Blast-furnace Cement Research Articles

The use of zeolite, lightweight aggregate and boiler slag in restoration renders

For the protection of walls against salt-damp, various renders with different aggregates are proposed. The purpose of this study is to investigate the impact of natural zeolite, lightweight aggregate and boiler slag additives in the production of cement-lime renders meant for salty walls. The article presents laboratory examinations of their basic physical parameters such as water absorption, capillary absorption, water vapour permeability, absorptivity, sorptivity, density, total porosity, compressive and flexural strength. In addition to studies of the basic physical properties of the renders, frost and chemical corrosion resistance tests were conducted. Special additives to improve the properties were used such as hydrophobizer, methyl cellulose – a water-retaining additive, ethylene vinyl acetate copolymer powder, as well as a redispersive additive to improve adhesion. Apart from white Portland cement CEM I 52.5 R, blast furnace cement CEM III was also used, wherein the composition contains coal ash.The highest efficiency of render corrosion protection was obtained by the renders with Portland Cement CEM I 52.5 R and boiler slag. The experimental results showed that the mortars modified by natural zeolites and boiler slag, thanks to their porous structure, are distinguished by good sorption properties and can accumulate in themselves a sufficient amount of salt and ice.

高炉スラグ微粉末の比表面積および置換率がコンクリートの長期強度発現に及ぼす影響

Reduction accompanied by no CO2 emissions to global warming has become an urgent task. CO2 emissions in the cement industry has also become an important issue, is valid expanded use of mixed cement as the method. ground granulated blast furnace slag is free to set the substitution ratio in accordance with the concrete application and conditions are expected as admixture since it is possible widespread use than blast furnace cement. Concrete with ground granulated blast furnace slag is enhanced long-term strength can be expected, there is for initial strength development is slow problem. It is effective to use the specific surface area increases the ground granulated blast furnace slag as its improvement. Currently, ground granulated blast furnace slag is the study of a range of specific surface area as specified in JIS A 6206 has been reported, the development of powder technology, ground granulated blast furnace slag powder having a specific surface area greater than it be so available became. Therefore, targeting a wide range of ground granulated blast furnace slag from a specific surface area of 4000 to 30000 (cm2/g) , and long-term study of strength development the usefulness of concrete combination of specific surface area and the replacement ratio was variously set. Moreover, it was quantitatively clarify the relationship between the conditions and the concrete strength development effect of such specific surface area and degree of substitution ground granulated blast furnace slag. (1) As various factors ground granulated blast furnace slag, substitution rate and specific surface area of the ground granulated blast furnace slag has revealed the effect on the strength. (2) Quantitatively examined the relationship between strength development effects of blast furnace slag concrete, ordinary Portland cement and ground granulated blast furnace slag strength development effect of the strength development effect as blast furnace slag concrete ordinary portland cement revealed.

Ecological Concrete Based on Blast-Furnace Cement with Incorporated Coarse Recycled Concrete Aggregate and Fly Ash Addition

Ecological Concrete Based on Blast-Furnace Cement with Incorporated Coarse Recycled Concrete Aggregate and Fly Ash Addition

新設コンクリート部材における水分特性と表層透気性に関する研究

Surface-layer air permeability depends strongly on the water content of concrete. Therefore, newly built structures, which contain a large amount of water, require water content evaluation during inspections. The relationships among the material age, surface-layer air permeability, relative humidity, and air permeability coefficient of newly cast concrete have been reported, but there have been few studies on the relationship between the water content and air permeability of young concrete. In this study, the effects of the water content of young concrete on surface-layer air permeability were investigated to propose a method for evaluating the durability of newly built concrete structures. To study the relationship between water behavior and air permeability in concrete in indoor and outdoor environments, specimens and actual-size walls containing embedded ceramic sensors were produced from ordinary Portland cement, Portland blast furnace cement type B, and fly ash cement. The relationships among the water content of concrete, Wenner method resistivity, and air permeability were determined. In addition, pore structure was analyzed by the mercury intrusion technique and discussed. The effects of the relationship between pore structure and water content on air permeability varied according to material age for different kinds of cement in an indoor environment. The results indicated that it is possible to evaluate the durability of concrete aged 28 days or older, for which the effects of structural changes can be removed.

