Blast Furnace Slag Concrete Research Articles

Influence of carbonation on fatigue of concrete with high volume of ground granulated blast-furnace slag

The effect of carbonation on fatigue performance of ground granulated blast-furnace slag concrete was investigated. Based on the static compression tests of carbonated GGBS-concrete, the correlation between carbonation depth and compressive strength was analyzed and an equation between carbonation depth and compressive strength was put forward. Meanwhile, fatigue S-N curves of various carbonation depths were fitted, and the influence of carbonation on fatigue life and strength was studied. Carbonation has a dual effect on the fatigue behavior of GGBS-concrete. A fatigue equation based on the depth of carbonation was established. Also, the probabilistic distribution of fatigue life of carbonated concrete at a given stress level was modeled by the two-parameter Weibull distribution.

Distinctive microstructural features of aged sodium silicate-activated slag concretes

Electron microscopic characterisation of 7-year old alkali-activated blast-furnace slag concretes enabled the identification of distinct microstructural features, providing insight into the mechanisms by which these materials evolve over time. Backscattered electron images show the formation of Liesegang-type ring formations, suggesting that the reaction at advanced age is likely to follow an Oswald supersaturation–nucleation–depletion cycle. Segregation of Ca-rich veins, related to the formation of Ca(OH)2, is observed in microcracked regions due to the ongoing reaction between the pore solution and available calcium from remnant slag grains. A highly dense and uniform interfacial transition zone is identified between siliceous aggregate particles and the alkali activated slag binders, across the concretes assessed. Alkali-activated slag concretes retain a highly dense and stable microstructure at advanced ages, where any microcracks induced at early ages seem to be partially closing, and the remnant slag grains continue reacting.

Prompt gamma ray evaluation for chlorine analysis in blended cement concrete

Single prompt gamma ray energy has been evaluated to measure chlorine concentration in fly ash (FA), Super-Pozz (SPZ) and blast furnace slag (BFS) cement concrete specimens using a portable neutron generator-based Prompt Gamma Neutron Activation (PGNAA) setup. The gamma ray yield data from chloride concentration measurement in FA, SPZ and BFS cement concretes for 2.86–3.10, 5.72 and 6.11MeV chlorine gamma rays were analyzed to identify a gamma ray with common slope (gamma ray yield/Cl conc. wt%) for the FA, BFS and SPZ cement concretes. The gamma ray yield data for FA and SPZ cement concretes with varying chloride concentration were measured previously using a portable neutron generator-based PGNAA setup. In the current study, new data have been measured for chlorine detection in the BFS cement concrete using a portable neutron generator-based PGNAA setup for 2.86–3.10, 5.72, and 6.11MeV chlorine gamma rays. The minimum detection limit of chlorine in BFS cement concrete (MDC) was found to be 0.034±0.010, 0.032±0.010, 0.033±0.010 for 2.86–3.10, 5.72 and 6.11MeV gamma ray, respectively.The new BFS cement concrete data, along with the previous measurements for FA and SPZ cement concretes, have been utilized to identify a gamma ray with a common slope to analyze the Cl concentration in all of these blended cement concretes. It has been observed that the 6.11MeV chlorine gamma ray has a common slope of 5295±265 gamma rays/wt % Cl concentration for the portable neutron generator-based PGNAA setup. The minimum detectable concentration (MDC) of chlorine in blended cement concrete was measured to be 0.033±0.010wt % for the portable neutron generator-based PGNAA. Thus, the 6.11MeV chlorine gamma ray can be used for chlorine analysis of blended cement concretes.

