Activated Ground Granulated Blast-furnace Slag Research Articles

Two-phase changes in workability of sand-bentonite mixture triggered by seawater and binder during seepage cut-off wall construction in marine environment

Phenomenal sea level rise is exacerbating the risk of seawater intrusion in coastal areas, especially those with sandy soil, causing land erosion. Seepage cut-off walls made of in-situ sand, bentonite and binder can be employed. However, the presence of salts in soil is detrimental to water retention ability of bentonite, which can be aggravated by binder-induced cation exchange reactions, causing constructability issues for two-phase cut-off walls. Therefore, this study aims to evaluate the workability properties, including flowability and bleeding of sand-bentonite-binder mixture in seawater environment. The mechanism of decrease in water retention of bentonite has been investigated using Atterberg limits, X-ray diffration (XRD) and scanning electron microscope (SEM) analyses. In phase-one construction, seawater significantly increased flowability of sand-bentonite mixture. During the second phase, binder inclusion increased flowability even further. Given comparable flowability, the bleeding in sand-bentonite-binder mixture containing seawater was much greater than in the non-seawater environment. This was ascribed to a loss in water retention capacity of bentonite, in which external cations from seawater and binder exchanged with bentonite, resulting in reduction in liquid limit. The Na-based montmorillonite was transformed into Ca-based montmorillonite, causing the morphology of bentonite particles to flocculate. Despite this, the study discovered a feasible sand-bentonite-binder mixture including reactive magnesia (MgO)-activated ground granulated blast-furnace slag (GGBS) and seawater-resistant bentonite, which impeded the increase in workability.

Stabilization/solidification of Mn-contaminated clay slurry by using CaO-GGBS: Effects of anions

Clay sediment is removed by dredging, resulting in the disposal of enormous waste sediment clay slurries that consumes land space, as well as risks the human health and the environment. Manganese (Mn) is often identified in clay slurries. Quicklime (CaO)-activated ground granulated blast-furnace slag (GGBS) can be used to stabilize/solidify (S/S) contaminated soils; nevertheless, few studies have been published on the S/S of Mn-contaminated clay slurries using CaO-GGBS. Moreover, the anions contained in clay slurries may affect the S/S efficiency of CaO-GGBS in treating Mn-contaminated clay slurries, but this effect has hardly been investigated. Therefore, this study investigated the S/S efficiency of CaO-GGBS in treating MnSO4-bearing and Mn(NO3)2-bearing clay slurries. The effect of anions (i.e. SO42− and NO3−) on the strength, leachability, mineralogy, and microstructure of Mn-contaminated clay slurries treated with CaO-GGBS was explored. Results showed that CaO-GGBS could improve the strength of both Mn-contaminated slurries to meet the strength requirement for landfill waste outlined by United States Environmental Protection Agency (USEPA). The Mn leachabilities of both Mn-contaminated slurries were decreased to be less than the Euro limit for drinking water after cured for 56 days. The MnSO4-bearing slurry generally produced higher UCS while lower Mn leachability than Mn(NO3)2-bearing slurry at the same CaO-GGBS addition. CSH and Mn(OH)2 were formed, thereby enhancing strength and reducing leachability of Mn. Ettringite in CaO-GGBS-treated MnSO4-bearing slurry, which was formed by the supply of SO42− from MnSO4, further contributed to the strength enhancement and the decrease of Mn leachability. Ettringite was the factor leading to the difference in strength and leaching properties between MnSO4-bearing and Mn(NO3)2-bearing clay slurries. Hence, anions contained in Mn-contaminated slurries significantly affected the strength and the Mn leachability, and need to be identified before CaO-GGBS was used to treat such slurries.

