Portland Cement Blast Furnace Research Articles

A strength model for cement-stabilized mud subjected to various curing temperatures and its early-stage quality control

The influence of curing temperature on the strength development of cement-stabilized mud has been well documented in terms of strength-increase rate and ultimate strength. However, the strength development model is not mature for the extremely early stages. In addition, there is a lack of studies on quality control methods based on early-stage strength development. This paper presents a strength model for cement-stabilized mud to address these gaps, considering various curing temperatures and early-stage behaviors. In this study, a series of laboratory experiments were conducted on two types of muds treated with Portland blast furnace cement and ordinary Portland cement under four different temperatures. The results indicate that elevated temperatures expedite strength development and lead to higher long-term strength. The proposed model, which combines a three-step conversion process and a hyperbolic model at the reference temperature, enables accurate estimate of the strength development for cement-treated mud with any proportions cured under various temperatures. With this model, a practical early quality control method is introduced for applying cement-stabilized mud in field projects. The back-analysis parameters obtained from a 36-h investigation at temperature of 60 °C demonstrated a sufficient accuracy in predicting strength levels in practical applications.

Assessment of pore structure characteristics and tortuosity of 3D printed concrete using mercury intrusion porosimetry and X-ray tomography

Extrusion-based concrete 3D printing is being increasingly used in the construction industry. This paper gives insights into the porosity and pore structure of 3D printed concrete elements using mercury intrusion porosimetry, and X-ray micro-computed tomography. The experiments were conducted with two different cement systems; among which a Portland cement-blast furnace slag blend and a calcium sulfoaluminate cement-limestone blended system. The study reveals that the interlayer region contains larger and interconnected pores with low tortuosity, which could lead to enhanced transport of ions. Using the MIP data, surface fractal dimension and tortuosity parameters were computed. It was observed that the calcium sulfo aluminate-limestone blended system has higher pore complexity and tortuosity than the Portland cement-blast furnace slag system. Compared to mercury intrusion porosimetry, the X-ray micro-computed tomography technique was able to characterize both open and closed pores present in the printed sample at the resolution of the scanning. A significantly higher open porosity and the presence of more elongated pores with a high aspect ratio were observed in the interlayer compared to the bulk region. The current study can be useful in understanding the transport of ions through different regions in printed elements to assess its durability performance.

Influence of grain size gradation of sand impurities on strength behaviour of cement-treated clay

In nature, soils are often composed of varying amounts of clay, silt and sand. Variation of the percentage of these compositions can affect the final strength of the soils when stabilised with cement. In this study, focus was placed on clayey soils with different gradation of sand impurities up to 40% in mass. An extensive study of such clayey soils treated with cement was investigated. For the results, it is noted that water:cement ratio was a major influence of strength development of cement-treated clayey soils. In contrast, the soil:cement ratio was found to have minor effects on the strength development. The presence of sand impurities has a significant reduction on the strength development of the cement-treated clayey soil mixture due to more free water available for hydration. The use of free-water:cement ratio is adopted which was shown to be capable of adjusting for such change in amount of free water and water holding capacity of the clay which is determined with Atterberg’s liquid limit tests. The effects of gradation (fine, coarse and well-graded) of the sand impurities were found to affect strength development minimally, owing to similarities in their liquid limits when mixed with clay. Ordinary Portland cement (OPC)-treated clayey soils produced a more rapid gain in strength but lower final strength at 28 days of curing as compared with Portland blast furnace cement (PBFC). This is found to be persistent for different gradation of sand impurities. A linear correlation can be established based on the log of the unconfined compressive strengths developed at different curing age, with slopes of these linear trends found to be similar for PBFC and OPC-treated clayey soil specimens. Finally, a strength prediction model comprising of these findings is developed. The parameters adopted in this model coincide with values proposed by past studies, thereby validating the robustness of the model. The practical benefits from this study offer a quality control scheme to forecast long-term performance of cement-treated clayey soils as well as optimise cement dosage in cement stabilisation to produce a more cost-effective and less environmental-invasive usage of the technology in geotechnical applications.