알칼리 자극제로서 미분시멘트와 순환골재가 고로슬래그 다량치환 콘크리트의 공학적 특성 및 미세구조에 미치는 영향

본 연구에서는 BS다량 치환 콘크리트의 알칼리자극제로서 순환골재 및 고분말도의 FC를 복합 사용한 콘크리트의 제반 공학적 특성 및 미시적 분석을 실시하였다. FC 치환에 따른 슬럼프 및 공기량은 큰 차이가 없었으며, 응결시간은 FC 치환에 따라 비례적으로 단축되는 것으로 나타났다. FC 치환에 따른 압축강도는 고분말도의 FC가 치환됨에 따라 촉진된 수화반응 및 순환골재의 미수화 시멘트의 알칼리 용출로 인해 BS의 잠재수경성 반응을 촉진시켜 초기 및 28일 재령에서의 Plain 대비 강도저하를 상당부분 회복할 수 있었으며, 특히 향후 재령이 경과함에 따라 포졸란 반응의 활성화로 추가적인 강도향상이 기대된다. 탄산화 저항성의 경우 큰 차이가 없으며, 세공분포의 경우 FC 치환률이 증가함에 따라 <TEX>$0.1{\mu}m$</TEX>이하의 미세 공극분포가 급격히 증가하는 경향을 보였고, SEM 측정결과 FC 치환에 따른 7일 및 28일에서의 C-S-H 및 <TEX>$Ca(OH)_2$</TEX>의 생성을 확인하여 FC가 BS 다량치환 순환골재 콘크리트의 알칼리 자극에 기여함을 확인 할 수 있었다. The aim of this study is to investigate experimentally the effect of the combination of fine particle cement with high Blaine fineness (FC) and recycled aggregates on the engineering properties and micro structure of high volume blast furnace slag (BS) concrete with 75% BS and 21 MPa. FC manufactured by particle classification at the plant with Blaine fineness of more than <TEX>$7000cm^2/g$</TEX> was used as additional alkali activator for high volume blast furnace slag concrete made with recycled fine and coarse aggregates. FC was replaced by 15, 20 and 25% OPC. Test results showed that the incorporation of FC resulted in an increase in the compressive strength compared to BS concrete without FC by as much as 30% due to accelerated hydration and associated latent hydraulic reaction. It was found that the use of FC and recycled aggregates played an important role in activating BS for high volume BS concrete by offering sufficient alkali.

Performance of BFS concrete: k-Value concept versus equivalent performance concept

Focusing on sustainability, the use of industrial by-products as cement replacing materials has become a common tendency and we are still trying to increase the replacement level without negatively affecting and even with the aim to improve some of the concrete’s properties (e.g. compressive strength, workability and durability). However, following the descriptions of the k-value concept of EN 206-1 (2000) and NBN B15-001 (2004) for type II additions, the use of high contents fly-ash (FA) or blast-furnace slag (BFS) is not allowed in more demanding environments and these concrete types can only be applied when the equivalent performance with a proper reference is proven (EN 206-1 (2000) and NBN B15-100 (2008)). Moreover, while the k-value concept is a generally known principle to determine the influence of these additions on strength, k-values are not commonly used for durability indicators. In this study, the two concepts (k-value concept and equivalent performance concept) are critically evaluated for BFS concrete.First, accelerated degradation tests were performed to investigate the resistance of Ordinary Portland cement (OPC) and BFS concrete against organic acids, carbonation, chloride ingress, sulphate attack (complete submersion) and the alkali–silica reaction. The cement replacement percentages varied from 50% to 85% and the influence of different curing periods was considered. The results showed that the performance of BFS concrete was better than that of OPC concrete, except for carbonation. Afterwards, the results were evaluated with the k-value concept and the equivalent performance concept. The latter method seemed to be the most promising one and application of the k-value concept, with respect to durability, seems to be ambiguous and laborious.

