Addition Of Granulated Blast Furnace Slag Research Articles

Correlations between unconfined compressive strength, sorptivity and pore structures for geopolymer based on SEM and MIP measurements

The objective for this research was to investigated the unconfined compressive strength, sorptivity, pore structures and their correlations of recycled concrete fine powder (RCFP) based geopolymers mixed with different granulated blast furnace slag (GBFS). The unconfined compressive strength and sorptivity tests were utilized to measure the unconfined compressive strength and sorptivity coefficient. The pore structures were analyzed using optical method (SEM) and mercury intrusion method (MIP). The particles (pores) and cracks analysis system (PCAS) and image-pro plus (IPP) software were employed to quantitatively characterize the multi-scale micropores in the SEM images. Furthermore, based on MIP measurement and two fractal theories, the variations in pore structural characteristics were evaluated. The findings demonstrate the incorporation of GBFS effectively reduced the sorptivity coefficient and enhanced the unconfined compressive strength, and this effect grew stronger with increasing content of GBFS. The sorptivity coefficient and 28-day unconfined compressive strength had a strong linear negative connection. According to SEM analysis, increasing GBFS facilitated the generation of that greater number of gelling products by improving the degree of reaction, which led to a refinement of internal pore structure and an increase in structural complexity. Meanwhile, the addition of GBFS and increasing its content could effectively facilitate the conversion of macropores into micropores by filling with gel products, and significantly reduce the porosity, threshold pore size and most probable pore size. The unconfined compressive strength and sorptivity coefficient had good linear relationships with its internal porosity. The pore structures of geopolymers had clear fractal features as a whole. Among the two models, the thermodynamic model was more suitable to evaluate the fractal characteristic of the pores for geopolymer. The unconfined compressive strength rose with increasing surface fractal dimension, while the sorptivity coefficent exhibited an opposite trend.

Influence of Recipe Factors on the Structure and Properties of Non-Autoclaved Aerated Concrete of Increased Strength

At present, the load-bearing enclosing structures of buildings and structures are designed and built considering the increasing requirements for energy efficiency and energy saving of such structures. This is due to the need for a thrifty attitude to the energy consumed and the need to strive for the greening of construction and increase the energy efficiency of buildings and structures. In this regard, one of the most effective and proven building materials is cellular concrete. The purpose of this study was to study the influence of some prescription factors on the structure formation and properties of non-autoclaved aerated concrete with improved characteristics. Standard test methods were used, as well as SEM analysis of the structure of aerated concrete. Non-autoclaved aerated concrete with the replacement of part of the cement with microsilica in an amount from 4% to 16% MS showed higher strength characteristics compared to aerated concrete, where part of the cement was replaced by the addition of granulated blast-furnace slag and a complex additive. The maximum value of compressive strength was recorded for aerated concrete with 16% MS addition. The largest increase in the coefficients of constructive quality was observed in compositions of aerated concrete with the addition of silica fume from 11% to 46% compared with the control composition. The addition of microsilica makes it possible to achieve an improvement in the thermal conductivity characteristics of non-autoclaved aerated concrete (up to 10%). Replacing part of the cement with slag and complex additives does not have a significant effect on thermal conductivity. The obtained dependencies were confirmed by the analysis of the structure formation of the studied aerated concrete at the micro level. An improvement in the microstructure of aerated concrete with the addition of microsilica in comparison with samples of the control composition has been proven.

Sodium Aluminate Activation of Non-ferrous Waste Foundry Sand: A Feasibility Study

The study was conducted to investigate the feasibility of sodium aluminate activation of nonferrous waste foundry sand. The aim was to solidify nonferrous foundry sand via geopolymerisation into useful civil engineering materials. Green foundry sand was mixed with sodium aluminate to make a paste which was filled into 50 × 50 × 50 mm3 mold. The mixture was cured in an oven for 5 days. The concentration of sodium aluminate, granulated blast furnace slag (GBFS) : waste foundry sand (WFS) ratio, liquid to solid ratio (L/S) and temperature were varied respectively to establish the optimum curing conditions. The results indicated that sodium aluminate has a high potential to be used as an alkaline activator in the synthesis of WFS geopolymers. The geopolymer prepared with 6 M sodium aluminate yielded the highest UCS of 3.59 MPa after curing for 5 days which did not meet the minimum requirements for ASTM C34-13, C129-14a and South African standard (SANS227: 2007). The addition of GBFS in the WFS geopolymer mix design enhanced the mechanical strength of WFS geopolymers. The GBFS modified WFS geopolymer prepared with 50% GBFS, 4M sodium aluminate, L/S ratio of 0.15 and cured at 80°C yielded the highest UCS of 10.57 MPa. The GBFS modified WFS geopolymer met the minimum requirements for ASTM C34-13, C129-14a and South African standard (SANS227: 2007). The results also show a, high potential ability to valorise WFS and GBFS reduce building material problems, while also providing the building and construction industry with a useful and inexpensive new raw material with less CO2 emissions.