Зарубіжний досвід утворення та використання доменних шлаків

We should regard an issue of efficient use of feedstock and, in particular, a transition to waste-free technology from the perspective of adjusting differences between economic growth (more resources in production required) and “productive capacity” of the environment (depletion of mineral resources, lowering of resources quality, disruption of environment balance). It is possible to adjust these differences not only by using resources rationally and comprehensively but also by processing generated industrial waste. In the Ukrainian metallurgical industry, these issues are very important because of the abundant practice of use of out-of-date resource and energy-intensive technologies and feedstock of poor quality. International experience shows that the metallurgical industry has rich potential in reducing generated waste. On average specific solid waste generation for a unit of product in the metallurgical industry in developed countries is 1.5-3 times lower than in Ukraine. One of the important processes of blast-furnace performance is the generation of slag; slag is one of the most valuable secondary materials. Recently international metallurgical enterprises started implementing a hundred percent recycling of use industrial waste. Moreover, for the past decade there were a lot of efforts made to process slag so to meet strict EU environmental requirements, hence we can regard it not as waste but as an industrial by-product. We use slag mainly in the road sector – for road construction, agriculture ‒ for liming of soils, metal industry – as an iron-containing substance for secondary melting in blast furnaces. The cement industry is the main consumer of blast furnace slag. EU regulations allow up to 35% of granulated blast furnace slag in Portland cement and up to 80% in Portland blast-furnace cement. The addition of blast furnace slag into the mixture increases the performance of blast furnaces and reduces fuel consumption by 15% and prime cost by 25-30 %. Apart from that the slag as an additive considerably improves several construction and technical peculiarities of cement. International experience and expert assessments say that Ukraine has not only huge potential in reducing blast furnace slag generation but also a need for its comprehensive processing with up-to-date technologies and state-of-the-art equipment that can bring an economic and environmental advantage.

Generalized hyperbolic formula capturing curing period effect on strength and stiffness of cemented clay

With the increasing popularity of stabilizing soft soils by a cementitious binder, accurate strength prediction of cemented clay with curing period is essential for quality control. In this study, a generalized hyperbolic was proposed to overcome the shortcomings of traditional logarithmic function with regard to both short-term and long-term prediction of strength development. Also, the generalized formula can be used for various cement types, soil types, and curing conditions. It was proved that the model works well for both Ordinary Portland cement (OPC) and Portland blast-furnace cement (PBFC) treated clay. Moreover, the model can also be adopted for stiffness prediction of cemented clay. Based on the proposed model, the predicted strength and stiffness of cemented clay shows high consistency with the measured data from previous literature.

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.

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.

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.

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.

Improvement of Properties of Portland Blast Furnace Cement Type B Concrete by Internal Curing Using Ceramic Roof Material Waste

The present study aims to investigate the effects of porous ceramic waste aggregate (PCA) coarse aggregate as an internal curing material on the compressive strength, porosity, and shrinkage of portland blast furnace cement type B concretes (BB) with a water-to-cement ratio (W/C) of 0.55, in which the replacement ratios of conventional coarse aggregate by PCA were 10 and 20% in volume and the specimens were exposed to drying at the ages of 3 and 7 days and cured under sealed condition. The results showed that internal curing using PCA to replace coarse aggregate by 10 and 20% in volume was effective in improving the compressive strength of BB compared with ordinary portland cement concrete and BB at the age of 28 days, independent of the exposure conditions. Moreover, 10% replacement by PCA was more effective than 20% replacement. Internal curing for BB was found to be effective in decreasing pore volume for specimens exposed to drying at the age of 3 days. However, the total pore volume of BB cured inter...

Solidification technology for fluorine, hexavalent chromium and boron in stabilized soil containing bassanite, coal ash and portland blast-furnace (B) cement

廃石膏ボードは，建築物や家屋の解体に伴う副産物として多量に排出されている。この廃石膏ボードを建設材料として有効利用できれば，廃石膏ボードの処理問題や建設産業における天然資源の枯渇問題が解決されていく可能性がある。本研究で対象とした半水石膏は，廃石膏ボードから得られる二水石膏を130℃以上に加熱することにより生産され，水を加えると固まる性質を有しているため，地盤改良材としての利用が期待されている。しかしながら，石膏に含まれているフッ素の溶出量が土壌の環境基準を上回る場合があるため，フッ素の溶出や流出を物理的および化学的に抑制させることが必要不可欠となる。そこで本研究では，フッ素の溶出を抑制するため，筆者らがこれまで対象とした高炉セメントB種に加え石炭灰を新たなアルミナ源として補足添加し，石炭灰添加に伴うエトリンガイト生成量の変化を検討している。その結果，土壌の安定処理材として少量の高炉セメントＢ種に加え石炭灰をさらに添加することによって石膏からのフッ素溶出濃度はさらに減少することが明らかとなった。また，ホウ素や六価クロムの溶出濃度も土壌の環境基準を満足していた。この主要因としては，石炭灰添加に伴うエトリンガイト生成量の増加が挙げられる。

