Ferronickel Slag Research Articles

Insight into the partial replacement of cement by ferronickel slags from New Caledonia

We investigate the mechanical characterisation of mortars incorporating ferronickel slags (FNS) as partial substitution for cement. The studied slags come from the ferronickel production in New Caledonia. The microstructural characterisation shows that these slags are polycrystalline heterogeneous material mainly composed of forsterite, quartz and enstatite in addition to silica glass. Cement is replaced by up to 20 wt.% of ferronickel slags in the mortars. This upper level of substitution is achieved without compromising mortar’s strengths. For all mixes, the maximum compressive and flexural strengths at all curing ages is obtained with a 5 wt.% replacement of cement by ferronickel slags. The larger effectiveness of FNS is attributed to its larger silica content, which increases the polymerisation degree of the silica chains in the calcium silicate hydrate (C-S-H) structure. Slag recycling reduces the storage time, waste management and environmental impact. It significantly lowers costs related to metallurgical processing. Slag substitution for cement, also lowers the carbon footprint.

Leaching kinetics and reactivity evaluation of ferronickel slag in alkaline conditions

This paper evaluates the reactivity of individual mineral phases of ferronickel slag (FNS) based on the backscattered electron images analysis (BSE-IA) and presents the leaching kinetics of FNS in NaOH solutions, aiming to reveal the interrelationships among physicochemical properties, leaching behavior and reactivity of FNS. There are three typical phases identified in water-quenched FNS, namely FNS I, II and III phase. The FNS I phase is more prone to dissolve and preferentially participate in the reaction process than the other two phases. The dissolved Mg from FNS is mainly involved in the formation of hydrotalcite and N-M-S-H gels. Cr could not be detected during the leaching process. The activation energy for the leaching of Si and Al is 80.47 and 49.45 kJ/mol, respectively. A method for rapid evaluation of the reaction activity of FNS given the evaluation index of the individual leaching ratio of Si and Al is proposed.

Enhancing the recyclability of air-cooled high-magnesium ferronickel slag in cement-based materials: A study of assessing soundness through modifying method

The air-cooled ferronickel slag is already selected as a raw material (aggregate) in concrete manufacturing, while the using as supplementary cementitious materials is still limited because of the high magnesium content. The objective of this study focuses on the practicality of air-cooled high-magnesium ferronickel slag (HMNS) blended Portland cement pastes, providing experimentally criterion for air-cooled HMNS's application. The different fineness on compressive strength and soundness of mixtures were investigated comprehensively. To be compared with the actual expansion of the HMNS blended Portland cement pastes, the mixtures containing MgO expansive agent addition (on the basis of the MgO content in the HMNS blended mixtures) were especially produced for autoclave expansion test. An optimum strength in practical application was obtained when the dosage of HMNS and its particle size were 20% and less than 50 μm respectively. The expansions of all mixtures were not only quite small (scattered around 0.09%) by traditional autoclave test, but the HMNS blended mixtures also exhibited the lower expansion when autoclave time is 6 h and 12 h. However, the expansive values of MgO expansive agent blended mixtures express more expansion than that of the HMNS blended mixtures in all autoclave times. This phenomenon was attributed to the form of magnesium in HMNS, where the primary phase of magnesium was clinoenstatite (MgSiO3) or forsterite (Mg2SiO4) and those phases showed inactive in this system by XRD, TGA and BSEM-EDS analyses. Therefore, HMNS used as supplementary cementitious material could not bring volume expansion, and this conclusion may present a great benefit to the recycling of HMNS in the field of construction materials.

Experimental behaviors of prefabricated members made of ferronickel slag concrete

As a by-product of nickel production, a large amount of ferronickel slag (FNS) puts great pressure on the environment. Therefore, there is an urgent need to treat the FNS to solve serious challenges to the environment. The FNS can be used as a partial replacement of Portland cement in concrete, so this industrial by-product may act as a suitable alternative of conventional building materials with high carbon footprint to achieve sustainable development. The concrete containing 0%, 15% and 30% FNS was prepared and assessed for its compressive strength, modulus of elasticity, tensile strength, resistance to chloride ions penetration and bond behaviors. The obtained results showed that the use of FNS had positive effects on the mechanical properties and durability of concrete due to the higher pozzolanic activity of FNS at the late hydration age and its finer particles than cement. Moreover, 15% FNS addition brought more significant increase in compressive strength, modulus of elasticity, tensile strength and bond strength than the use of 30% FNS as a replacement of cement. But the increasing FNS content resulted in the increase of resistance to chloride ions penetration of concrete. In addition, static loading tests and cyclic loading tests were carried out to assess the effects of the FNS on the overall structural behaviors of the prefabricated members. The specimens exhibited similar failure modes which mainly involved yielding of longitudinal steel bars. The ultimate bearing capacity attained by FNS concrete members was similar to that of conventional concrete members, but the specimens made of FNS concrete exhibited higher ductile capacity. The FNS concrete members also experienced more cracking and concrete crushing at the end of test, thus showing better energy dissipation capacity.

