Showing papers on "Ground granulated blast-furnace slag published in 2001"

Microcracking and strength development of alkali activated slag concrete

Abstract: Alkali activated slag concrete (AASC) is made by activating ground granulated blast furnace slag with alkalis without the use of any Portland cement. This study investigates the level of microcracking which occurs in AASC when subjected to various types of curing regimes. The corresponding compressive strength developments of AASC were monitored. The level of microcracking were measured using three different types of tests: (1) frequency and size of surface cracks using crack-detection microscope (2) water sorptivity tests measuring absorption of water by capillary attraction and (3) mercury intrusion porosimetry (MIP) tests which measured the pore size distribution of AASC and AAS pastes (AASPs). The results show that the lack of moist curing of AASC increased the level of microcracking measured using all three different tests mentioned above. The strength development of AASC is also significantly reduced by lack of moist curing.

Feasibility of Rotary Cup Atomizer for Slag Granulation

Abstract: At the present molten slag from a blast furnace (B.F.) is granulated by impinging much water without any recovery of its much sensible heat (1 823 K), polluting water and atmosphere. To solve these problems, we studied the dry granulation of molten slag by Rotary Cup Atomizer (RCA), in which the influence of the rotating speed of the RCA on slag drop size was mainly examined. In the experiment, the molten B.F. slag was supplied to the center of RCA with air blast. Slag drops flown from the cup lip due to centrifugal force were collected and examined from viewpoints of shape, dimension and the flown distance of the drop. Most significantly, molten slag was successfully granulated under the dry conditions without water impingement. The rotating speed of the RCA influenced the diameter and shape of slag drop very strongly. The higher rotating speed made the slag drops smaller, more spherical and more uniform. Drops with 5 to 6 mm of average dimension were obtained at the rotating speed of 15 rps (900 rpm), and drops with less than 1 mm, at that of 50 rps (3 000 rpm). In the former case, the shape of drop obtained was distributed, changing from sphere to stick at the further place from the center of RCA. The results revealed a possibility of alternative, new slag granulation process with many benefits.

Plant availability of phosphorus sorbed to potential wastewater treatment materials

Abstract: Ecologically engineered wastewater treatment facilities, such as constructed wetlands and infiltration plants, can be further improved in their P retention by using reactive media with a high P-retention capacity. In a sustainable system, the sorbed P should be recycled in agricultural production. The objective of the present study was to determine the plant availability of P sorbed to different P-retention media. The studied media were: crystalline and amorphous blast furnace slag, natural and burned opoka (a bedrock from Poland), limestone, burned lime, soil from a spodic B horizon, and light expanded clay aggregates (LECA). They were soaked in a P solution, rinsed and dried before incorporation into soil. An additional aim was to compare P taken up by barley with amounts chemically extracted for the estimation of plant-available soil P. P sorbed to the crystalline slag was delivered to the barley plants more efficiently than P added in K2HPO4 fertiliser. Soil extraction with acid ammonium lactate correlated well with P taken up by barley and indicated that P bound to Ca is more available to plants than P bound to Al and Fe. The Mg content of the used slag may replace Mg fertilisation in certain soils. It was concluded that among the investigated filter materials, crystalline slag was the most suitable sorbent from an agricultural point of view, since it possessed a large P-sorption capacity and the sorbed P was largely plant available. The heavy metal content of sorption materials must be examined carefully before their application to agricultural soils.

Effect of additives on dechlorination of PVC by mechanochemical treatment

Abstract: Polyvinyl chloride (–CH2–CHCl–)n (PVC) was ground with a powdered inorganic material (CaO, CaCO3, SiO2, Al2O3, or slag) in a planetary ball mill under atmospheric conditions to investigate the effect of additions on its dechlorination. The grinding causes a dehydrochlorinating reaction, forming a mixture of partially dechlorinated PVC and inorganic chloride, depending on the grinding time. The dechlorination increases as the grinding progresses, and is improved with increasing amounts of additives. The most effective additive is a mixture of CaO, SiO2, and Al2O3, which has the same constituent components as blast furnace slag. CaO, a mixture of CaO, SiO2, and blast furnace slag, are also effective, but CaCO3 is the least effective additive tired.

