Addition Of Blast Furnace Slag Research Articles

Multiple Light Scattering 분석법을 이용한 천연수경성석회의 초기경화 거동

본 연구에서는 무기질 첨가재를 혼합한 천연수경성석회의 초기경화 거동분석을 위해 multiple light scattering 분석법을 이용하였다. 자체 제조한 천연수경성석회의 물성향상을 위해 고로수쇄슬래그 및 3종류의 석고를 혼합비에 따라 혼합하였으며 물-고체비 0.6으로 페이스트를 제조하였다. 제조한 페이스트를 이용하여 원통형의 용기에 일정량을 담아 장비(Turbiscan LAB, Formulaction)에 장입하여 분석을 실시하였다. 페이스트로부터의 backscattering flux(BS, %)는 <TEX>$23^{\circ}C$</TEX>의 온도에서 분석용기 전체높이(55 mm)에 대해 24시간 동안 10분 간격으로 측정되었다. 모든 시료에서 전체적으로 BS는 시간경과에 따라서 증가하는 경향성을 보였다. 고로수쇄슬래그와 석고를 첨가함에 따라서 시간에 따른 BS의 증가 속도는 0.02에서 0.38 BS %/hour 까지 증가하였다. 반수석고를 혼합하였을 경우 가장 높은 backscattering flux와 BS의 증가속도를 보였다. In the present study, the multiple light scattering method was used for analysis of early hardening behavior of natural hydraulic lime (NHL) containing inorganic additives. In order to improve the properties of self-manufactured NHL, blast furnace slag and three types of gypsum were mixed with mixing ratio, and a water/solid ratio of fresh NHL paste was fixed 0.6. The fresh pastes in flat-bottomed cylindrical glass tubes were placed in the instrument. The backscattering flux (BS) of light from fresh pastes was then periodically measured at 10 minutes intervals the entire length of the sample (55mm) at <TEX>$23^{\circ}C$</TEX> for 24 hours. The rate of increase of BS, slope of a linear equation to the mean value of BS (%) as a function of hydration time, was increased from 0.02 to 0.38 BS %/hour due to addition of blast furnace slag and gypsum. In the case of addition of hemi-hydrate, BS (%) and rate of increase in BS were highest.

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’.

Effects of crack and ITZ and aggregate on carbonation penetration based on 3D micro X-ray CT microstructure evolution

Previous researchers have made a lot of contributions on carbonation reaction. However, effects of multi-cracks and interfacial transition zone (ITZ) on the diffusivity of carbon dioxide are critical and thorny problems. In this study, numerical simulation of carbonation process using the COMSOL Multiphysics are presented based on in-situ 3D microstructure evolution of X-ray CT. Firstly, micro X-ray computed tomography (X-ray CT) was used to monitor the carbonation depth evolution of cement mortar with different additions of blast furnace slag (BFS). It is shown that the optimal addition of blast furnace slag (BFS) against the carbonation is no more than 50%. In addition, COMSOL Multiphysics numerical model based on micro X-ray CT image was used to investigate effects of transverse crack and interfacial transition zone (ITZ) on the diffusivity of carbon dioxide. Finally, effects of different crack width, length, ITZ of polygon Random Aggregate Structure (RAS), and aggregate size and content on the diffusivity of carbon dioxide have been investigated.

Self-healing at early-age, a way to improve the chloride resistance of blast-furnace slag cementitious materials

Having a good chloride penetration resistance, blast-furnace slag cementitious materials are often used in coastal and marine structures. This type of civil engineering structures however can present cracking at early age (<28days) due to restrained shrinkage and thus their ability to limit chloride penetration can be significantly affected. In order to quantify the capacity of self-healing to improve their durability, chloride migration tests were performed on self-healed mortar mixtures with different contents of blast-furnace slag cracked at early age. The effect of different parameters on the chloride migration is analyzed: the presence of a traversing crack, the addition of blast-furnace slag, the self-healing and its kinetics. Analytical and numerical simulations on a cracked specimen are performed in order to improve our understanding of the chloride migration, especially in the case of self-healed cementitious material, and to evaluate the parameters (crack width, tortuosity and constrictivity) affecting it. Results clearly indicate that self-healing limits the chloride penetration and improves the structural durability, particularly for mixtures containing blast-furnace slag. Moreover, it is shown that the chloride migration test is an adequate method to monitor the self-healing process. Finally, self-healed specimens can be simply regarded as specimens characterized by a smaller crack. This is quite an important result for life assessment of concrete structures cracked at early-age.

