Blended Blast Furnace Slag Research Articles

Nano-silica and Ground Granulated Blast Furnace Slag Blended Concrete: Impact of Temperature on Stress–Strain Constitutive Model

Nano-silica and Ground Granulated Blast Furnace Slag Blended Concrete: Impact of Temperature on Stress–Strain Constitutive Model

Accelerated carbonation of alkali-activated blended blast furnace slag and wood fly ash: Carbon capture kinetics, chemical and mechanical evolutions

The influence of fly ash/slag ratio, alkaline activator silica modulus (Ms), and curing method have been evaluated on the carbonation of biomass fly ash and blast furnace slag blends. In addition to quantifying the CO2 sequestration capacity, the influence of carbonation on the chemical and mechanical properties of materials was explored to assess their durability. Results show that higher fly ash contents lead to higher CO2 diffusion, while slag limits carbonation to the surface of specimens. A higher fly ash content induces higher carbonation at Ms= 0 (as high as 0.36 mmol/g), while the most significant adsorption at a high slag content is obtained at Ms= 1.32 (as high as 0.33 mmol/g). Carbon capture and storage values as high as the pressure decay chamber recorded 0.36 mmol/g, while TGA shows the adsorption capacity of the binder as high as 3.69 mmol/g. Mechanical strength variation is proved to be a function of Ca/Si and is evaluated accordingly.

Non-Destructive Evaluation of Mortar with Ground Granulated Blast Furnace Slag Blended Cement Using Ultrasonic Pulse Velocity.

Non-destructive evaluation using ultrasonic pulse velocity (Vp) testing has extensive applications in the concrete industry. With advances in construction technology, the use of ground granulated blast furnace slag (GGBFS) as a partial replacement to cement in a concrete mix is growing in popularity primarily because it reduces the initial capital cost of raw materials and the associated energy costs. This paper investigates the effect of the water-to-cement (wc) ratio and the cement content replaced by GGBFS on the development with time of the ultimate compressive strength () and the compression wave velocity (Vp) of mortar. The results showed that in the case of mortar with higher percentages of GGBFS replacement (where nucleation surfaces are more abundant), increasing wc can increase but cause a decrease in Vp. The posterior hydration process is highly dependent upon the water particles in the mixture after the first stage of hydration. After 7 days of curing, experimental results show that the of slag blended cement mix design wc ratio of 0.6 surpassed the value of an Ordinary Portland cement. A regression model correlating the and Vp of slag blended mortar is developed, which can be used to predict at concrete ages ranging from 1 day to 28 days for mixes with GGBFS percentage replacement values ranging from 15% to 45%.

Reactivity Effect of Calcium Carbonate on the Formation of Carboaluminate Phases in Ground Granulated Blast Furnace Slag Blended Cements

The reactivity effect of calcium carbonate, present in ground oyster shells and limestone filler, on the formation of carboaluminate phases in ground granulated blast furnace slag blended cement pastes was reported in this paper. Six different binary and ternary blended cement pastes were prepared using ground granulated blast furnace slag, ground oyster shells and limestone filler with different replacement levels (from 5 to 35%). The carboaluminate formation was assessed and quantified directly using X-ray diffraction (XRD), and indirectly by following the aluminate phase’s reaction (heat flow) and consumed calcium carbonate using Isothermal Calorimetry (IC) and Thermogravimetric Analysis (TGA), respectively. Further, the overall reaction degree calculated based on TGA results and the compressive strength were determined to support the findings obtained. The results revealed that the calcium carbonate present in ground oyster shells is more reactive when compared to that present in limestone filler, where more formed hemi- and monocarboaluminate phases were observed in mixtures containing ground oyster shells. An enhancement in compressive strength and overall reaction degree was observed by adding 5% ground oyster shells as cement replacement.

Investigation on the Performance of Hybrid Fiber Reinforced Geopolymer Concrete Made of M-Sand under Heat Curing

Due to the elevating demand to replace the conventional cement concrete with any other building material, there has been a continuous effort to promote the properties of geopolymer concrete. The objective of this paper is to reduce the brittleness of geopolymer concrete. This research paper goes for exploring the impact of high and low young’s modulus fiber in geopolymer concrete made of M-sand. Mix proportion of various materials is based on the Rangan’s proposed Mix design. Geopolymer concrete used in this investigation is the Fly ash – Ground Granulated Blast Furnace Slag blend based. Concoction of NaOH solution and Na2SiO3 solution is used as the alkali solution. Sine 80 percent of the source material is flyash, the specimens are exposed to heat curing. Fresh property and hardened characteristics like workability, ductility factor, compressive, split tensile, flexural and impact strength are assessed in this study. Significant increase in the engineering properties is observed with respect to both the fibers. This work unveils lot of potential in the vicinity of Geopolymer concrete.