Optimum reaction ratio of coal fly ash to blast furnace cement for effective removal of hydrogen sulfide

Reducing hydrogen sulfide concentration in eutrophic marine sediments is crucial to maintaining healthy aquatic ecosystems. Managing fly ash, 750 million tons of which is generated annually throughout the world, is another serious environmental problem. In this study, we develop an approach that addresses both these issues by mixing coal fly ash from coal-fired power plants with blast furnace cement to remediate eutrophic sediments. The purpose of this study is to optimize the mixing ratio of coal fly ash and blast furnace cement to improve the rate of hydrogen sulfide removal based on scientific evidence obtained by removal experiments and XAFS, XRD, BET, and SEM images.In the case of 10 mg-S L−1 of hydrogen sulfide, the highest removal rate of hydrogen sulfide was observed for 87 wt% of coal fly ash due to decreased competition of adsorption between sulfide and hydroxyl ions. Whereas regarding 100 mg-S L−1, the hydrogen sulfide removal rate was the highest for 95 wt% of coal fly ash. However, for both concentrations, the removal rate obtained by 87 wt% and 95 wt% were statistically insignificant. The crushing strength of the mixture was over 1.2 N mm−2 when the coal fly ash mixing ratio was less than 95 wt%. Consequently, the mixing ratio of coal fly ash was optimized at 87 wt% in terms of achieving both high hydrogen sulfide removal rate and sufficient crushing strength.

Research for the production of blast furnace cement mortar using an alkaline activation method

This study was performed in order to obtain the effect of the compressive strength of the cured product with manufacturing conditions (amounts of fine aggregate and different types of alkali activator). Material which is the basis of the cured product was used for the blast furnace slag, which has a latent hydraulic activity. Consequently, when using sodium hydroxide as the alkali activator, it is possible to obtain a higher compressive strength than using the calcium hydroxide. And also, it can be added a 10% of fine aggregate with blast furnace slag to improve the compressive strength.

Application of a recently developed geotechnical carbon calculator in Europe

Recent research regarding soil stabilization has been increasingly concerned with environmental performance. The present paper applies the newly developed CO2(eq) geotechnical calculator, created by the European Federation of Foundation Contractors and the The Deep Foundations Institute, to assess the behavior of three different binders used in the construction of cutter-soil mixing columns, which formed an embankment/bridge transition wedge. The binders were based on ordinary Portland cement, on a blast furnace slag and cement blend and alkali activated fly ash. Results show that the last two binders are significabtly more effective, in terms of environmental performance, than the more traditional cement-based binder. Although the blast furnace slag cement, at this early stage of the geopolymeric binders, appears as the most interesting option, the fact that the CO2/cost ratio of both options is very similar stands out.

Structural and durability properties of hydraulic lime–pozzolan concretes

This paper discusses the results of a suite of tests designed to assess the structural and durability characteristics of hydraulic lime–pozzolan concretes. Specifically, this paper reports on the rate of strength development, elastic modulus, linear shrinkage and rate of carbonation of four hydraulic-lime–pozzolan concretes. The purpose of this investigation was to ascertain the technical feasibility of producing high strength concretes using hydraulic lime and pozzolans as an alternative binder to Portland cement. Results have demonstrated that 28-day compressive cube strengths of 35MPa can be attained by water-cured lime–pozzolan concretes. The results are presented alongside comparable test results for Portland-cement (CEMI) and blastfurnace cement (CIII/A) concretes. Similarities and differences in material characteristics are discussed in terms of fundamental material properties and in terms of the emergent threats and opportunities for the potential development of these novel concretes.