Ageing and durability of concrete in lab and in field conditions: investigation of chloride penetration

Long-term studies under various natural exposure conditions are still needed in order to understand and quantify ageing and durability of concrete structures, in particular in the case of mixtures which incorporate supplementary cementitious materials (e.g. fly ash). With this purpose, a large-scale and long-term experimental program was initiated a lot of years ago by the LPC network within the framework of the French national project “BHP 2000.” From then, further researches have been carried out in order to complement the program. The present paper focuses on chloride penetration in concrete samples in lab conditions and in reinforced concrete (RC) structural elements exposed for 10 years to two different natural environments (tidal zone in marine environment, as well as road and cold environment). Numerous mixtures (28 day cylinder compressive strengths ranging from 20 to 130 MPa) were studied in these various conditions, e.g. high-performance materials with or without silica fume (SF), as well as normal-strength fly-ash (FA) concretes. Carbonation and chloride penetration depths, along with total chloride concentration and degree of saturation profiles, have been measured on the RC structural elements and analyzed as a function of the exposure conditions and of the mix-parameters. In addition, the chloride data have been compared to lab results. Apparent chloride diffusion coefficients, as well as chloride binding isotherms and capacities, have also been assessed on these structural elements and compared to lab results. Good consistence between results in field and in lab conditions has been highlighted, except when carbonation has affected the field results. In addition, the good performance of SF-HPCs and mature FA concretes has been pointed out in the tested outdoor conditions, as well as that of the mature ground granulated blast furnace slag concretes tested in lab.

Unrestrained Short-Term Shrinkage of Calcium-Hydroxide- Based Alkali-Activated Slag Concrete

A total of 34 concrete mixtures were tested to examine the unrestrained shrinkage behavior of calcium-hydroxide (Ca(OH)2)-based alkali-activated (AA) ground-granulated blast-furnace slag (GGBS) concrete. The main parameters investigated were water-binder ratio (w/b), unit water content (Wc), and fine-aggregate-to-total-aggregate ratio (S/A). From the regression analysis of test results, the comprehensive basic design equations were formulated to predict the 28-day shrinkage strain and time function, which can be expanded to long-term shrinkage strain or ultimate results of Ca(OH)2-based AA-GGBS concrete. The test results showed that the increasing rate of shrinkage strain against age and the amount of 28-day shrinkage strain of Ca(OH)2-based AA-GGBS concrete were significantly affected by the w/b, Wc, and the type of auxiliary activators, while they were minimally influenced by the S/A. When the w/b was higher than 0.35, a higher 28-day shrinkage strain was observed in Ca(OH)2- and Na2CO3 activated GGBS concrete than in Ca(OH)2- and Na2SiO3-activated GGBS concrete. The proposed equations showed a significantly better accuracy in the test results than the existing empirical models of which agreement was dependent on the mixing proportions of the concrete tested.

Carbonation of slag concrete: Effect of the cement replacement level and curing on the carbonation coefficient – Effect of carbonation on the pore structure

Abstract Concrete containing supplementary cementitious materials as, e.g. fly-ash (FA) or blast-furnace slag (BFS) is more vulnerable to carbonation than ordinary Portland cement concrete. In order to know whether carbonation-initiated corrosion is a risk within the life span of the concrete structure, the carbonation depth after several years (e.g. 50 years) is mostly predicted based on accelerated carbonation tests on young concrete specimens. However, these predictions do not take into account the positive effect of the continuing hydration of slag and fly-ash particles over a longer time. In this study, accelerated carbonation tests (10 vol.% of CO 2 ) were performed on concrete specimens containing different amounts of blast-furnace slag (slag-to-binder ratios of 50%, 70% and 85%) after different curing times (1, 3, 6 or 18 months). Based on these tests, a new method, which takes into account the effect of the ongoing hydration, is described in order to predict the carbonation depth of these special types of concrete over a long time more realistically. The tests revealed that, although BFS concrete has a lower carbonation resistance than OPC concrete, the depth of carbonation at the end of the concrete’s life (50 years) can still be acceptable in normal environments.