Development of solidification technology for fluorine contaminated Bassanite using Portland blast-furnace (B) cement

廃石膏ボードは，排出プロセスの違いから「製造時廃材」，「新築時廃材」，「解体時廃材」の3つに区分することができ，その発生量は2007年度で150万トンに上っている。半水石膏は，廃石膏ボードから得られる二水石膏を130°C以上に加熱することにより生産され，水を加えると固まる性質を有していることから，ヘドロの堆積や軟弱粘性土などの地盤改良材としての利用が期待されている。しかしながら，石膏に含まれているフッ素の溶出量が土壌の環境基準をオーバーする場合があることから，半水石膏の適用に関してはフッ素の溶出や流出を物理的および化学的に抑制させる研究が必要不可欠である。そこで本研究では，フッ素の溶出を抑制するため，高炉セメントB種による半水石膏のフッ素不溶化技術を開発した。この結果，土壌の安定処理材として高炉セメントB種を5%程度添加することによって今回対象とした半水石膏添加率の範囲では石膏からのフッ素溶出濃度は養生期間とともに減少し，土壌の環境基準をクリアーする結果を得た。

Liquid Air Energy Storage System. Study of Air Liquefaction Characteristics Using a Concrete-Type Cool Storage Unit.

Technical feasibility of the concrete-type cool storage unit used for the liquid air energy storage system was evaluated. The blending composition for cool storage material was selected as Portland blast furnace cement+sand+air entraining low-water agent+steel fiber. Thermal conductivity was about 20% higher than regular concrete and stainless fiber concrete. Material cost was lower than that of stainless fiber concrete. The liquefaction examination was performed for conditions assuming an actual plant with the concrete-type cool storage unit. If enough insulated treatment was given, the prospect was obtained for a stable liquefaction rate of 70% or more.

임피던스 측정법을 이용한 포틀랜드 시멘트 -고로 슬래그계의 초기수화

임피던스 측정법을 이용한 포틀랜드 시멘트 -고로 슬래그계의 초기수화

Effects of atmospheric acids on Portland cements

AbstractMortar prisms made from three Portland cement types, were exposed at a city centre site (London) and at a suburban site (Horsted). At each site, a set of prisms was exposed either open to the rain or sheltered from it. The chemical analysis of the cements and of the collected rainwater during the experimental period are reported, together with estimates of dry deposited pollutants. The effects of the exposure were assessed by various physical and physicochemical tests of the surface and of the bulk properties of the exposed prisms. The weight increase, the most sensitive indicator of weathering effects, was greater for the sheltered prisms than for prisms open to the rain; the latter, however, showed more visual weathering. Increase in the porosity of the mortars resulted in increased mass gain. The higher acidity of the rain at the Horsted site had an insignificant effect on the percentage mass increase. The effect of this higher acidity was reflected, though inconclusively, by the lower bulk porosity of prisms made from Sulphate Resisting Portland Cement (SRPC) exposed at the Horsted site compared with the set similarly exposed at the London site. The effect of the cement type on the properties of the tested prisms was clearest in the decrease in the ultrasonic pulse velocity (UPV) of the exposed prisms made from Portland Blast Furnace Cement (PBFC) compared with the increase in UPV in prisms made from the other two cements. It seems that the changes in the properties of the prisms exposed to the atmosphere were associated both with the products of the reaction of atmospheric acids with the cement components and the products of continued hydration beyond the 28‐day curing period.© 2001 Society of Chemical Industry