Enhancement in compressive strength of carbide slag activated ground granulated blast furnace slag by introducing CaCl2 and NaCl

Alkali-activated materials was the green and low carbon cementitious materials. In this study, the calcium chloride (CC) and sodium chloride (SC) were used as accelerator to promote the compressive strength of carbide slag (CS) activated ground granulated blast-furnace slag (GGBFS). The compressive strength of samples was investigated and the related mechanism was comprehensively characterized with hydration heat, XRD, TG-DTG, SEM, 29Si NMR and MIP in details. These results showed that 5% SC and CC significantly improved early strength with an increase of 58.8% and 127.1% at 3 days, respectively. Interestingly, the presence of CC also increased the 28-day and 90-day strength from 16.6 MPa and 30.4 MPa to 50.2 MPa and 70.5 MPa, respectively. These results citified that the addition of CC and SC accelerated the consumption of CS at early age. At late age, the enhancing effect of SC was lower than CC, reflecting the Ca2+ made a greater contribution to strength development than Na+. The addition of CC still accelerated the rapidly precipitation of aluminium phase in the form of hydrocalumite, which could improve further dissolution and hydration of GGBFS at late age. Therefore, the addition of CC produced more hydration products that would refine microstructure and enhance strength at late age. These findings suggested a novel way to improve the mechanical properties of alkali-activated GGBFS.

Treating Pb-contaminated clay slurry by three curing agents.

Each year, extensive dredged clay slurries containing heavy metals need to be treated before being reused; in such contaminated slurries, lead (Pb) is frequently identified. Quicklime (CaO)-activated ground granulated blast-furnace slag (GGBS), magnesium (MgO)-activated GGBS, and ordinary Portland cement (OPC) are usually used to remediate the lead (Pb)-contaminated soil; nevertheless, using these curing agents (or binders), particularly CaO-GGBS and MgO-GGBS, to treat Pb-contaminated slurry with high water content is rarely reported. Moreover, inconsistent results were obtained from previous studies in terms of the mechanical and leaching performance of Pb-contaminated soils with the three binders. Based on the above-mentioned reasons, this study used CaO-GGBS, MgO-GGBS, and OPC to treat the Pb-contaminated clay slurry, and compared the effectiveness of the three binders in improving the mechanical and leaching properties of the slurry. Laboratory tests were performed to examine the leaching, strength, mineralogical, and micro-structural performance of treated clay slurries. The results showed that GGBS-based binders were more effective than OPC in improving the strength and Pb leachability of contaminated slurries. When suitable ratios between activators (CaO and MgO) and GGBS were used, a similar or even higher UCS was produced by CaO-GGBS than MgO-GGBS. Similar leachate pH and Pb leachability could be achieved between CaO-GGBS- and MgO-GGBS-treated contaminated clay slurries. Therefore, it is not rigorous to state that MgO-GGBS is better in improving the strength and leachability of Pb-contaminated soils than CaO-GGBS only by comparing the two GGBS-binders based on the same activator/GGBS ratio, as reported in some previous studies. The leachability of Pb was affected by the pH, but the addition of GGBS facilitated the decrease of Pb leachability in slurries. The XRD result showed the formation of CSH and Pb(OH)2, which facilitated the reduction of Pb leachability.

Effects of cation in sulfate chloride and nitrite on Ca(OH)2 activated ground granulated blast-furnace slag

This study explores the effects of the cations in sulfates, chlorides, and nitrites on calcium-hydroxide activated blast-furnace slag. Using several methods, it was demonstrated that the activators investigated could improve early strength development. Compared with chlorides and nitrites, the type of sulfate has a significant influence on slag hydration. Compared with K2SO4 and Na2SO4, the promotion of slag hydration in MgSO4, at an early age, is limited due to the precipitation of gypsum and brucite which retard the formation of hydrates and limits hydration kinetics during the initial stage. The high concentration of sulfate ions in the pore solution causes some ettringite to remain, promoting strength development. It was observed that the mechanism of pH increase in K2SO4 and Na2SO4 is due to the synergistic reactions between the sulfates and Ca(OH)2, while the low pH of MgSO4 due to the low solubility of brucite inhibits slag dissolution. The critical pH for promoting slag hydration was determined to be 13.1.