GRANULATED BLAST FURNACE SLAG AS A SUPPLEMENT ENHANCING FIRE RESISTANCE OF PORTLAND CEMENT MORTAR

Using steel slag in the cement industry has been considered a green recycling solution to the solid waste problem. Granulated blast furnace slag (GBFS), in fact, is used as an additive to counteract the sulfate attack of Portland cement; however, its ability to undergo fire or heat exposure has not been highlighted yet. Therefore, this study focuses on compressive strength behaviour at high temperature along with workability of cement paste of cement containing GBFS. Here, a set of blended mixture prepared with OPC was replaced by GBFS at 10, 20, 30, 40 wt.%. Setting time of pure OPC and blended OPC and GBFS was carried out to evaluate workability of all mixtures. After 28 days of curing, compressive strength of samples exposed to heat at 200, 400 and 600 °C was measured. Along with that, the mass loss of the sample to predict thermal resistance was analyzed by thermogravimetric analysis (TGA); moreover, microstructure of hardened samples in terms of mineral composition, distribution was analyzed by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). Results of the conducted study showed that GBFS addition into OPC could enhance fire resistance through the slight increase in compressive strength compared to the OPC one at 600 °C and the mass loss; moreover, the blended cement containing different amount of GBFS maintain workability of cement paste.

High temperature resistant restoration mortar with fly ash and GGBFS

Nowadays, the development of sustainable building materials is of loom large in for the preserve resources and reducing CO2 emission and environmental pollution effects. Exposure to fire or other high temperatures of mortars produced with calcium-based binders (cement or hydraulic lime) adversely affects their mechanical properties. In addition, the effect of high temperature may cause a change in the pore structures, causing cracking and spalling. Protecting the integrity of historical buildings exposed to high temperatures is important for cultural sustainability. In this study, natural hydraulic lime (NHL) used as a binder in mortars was replaced with 15, 30 and 60% fly ash (FA) and granulated blast furnace slag (GBFS). In the mixtures, 1.5% (by volume) polypropylene fiber (PF) was also used. Test results reveal that while the mortars’ workability increased as the FA and GBFS content increased, PF decreased the flow diameters of the mortars. It has been determined that the paste content affects the porosity and water absorption rates of mortars. With the addition of FA content, paste content increased and porosity reduced. Compressive strength over 10 MPa was obtained by using 30% FA in 90-day lime mortars. As the addition of GBFS, the compressive and flexural strength were negatively affected. PF has reduced the porosity and water penetration depth of the mortars thanks to its micro filler effect. FA-based mixtures were more resistant to high temperatures than GBFS-based mixtures. Compressive strength was measured between 4.3 and 8.6 MPa after 600 °C temperature in FA-based mixtures. In fibrous mixtures, increment of mass loss was more with high temperature. C-S-H gels were observed in XRD and SEM analyzes of mortars exposed to high temperatures. PF was observed in stereomicroscope images of mixtures exposed to 200 °C. Since the porosity of the mortars is relatively high (19.7%–30.8%), the PF in the mixtures exposed to 200 °C did not melt completely but was damaged. As a result, it would be more appropriate to use 30% of FA and 15% of GBFS in NHL mortars.

Rheology and Mechanical Properties of Fly Ash-Based Geopolymer Mortars with Ground Granulated Blast Furnace Slag Addition

Geopolymers are less energy-demanding alternatives to Portland cement binders. The subject of geopolymer rheology has not yet been fully explored, and the available literature is limited to a narrow range of material compositions. This paper presents the rheological and mechanical response of fly-ash based geopolymer mortars. Investigations were made of the effect of different levels of ground granulated blast furnace slag (GGBFS) addition levels on the rheological properties of fresh geopolymers as well as their mechanical performances at 2, 14 and 28 days. The aim of the study was to obtain flow curves and to establish the correlation between shear stress and shear rate. The results have shown that geopolymer mortar is a pseudoplastic liquid presenting shear thinning behavior, moreover, with the increase of GGBFS content, higher material strengths were obtained and the total porosity was reduced.

Orthogonal Experimental Studies on Preparation of Mine-Filling Materials from Carbide Slag, Granulated Blast-Furnace Slag, Fly Ash, and Flue-Gas Desulphurisation Gypsum

Environmentally friendly and cheap composite green cementitious materials have been prepared from carbide slag, fly ash, flue-gas desulphurisation (FGD) gypsum, and granulated blast-furnace slag (GBFS) without using cement clinker. Orthogonal testing was used to investigate the effects of the raw materials on the amount of water required for reaching standard consistency and consistency, setting time, slump value, and strength of the produced materials after curing for 7 d and 28 d. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used for the analysis of the sample microstructure and hydration products as well as for the exploration of possible hydration mechanisms. We found that, among the utilised raw materials, the addition of FGD gypsum had the most significant effect on the setting time and amount of water required for reaching standard consistency and consistency, while the addition of GBFS deeply affected the slump value. The optimal activation results were obtained when the mass ratio of carbide slag : fly ash : GBFS : FGD gypsum was equal to 12.1 : 60.6 : 18.2 : 9.1.