The Special Features of Cement Standards in China

Abstract A large amount of blended cement, special cement, and shaft kiln manufactured cement is produced in China. These cements form the basis for China's cement standards. These standards have many special features and constitute a unique cement standard system. The standard cements are divided into three groups: common cement, special performance cement, and special purpose cement. As common cements, which include ordinary portland cement, portland blast-furnace cement, portland pozzolana cement, and portland composite slag cement, etc., the required and allowable blended materials incorporated in their specifications are somewhat like those in the European cement standard EN V 197, but some kinds of metallurgical slags are allowed into composite portland cement to make good use of industrial wastes, and a series of strength grades (including type R, which have higher early strength criteria) are stipulated for satisfying the various technical level of cement production and the different construction requirements. As to the special performance cement group, there are several series of cements such as portland cement, aluminatc cement, sulfo-aluminate cement, and ferro-aluminate cement, etc. The specifications for these cements are characteristic of their performance requirements: moderate-heat portland cement stipulates the criteria for heat of hydration; rapid-hardening aluminate cement defines criteria for strength within three days; expansive sulfo-aluminate cement requires criteria for rate of expansion; and self-stressing ferro-aluminate cements need criteria for self-stressing values, etc. In addition, oil well cement and masonry cement, etc., belong in the special purpose cement group. A graphical standards system is presented which includes fundamental standards, product standards, and test method standards. Owing to the different strength of the test methods, the cement strength value cannot be compared between different countries. The author suggests an international cooperative test program be organized for establishing the interrelation of mortar strength between different testing methods and the ISO method to facilitate international trade and to exchange information.

The effect of various types of cement dust on sulphur dioxide oxidation in the air

The effect of various types of cement dust on the behaviour of sulphur dioxide in the air was investigated on model systems in different experimental conditions.Experiments were carried out with PC-15z-45s (Portland-blast furnace cement containing 15% blast furnace slag), PC-25p-35s (Portland-pozzolan cement containing 25% pozzolan) and EFD (electrofilter dust).EFD most effectively removed SO2 from the air stream. The next efficacious was PC-15z-45s, whereas PC-25p-35s was the least efficient. The efficacy of cement dusts for SO2 removal from the air stream depended on their chemical and granulometric composition and in particular on the size of specific surface.The rate of reaction was also influenced by experimental conditions-relative humidity, the length of contact, that is, the flow rate of gaseous mixture through the reactor, and the amount of cement dust.The experimental data show that in the contact between SO2 and cement dust catalytic oxidation of SO2 to sulphates takes place. Sulphates remain bound to the surface, from which they cannot be thermally desorbed, but can be released by extraction in the Soxhlet apparatus.

Carbonation – comparison of results for concretes containing PFA, cementitious slag, or alternative aggregates

Depths of carbonation on specimens of concretes aged for up to 10 years are compared. Both good and poor curing conditions, with either indoor or outdoor exposure are considered. It is demonstrated that the carbonation depth is related systematically to the standard cube strength in dense concretes containing up to and including 40% replacement of Portland cement by pulverized fuel ash (PFA) or up to and including 60% by ground granulated blast furnace slag (GGBFS) or ground pelletized blast furnace slag (GPBFS). The main implications of these findings to methods of specifying concrete (BS 5328: 1981) are that designed mixes may give higher rates of carbonation for low-heat Portland blast furnace cement, but not for other permitted cement replacements, and that prescribed mixes will usually give higher rates if Portland cement is partially replaced by any permitted quantity of cement replacement. Depths of carbonation in concrete containing porous aggregate are more closely related to total water/cement ratio than to standard cube strength. This is probably a result of a closer relationship between total water/cement ratio and pore structure, which controls the rate of carbonation. A comparison has been made between concretes containing porous aggregate and those containing cement replacements by introducing an efficiency factor (k) for cement replacements similar but not always identical to the cementing efficiency factor.MST/690

The chemistry and mineralogy of some granulated and pelletized blastfurnace slags

AbstractSamples of granulated slag from Scunthorpe, Humberside, collected over several years, vary somewhat in chemical composition reflecting differences in iron-making practice. All contain some melilite and oldhamite crystals and minor amounts of iron along with the glass. Granulated slag from Usinor, Dunkirk, France, has a little more CaO than the Scunthorpe material with crystals of merwinite and oldhamite. Pelletised slag from Redcar, Teeside, is much more vescicular than the granulated material and contains melilite and oldhamite.The melilite crystals contain many inclusions of oldhamite and iron. They span a wide range within the akermanite-gehlenite series and are non-stoichiometric in composition. The merwinite may have formed largely by quench crystallization. Oldhamite is probably the first phase to form in all the slags. The silicate mineralogy can be explained in terms of the phase relationships within the CaO-SiO2-Al2O3-MgO quaternary system. The small difference in composition of the French slags is sufficient for them to fall into the primary phase field of merwinite rather than melilite. Assuming that only a minor proportion of crystals is acceptable in slags for use in Portland Blastfurnace Cement, the present low Al (< 11 % Al2O3) British and French slags are approaching an optimum composition.