Effect of organic alkali on hydration of GGBS-FA blended cementitious material activated by sodium carbonate

Sodium carbonate (SC) activated ground granulated blast-furnace slag (GGBS) and fly ash (FA) is a potential substitute of traditional cement with ultra-low carbon footprint. However, its hydration rate and strength growth are limited, owing to the slow leaching of ions during the activation of weak base. In this work, 60% wet-grinded GGBS and 40% FA were blended as the binder, and two organic alkalis, i.e. triethanolamine (TEA) and triisopropanolamine (TIPA), were adopted to facilitate the ions dissolution and pozzolanic reaction of SC activated GGBS-FA blended cementitious material (SCSF). The compressive strength was tested and the hydration kinetics was studied by hydration heat and chemical shrinkage. Besides, ions leaching behavior was characterized by ICP; hydrates and microstructure were also detected by XRD, TG-DTG and SEM. Results indicated that the addition of TEA or TIPA significantly promoted the ions dissolution. 0.05% TEA increased the concentration of leached Ca 2+ , Al 3+ and Fe 3+ by 36%, 33% and 1545%, respectively. This solubilizing effect was also found in TIPA. Moreover, these two chemicals could promote the formation of hydrates, such as C-S(A)-H gel, hydrotalcite, calcite and aragonite, especially at the early period; these also activated the hydration process of SCSF effectively, and the compressive strength of the mortar reached above 40.0 MPa at 7 d and 48.0 MPa at 28 d. The carbon emission of the designed system is 85.9% and 55.9% lower than that of PC and strong base activated GGBS system, respectively.

Effect of accelerators on Ca(OH)2 activated ground granulated blast-furnace slag at low curing temperature

The early effects of three accelerators on a Ca(OH)2 activated ground granulated blast-furnace slag binder at low curing temperatures are discussed. The compressive strength, hydration kinetics, hydration products, and microstructures were investigated by isothermal calorimetry, X-ray diffraction, mercury intrusion porosimetry, scanning electron microscopy, and nuclear magnetic resonance. Results show that accelerators continue to promote the strength development of pastes in the early stage during low-temperature curing, especially with sodium sulfate, which exhibits a higher strength and hydration degree in the early stage. However, accelerators cannot effectively improve the pore structure at low-temperature curing, which severely restricts the development of strength, compared with that at 20 °C. Furthermore, a good correlation was found between the initial strength development and the limit equivalent ionic conductivity (LEIC), suggesting that LEIC influences the reaction acceleration of blast-furnace slag at an early age.

Correction to: Influence of cellulose nanofibrils on the rheology, microstructure and strength of alkali activated ground granulated blast-furnace slag: a comparison with ordinary Portland cement

Correction to: Influence of cellulose nanofibrils on the rheology, microstructure and strength of alkali activated ground granulated blast-furnace slag: a comparison with ordinary Portland cement

Influence of cellulose nanofibrils on the rheology, microstructure and strength of alkali activated ground granulated blast-furnace slag: a comparison with ordinary Portland cement

This paper reports on the effect of cellulose nanofibrils (CNFs) on the fresh-state properties of alkali activated ground granulated blast-furnace slag (GGBS). Surface functionalized (oxidized) CNFs were added to alkali activated GGBS water suspensions (hydraulic pastes). The rheological behaviour of the pastes was compared with OPC and interpreted based on the CNF-mineral surface interaction, and on the CNF-water interaction and swelling. The water dispersion of CNFs with different surface functionalization degrees resulted in gels of different viscosity and yield stress, due to their different hydrophilicity and water adsorption properties. On increasing the CNFs surface oxidation degree, the viscosity of the CNF water dispersion decreases and the CNF water adsorption increases, while the viscosity of fresh pastes increases because of the reduced amount of available mixing water. In the hardened state, the hydraulic pastes show differences in mechanical strength related to the type and the amount of CNF influencing the porosity of the matrix as evidenced by the microstructural investigation performed by X-ray microtomography. The presence of higher amounts of CNFs induces the formation of porous agglomerates that may act as stress concentrators due to the swelling ability of nanofibrils.