Early-age heat development in GGBS concrete structures

China accounts for approximately half of global steel production and more than 80 Mt of blast-furnace slag is generated every year as a by-product. About 80% of blast-furnace slag is recycled in China and the majority of this is used as an additive in low-grade composite cement or ‘blast-furnace cement’. This paper discusses the technical feasibility of using ground granulated blast-furnace slag (GGBS) in structural concrete for high-value applications in China. The effects of the slag on concrete compressive strengths are investigated experimentally at different curing temperatures. The influence of partial replacement of CEM I with GGBS on the heat development of concrete is investigated through isothermal calorimetry tests. The presence of slag contributes to a reduced heat output rate. The results obtained from the isothermal calorimetry tests are also used to simulate the heat liberation process in suspended concrete slabs using finite-element software. Finite-element modelling results, validated by semi-adiabatic calorimetry tests, indicate that partial replacement of CEM I cement with GGBS contributes to a reduced peak hydration temperature and this has a beneficial effect in hot-weather concreting.

Performance characteristics of concrete based on a ternary calcium sulfoaluminate–anhydrite–fly ash cement

This paper reports an assessment of the performance of concrete based on a calcium sulfoaluminate–anhydrite–fly ash cement combination. Concretes were prepared at three different w/c ratios and the properties were compared to those of Portland cement and blast-furnace cement concretes. The assessment involved determination of mechanical and durability properties. The results suggest that an advantageous synergistic effect between and ettringite and fly ash (Ioannou et al., 2014) was reflected in the concrete’s low water absorption rates, high sulfate resistance, and low chloride diffusion coefficients. However, carbonation depths, considering the dense ettringite-rich microstructure developed, were higher than those observed in Portland cement concretes at a given w/c ratio. It was concluded that the amount of alkali hydroxides present in the pore solution is as important factor as the w/c ratio when performance of this type of concrete is addressed.

Assessment of Blended Cements Effectiveness Against ASR by Mortar and Concrete Expansion Tests

The effectiveness of blended cements (three pozzolanic cements two with natural pozzolana and one with coal fly ash – and one blast-furnace cement) in counteracting alkali-silica reaction (ASR) was assessed by using both the ASTM C1567 accelerated mortar bar expansion test and the accelerated concrete prism expansion test at 38°C and 100% RH. A low-alkali Portland cement was also tested as ASR inhibitor. The results of the mortar and concrete expansion tests were analyzed through a kinetic-based model (KAMJ model) to evaluate the expansion rate constant, k, and the Avrami exponent M. These two kinetic parameters were taken as efficacy parameters for each type of inhibitor. The results of the concrete prism expansion tests were also analyzed through an innovative methodological approach and a third efficacy parameter, such as the potential minimum alkali contribution by the inhibitor to concrete (Lim), was evaluated. It was found that the values of ln(k)mb =-6.0 for mortar bars and ln(k)cp = -7.7 for concrete prisms were appropriate efficacy criteria for discriminating between deleteriously expansive and non-deleteriously expansive mortar or concrete mixes, respectively. In the case of concrete mixes, a good relationship between the efficacy parameter Lim and the kinetic parameter Mcp was found, thus demonstrating the suitability of Mcp as a criterion for ranking not expansive concrete mixes. With respect to the kinetic parameters ln(k)cp and Mcp, the efficacy parameter Lim appears to be of greater technological interest, the last being strictly related to the composition of the concrete mix.

Si/Al 복합 조성물과 다환형 올리고머 축합물을 혼입한 모르타르의 내염해성 및 수축제어 향상에 관한 연구

Reinforced concrete structures in harbors or sea shores are typically contacted with sea waters and exposed to brine and humid environment from the start of the construction stage thus erosion in the durability of the structures are aggravated. Especially, the SOC structures suffered drying shrinkage accompanying the through cracks, facilitate the penetration of chlorine ion. In this study, the durability improving admixture(DIA) mixed with oligomer condensate and Si/Al composition was developed. The DIA countervails the drying shrinkage of concrete and mortar, fixes the chlorine ion, and prevents the erosion from the sulfate ion. In the experiments of this study, the mortar having excellent resistibility against salt damage was produced by mixing the DIA with the binder replaced the fine blast-furnace slag and cement. The whole 3 mixtures including the one mixed only with the cement (OPC) and another one replaced the blast-furnace slag (BSC), and the other one mixed with the DIA were tested. Using the 3 mixtures, the experiments to identify restraint drying shrinkage, chlorine ion penetration and the erosion from the sulfate ion were conducted. In all conducted experiments, the excellent resistibility against salt damages and drying shrinkage were identified in the order of DIA, BSC, and OPC.

