Effects Of Ground Granulated Blast Furnace Slag Research Articles

Effects of GGBFS:FA ratio and humid-heat-treating on the mechanical performance and microstructure of the steel slag-based ternary geopolymer

In order to improve the comprehensive utilization of steel slag in China, the ternary geopolymer with ground granulated blast furnace slag (GGBFS), fly ash (FA), and steel slag (SS) was prepared under the fixed addition of 50% SS in this research. The GGBFS:FA ratio was optimized to improve the mechanical performance of ternary groups. Humid-heat-treating ranging from 60 °C to 195 °C was adopted as the accelerated method to try to further strengthen the geopolymers compared with the standard curing. The strength development and hydration mechanism with different GGBFS:FA ratios were studied. The result revealed that appropriate humid-heat-treating significantly improved the geopolymers’ strength, which built a mountain-shaped response surface with the variations of the GGBFS:FA ratio and the corresponding treating parameters. The reasons for this phenomenon were the different activities of GGBFS, FA, and SS under different treating conditions, as well as the change of Ca/(Si + Al) ratio in hydration products that cause massive matrix gels with low Ca/(Si + Al) crystallized to crystal calcium silicate hydrated with high Ca/(Si + Al). The crystallization of massive matrix gels made the initial dense structure break up, resulting in a loss of strength in geopolymers. The suggested Ca/(Si + Al) ratio value in whole raw material mixtures of GFS should be lower than 1.0, which reflects the GGBFS:FA = 4:1 in the system with 50% SS. Hence, the treating parameters needed to be controlled and selected in practical application, respectively.

Effects of GGBFS on hydration and carbonation process, microstructure, and mechanical properties of NHL-based materials

Natural hydraulic lime (NHL) is an inorganic building material with hydraulic and air-hardening properties, having exceptional application in restoring ancient buildings compared to Portland cement and ancient air-hardening lime. However, the characteristic of slow performance development limits its application field. This study used ground granulated blast furnace slag (GGBFS) to replace parts of NHL. The hydration heat release, phase composition, micromorphology, pore structure, and physical and mechanical properties of GGBFS-NHL (S-NHL) based materials in the hardening process are investigated in-depth. The influence of GGBFS on the hardening process and performance development of NHL are systematically evaluated. The NHL is dominated by the hydration reaction of C2S to produce C–S–H in the early stage (less than 28 days). Moreover, C3AH6, CASH4, C4AĈH11, and C–S–H gel generated by the reaction of GGBFS with Ca(OH)2 changes the composition of hardened products, including the microstructure of the hardened paste. The higher the dosage of GGBFS, the more the hydration products in the NHL-based paste. The NHL-based paste gradually hardens with increasing age, mainly due to carbonation reaction. Moreover, its pore structure gradually densifies with curing age, and the average pore size and total pore volume of S-NHL decrease gradually with increasing GGBFS content. GGBFS significantly influences the mechanical properties and weight of the NHL-based mortar development. In addition, the S-NHL mortar's early and long-term mechanical strength increased significantly with increasing GGBFS.

Effect of steel slag on the mechanical behavior of surficial yellow marl of Tabriz

Fine-grained soils usually have low shear strength and bearing capacity and high swelling potential in the wet state, therefore, they have often to be stabilized by additives. The main objective of this study is to determine the possible effects of ground-granulated blast-furnace slag on the physical and mechanical properties of fine-grained soil. For this purpose, a number of Atterberg, compaction, California bearing ratio (CBR), unconfined compression and freeze-thaw tests were conducted on fine-grained soil. Steel slag (SS) inclusion reduced plasticity index of soil from 44% to 20% when slag content increased from 0% to 55.0%. Moreover, the slag addition improved soil CBR with maximum improvement rate in the sample consists to 55% slag. This increment in CBR was about 140% and 154% for 2.54 mm and 5.08 mm penetration respectively. In addition, slag inclusion raised soil strength with a maximum increment of 132% for clay mixed with 55% slag. Water content and volume changes in freeze-thaw cycles also decreased with increasing percentage of SS, therefore mixtures durability increased.

Effects of Ground-Granulated Blast-Furnace Slag Used as Filler in Dense Graded Asphalt

Industrial waste materials are increasingly being used in asphalt to improve pavement quality and reduce environmental impacts. The aim of this research was to test the pavement distress-related effects of using ground-granulated blast-furnace slag (GGBFS) as a filler in hot mix asphalt. There is potential for GGBFS to be integrated into Western Australian (WA) asphalt pavements. GGBFS was used as a replacement for the conventional hydrated lime (HL) filler used in mix designs of the Main Roads WA specifications. A control mixture (1.5% HL) was compared with three prototype mixtures containing 1.5%, 3% or 5% GGBFS instead of HL. To investigate their characteristics, we conducted wheel tracking tests, four-point bending tests, and assessments with an asphalt mixture performance tester (AMPT). The findings support the use of GGBFS in asphalt pavements. The mixture with 3% GGBFS had the best fatigue life, rutting resistance and AMPT results.