Mechanical Properties, Resistance to Fire and Durability for Sulfate Ions of Alkali activated Cement made from Blast furnace Slag- Fine Metakaolin

The characterization of alkali activated cement prepared by blending blast furnace slag (BFS) and fine metakaolin (FMK) are studied. MK of particle size 45 μm and blain area 6530 cm2/kg is used as 20%, 40%, 60% and 80% replacement of BFS in the production of alkali activated cement. The alkaline activator used was mixture of NaOH and Na2SiO3 with various molar ratios. The prepared specimens are cured under humid conditions up to 90 days. All specimens are characterized regarding setting times, compressive strength and water absorption. The formed hydrates are studied using XRD analysis, FTIR spectroscopy and SEM. The durability of the prepared geopolymer are determined via studying the fire resistance at 300 o, 600 o and 800 oC and sulfate ions attacks after time intervals extended up to 1 year. The results indicate that the specimens made from 60% BFS and 40% FMK and activated by (1:1) NaOH and Na2SiO3 were revealed the best overall behavior.

Mechanical and thermal properties of aluminate cement paste with blast furnace slag at high temperatures

The effect of blast furnace slag (BFS) on the mechanical and thermal properties of calcium aluminate cement (CAC) subjected to high temperature was evaluated in this study. The hydrate phase, micromorphology, and porous structure characteristics were determined by differential thermal analysis/thermogravimetry, X-ray diffraction (XRD), scanning electron microscopy, and nitrogen adsorption–desorption. The thermal conductivity of the pastes was evaluated using a thermal conductivity analyzer. The results indicated that with an increase in BFS, the thermal conductivity of CAC–BFS blend samples increases initially and decreases subsequently, and the compressive strength of the CAC–BFS blend samples exhibits the same trend. The addition of 30–40% BFS positively influenced the pore size distribution of cement paste and improved the thermal conductivity (λ) of the CAC-based composites subjected to high temperature, enhancing the mechanical properties of the CAC-based composites. Thermal conductivity also decreases at increased temperatures and correlates with pore structure. The experimental results indicate that the amount of BFS added considerably affects thermal conductivity and compressive strength, and that the optimal amount of BFS can be determined.

Investigation of Wear Strength of Blast Furnace Slag Blended Polymer Materials

Investigation of Wear Strength of Blast Furnace Slag Blended Polymer Materials

Comparison of calorimetric methods for the assessment of slag cement hydration

ABSTRACTThis study aims to contribute to future-proofing the supply of cement powders for the UK’s nuclear waste cementation program, by enabling rapid and reliable assessment of heat evolution from candidate grout formulations. Isothermal conduction calorimetry and semi-adiabatic calorimetry experiments were carried out at room temperature, to monitor the heat of hydration of blended blast furnace slag (BFS)-Portland cement formulations of relevance for wasteform grout applications. By changing the particle size distribution of the BFS, the physical and chemical properties of the cement grout are altered, and this can be monitored and understood through comparison between the two calorimetry methods.

Effect of Limestone Powder and Gypsum on the Compressive Strength Mixture Design of Blast Furnace Slag Blended Cement Mortar

Effect of Limestone Powder and Gypsum on the Compressive Strength Mixture Design of Blast Furnace Slag Blended Cement Mortar

Quantitative Evaluation of Crack Resistance Mechanism of Blast Furnace Slag Blended Cement Concrete via Restrained Shrinkage Stress Analysis

Quantitative Evaluation of Crack Resistance Mechanism of Blast Furnace Slag Blended Cement Concrete via Restrained Shrinkage Stress Analysis

Mechanical and durability properties of alkali-activated mortar based on sugarcane bagasse ash and blast furnace slag

Sugarcane bagasse is an agricultural waste which can be transformed, for cementing purposes, into an interesting material by combustion. Specifically, the ash (SBA) obtained by auto-combustion was used for preparing alkali-activated cements by blending blast furnace slag (BFS). SBA had a large amount of quartz; however, it reacted in high alkaline medium. Mixtures of BFS/SBA have been used for preparing alkali-activated mortars, by using NaOH (8M solution), sodium silicate (8M solution in Na+ and SiO2/Na2O molar ratio of 0.5) and KOH (8M solution) as activating solutions. Replacements of 25%, 33% and 50% of BFS by SBA were carried out and compressive strengths in the range 16–51MPa were obtained after 90 curing days. Microstructural studies demonstrated that the hydration products formed in the activation of BFS are not significantly affected by the presence of SBA in the mixture. The durability of alkali-activated mortars was compared to ordinary Portland cement (OPC) mortar in the following media: hydrochloric acid, acetic acid, ammonium chloride, sodium sulphate and magnesium sulphate. The behaviour of alkali-activated mortars with BFS and BFS/SBA was better than that found for plain OPC mortars, especially in ammonium chloride, acetic acid and sodium sulphate media. After 200 days of testing in ammonium chloride solution, the compressive strength loss for Portland cement mortar was about 83.3%. For the same test conditions, alkali-activated mortars presented a maximum reduction of 48.4%. The presence of SBA in alkali-activated BFS mortars did not produce any serious problems in durability. As a general conclusion, sugarcane bagasse ash (SBA) obtained by auto-combustion showed good cementing properties as a mineral precursor blended with blast furnace slag (BFS) in alkali-activated systems.

