Blast Furnace Slag Concrete Research Articles

Carbonation rates of concretes containing high volume of pozzolanic materials

The project studies the influence of fly ash and slag replacement on the carbonation rate of the concrete. The experimental work includes samples of pure Portland cement concrete (CEM I 42,5 R), blast-furnace slag concrete (CEM III-B), and fly ash blended concrete. To reveal the effect of curing on carbonation rate, the concretes were exposed to various submerged curing periods during their early ages. After that, the samples were subsequently exposed in the climate room controlling 20 °C and 50% RH until the testing date when the samples had an age of 5 months. Then, the accelerated carbonation test controlling the carbon dioxide concentration of 3% by volume, with 65% relative humidity were started to perform. The depth of carbonation can be observed by spraying a phenolphthalein solution on the fresh broken concrete surface. Finally, according to Fick's law of diffusion theoretical equations are proposed as a guild for estimating the carbonation rate of fly ash and blast-furnace slag concretes exposed under natural conditions from the results from accelerated carbonation tests.

The effect of slaked lime, anhydrous gypsum and limestone powder on properties of blast furnace slag cement mortar and concrete

Basic properties of blast furnace slag cement mortar and concrete are investigated by adding inorganic activators. The result of this research concludes that slag cement mixed with suitable activator agents such as lime, gypsum and limestone powder could accelerate the compressive strength and tighten pore structure at early age. The addition of activator into mortar and concrete containing slag cement produces superior properties, reduced shrinkage and less carbonation compared to mortar and concrete containing slag cement without the addition of activator. Consequently, there are possibilities for manufacturing blast furnace slag cement, which could compensate the weak properties at early curing age. When compared with ordinary Portland cement, this cement has superior characteristics for long curing age.

Use of Granulated Blast-Furnace Slag in Concrete as Fine Aggregate

Experimental studies were performed on the use of non-ground-granulated blast-furnace slag as an aggregate in concrete. Using industrial by-products can help reduce greenhouse gas emission, and can be more economical than normal Portland cement concrete. While grinding the slag puts an additional burden of cost into production, using them as a partial fine aggregate does not increase the cost. This paper performed studies on compressive and flexural strength, water absorption, unit weight, durability of high temperatures, freezing and thawing, and rapid chloride permeability tests establish that non-ground-granulated blast-furnace slag can used as a fine aggregate in concrete.

Influence of GGBS on durability and corrosion behavior of reinforced concrete

The durability of ground granulated blast furnace slag (GGBS) concretes and the corrosion behavior of reinforced concrete beams under various loading ratios were investigated. Prismatic beam specimens with a size of 150mm×150mm×900mm were subjected to various sustained loadings (37 and 75% of the ultimate load) and exposed to 3.5% NaCl solution. A direct current (1mAcm−2) was applied to accelerate the corrosion process. Open circuit potential (OCP) and direct current polarization resistance were obtained to evaluate the rebar corrosion. Deflection and residual loading rigidity of the beam were measured at the end of the experiment. In addition, rapid chloride penetration test (RCPT) and permeability test were conducted on GGBS concretes. Test results indicate that partial replacement of cement by GGBS has inhibiting effects on both total charge-pass and permeability. Slag addition and sustained loading have significant effect on corrosion rate and flexural rigidity of reinforced concrete beams.

고로슬래그를 함유한 콘크리트의 자기수축 특성

초록 · 키워드 목차 오류제보하기 등록된 정보가 없습니다. ABSTRACT1. 서론2. 실험 연구3. 실험결과 및 분석4. 자기수축 예측 모델5. 결론참고문헌요약

고로슬래그미분말을 사용한 콘크리트의 염화물이온에 의한 철근부식 저항성 연구

초록·키워드 목차 오류제보하기 등록된 정보가 없습니다. Abstract1. 서론2. 사용재료 및 배합선정3. 염화물의 침투저항 및 실험방법4. 시험결과 및 고찰5. 결론참고문헌요약

Investigation of hydraulic activity of ground granulated blast furnace slag in concrete

Ground granulated blast furnace slag (GGBFS), a by-product of the steel manufacturing industry, being used as an effective partial cement replacement material, has already been proven to improve several performance characteristics of concrete. The reactivity of GGBFS has been found to depend on the properties of slag, which vary with the source of slag, type of raw material used, method and the rate of cooling. The present work aims at bringing out a novel relationship between the Hydraulic Index (HI) of slag at 7 and 28 days (HI7 and HI28) and the influencing properties of slag, namely, glass content, fineness and chemical composition by employing multiple regression analysis on 37 slag samples from various sources. HI7 and HI28, thus obtained, have been mapped onto a Slag Activity Index (SAI) plot, giving an indication of the ranges of strength of slag.