Leachability of chromium and barium from concrete samples with blast furnace slag addition

The paper presents the results of leachability testing of selected heavy metals from the concrete composites of various compositions in order to assess the degree of a contamination risk of the environment. Tested concrete samples contained various amounts of special ingredients based on the blast furnace slag (65%, 75%, 85% and 95% of Portland cement replacement). Leaching tests have been performed by using distilled water. The concentrations of chromium and barium ions in the leachates were measured after period of 30 and 240 days. Changes in pH and conductivity values in leachates have been also observed.

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).

Pore Structure Analysis of Portland Cement and Blended Portland Cements Cured under Hydrothermal Conditions

The pore structure of Portland cement pastes cured under different hydrothermal regimes was analyzed. Pore size distribution (PSD), hydraulic permeability coefficient (HK) and porosity (P) were found depending on temperature and steam pressure. With increasing hydrothermal characteristics, the pore structures degraded causing the depletion in compressive strength. Then, blast furnace slag (BFS) and silica fume (SF) were added to PC and cured under similar conditions. It was found that the pore structure was greatly improved. The effect of hydrothermal curing may be interpreted by the intensity and position of the peak, by the length and bimodal characteristic of PSD. The maximum concentration of pores of reference cement paste lies in the range 10 – 103 nm, and changes progressively to the size &lt; 10 nm with increasing addition of BFS and SF. This behavior is attributed mainly to the presence of SF. Microstructure analysis shows hydrate products like needle CSH and CASH, which were stable under hydrothermal curing.

Processing and Wear Analysis of Blast Furnace Slag Filled Polypropylene Composites Using Taguchi Model and ANN

Abstract This paper analyses and reports on processing and solid particle erosion wear response of a new class of hybrid composites prepared by reinforcement of short glass fibers (SGF) in blast furnace slag (BFS) filled polypropylene (PP) matrix. In this investigation, composites with different BFS content (0, 10, 20 and 30 wt%) in a polypropylene matrix base, with and without 20 wt% SGF reinforcement, are prepared by injection molding route. To study the erosion wear response of these BFS filled composites, a plan of experiments based on the Taguchi technique is followed to acquire the wear data in a controlled way. This systematic experimentation has led to identification of significant process parameters and material variables that predominantly influence the erosion rate and also enables us to determine optimal parameter settings that lead to minimization of the erosion rate. An artificial neural network (ANN) approach is also implemented to predict the wear rate of the composites. The morphology of eroded surfaces is then examined by scanning electron microscopy (SEM) and possible erosion mechanisms are discussed. This study reveals that addition of blast furnace slag improves the erosion resistance of glass-polypropylene composites significantly and thus makes them suitable for tribological applications.

Durability Study of Geopolymer Paste Blended with Blast Furnace Slag

In this program consequence of incorporating blast furnace slag on mechanical properties and durability of resulting fly ash geopolymer paste sample was investigated. The program consisted immersion of geopolymer samples having percentage blast furnace slag ranging from 10 to 20 of fly ash in a 10% magnesium sulfate solution up to a period of 15 weeks and evaluation of its resistance in terms visual appearance, change in weight and compressive strength at regular interval. Addition of blast furnace slag considerably improved mechanical properties and durability of geopolymers paste.