Strength characteristics and stability analysis of GGBS stabilised fly ash-overburden dump

ABSTRACT Stability of OB dump slope has been a major concern and require a proper design for safe mining operation. Utilisation of fly ash with OB material for construction of mine haul road and external dumping, may provide an alternative mode of fly ash disposal. In this study, fly ash was mixed with OB material at different percentages to evaluate the compaction characteristics, California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS) and shear strength parameter. Tests were also performed with the addition of a different percentage of Ground Granulated Blast Furnace Slag (GGBS) with fly ash-OB mix. Further, the effects of GGBS at various curing period on CBR and UCS characteristics were highlighted. Numerical modelling was carried out for dump containing OB material, fly ash and GGBS at different proportions to evaluate the Factor of Safety (FoS) and to suggest the optimum dump geometry. Experimental result infers that maximum CBR and UCS values were obtained for 78% OB material, 10% fly ash and 12% GGBS at 28 days curing period. Based on the observed FoS from numerical modelling, an optimal multiple regression model and artificial neural network model have been suggested for the direct prediction of FoS by various input parameters.

Effect of ground granulated blast-furnace slag on the hydration and properties of cement paste

The hydration process of cement paste blended with ground granulated blast-furnace slag (GGBS) was investigated using calorimetric and electrical methods. The effect of GGBS on early-age hydration was studied by examining electrical resistivity curves, heat of hydration curves and their rate curves. Through comparisons of the setting time and four other critical moments in early-age hydration evolution obtained from electrical resistivity and hydration heat tests, the application of electrical resistivity to characterise the setting behaviour of cement paste was proven to be effective, through the peaks on the rate curve of resistivity and the inflection point on the electrical resistivity–log time curve. The effects of GGBS on autogenous shrinkage and compressive strength development were also studied. It was found that compressive strength at 3 d could be predicted by electrical resistivity at 1 d. A positive linear correlation between autogenous shrinkage and compressive strength before 28 d was found. A relationship relating GGBS content to 28 d autogenous shrinkage and 28 d compressive strength was also developed. Scanning electron microscopy observations confirmed the macroscopic experimental results.

Time and cold joint effect on chloride diffusion in concrete containing GGBFS under various loading conditions

The stress due to volume change causes cracking in concrete, so that construction joint is intentionally prepared for an efficient construction and crack controlling in mass concrete structure. Cold joint means a weak joint area which may occur due to imperfect treatment of pre-placed concrete surface and delayed concrete delivery. Many researches have been performed for a quantitative evaluation of chloride ingress in cold joint concrete, which puts an emphasis on the more rapid penetration of chloride ions. The applied loading condition is one of the major reasons for concrete cracking and it also has a great effect on chloride penetration before the stage of cracking. Steel corrosion in concrete is accelerated when concrete cover has unsound area such as crack and cold joint. Chloride diffusion behavior varies with reduction of porosity and enhancement of hydrates, so called time effect on chloride diffusion. The effect of time and of cold joint on chloride diffusion is an important parameter for quantitative durability design for RC (Reinforced Concrete) structures exposed to various loading conditions.This paper investigates changes in chloride diffusion coefficient in cold joint concrete considering time effect and various loading conditions. Concrete samples with 0.6 of w/b (water to binder) and 40% replacement ratio of GGBFS (Ground Granulated Blast Furnace Slag) were prepared, and the chloride diffusion coefficients were measured for 1 year-cured concrete considering tensile and compressive loading conditions. The results were analyzed with the previous results in 91 days-cured concrete for evaluation of time effect. In the work, the time dependent chloride diffusion behaviors were quantitatively evaluated and discussed considering various effects of GGBFS, tensile and compressive stress levels, and cold joint.

Ground-Granulated Blast-Furnace Slag as Potential Filler in Polyester Grout: Compressive Strength Development

This paper examines the possibility of using ground-granulated blast-furnace slag (GGBFS) as a partial replacement of filler in polymer grout. In this study, river sand was replaced by GGBFS at levels of 0 (control), 10, 20, and 30% by weight. The effects of five curing conditions on compressive strength at the ages of 7, 28, 90, 180, and 365 days were studied. Three specimens were used at each specific age and curing condition. After 1 year, the samples' microstructures, which were cured under natural weather and seawater, were studied using scanning electronic microscopy (SEM). A comparison was also made regarding the development of compressive strength between polyester grout with and without GGBFS. From the results, it was observed that GGBFS used as filler in the polyester grout matrix resulted in a better long-term compressive strength than that of the control resin. The positive effects of GGBFS on the compressive strength of polyester grout against Malaysia's hostile environment, along with its environmental and economic advantages, make this material a feasible additive.