WITHDRAWN: Assessment of young’s modulus of alkali activated ground granulated blast-furnace slag based geopolymer concrete with different mix proportions

To Prepare the Eco-friendly concrete we require alkali solutions like Sodium hydroxide and sodium silicate. Organize the alkali solutions, by taking into consideration of dissimilar molarities of Sodium hydroxide (NaOH) resembling 9 M, 14 M, and 19 M and dissimilar concentrations of sodium silicate (Na 2 SiO 3 ) resembling 20%, 35%, and 50%. Get ready the alkali-solution of NaOH & Na 2 SiO 3 alone 1 h earlier to the combination of Geopolymer Concrete. The result shows the mechanical properties such as compressive strength, young are modulus and density of Geopolymer Concrete. The specimens be hardened after 28 days of ambient curing. The investigational result shown that mix proportion of 1:1:2 mix produces compressive strength and Young’s Modulus values.

Heat of hydration, bleeding, viscosity, setting of Ca(OH)2-GGBS and MgO-GGBS grouts

Hydrated lime (Ca(OH)2)- and reactive magnesia (MgO)-activated ground granulated blast-furnace slag (GGBS) have shown advantages in geotechnical applications compared with Portland cement (PC). To apply these two novel binders in slurry form to field applications, the properties of their grouts need to be investigated, which is the objective of this study. The heat of hydration, bleeding, viscosity, and setting behavior of Ca(OH)2-GGBS and MgO-GGBS grouts were investigated and compared with PC and pure GGBS grouts in this study. All grouts indicated a decrease in bleeding and setting time, but an increase in viscosity with decreasing the water/cementitious material (W/C) ratio. Compared with the PC grout, the pure GGBS grout with the same W/C ratio demonstrated higher bleeding and setting time, and lower heat rate and viscosity. Bleeding and setting time decreased and peak heat rate and viscosity increased with an increase in the activator (Ca(OH)2 or MgO)/GGBS ratio within GGBS-based grouts. The peak heat rate in Ca(OH)2-GGBS grouts was higher than that of pure GGBS or Ca(OH)2 grout, indicating that Ca(OH)2 was effective on activating hydration of GGBS. The peak heat rate in MgO-GGBS grouts was significantly lower than MgO grout and the heat rate was limited after 8 h. The bleeding and setting times of MgO-GGBS grouts were significantly lower than those of Ca(OH)2-GGBS grouts, which was primarily attributed to the hydration of MgO.

Suppressing Ettringite-Induced Swelling of Gypseous Soil by Using Magnesia-Activated Ground Granulated Blast-Furnace Slag

Ettringite usually is formed in lime- and cement-stabilized gypseous soils, resulting in significant swelling upon wetting and thereby causing damage to pavements and foundation systems. To reduce the ettringite formation and the associated swelling, magnesia (MgO)-activated ground granulated blast-furnace slag (GGBS) was investigated for stabilizing gypseous soil. Experimental tests, including swelling, unconfined compression strength, X-ray diffraction (XRD), and scanning electron microscopy (SEM) studies, were conducted to examine properties of MgO-GGBS-treated gypseous soil. Test results illustrated that the swelling of MgO-GGBS-stabilized soils (0.4%–2%) was much lower than that of cement-stabilized soil (6.1%), whereas the strength of MgO-GGBS-stabilized soils after soaking (1.2–2.8 MPa) was significantly higher than that of cement-stabilized soil (0.3 MPa). XRD and SEM results showed that no ettringite was formed in MgO-GGBS-stabilized soils, which primarily was responsible for the lesser swelling and higher strength compared with that of the cement-stabilized soil after soaking. Overall, test results indicated the potential of MgO-GGBS for effective stabilization of gypseous soils.

Alkali-activated GGBS and enzyme on the swelling properties of sulfate bearing soil

Use of cement in stabilizing the sulfate-bearing clay soils forms ettringite/ thaumasite in the presence of moisture leads to excessive swelling and causes damages to structures built on them. The development and use of non-traditional stabilisers such as alkali activated ground granulated blast-furnace slag (AGGBS) and enzyme for soil stabilisation is recommended because of its lower cost and the non detrimental effects on the environment. The objective of the study is to investigate the effectiveness of AGGBS and enzyme on improving the volume change properties of sulfate bearing soil as compared to ordinary Portland cement (OPC). The soil for present study has been collected from Tilda, Chhattisgarh, India and 5000 ppm of sodium sulfate has been added. Various dosages of the selected stabilizers have been used and the effect on plasticity index, differential swell index and swelling pressure has been evaluated. XRD, SEM and EDX were also done on the untreated and treated soil for identifying the mineralogical and microstructural changes. The tests results show that the AGGBS and enzyme treated soil reduces swelling and plasticity characteristics whereas OPC treated soil shows an increase in swelling behaviour. It is observed that the swell pressure of the OPC-treated sulfate bearing soil became 1.5 times higher than that of the OPC treated non-sulfate soil.