Resistance of concrete with blast-furnace slag against chlorides, investigated by comparing chloride profiles after migration and diffusion

The effect of partial replacement of ordinary Portland cement (OPC) by blast-furnace slag (BFS) on concrete’s resistance to chlorides was examined by comparing chloride profiles and colour change boundaries after non-steady state migration and natural diffusion tests, cfr. NT Build 492 and NT Build 443, respectively. Chloride profiles were obtained by means of potentiometric titration and the colour change boundaries by spraying 0.1 M AgNO3-solution. One OPC mixture and three BFS mixtures, with cement replacement levels of 50, 70 and 85 %, were tested. It was found that, compared to OPC concrete, migration coefficients of 50 and 70 % BFS concrete are decreased with 32 and 57 %, respectively. Diffusion coefficients are reduced by 66 and 50 %, respectively. Nevertheless, the chloride binding capacity of BFS concrete, determined from the difference between total and free chlorides, was lower than for OPC concrete. The results for 85 % BFS concrete differ from the results for 50 and 70 % BFS concrete, since higher migration and diffusion coefficients are found. Besides, free chloride concentrations at the colour change boundary (ccb), obtained after spraying with AgNO3-solution, amounted to 0.30 mol/l on average. There was no clear relation between the free chloride content at ccb and the BFS content.

Performance of Ground Granulated Blast Furnace Slag Concrete with Partial Replacement of Sand by Saw Dust

The Ground granulated Blast furnace slag (GGBFS) is a waste of industrial materials, it is relatively more recent pozzolanic material that has received considerable attention in both research and application. It is a non-metallic product consisting essentially of Silicates and Aluminosilicates of calcium's developed simultaneously with iron in a blast furnace and is granulated by quenching the molten material in water or steam, and air. The present Investigation has been undertaken to study the effect of Ground granulated blast furnace slag and saw dust on the mechanical properties of concrete, when coarse aggregates is replaced by Ground granulated blast furnace slag and saw dust is replaced in different percentages i.e. 0%,5%,10%,15%,20%,and 25% with the Fine aggregates(sand). The main parameters investigated were cube compressive strength and weight of concrete. The tests were conducted on concrete with ratio 1:1.5:3.The test results indicate that with the use of blast furnace slag by fully replacing coarse aggregates and partially replacing saw dust by fine aggregates in different percentages i.e. 0%,5%,10%,15%,20%,and 25%,the weight of concrete decreases with the increase in the percentage of saw dust. The compressive strength decrease with the increase in percentage of saw dust. The reduction percentage in the compressive strength is 27.14%, 44.16%, 50.46%, 64%, 76.53%, 80.60% Replacement of sand by saw dust reduce the unit weight of concrete and make it light weight. The cost of concrete also decreases with the increase in percentage of saw dust. Test result show that, the concrete become lighter than conventional concrete and reducing the environmental hazard and making the concrete economical.

Investigation of the influence of blast-furnace slag on the resistance of concrete against organic acid or sulphate attack by means of accelerated degradation tests

Replacement of ordinary Portland cement (OPC) by blast-furnace slag (BFS) alters the durability behaviour of concrete. In this research, the influence of BFS on the concrete's acid or sulphate resistance is investigated by accelerated degradation tests and the results are related to microstructural and physico-chemical parameters. A significant reduction of acid deterioration was recorded for BFS concrete, which is mainly attributed to the different chemical composition of the binder. General durability indicators like open porosity cannot solely explain the different performances of OPC and BFS concrete. In contrast, the resistance of concrete cyclically and partially submerged in sulphate solutions decreases when high amounts of cement are replaced by BFS. Crystallisation pressure causes more severe deterioration in these cases.

Evaluation of Fiber and Blast Furnace Slag Concrete Chloride Penetration through Computer Simulation

Durability of concrete is an important issue, and one of the most critical aspects affecting durability is chloride diffusivity. Factors such as water.cement ratio, degree of hydration, volume of the aggregates and their particle size distribution have a significant effect on chloride diffusivity in concrete. The use of polypropylene fibers(particularly very fine and well dispersed micro fibers) or mineral additives has been shown to cause a reduction in concrete's permeability. The main objective of this study is to evaluate the manner in which the inclusion of fiber(in terms of volume and size) and blast furnace slag(BFS) (in terms of volume replacement of cement) influence the chloride diffusivity in concrete by applying 3D computer modeling for the composite structure and performing a simulation of the chloride penetration. The modeled parameters, i.e. chloride diffusivity in concrete, are compared to the experimental data obtained in a parallel chloride migration test experiment with the same concrete mixtures. A good agreement of the same order is found between multi.scale microstructure model, and through this chloride diffusivity in concrete was predicted with results similar to those experimentally measured.