Ground iron blast furnace slag as a matrix for cellulose-cement materials

Abstract: The use of ground iron blast furnace slag (BFS) as a low-cost alternative to ordinary Portland cement (OPC) binders in fibre-cement products was examined. Both high quality softwood fibres and residual sisal from agricultural waste were chemically pulped and used as reinforcement. Composites based on several different binder formulations consisting of slag chemically activated by mixtures of gypsum and hydrated lime displayed their optimum strength and fracture toughness properties at fibre contents between 8% and 12%, with values in the ranges of 14.7–24.5 MPa and 1.13–2.36 kJ/m2, respectively. Corresponding flexural moduli lay in the range 4.3–7.8 GPa and, at 12% fibre content, the composites possessed water absorption values up to 34% by mass and densities in the region of 1.3 g/cm3. A formulation of BFS activated by 10% gypsum and 2% lime presented a good compromise between strength and energy absorption combined with a reasonable price.

Performance of cement concrete with mineral admixtures

Abstract: The scope of manufacturing blended cements in India and the resultant saving in energy consumption were identified The characterisation of the two main mineral admixtures, namely fly ash (FA) and blast furnace slag (BFS), was based on their chemical and mineralogical composition and their particle characteristics It was found that all the three factors are important from the point of view of selection of appropriate mineral admixture for blending with cement The durability performance of concrete with blended cements was improved in terms of its resistance to the three deteriorating factors, namely alkali±silica reaction (ASR), sulphate attack and the corrosion of steel reinforcement The improved resistance towards the ASR was due to the higher retention of alkalis and the refinement of pore structure, and is due to formation of secondary calcium silicate hydrate (C-SH) during the hydration of FA or BFS components in cement Its resistance towards the Na2SO4 expansion is on account of lower content of

Particle coated bonding systems for hydratable cementitious composition casting and methods for making same

Abstract: Coated articles, methods for making such articles, and waterproofing systems incorporating these. An exemplary coated article comprises a body with surface coating of inorganic particles reactive with hydroxide generated from hydration of concrete or mortar to form hydration products. The articles are designed to be used with cast concrete or masonry. The inorganic particles comprise at least one of (a) aluminum oxide trihydrate; (b) silica dioxide; (c) fly ash; (d) blast furnace slag, (e) silica fume; (f) an alkali or alkaline earth metal salts; or mixture thereof. The particles improve bonding with hydratable cementitious compositions that are cast against the coated surface and allowed to set.

Mechanical Properties and Durability of Concrete Made With Portland Limestone Cement

Abstract: European countries have a great deal of experience in the use of Portland Limestone Cements (PLC). In Latin America, most of the cement plants use limestone as a raw material and an increase in cement production is expected in the next few years. The manufacture of this cement would represent a rapid increase of production without environmental consequences. This paper synthesizes data from a research program carried out over two years to determine the effects of limestone filler on concrete and mortar behavior. At early age, the influence of limestone filler on workability, bleeding, initial curing and mechanical behavior (modulus of elasticity, compressive and tensile strength) was studied. Sulfate resistance and chloride penetration, the most important durability problems related with PLC, were also studied. The addition of slag was also investigated to improve the long-term strength and the durability of PLC. Results show that cements containing around 10% of limestone filler provide similar or better mechanical behavior than portland cement concrete, without compromising their durability properties where low chloride diffusion and high sulfate resistance is required. In this case, the environmental impact of cement manufacture decreases because the energy consumption and the carbon dioxide emission are reduced per ton of cement and the combination with supplementary cementing materials (slag, fly ash or natural pozzolan) can improve these aspects.

Early age strength and workability of slag pastes activated by sodium silicates

Abstract: This article reports the results of an investigation on the activation of blast furnace slag with emphasis on the achievement of equivalent one-day strength to Portland cement at normal curing temperatures and reasonable workability. The effects of varying dosages of sodium silicate activators are discussed in terms of strength of mini cylinders and also workability by the mini slump method. The results are mainly based on pastes but comparisons are also made with mortar and concrete results. The effects of preblended gypsum dosage within the slag, as well as the effect of ultra fine slag on workability are reported. The results of trials with various water reducing admixtures and superplastisers and their effects on strength and workability are reported.

Isothermal Calorimetry Study of Blended Cements and its Application in Numerical Simulations

Abstract: Apparent activation energy (E) is generally used to consider the effect of temperature on the kinetics of cement hydration in the numerical simulation of cement hydration processes. This paper deals with an experimental study on the kinetics of Portland cement and blast furnace slag cement using isothermal Calorimetry at 20, 30, and 40°C. Two different water/cement ratios were used, viz. 0.4 and 0.6. Based on the experimental data, E, for Portland cements and blast furnace cement was calculated dynamically with the progress of hydration. It was found that E. exhibits dependence on degree of hydration, water/cement ratio, and temperature. Variation of E. along with degree of hydration may suggest a change in the mechanisms of hydration. Numerical simulation was done using HYMOSTRUC model with a new expression of E. and good agreement with experimental data was found.