Modelling the yield stress of ternary cement–slag–fly ash pastes based on particle size distribution

Mineral admixtures are blended with Portland cement to improve strength and durability, and/or to reduce the cost and environmental footprint of concrete mixes. Some mineral admixtures such as fly ash have also been reported to enhance workability of blended cements. This study shows that the key parameter controlling the yield stress of ternary Portland cement–blast furnace slag–fly ash pastes, in the absence of an added rheology-modifying admixture, is the width of the particle size distribution (PSD) at a given water/solid mass ratio. A small addition of fly ash has a significant effect on workability because of its broad PSD, and any other precursors with a similar PSD could possibly have a comparable effect. A model to predict the yield stress is therefore derived based on the Rosin–Rammler PSD width parameter, n, and the water/solid mass ratio, which provides a good description of the experimental yield stress data. It is believed that a broader PSD provides a higher packing density of particles which reduces the volume of water volume required to fill the voids. The excess water is then used to disperse particles and reduces inter-particle forces, hence yield stress. Therefore, at a given water/solid ratio, PSD width is able to be used as a sole parameter to correlate the yield stress of such concentrated suspensions. Also, a very low yield stress can be approached if the PSD is broad enough, in the absence of any rheology-modifying admixtures.

Portland cement-blast furnace slag mortars activated using waterglass: Effect of temperature and alkali concentration

Mortars of portland cement with 50% of blast furnace slag were alkali activated with 0–10%Na2O using waterglass and cured at 10–40°C. The presence of the slag reduced the strength of 0%Na2O blends and the alkaline activation with 4%Na2O resulted in even lower values; 6%Na2O gave similar results as 0%Na2O and 10%Na2O rendered strengths similar or higher than those of neat portland cement. The combination of higher temperature and higher alkalinity favored the reactivity and strength. The formation of N–C–S–H and delayed hydration of portland cement appeared to be the causes of the low strengths observed in alkali activated systems.

Application of an innovative methodology to assessing the alkali-silica reaction in concrete

A new methodological approach, based on two innovative parameters such as the threshold alkali level (TAL) of aggregates and the tolerable driving force (Δtol) provided by an inhibitor of the deleterious alkali-silica reaction (ASR), was used for the assessment of the ASR expansivity of concrete mixes made with different alkali-reactive aggregates and different cements (one limestone-Portland (or Portland) cement, three pozzolanic cements and one blast furnace cement). Concrete prism expansion tests were performed under two different test conditions: 38 °C and 100 % RH or 60 °C and 100 % RH. The alkali-reactivity of the aggregates was also evaluated by using the petrographic examination and the ultra-accelerated mortar bar expansion test in 1 M NaOH solution at 80 °C. The test results were interpreted according to the innovative methodological approach, as well as according to a traditional approach based on pass-fail criteria. It was found that the two parameters, TAL and Δtol, are appropriate for both assessing the alkali-reactivity of aggregates (TAL) and comparing the efficacy of blended cements as ASR inhibitors (Δtol). These two parameters may be rapidly evaluated (150 days of testing) by using the accelerated concrete prism expansion test at 60 °C and 100 % RH.

A novel solidification technique for fluorine-contaminated bassanite using waste materials in ground improvement applications

This study investigates the development of solidification technology, based on the formation of ettringite, for fluorine-contaminated bassanite using waste and recycled materials. Recycled bassanite is mixed with coal ash, blast furnace slag and furnace cement type B in varying proportions to obtain the optimal ettringite production, based on the chemical response. Leaching tests are performed on the different admixtures to measure the solubility of fluorine. Scan electron microscope and X-ray diffraction tests are conducted on the samples to explore the formation and intensity of ettringite. The results show that the suggested admixture has a significant effect on the production of ettringite and increasing the cement content in the admixture increases the formation of ettringite. The increase of the ratio of cement in the admixture has a clear effect on the production of ettringite and the reduction of fluorine solubility compared to the case of cement–bassanite mixture. Both size and length of ettringite crystals increase with an increase in the ratio of cement-admixture/bassanite and intensity of ettringite in the material matrix. The solubility of fluorine decreases with the increase of admixture content because of the concomitant increase in the production of ettringite. The dimensions of the ettringite crystals have a significant effect on the reduction of the solubility of fluorine, i.e., an increase in ettringite prisms size decreases the fluorine solubility. The investigated limits of the suggested admixture do not show any adverse effect on the geo-environmental properties in terms of fluorine release. The suggested admixture is recommended as a stabiliser material for soft clay soil because it is environmentally friendly, economical and meets the environmental standards.