Optimizing the Acid Resistance of Concrete with Granulated Blast-Furnace Slag

Concrete for agricultural or industrial applications is often subject to intense acid attack. Most affected structures are sewage structures and biogas plants, natural draught cooling towers or silage silos. Widely independent from acid type, in most cases the acid attack on concrete runs the same way, starting with dissolution of easily soluble calcareous phases like calcium hydroxide. With ongoing attack, calcium-silicate-hydrate crystals (CSH) are also affected by acidic media. In contrast, siliceous phases like silicon-dioxide (SiO2) are widely unaffected by acid attack. While the dissolution of the matrix is increasing with ongoing attack, quarzitic aggregates remain unchanged. Beside the use of coarse SiO2-aggregates, the resistance against acid attack is mainly increased by a minimization of the porosity. For this purpose on one hand, a low water/cement-ratio has to be sought, on the other hand also the fines should be distributed with an optimized grading curve (e.g. Fuller-principle). In practice, this results in a combination of various fine and ultra-fine components, e.g. fly ash, GGBS, silica fume or metakaolin. Such binder compositions lead to a particularly dense microstructure, especially at pore sizes below 1 micron, and a higher chemical resistance due to a lower Ca(OH)2 content. This paper gives an overview on typical acid-resistant concretes, most common applications as well as the effects of the related acid attack and points out the potential of granulated blast furnace slag addition to such concretes.

Influence of superabsorbent polymer on shrinkage properties of reactive powder concrete blended with granulated blast furnace slag

This study involved investigating the contributions of granulated blast furnace slag (GBFS) and internal curing (IC) by means of superabsorbent polymer (SAP) on shrinkage behaviour, hydration heat, and mechanical strength of reactive powder concrete (RPC). The results indicated that autogenous shrinkage decreased with an increase in GBFS content, and a combination with IC completely mitigated autogenous shrinkage and even led to a net expansion. The mechanical strength decreased with the addition of GBFS. However, compressive strength still exceeded 100MPa even when the replacement level of GBFS corresponded to a maximum of 50%. Although IC by means of SAP slightly reduced the strength, this reduction was acceptable given the important role that it played on mitigating autogenous shrinkage. The drying shrinkage and mass loss increased significantly with an increase in the GBFS content. The IC did not exhibit an obvious effect on drying shrinkage and mass loss. However, it counteracted high drying shrinkage by significantly reducing autogenous shrinkage. The total shrinkage of RPC with IC and GBFS was significantly lower than that without IC and GBFS. The combination of GBFS and IC can adequately solve serious shrinkage deformation and provide an environmental friendly and low cost method to produce RPC.

Long-term Compressive Strength of Mortars Modified with Hardening Accelerating Admixtures

Nowadays producers of fresh concrete and reinforced concrete precast elements wants to shorten time of curing. This is beneficial for the sake of organization of building and manufacturing process. Constructional elements gain strength faster. They can be demoulded, transported and loaded earlier. Economic benefits are gained because formworks may be rent for shorter periods and moulds for precast elements may be filled up with next element earlier so the production is more efficient. The shortening of curing time may be achieved by usage of hardening and set accelerating admixtures. Other benefit is possibility of concreting during winter time. Besides obvious advantages showed before there are drawbacks of such admixtures. One of the most dangerous is lowered final compressive strength in comparison with non-modified concrete. Long-term (28, 90, 180 and 360 days) compressive strength of cement mortars were tested. Samples were made with usage of Portland cement and cement with 35% ground granulated blast furnace slag addition. In case of CEM I 52.5R decline of long-term compressive strength caused by hardening accelerating admixtures is always visible but its scale is not very large and depends on type of admixture. In case of cement with slag addition the decrease of compressive strength does not occur after modification by accelerator based on CSH crystal seeds in both dosages (50% and 100% of maximal allowed by producer) and for calcium nitrate in half of maximal dosage. According to statements above it is not allowed to say that every hardening accelerating admixture cause decline of compressive strength in long period of time in case of every kind of cement. Performed examinations are part of PhD thesis entitled ‘The possibility of early compressive strength enhancing of cements with ground granulated blast-furnace slag addition’.