Physical–mechanical and microstructural properties of alkali-activated fly ash–blast furnace slag blends

This paper investigated physical–mechanical and microstructural properties of alkali-activated binders based on blends of fly ash (FA) and blast furnace slag (BFS). FA–BFS blends were alkali-activated with sodium silicate (water glass) solution. The synthesis of alkali-activated binders was conducted at 95°C during 24h, with different FA–BFS mass ratios (100:0; 75:25; 50:50; 25:75; 0:100), different moduli of alkali activator (SiO2/Na2O: 0.5; 1.0; 1.5) and different alkali activator concentration (% Nа2О: 4; 7; 10). The influence of alkali activation conditions on the flexural and compressive strengths, setting time, drying shrinkage and the microstructure of synthesized binders was investigated. It was found that the compressive strength mostly depended on the composition of the FA–BFS blends and the water/binder ratio. The setting time highly depended on the activator concentration, while the drying shrinkage was mostly affected by the curing temperature. The blend comprising FA 25%–BFS 75%, activated with the activator of modulus 1.0 and the activator concentration of 10% Na2O yielded optimal mortar regarding investigated physical–mechanical characteristics. Microstuctural examination showed that the chemical composition of the binding phase varied as a function of the blend composition. Predominance of FA alkali reaction products in the binding phase positively influenced the flexural strength, while the predominance of BFS alkali reaction products positively affected the compressive strength. Optimal characteristics of alkali-activated binder were related to the following chemical composition of the binding gel: Ca/Si=0.34–0.50, Al/Si=0.15–0.24, Mg/Si=0.07–0.16 and Na/Si=0.21–0.37. Empirical values of optimal gel composition could serve as a basis for tailoring the properties of alkali-activated binders based on different industrial waste precursor material.

Strength and Permeation Properties of Slag Blended Fly Ash Based Geopolymer Concrete

Geopolymer is a binder that can act as an alternative of Portland cement. Geopolymers use by-product substances such as fly ash, and can help reduce carbon dioxide emission of concrete production. This paper presents the results of a study on the fly ash based geopolymer concrete suitable for curing at ambient temperature. To activate the fly ash, a combination of sodium hydroxide and sodium silicate solutions was used. The setting and hardening of geopolymer concrete were obtained by blending blast furnace slag with fly ash instead of using heat curing. Ground granulated blast furnace slag (GGBFS) was used at the rate of 10% or 20 % of the total binder. The tests conducted include compressive strength, tensile strength, flexure strength, sorptivity and volume of permeable voids (VPV) test. The geopolymer concrete compressive strength at 28 days varied from 27 to 47 MPa. Results indicated that the strength increased and water absorption decreased with the increase of the slag content in the geopolymer concrete. In general, blending of slag with fly ash in geopolymer concrete improved strength and permeation properties when cured in ambient temperature.

Carbonation durability of blended cement pastes used for waste encapsulation

Blended cement pastes are currently used for encapsulation of low level and intermediate level nuclear waste in the UK. However, there is still little information on the long-term durability of those mixes to some chemical attacks. Accelerated testing may predict the long-term durability or at least help the selection of more durable formulations. In this work, blended blastfurnace slag (BFS)/Portland cement (OPC) pastes containing 60, 75 and 90% BFS and pulverised fuel ash (PFA)/OPC pastes with 40, 55 and 75% PFA were cured at 20 and 60°C for 90 days then submitted to natural and accelerated carbonation (5% CO2). The effects of the curing temperature as well as the OPC replacement level on the carbonation ratio are presented. Results showed a good correlation between natural and accelerated carbonation for the pastes studied. Carbonation was found to be governed by the amount of calcium hydroxide available in the mixes before the process started.