Eco-friendly concretes with reduced water and cement content – Mix design principles and application in practice

The major environmental impact of concrete is caused by the CO2-emission during the cement production. Great potential for the reduction of the impact is seen especially for concretes with normal strength. The use of superplasticizer and high reactive cements as well as the optimization of the particle size distribution and the reduction of the water content allows a significant reduction of the Portland cement clinker in the concrete. Essential is the addition of mineral fillers (e.g. limestone powder) to provide an optimal paste volume. In addition the already practicable substitution of the cement clinker by secondary raw materials like fly-ash or furnace-slag is an appropriate opportunity but limited by the availability of these resources.In several test series the fresh and hardened concrete properties of water and cement reduced concretes were investigated, especially the workability, the strength development, the design relevant mechanical properties as well as durability aspects like carbonation. It was shown that concretes with cement contents lower than 125kg/m3 were able to meet the usual required workability, strength (app. 40MPa) and mechanical properties. The carbonation depth of concretes with 150–175kg/m3 of cement was equal or lower than the depth of the conventional reference concretes for exterior structures. The ecological advantages were identified, using the environmental performance evaluation. A reduction up to 50% in environmental impact compared with the conventional concrete and a reduction of more than 65% by using blast furnace cement was calculated. The application in practice was verified conducting full-scale tests in a precast and ready-mix concrete plant. The special requirements on workability and early strength were fulfilled with a cement content of 150kg/m3.

Selected Properties of Cementitous Composites with Portland Cements and Blended Portland Cements in Extreme Conditions

The paper is focused on research of physico-mechanical properties of concretes with Portland-limestone cement, Blastfurnace cement and Portland-composite cement in comparisom with concrete with Portland Cement CEM I. Following physico-mechanical properties of concretes exposed to extreme conditions were tested: compressive strength, flexural strength, tensille splitting strength, velocity of propagation of ultrasonic pulse, dynamic elasticity modulus and density of hardened concrete. Following environments were used in tests: sulphates, magnesic ions, nitrates, gaseous CO2, high temperatures.

Measuring the Effectiveness of Hydrophobic Layers Using a Non-Destructive Method

The paper focuses on the relationship between the effective hydrophobic layer thickness and the durability of impregnated hydrophobic treatments using single-sided nuclear magnetic resonance measurements. Weathered and non-weathered specimens were compared to detect the influence of different exposures on the performance of hydrophobic layers. The results show that structural changes caused by carbonation of blast furnace cement based concrete have an effect on the hydrophobic layer thickness while the carbonation of Portland cement concrete has none.

The Cement Type Effect on Freeze – Thaw and Deicing Salt Resistance of Concrete

This paper analyzes the effect of the four types of cement (Portland cement, blast-furnace Portland cement, limestone Portland cement and blast-furnace cement) on freeze-thaw and deicing salt resistance of concrete. Eight compositions of concrete with different cements were tested. Four compositions contained hydration retarder added at 0.3 wt% and 0.5 wt% by mass of cement and four compositions were without the retarder. All compositions contained 0.6 wt% of superplasticizer. 3% NaCl solutions was used as a freezing agent in freeze-thaw tests. The mass loss (the weight of scaled material), ultrasonic pulse velocity and residual deformations were measured every seven freeze-thaw cycle. The test results showed that the highest freeze-thaw and deicing salt resistance is observed in concrete made of blast-furnace cement (CEM III/B 32.5N - LH) and the lowest freeze-thaw resistance is observed in concrete made of Portland cement (CEM I 42.5 R) and Portland blast – furnace cement (CEM II/A-S 42.2N). Cement hydration retarder was found to have a negative effect on freeze-thaw and deicing salt resistance of concrete.