that plays a significant role in macroscopic performance. This paper is dedicated to examining the multifractal property of microstructure in cement paste, based on which the microstructural heterogeneity could be quantified meanwhile. In particular, the X-ray computed tomography is adopted to acquire the realistic three-dimensional (3D) microstructure. Then, a thorough examination is performed on the multifractal property with respect to the partition function, the generalized dimension and the multifractal spectrum. Results indicate that the multifractal property in terms of local porosity can be recognized for the heterogeneous microstructure in both ordinary and blast furnace slag blended Portland cement pastes. The multifractal spectrum or singularity width is available to account for the degree of heterogeneity.

Property Comparison of Alkali-Activated Carbon Steel Slag (CSS) and Stainless Steel Slag (SSS) and Role of Blast Furnace Slag (BFS) Chemical Composition.

In order to compare the properties of alkali-activated carbon steel slag (CSS) and stainless steel slag (SSS), the effects of sodium hydroxide/sodium silicate solution mass ratio (NH/NS), liquid/solid ratio and blast furnace slag (BFS) dosage on the compressive strength, hydration products and hydration degree of CSS and SSS were studied. Furthermore, a combination of X-ray diffraction (XRD), thermo-gravimetric analysis coupled with differential thermal analysis (TGA-DTA), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope-energy dispersive spectrometer (SEM-EDS) were used to characterize the morphology and structure of alkali-activated CSS-BFS and SSS-BFS cementitious materials. As the results revealed, the primary hydrate of alkali-activated CSS and SSS is C-(A)-S-H with Q2 [SiO4] units, which has a low Ca/Si ratio and includes inert phases like a CaO-FeO-MnO-MgO solid solution (RO) in CSS while cuspidine, magnesiochromite etc. in SSS. More active C3S and β-C2S promote the alkali activation of CSS, whereas the less active γ-C2S hinders the depolymerization of SSS. The incorporation of BFS does not change the hydrate, whose seed effect is helpful for accelerating the depolymerization and polycondensation of CSS and SSS, especially for SSS, and makes the hydrate increase significantly. Owing to the high SiO2 and Al2O3 contents of SSS, the C-(A)-S-H chain length is increased, thus facilitating the polycondensation effect. In this study, the optimal NH/NS of CSS and SSS is NH/NS= 1:2, and the optimal liquid/solid ratio is 0.29. Compared to CSS–BFS, the C-(A)-S-H gel produced by SSS–BFS has lower Ca/Si and Al/Si ratios. Unlike CSS, pure SSS is inappropriate as an alkali-activated precursor and needs to be co-activated with BFS.

Eco-concrete with incorporation of blast furnace slag as natural aggregates replacement

This study focused on studying the possibility of using concrete with incorporation of slag from blast furnace in the filling of short steel columns. The natural sand was totally or partially replaced by the sand slag in the composition of the concrete. The characterization of these concretes was made based on their physical properties (apparent and specific densities, porosity and fineness modulus), mechanical properties (compressive and tensile strengths) and the microstructure analysis by scanning electron microscopy (SEM). The comparison with the conventional concrete was made. The experimental results show that the percentages of sand slag on the concrete composition have an important effect on the enhancement of the mechanical proprieties. The comparison of the different determined characteristics shows the benefits of the use of sand slag in the concrete composition compared with the conventional concrete.

Preparation and properties of geopolymer from blast furnace slag

In this paper, blast furnace slag was investigated as a source of the basic Si–Al ingredient of geopolymer. On the basis of compressive strength, the effects of grinding time on the activity of blast furnace slag and the effects of activator types, compound activator and particle size of blast furnace slag on the compressive strength were studied. The results showed that the optimum parameters were as follows: the grinding time was 12 hours, the granularity of blast furnace slag powders was 0·053–0·075 mm, the incorporation of blast furnace slag was 90 wt-%, the mass ratio of water glass/NaOH was 7:3, the liquid-to-solid mass ratio was 0·25, Additionally, X-ray diffraction, infrared spectroscopy and scanning electron microscope with energy dispersive spectrometer analysis were used to analyse the composition and polymerisation mechanism of the geopolymer. The reaction products of slag-based geopolymer paste was composed of two separate amorphous phases (geopolymeric and CSH gel).