Mechanical properties and reaction characteristics of asphalt emulsion mixture with activated ground granulated blast-furnace slag

In this study, ground granulated blast-furnace slag (GGBS) activated by hydrated lime (HL) is used to replace the limestone filler and design base course asphalt emulsion mixture (AEM). The mechanical properties, moisture resistance and permanent deformation of AEM with GGBS and HL are investigated and compared with those of AEM contained ordinary Portland cement (OPC). Furthermore, the reaction mechanism of GGBS activated by HL in asphalt emulsion is analyzed by means of Fourier transform infrared (FTIR) spectrometer, X-ray diffraction (XRD) analyzer, and environmental scanning electron microscope (ESEM). The results indicate that the AEM with GGBS and HL can be used for pavement base course as a substitute of AEM with OPC. The materials’ proportions and curing periods should be both considered during the mixture design. Compared with the hydration reaction in GGBS-HL paste, the hydration process of GGBS in asphalt-GGBS-HL mastic is delayed by the encapsulation of asphalt binder. The hydration products in the mastic enhance bond strength of mastic-aggregates interface and asphalt stiffness. These positive effects can explain the performance characteristic of AEM with GGBS and HL.

Mechanism of reactive magnesia – ground granulated blastfurnace slag (GGBS) soil stabilization

Reactive magnesia (MgO)-activated ground granulated blastfurnace slag (GGBS), with fixed GGBS dosages but varying MgO/GGBS ratios, was used for stabilization of two soils and compared with brucite (Mg(OH)2)-activated GGBS and hydrated lime (Ca(OH)2)-activated GGBS. A range of tests, including unconfined compressive strength testing, X-ray diffraction, and scanning electron microscopy, was conducted to study the mechanical, chemical, and microstructural properties of the stabilized soils, and then to investigate the mechanism of MgO–GGBS soil stabilization. Results indicate that the Mg(OH)2had a minimal activating efficacy for GGBS-stabilized soil, while the reactive MgO yielded a higher activating efficacy than the Ca(OH)2. The activator–soil reactions in the stabilized soil slowed down the activating reaction rate for GGBS; this effect was less significant in MgO–GGBS-stabilized soil than in Ca(OH)2–GGBS-stabilized soil, and hence the GGBS hydration rate in the former was less reduced by the soil than the latter. The Mg2+and OH−ions produced from MgO dissolution participated in the GGBS hydration reactions without precipitating Mg(OH)2. The common hydration products in all GGBS-stabilized soils were calcium silicate hydrate–like compounds. Additionally, hydrotalcite and calcite could be produced in MgO–GGBS- and Ca(OH)2–GGBS-stabilized soils, respectively, especially with a high activator/GGBS ratio.

Influence of four additional activators on hydrated-lime [Ca(OH)2] activated ground granulated blast-furnace slag

The influences of four supplementary activators were investigated on Ca(OH)2-activated slag system. The additives significantly affected the (1) early strengths, (2) reaction degrees of slag, (3) types of hydration products, and (4) local structures of Si and Al; however, the 28-day strengths were not improved, but the reduction of water content improved the strength more effectively due to a reduction in porosity. In this study, the Na-based additives were less desirable than the Ca-based ones in the Ca(OH)2-activated system because (1) the Na-additives tended to produce lower 28-day strengths; (2) they synthesized U-phases, which may cause expansive failures at later ages and (3) they might suppress the dissolution of Ca(OH)2. Although sulfate ions generally appear to improve 28-day strength in literature, the sulfate-bearing additives in this study did not improve the strengths because the original slag contained a high sulfate content; adding more sulfate may have exceeded the optimal content.