Effect of sulfur aggregates on mechanical resistance and durability for SFRHPC with the addition of slag

The transformation of sulfides present in the aggregate to sulfates causes internal sulfate attack (ISA) by formation of secondary ettringite in the hardened concrete. This pathological ettringite crystallizes, the generated pressure is greater than the tensile strength of the concrete. It generates internal swelling and causes disorders that can severely damage the structures. Favors to their structural and economic performance, high performance concrete steel fiber (SFRHPC) are increasingly used in construction. Increase productivity and reduce construction time on site. They provide substantial weight savings, therefore it is possible to build with less formwork, less concrete to set up and fewer reinforcement than ordinary concrete. The purpose of this study is to determine the effect of sulfur present in the hornfels crushed aggregates, on the mechanical strength, durability, and the microstructure of SFRHPC with the addition of blast furnace slag. In ordinary concrete, the pyrite aggregates cause cracking by expansion when they are in wet land. In high performance concretes this phenomenon is greatly reduced or absent. This is the result of a very low porosity, reduced flow of moisture that cannot propagate to aggregate. And sulfide is stable and cannot be transformed into aggressive sulfate.

Applicability of alkali activated slag-seeded Egyptian Sinai kaolin for the immobilization of 60Co radionuclide

The present work was established to determine the applicability of local Egyptian kaolinite and blast furnace slag (BFS) as raw materials toward the synthesis of geopolymers and subsequent immobilization of cobalt-60, which is one of the most abundant radionuclides generated in radioactive waste streams in Egypt. XRF, XRD, FT-IR, and SEM techniques were used to characterize the local raw materials and their corresponding alkali activated products. Metakaolin (MK) was obtained by thermal treatment of Egyptian Sinai kaolin 750°C/4h. MK and five different BFS content (5, 10, 30, 50 and 80%) were used to synthesize geopolymeric matrices using an alkaline activator of Si-modulus=1.35 at solid/liquid ratios of 0.8. Compressive strength tests were performed indicating that 50% BFS addition gave the highest values of compressive strength. The IAEA standard leaching tests of cobalt-60 from the solidified waste matrices were carried out. The effective diffusion coefficients of cobalt-60 radionuclides from the solidified waste matrices were calculated to be in the order of 10−14cm2/s. Leaching of radionuclides was examined to be controlled by the wash-off mechanism with very acceptable values. These results gave encouragement that the tested Egyptian raw materials can be conveniently applied for the synthesis of geopolymers that can be used as a low-cost and high-efficiency materials for the immobilization of radioactive waste.

Some Considerations for Applicability of Seawater as Mixing Water in Concrete

According to the report of the World Meteorological Organization (WMO), more than half of the world’s population will not have enough drinking water by 2025. To save drinking water, use of seawater in the concrete industry seems imperative. In the present study, the possibilities of seawater as a material of concrete are discussed as a result of the literature-based and experimental investigations. From the results of the literature-based study, more than half of the papers collected in this study had positive opinions about concrete mixed with seawater by adding the mineral admixture such as blast furnace slag (BFS). In addition, some results of long-term exposure tests indicated the high possibility of using seawater as a material of concrete. The experimental data obtained in this study indicated that the addition of BFS might contribute significantly to the corrosion resistance of steel bar, because of the low oxygen environment around steel bar and chloride immobilization.

Effect of blastfurnace slag addition to Portland cement for cationic exchange resins encapsulation

In the nuclear industry, cement-based materials are extensively used to encapsulate spent ion exchange resins (IERs) before their final disposal in a repository. It is well known that the cement has to be carefully selected to prevent any deleterious expansion of the solidified waste form, but the reasons for this possible expansion are not clearly established. This work aims at filling the gap. The swelling pressure of IERs is first investigated as a function of ions exchange and ionic strength. It is shown that pressures of a few tenths of MPa can be produced by decreases in the ionic strength of the bulk solution, or by ion exchanges (2Na + instead of Ca 2+ , Na + instead of K + ). Then, the chemical evolution of cationic resins initially in the Na + form is characterized in CEM I (Portland cement) and CEM III (Portland cement + blastfurnace slag) cements at early age and an explanation is proposed for the better stability of CEM III material.

Experimental investigation of the fatigue behaviour of asphalt concrete mixtures containing waste iron powder

The use of additives and admixtures in the construction of asphalt concrete pavements to strengthen them against dynamic loads has increased considerably in recent years. Recent research has shown that employing desirable waste materials in hot mix asphalts (HMAs) improves their dynamic properties noticeably. The study of some special cases, such as the addition of blast furnace slag and metallic materials of waste electronic instruments to HMA, has led to a considerable increase in the ability of HMAs to tolerate fatigue phenomena and repeated loading. Based on experimental studies, a model is proposed to describe the fatigue behaviour of asphalt mixtures containing waste iron powder. The results of this research show an important increase in the strength of asphalt mixtures containing waste iron powder against fatigue phenomena in comparison to conventional HMAs.