Freezing and de-icing salt resistance of blast furnace slag concretes

This paper presents the results on investigations made into a concrete containing cement rich in granulated blast furnace slag (57%). Whereas slag cement concretes have proved successful in structures subjected to chemical attack, their use in structures subjected to freezing and de-icing salt attack is a problem of numerous investigations. The results concerning water/cement ratio and air content in concrete mixtures are presented in this paper. The effect of polypropylene microfibre addition to the concrete was also analysed. The research shows that air entraining the concrete mix up to the level of 5–6% guarantees obtaining high resistance to the action of de-icing agents, even at relatively high values of water/cement ratio. Apart the air content, the addition of microfibre to the concrete mixture was highly effective. For these samples scaling was the lowest. Phase composition investigations confirm that calcite and aragonite (as the carbonation products) were present on the surface of concrete.

Comparison of the strength and durability performance of normal- and high-strength pozzolanic concretes at elevated temperatures

The strength and durability performance of normal- and high-strength pozzolanic concretes incorporating silica fume, fly ash, and blast furnace slag was compared at elevated temperatures up to 800°C. The strength properties were determined using an unstressed residual compressive strength test, while durability was investigated by rapid chloride diffusion test, mercury intrusion porosimetry (MIP), and crack pattern observations. It was found that pozzolanic concretes containing fly ash and blast furnace slag give the best performance particularly at temperatures below 600°C as compared to the pure cement concretes. Explosive spalling occurred in most high-strength concretes (HSCs) containing silica fume. A distributed network of fine cracks was observed in all fly ash and blast furnace slag concretes, but no spalling or splitting occurred. The high-strength pozzolanic concretes showed a severe loss in permeability-related durability than the compressive strength loss. Thirty percent replacement of cement by fly ash in HSC and 40% replacement of cement by blast furnace slag in normal-strength concrete (NSC) was found to be optimal to retain maximum strength and durability after high temperatures.

Autogenous Shrinkage of Ground-Granulated Blast-Furnace Slag Concrete

This investigation was carried out to study the effects of replacement percentage and fineness of ground granulated blast-furnace slag (GGBFS) on the autogenous shrinkage of high-performance concrete. All the mixtures had the same water-cementitious materials ratio (w/cm = 0.30) and the same volume of binder at 31 % of the total volume of concrete. The 91-day compressive strengths of all the concretes were above 80 MPa. Test results revealed that the 50% GGBFS concrete had the highest compressive strength at 91 days and the highest autogenous shrinkage. It was also found that concrete specimens containing finer GGBFS particles showed faster compressive strength development and greater autogenous shrinkage strains.

Durability of Portland blast-furnace slag cement concrete

This paper summarizes the results of studies carried out at the Building Research Establishment in the UK, on the performance and long-term durability of concrete where ground glassy blast-furnace slag (granulated and pelletized) has been used as a cementitious material. Using data from tests on site structures and laboratory and exposure site studies, comparisons are made of the properties and performances of the slag cement concretes with normal Portland cement concretes of similar mixture proportions. A number of recommendations are given for the effective use of ground glassy blast-furnace slag in concrete. The many technical benefits available to the concrete user, such as reduced heat evolution, lower permeability and higher strength at later ages, decreased chloride ion penetration, increased resistance to sulfate attack and alkali silica reaction were affirmed. However, a cautionary warning of the importance of good early curing is made to ensure that the adverse effects of higher rates of carbonation, surface scaling and frost attack are minimized. The paper is intended to provide guidance for those concerned with the design, specification, application and performance of concrete in practice where slag can also help to reduce costs and energy demands in the production of cement compared with normal Portland cement.

Curing and the durability of OPC, fly ash and blast-furnace slag concretes

This paper presents preliminary results of a research project into the influence of moist curing on the potential durability of concrete. Durability is characterized by measuring the oxygen permeability and water absorption at various depths in the covercrete. Concretes containing plain OPC, an OPC-FA blend and an OPC-GGBS blend were used. A range of strength grades was tested for each of these binder types. Concretes were exposed to moist curing conditions for 1, 3, 7 and 28 days before being tested at 28 days after casting. The main conclusions are: (i) moist curing has a marked influence on the potential durability of concrete and (ii) a relatively greater influence on durability can be effected by extending the duration of early-age moist curing rather than decreasing the binder/water ratio.

Suitability of GGBFS as a cement replacement for concrete in hot arid climates

Three ground granulated blast-furnace slag (GGBFS) concretes (30, 50 and 70% cement replacement) together with an OPC control, all designed for equal workability and 28-day water-cured strength, are compared when subjected to a variety of curing methods and exposure in both a temperate and a hot arid climate. The effect of replacement level on cube and core strengths, ultrasonic pulse velocity, surface hardness, water absorption and permeability are reported. The test showed conclusively that the 50%, replacement level was best and that a GGBFS concrete can be superior to an equivalent all-OPC concrete in a hot climate, provided that proper curing is provided.

BEHAVIOR OF ASPHALT PAVEMENTS IN CIRCULAR ROAD TESTS AND ITS ANALYSES

In order to evaluate the performance of asphalt pavement with a slag base, truck tests were conducted on a 12m radii circular test road consisting of various pavement sections. The new slag base material tested was a compound slag (mixture of 50% by weight of steel-making slag, 30% of blast-furnace slag, and 20% of granulated slag), and the reference materials utilized were a blast-furnace slag, crushed stone, and asphalt concrete. Through five series of truck tests, the data of performance such as deflection, cracking, and rutting were periodically collected and compared to evaluate relative performance. Moreover, for the purpose of generalizing the performance data observed, three theoretical procedures regarding structure analysis, fatigue prediction, and rutting prediction were proposed and examined through the observation data. This paper describes the performance data observed and discusses the applicability of the analytical methods proposed.