Comparison of reactive magnesia- and carbide slag-activated ground granulated blastfurnace slag and Portland cement for stabilisation of a natural soil

In this study, reactive magnesia (MgO)- and carbide slag (CS)-activated ground granulated blastfurnace slag (GGBS) were used to stabilise a natural soil in comparison to Portland cement (PC). X-ray diffraction (XRD), scanning electron microscopy (SEM), and unconfined compressive strength (UCS) test were employed to investigate the microstructural and mechanical properties of stabilised soils. The results indicated that the main hydration products of CS-GGBS stabilised soil included calcium silicate hydrates (CSH), calcium aluminate hydrates (CAH), and ettringite. For MgO-GGBS stabilised soils, CSH was the only hydration product detected. These hydration products had different microstructure and binding ability, affecting the strength of stabilised soils. There was an optimum MgO or CS content, in a range of 10–20%, for yielding the highest UCS of MG-GGBS or CS-GGBS stabilised soil at the same age. The 90-day UCS of the optimum MgO-GGBS and CS-GGBS stabilised soils was 3.0–3.2 and 2.4–3.2 times that of the PC stabilised soil, respectively.

An exploratory study on sodium sulfate activated slag modified with Portland cement

In this work, the effect of different contents of Portland cement (PC) on the heat of hydration, pH value, compressive strength and drying shrinkage of 1 % Na2O equivalent of Na2SO4 activated ground granulated blast-furnace slag (hereafter referred as slag) has been investigated and compared to slag activated with other common activators. Slag was partially replaced with PC at levels of 0, 5, 10 and 15 %, by weight. The various decomposition phases formed were indentified using X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The results showed an increase in the heat of hydration and compressive strength with the inclusion of 10 and 15 % PC. On the other hand, 5 % PC reduced the compressive strength. The pH value increased with increasing PC content, whilst drying shrinkage decreased with increasing PC content.

Compressive Strength and Density of Cementless Unfired Lightweight Brick Utilizing Coal Ash from Coal-Fired Thermal Power Plant

Millions tons of coal ash which constitute of fly ash and bottom ash were produced annually throughout the world. They were significant to be developed as masonry brick to substitute the existing widely used traditional material such as clay and sand brick which were produced from depleting and dwindling natural resources. In the present study, the coal ash from coal-fired thermal power plant was used as the main raw material for the fabrication of cementless unfired lightweight brick. The binder comprising of Hydrated Lime (HL)-activated Ground Granulated Blastfurnace Slag (GGBS) system at binding ratio 30:70, 50:50 and 70:30 were used to stabilize the coal ash in the fabrication process of the brick. Foam was used to lightweight the brick. The compressive strength and ambient density were evaluated on the brick. The results indicated that the brick incorporating HL-GGBS system achieved higher strength of 20.84N/mm2 at 28 days compare to the HL system with strength of 13.98N/mm2 at 28 days. However, as the quantity of foam increase at 0%, 25%, 50%, 75% and 100%, the strength and density for the brick decreased.

Effect of water–binder ratio on the mechanical properties of calcium hydroxide-based alkali-activated slag concrete

This paper presents mechanical properties of calcium hydroxide (Ca(OH)2)-activated ground granulated blast-furnace slag (GGBS) concrete with different auxiliary activators in order to provide basic data for developing the mixing procedure and design models for structural concrete. Twelve concrete mixes were prepared with the main parameters of water–binder (W/B) ratio. The measured mechanical properties were compared, wherever possible, with design equations specified in ordinary Portland cement (OPC) concrete code provisions. The investigated Ca(OH)2-based AA GGBS concrete showed an enhanced workability, delayed slump loss and similar increasing rate of compressive strength against W/B ratio to that observed in OPC concrete. Similarly to OPC concrete, mechanical properties of Ca(OH)2-based AA GGBS concrete could be expressed as a power function of compressive strength (fc′). The values of the power in the determined equations could be approximately set to be 0.5 for modulus of elasticity, 0.65 for modulus of rupture, tensile strength and direct shear strength, and 0.75 for bond strength. Overall, the present test results revealed that the tested Ca(OH)2-based AA GGBS concrete has a considerable potential for practical application to structural concrete when the W/B ratio is lower than 30%.