Improvement of the strength of acrylic emulsion polymer-modified mortar in high temperature and high humidity by blast furnace slag

Polymer modification was widely used to improve the properties of construction materials. The concept of polymer modification for mortar and concrete was put forward 80 years ago. It was known that the use of polymers for modification can greatly improve the strength, adhesion, resilience, impermeability, chemical resistance and durability properties of mortars and concrete. In southern Vietnam, a tropical weather country, the environment was usually hot with high humidity. The durability of mortar or concrete coating was reduced over time in such a condition. This study examines the strength of polymer-modified mortars in high temperature and high humidity. Moreover, the results included the improvement of strength of acrylic emulsion polymer-modified mortar (PMM) by the addition of blast furnace slag. Fifteen percent cement was replaced with blast furnace slag (BFS) in a mix proportion in order to improve strength of PMM. The specimens were cured in cycles 50±2°C, RH 90±3%, for 5 hours and 20±2°C, RH 60±3 %, for 19 hours per day. The strength of PMM was measured at the age of 3, 7, 14, 21 and 28 days, 3 and 6 months and 1 year in a high temperature and high humidity cycles.

Cementitious composites of pulverised fuel ash and blast furnace slag activated by sodium silicate: effect of Na2O concentration and modulus

Pastes of pulverised fly ash (PFA) and blast furnace slag (BFS) in proportions of 100–0, 75–25, 50–50, 25–75 and 0–100 (wt-%) were chemically activated using sodium silicate with modulus (SiO2/Na2O) of 0, 0·75, 1, 1·5 and 2; the %Na2O was added at 4, 6 and 8% relative to the binder weight. The pastes were cured for 24 h at 75°C and then 28 days at 20°C. For 100%PFA pastes, the higher %Na2O, the better the strength; 4%Na2O was ineffective, whereas the highest strength of 25 MPa was reached using modulus 1. For 100%BFS pastes, the highest strengths were for 4%Na2O (80–85 MPa); the optimum modulus was 1·5. The addition of BFS to PFA rich pastes was favourable; for 50% blends, the strengths were between the above mentioned figures and the best modulus was 1–1·5 (45–48 MPa). The lower glass content of PFA (70%) compared with the BFS (>90%), together with the porous nature of the PFA, were considered to have reduced the strength in PFA blends.

フェロニッケルスラグ細骨材コンクリートのブリーディングの低減と耐凍害性および水密性に関する研究

Many reports have been published on various properties of concrete with ferro-nickel slag fine aggregates, and it has been pointed out that the concrete with such aggregate showed the nearly same strength as that of normal concrete. A total of five ferro-nickel slag fine aggregates were examined in this study. The experiments were conducted by fixing the volumetric mixture ratio of slag 50%, except crushed air granulated slag used for single fine aggregates, to investigate the efficiency of chemical admixtures and the water demand in the ferro-nickel slag concrete as compared with those of natural sand concrete. In addition, the bleeding properties of those concretes were fully investigated. The reduction of unit water content, by applying a high range water reducer, could be expected to the same degree as that of normal concrete, which also resulted in the decrease of bleeding. The additions of blastfurnace slag, silica fume and lime stone powder pronouncedly improved the compressive strength and the bleeding of ferro-nickel slag concrete. And then, the freeze-thaw resistance was improved by the addition of lime stone powder, but hardly improved by the addition of silica fume. It can be considered that the watertightness of ferro-nickel slag concretes is the same as that of natural sand concrete.

セメント中のアルカリ硫酸塩がコンクリートの諸性状に及ぼす影響

An experimental study was performed to clarify the influence of high alkali content of portland cement on the properties of concrete by addition of potassium sulfate. The results suggest that increase of alkali content in cement not only causes the flash set of fresh concrete resulting in slump loss but reduces the strength of concrete. Addition of blast furnace slag to these high alkali cements makes up for the loss in slump and strength to a large extent.