Influence of Silicon Carbide and Electrocorundum on the Thermal Resistance of Cement Binders with Granulated Blast-furnace Slag

The aim of this work was to compare the influence of the electrocorundum and silicon carbide on the strength and the microstructure of the cement composite with the addition of granulated blast-furnace slag, before and after exposition to higher and high temperature. Research proved that compressive strength of the cement composite with addition of Al2O3 in the amount of at least 2wt.% increased in comparison to the referential samples, regardless of the high temperature, by about 25%, and the best results in the whole temperature range were obtained in case of cement binder with 6wt.% addition of electrocorundum. On the other hand, addition of silicon carbide resulted in a relevant increase of the sample resistance (by 20-30%) only when added in the amount of at least 10wt.%.

Impact of calcium ions leaching caused by biogenic acid attack on durability of cement composites

Leaching of calcium ions increases the porosity of cement-based materials, consequently resulting in a negative effect on durability since it provides an entry for aggressive harmful ions, causing corrosion of concrete. Sulphuric acid corrosion of concrete can be caused due to attack of aggressive media naturally existing in the environment. Another possibility of corrosion formation is biogenic acid effect through the agency of microorganisms. The paper is focused on the investigation of the influence of biogenic acid attack on the cement composites affected with bacteria Acidithiobacillus thiooxidans. The concrete specimens with 95% wt. addition of antimicrobial activated granulated blast furnace slag as durability increasing factor as well as without any addition were studied. The experiments proceeded during the nine 7-day cycles. The pH values and chemical composition of leachates were measured and evaluated after each cycle. The higher resistance of concrete samples with the addition of 95% wt. of antimicrobial activated granulated blast furnace slag to the aggressive environment was confirmed. The leaching of calcium ions of concrete sample affected with bacteria Acidithiobacillus thiooxidans was 1.13 times lower (736.6 mg/L of leachate) for concrete sample with antimicrobial activated granulated blast furnace slag addition comparing to concrete sample of ordinary CEM I Portland cement without any additives (832.0 mg/L of leachate).

Physico-mechanical and microstructural properties of rehydrated blended cement pastes

This study aims to investigate the effect of high temperatures of up to 1200°C and rehydration on the mechanical properties, microstructure and phase composition of blended cement pastes prepared from Portland cement (PC), granulated blast furnace slag (GBFS), high-temperature fly ash (FA) and ground limestone (GL). It has been found that the heating process induces a reduction in bulk density, flexural and compressive strength. The proportion of pores with a diameter higher than 0.1μm increases with increasing temperature. The addition of GBFS or FA improves the strength properties of dehydrated cement paste (DCP), but this effect was not observed after rehydration. Cement paste with added GBFS has the best resistivity to high temperatures, but after rehydration, GL cement paste shows better mechanical properties.

Study on Properties of Self-Compacting Concrete with Recycled Powder

To utilize the recycled powder as concrete additives, self-compaceing concerte with recycled powder, granulated blast-furnace slag and granulated limestone were tested for slump-flow, compressive strength, modulus of elasticity and drying shrinkage. Reduction in superplasticizing effect of high-range water reducer was found for concrete with recycled powder. Compressive strength of concrete with recycled powder were the same as those with granulated limestone, and lower than those with granulated blast-furnace slag. Concrete with recycled powder showed lower elastic modulus and higher drying shrinkage than those with granulated blast-furnace slag and granulated limestone. The addition of granulated blast-furnace slag together with recycled powder to self-compacting concrete improved superplasticizing effect of high-range water reducer and properties of concrete.

粉化転炉スラグ‐高炉水砕スラグ混合物の強度発現性と反応生成物の特徴

Recently, basic oxygen furnace slag produced by a new steel-making process is supplied as powdered particles containing a high content of free lime. When this slag is used as a material for the base course of road, its unfavorable self-deterious property may become an important problem. It is considered that the addition of granulated blastfurnace slag, which is a porous and stable material, to the powdered basic oxygen furnace slag can improve both the strength and durability of compacted mixtures.This paper deals with the effective utilization of powdered basic oxygen furnace slag and granulated blastfurnace slag in road construction. The suitability of compacted mixtures of two slags was investigated utilizing such characteristics as resistance to immersion in water, compressive strength and CBR value. Reaction products and microstructural features of the compacted slag mixtures were also elucidated by DSC-TG analysis, X-ray diffraction analysis and SEM observations. From the results, it was made clear that the addition of granulated blastfurnace slag to powdered basic oxygen furnace slag increased the strength and reduced the expansion in immersion in water, and that the compacted slag mixtures fully satisfied the requirements of strength and durability for the base course of road.

Properties of Dolomite Plaster Affected the by Addition of Granulated Blast-furnace Slag and Al2 (SO4) 3

Properties of Dolomite Plaster Affected the by Addition of Granulated Blast-furnace Slag and Al<SUB>2</SUB> (SO<SUB>4</SUB>) <SUB>3</SUB>