Modeling of early age behavior of blast furnace slag concrete based on micro-physical properties

A multi-scale system called DuCOM was enhanced to model behaviors of blast furnace slag (BFS) concrete. Tests on the strength and micro–hygro–physical properties of BFS concrete and Portland cement concrete were conducted. The current model was found to underestimate the strength of BFS concrete at later ages owing to underestimation of the water content inside C–S–H gel pores. To remedy this, enhanced modeling of porosity allowing proper simulation of the porosity of the BFS paste matrix and higher strength development at later ages is proposed. Furthermore, based on the enhanced porosity model, the moisture loss and pore size distribution of the BFS paste matrix were investigated. The pore size distribution was found to be coarser than the test at later ages in the model, resulting in overestimation of moisture loss. Hence, the pore size distribution was enhanced as well, allowing simulation of a finer pore structure of the BFS matrix. Finally, verifications showed that the enhanced model better predicts water desorption, moisture loss and drying shrinkage behaviors.

Durability of High-Volume GGBS Concrete

To improve structure durability of Cao’e River Floodgate in China, durability and lifetime prediction of high-volume ground granulated blast-furnace slag (GGBS) concrete were investigated. Chloride ion permeability was analyzed with nature soaking method and RCM method. High-volume GGBS concrete had better capability to resist chloride ion penetration with lower diffusion coefficient of chloride ion than ordinary Portland concrete (OPC) had. Experiment of steel-bar corrosion in dry-wet environments proved that high-volume GGBS concrete had better performance to protect steel-bar than OPC had. In the sulfate solution, high-volume GGBS mortar bars only produced small expansion which was 40% of that of Portland cement mortar bars. The performance of frost resistance of high-volume GGBS concrete was favorable. GGBS debased the capability of carbonation resistance. Lifetime prediction illuminated high-volume GGBS concrete was beneficial to extended project lifespan. The results show that high-volume GGBS concrete can solve the facing durability problem of Cao’e River Floodgate.

Analysis the Corrosion Protective Efficiency of Galvanizing Rebar in Ground Granulated Blast Furnace Slag Concrete

Analysis the Corrosion Protective Efficiency of Galvanizing Rebar in Ground Granulated Blast Furnace Slag Concrete

Development of blast furnace slag mixtures against frost salt attack

Carbonation is considered to be one of the most detrimental processes contributing to the frost salt attack deterioration of blast furnace slag (bfs) concrete. In this paper, the application of sodium monofluorophosphate (Na-MFP) as a curing solution or surface pre-treatment compound to improve frost salt scaling resistance of carbonated bfs mortar was studied. It was found that the treated specimens were more durable against frost salt attack than a conventional mortar with air-entrainment. The optimum mixture design can be achieved by using a suitable dosage of air-entraining agent, along with the Na-MFP application. The experimental results show that the optimized mixtures have an acceptable frost salt scaling durability that is comparable to the performance of ordinary Portland cement mixtures. The results obtained from a natural exposure confirm this healing phenomenon.

슬래그 미분말 혼합 콘크리트의 공극구조와 염화물 확산계수와의 관계에 대한 실험적 연구

바닷물에 의한 염해와 동결융해 환경에 노출된 철근 콘크리트구조물의 내구성을 평가하기 위해서는 콘크리트의 미세구조적 특성 및 염화물 침투성에 대한 콘크리트의 확산 저항성을 동시에 분석하는 것이 중요하다. 이 연구에서는 고로슬래그 미분말(GGBS)을 혼합한 콘크리트에 대하여 수은압입법(MIP)에 의해 얻어진 콘크리트의 미세공극 구조와 장기 및 단기 재령의 염화물 확산성과의 상관성에 대하여 연구하였다. 물시멘트비는 40, 45, 50%로 변화시키고, 단위시멘트량을 300, 350, 400, 450 kg/m3으로 변화시킨 OPC 및 GGBS 콘크리트 시편에 대하여 동결융해에 의해 손상된 GGBS 콘크리트에서의 확산성과 미세구조의 변화를 관찰하였다.