Composition and microstructure of 20-year-old ordinary Portland cement–ground granulated blast-furnace slag blends containing 0 to 100% slag

The morphology of outer-product (Op) C–S–H in 20-year-old slag–cement pastes appeared in most blends to be finer than at younger ages. The Ca/Si and Ca/(Si + Al) ratios of the Op C–S–H decreased with increasing slag content, and the Al/Si ratio increased. The Ca/Si ratio of C–S–H in the slag-containing pastes was lower at 20 years than at 14 months and the amount of Ca(OH) 2 was reduced indicating that additional slag must have reacted. The mean aluminosilicate chain length of the C–S–H was very long in all the samples and would be expected to have increased with age. The TEM-EDX and NMR data are consistent with nanostructural models for C–S–H. The Mg/Al ratio of the Mg–Al layered double hydroxide phase (LDH) was lower at 20 years than at 14 months in all cases except for the neat slag paste; aluminium hydroxide-based structure might be interstratified with those of the Mg–Al LDH.

Evaluation of Binary and Ternary Blends of Pozzolanic Materials Using the Rapid Chloride Permeability Test

The effect of replacing cement by pozzolanic materials was investigated. This was done by a systematic increase in pozzolanic material inclusion, and was evaluated using the Rapid Chloride Permeability Test. The materials used were fly ash, blast furnace slag (BFS), and silica fume. The blending was at the increasing levels of 25, 50, and 70% of fly ash or BFS, with or without addition of silica fume at 10% cement replacement to form binary and ternary blends. A commonly practiced initial curing regime of seven days was administered. The experimental results obtained in this study were analyzed using statistical methodology. The results indicated that an increase in fly ash content increased the charge passed in the specimens but the reverse trend was observed with increase in the BFS content in the absence of silica fume. Silica fume alone as well as its ternary blend with 25% fly ash showed lower charge when compared with the control or with the binary blend of cement and fly ash. However, in ternary blends containing fly ash at more than 25%, the presence of silica fume did not cause a reduction in the charge. All ternary blends comprising BFS and silica fume passed lower charges than the respective binary blends. These ternary blends exhibited dense microstructure compared to the corresponding binary fly ash blends. The highest percentage replacement of cement with 70% BFS and silica fume was comparable with the addition of silica fume alone. The results showed that concretes with BFS blends exhibit lower charge passed and higher compressive strength than comparative blends using fly ash.

Characteristics of a NaOH‐Activated Blast Furnace Slag Blended with a Fine Particle Silica Waste

Mortars of blast furnace slag blended with a geothermal silica waste at various replacement levels of 0%, 5%, 10%, 15%, and 20% were cured for up to 90 days. The binder was activated by 6 wt% Na2O equivalent of sodium hydroxide. Lime was added as an activating agent and also to promote pozzolanic reaction with the silica. It was found that the presence of the silica waste increased the reactivity of the cementitious materials, as measured by means of nonevaporable water. The compressive strength was increased in the presence of the silica, except at the highest replacement level of 20%, the optimum silica replacement was that of 5%–10%. The microstructures of blended slag showed less porosity than those of neat slag mortars. The lime was completely consumed after 90 days of hydration.

Studies on high-strength slag and fly ash compound cement

High-strength composite portland cement blending blast furnace slag (BFS) and fly ash was obtained by using activators. The influence of the activators on the composite portland cement has been studied. Hydration phases and hydration mechanism were investigated by means of XRD, SEM, and DTA tests.

Chloride Induced Steel Corrosion in Concrete: Part I—Corrosion Rates, Corrosion Activity, and Attack Areas

This paper presents results from a major long-term study on chloride-induced steel corrosion in concrete. The performance of a set of 50 reinforced concrete slabs made with a range of portland and blended cement binders was evaluated. Two portland cements, a high C3A and a low C3A, a blended fly ash cement, and a blended blast furnace slag cement were used. All reinforced concrete slabs were exposed to high chloride conditions by partial immersion in a 3% NaCl solution modeling seawater conditions. The reinforcement was cleaned and weighed prior to inclusion into the concrete slabs. Periodic nondestructive measurements of concrete performance included half cell potential monitoring, concrete resistivity, and electrochemical measurements of rates of corrosion of steel in concrete using potentiodynamic anodic procedures. Individual slabs were broken for reinforcement recovery at predetermined times during the study. Measurements were made of the area of corrosion and the weight loss of steel through corrosion. This information was related to the nondestructive data acquired on the slabs. In Part 1, estimated corrosion current (Ic) data and areas under the Ic versus time envelope for reinforcement within concrete slabs is presented. These data were obtained using potentiodynamic anodic polarization techniques. Measurements of the reinforcement corroded area in concrete are also presented and related to the electrochemical measurements taken. It was found that concrete water:binder ratio significantly influenced the corrosion rate of steel in concrete. Relationships were established between corrosion activity and the area of chloride-induced steel corrosion. Observed relationships were different for reinforcement within portland cement concretes and blended cement concretes considered.