高粉末度スラグのコンクリートへの利用の現状と展望

高炉スラグの潜在水硬性を利用して, 古くから高炉セメントとして広く用いられてきた高炉スラグ粉末は, さらに近年, 粉砕技術の発達とも相まって高粉末度スラグが量産されるようになってきた。ここでは, 主として多量の高粉末度スラグを用いた低熱セメントについて, その開発の経緯, 諸外国の関連規格, 特性, 問題点を述べるとともに, 利用の現状と展望を示す。

Alkali activated ground granulated blast-furnace slag concrete: Preliminary investigation

This report presents results of a preliminary investigation dealing with the compressive strength development of alkali activated ground granulated blast-furnace slag concretes. These concretes incorporated sodium silicate as an activator but did not contain any portland cement. The five concrete mixtures studied were proportioned using sodium silicate and small amounts of hydrated lime. The water-to-binder ratio of the mixtures ranged from 0.34 to 0.50. The air-entrained concrete produced satisfactory workability. The 1-day and 28-day compressive strengths of the concretes ranged from 20.4 to 38.9 MPa and from 45.5 to 59.6 MPa, respectively. 2he 7- and 14-day flexural strengths were of the order of 5 MPa.

A comparison of the properties of OPC, PFA and ggbs concretes in reinforced concrete tank walls of slender section

This Paper compares the properties of cores taken from the walls (250 mm thick) of a 2·5 year old reinforced concrete tank constructed using ordinary Portland cement (OPC), pulverized fuel ash (PFA) and ground granulated blastfurnace slag (gghs) concretes of equal strength grade. Measurements taken during and shortly after construction showed the PFA and ggbs to be beneficial in terms of reducing hydration temperatures and the amount of secondary steel required to control thermal and shrinkage cracking. Ultrasonic pulse velocity measurements carried out on the tank walls before coring showed no significant difference between the three concretes, and laboratory tests on cores showed them to have comparable compressive and tensile strengths. The PFA and ggbs concretes showed greater carbonation depths than the OPC concrete, although the PFA concrete was significantly less permeable to both gas and liquid. These results are discussed with reference to pore structure measurements, which show the PFA concrete to have a coarser pore structure than the OPC concrete close to the surface—at depth the situation is reversed. Generally, the results show the three concretes to have very similar properties, suggesting that the early-age benefits observed for concretes containing PFA and ggbs can be achieved in slender concrete elements without compromising strength and durability requirements.

Corrosion of Reinforcing Steel in Concrete Containing Slag or Pozzolans

Abstract Use of fly ash, silica fume, natural pozzolans, and blast-furnace slag in concrete is becoming increasingly common. Incorporation of these materials improves the durability of concrete. But as yet there are few quantitative data available on the effect of these materials on long-term corrosion of steel reinforcement. Such data will help the concrete technologists to select the proper type of materials to produce dense and impermeable concrete to withstand aggressive service environments. In this investigation, the long-term corrosion-resisting characteristics of concretes made with two fly ashes, a natural pozzolan, a blast-furnace slag cement, and a preblended portland-fly ash cement were evaluated. Specimens were immersed in 5% sodium chloride solution for a period of more than five years, and the corrosion activity was evaluated by monitoring the half-cell potentials and measuring the corrosion rate of embedded steel using linear polarization resistance technique. Results indicate that addition of pozzolans or slag increases the corrosion-resisting characteristics of concrete. The corrosion rate of steel in concrete made with blast-furnace slag cement is lower than in other concretes.

Strength development of slag and ternary blend concrete

Ground granulated blast furnace (GGBF) slag is increasingly used in concrete construction due to its technical and economic benefits. This paper describes the strength development of 3 grades of plain cement concretes, portland blast furnace slag (slagment) concretes and concretes in which 15 and 35% of slagment was replaced by flyash (ternary blends). These concretes were cured in standard and nonstandard curing conditions using standard and nonstandard cylindrical specimens. The straight replacement of portland cement by slagment (65% cement and 35% slag) gave higher strength for low to medium strength concretes (20 and 35 MPa). The results also suggest that the strength of the concretes made with slagment was less affected under inadequate curing conditions as compared to the strength of the plain cement concretes. It was also found that the indicated strength of the smaller cylinders (75×150 mm) was adversely affected in the drying curing regimes whereas it was only marginally different from the strength of 150×300 mm cylinders under continuous fog curing. For all the concretes tested, initial curing for 7 days seems to be the most appropriate as it is both practicable and gives adequate strength.

Hydration, Structure, and Properties of Blast Furnace Slag Cements, Mortars, and Concrete

Hydration, Structure, and Properties of Blast Furnace Slag Cements, Mortars, and Concrete