Influence of Si:Al ratio on the microstructural and mechanical properties of a fine-limestone aggregate alkali-activated slag concrete

Three series of fine limestone aggregate, alkali-activated blast furnace slag (AAS) concretes were fabricated and tested; two through activation with waterglass/NaOH solution, of which one included NaCl as a retarding agent, and one activated by Na2CO3. Each of these series was made up of three formulae containing different amounts of Al2O3. The compressive strengths of the series activated by waterglass/NaOH after 28 days were ≈65 ± 5.3 MPa, a 22% increase compared to previously reported formulae containing no additional Al2O3. Increasing the amount of Al2O3 did not further increase strength, however. The Na2CO3-activated formulae had strengths of ≈35 ± 3 MPa after 28 days, representing no increase in strength over formulae not containing Al2O3 previously reported. X-ray diffraction showed the main binding phase to be calcium silicate hydrate (C–S–H) gel, as is commonly found in ordinary Portland cement (OPC). Fourier transform infrared spectroscopy showed little difference from the previously reported results for formulae not containing Al2O3 and strongly resemble the spectra reported elsewhere for C–S–H. Electron microscopy, coupled with energy dispersive spectroscopy, showed the cementing phase to be a single homogenous phase—not a mixed system of geopolymer and C–S–H gel—with a lower volume fraction of unreacted slag than formulae without Al2O3. The reason for the increase in strength of Al2O3-containing formulae is unclear, but is unlikely to be ascribed to the formation of large amounts of ‘geopolymers’ and may be related to a possible increase in reaction temperature of between 2 and 5°C, depending on amount of additive.

Prompt Gamma-Ray Analysis of Steel Slag in Concrete

Blast furnace slag (BFS) is added to Portland cement concrete to increase its durability, particularly its corrosion resistance. Monitoring the concentration of BFS in concrete for quality control purposes is desired. In this study, the concentration of BFS in concrete was measured by utilizing an accelerator-based prompt gamma-ray neutron activation analysis (PGNAA) setup. The optimum size of the BFS cement concrete specimen that produces the maximum intensity of gamma rays at the detector location was calculated through Monte Carlo simulations. The simulation results were experimentally validated through the gamma-ray yield measurement from BFS cement concrete specimens having different radii. The concentration of BFS in the cement concrete specimens was assessed through calcium and silicon gammaray yield measurement from cement concrete specimens containing 5 to 80 wt% BFS. The yield of calcium gamma rays decreases with increasing BFS concentration in concrete while the yield of silicon gamma rays increases with increasing BFS concentration in concrete. The calcium-to-silicon gamma-ray yield ratio has an inverse relation with BFS concentration in concrete.

Predicting the compressive strength of ground granulated blast furnace slag concrete using artificial neural network

In this study, an artificial neural networks study was carried out to predict the compressive strength of ground granulated blast furnace slag concrete. A data set of a laboratory work, in which a total of 45 concretes were produced, was utilized in the ANNs study. The concrete mixture parameters were three different water–cement ratios (0.3, 0.4, and 0.5), three different cement dosages (350, 400, and 450 kg/m 3) and four partial slag replacement ratios (20%, 40%, 60%, and 80%). Compressive strengths of moist cured specimens (22 ± 2 °C) were measured at 3, 7, 28, 90, and 360 days. ANN model is constructed, trained and tested using these data. The data used in the ANN model are arranged in a format of six input parameters that cover the cement, ground granulated blast furnace slag, water, hyperplasticizer, aggregate and age of samples and, an output parameter which is compressive strength of concrete. The results showed that ANN can be an alternative approach for the predicting the compressive strength of ground granulated blast furnace slag concrete using concrete ingredients as input parameters.