Fresh and hardened properties of high strength self-compacting concrete using by-product ferronickel slag fine aggregate

Concrete nowadays is the most frequently used building material all over the world. This is causing a tremendous pressure on the supply of its constituents like natural sand which is traditionally used as the fine aggregate. Therefore, it is essential to search for alternative materials in order to meet the increasing demand of concrete and improve the sustainability of concrete industry. This study investigated the effect of using by-product ferronickel slag (FNS) as a partial replacement of natural sand in high strength self-compacting concrete (SCC). Utilization of by-product FNS will also lessen the risk of environmental pollution. Results show that concrete containing up to 40% FNS fine aggregate met all the recommended criteria of EFNARC for SCC without any segregation in the flow and J-ring tests, and no blockage in the L-box and V-funnel tests. The increase of FNS to 60% resulted in significant segregation and reduced flowability due to the larger size, angular shape and higher density of FNS as compared to sand. The 28-day uncompacted compressive strength of concrete with 40% FNS was 66 MPa, which was almost same as that for the vibrated concrete of same mixture, confirming the achievement of self-compaction property. Tensile strength could be conservatively predicted from compressive strength by using the ACI318 and AS3600 equations. The volume of permeable voids and water absorption of the SCC using up to 60% FNS were in the category of “Excellent” and “Low” as per the VicRoads specifications. Sorptivity values were far less than the recommended value of 27.11 × 10−3 mm/s0.5. The charge passed in the rapid chloride permeability test was less than 1000 Coulombs. Therefore, FNS content up to 40% was found as an environmentally friendly substitute of natural sand for the production of high strength SCC of good durability.

COMPRESSIVE STRENGTH OF GEOPOLYMER MORTAR USING GROUND FERRONICKEL SLAG AND FLY ASH

A huge amount of ferronickel slag is produced as a by-product of manufacturing ferronickel, which is used in stainless steel and nickel alloy. This paper presents the effect of using different percentages of ground ferronickel slag (GFNS) with fly ash (FA) on the workability and compressive strength of geopolymer mortar. A mixture of NaOH and Na2SiO3 solutions was used as the alkaline activator. It was found that the flow of fresh mortar decreased with the increase of GFNS content. This is attributed to the higher fineness and angular shape of GFNS particles as compared to spherical fly ash particles. The mortar cube specimens were heat-cured at 60 °C for 24 hours. The compressive strength of geopolymer mortar using 100% FA was 54 MPa and it increased by 17%, 21% and 36% for using 25%, 50% and 75% GFNS as fly ash replacement, respectively. The strength increase is attributed to the increase of Si/Al ratio by GFNS that favoured the production of alkali aluminosilicate reaction products.

Utilization of Industrial Waste Slags to Enhance Ground Waste Concrete-Based Inorganic Polymers

Recycling and utilization of waste concrete and industrial waste slags is a significant step towards the protection of the environment and sustainable development. Industrial waste slags including ferronickel (Greece) and fayalite (Finland) slags were mixed with ground waste concrete for the production of inorganic polymers (IPs). The effects of different parameters during alkaline activation such as solution concentration (6 to 12 M NaOH), curing temperature (60 to 80 °C), and aging period (7 to 28 days) upon the uniaxial compressive strength of the produced specimens were determined. The optimum conditions for ground concrete waste-based inorganic polymers were found to be the use of alkali activator with mass ratio of Na2SiO3 to NaOH 1 and L/S 0.3 cured at 80 °C for 24 h and aged for 7 days with compressive strength of 16 MPa. Molar ratios of $$\frac{{{\text{SiO}}_{2} }}{{{\text{Al}}_{2} {\text{O}}_{3} }}$$ and $$\frac{{{\text{H}}_{2} {\text{O}}}}{{{\text{Na}}_{2} {\text{O}} + {\text{K}}_{2} {\text{O}}}}$$ in the reactive paste were 16.03 and 13.02, respectively. IPs produced from ground concrete waste (GWC), fayalitic (FS), and ferronickel (LS) slag mixtures; in particular, a mix ratio of 25GWC-25FS-50LS (Na2SiO3 to NaOH 1 and L/S 0.2, cured at 60 °C for 24 h and aged for 7 days) obtained high compressive strength (47 MPa). Molar ratios of $$\frac{{{\text{SiO}}_{2} }}{{{\text{Al}}_{2} {\text{O}}_{3} }}$$ and $$\frac{{{\text{H}}_{2} {\text{O}}}}{{{\text{Na}}_{2} {\text{O}} + {\text{K}}_{2} {\text{O}}}}$$ in the reactive paste were 9.59 and 16.81, respectively. Structural integrity of selected IPs (25GWC-25FS-50LS) was observed when immersed in acidic H2SO4 and salt Na2SO4 solutions of 0.5 M and/or subjected to high-temperature firing (up to 400 °C).

Partial substitution of cement by the association of Ferronickel slags and Crepidula fornicata shells

Environmental impacts of building materials can be achieved by reducing the amount of cement in cementitious composites, specifically when incorporating wastes as partial replacement of Portland cement. In this work we substitute cement by shell by-products and Ferronickel Slags (FNS) while keeping interesting specific properties. FNS associated to Crepidula fornicata shells (CR) are good candidates to replace part of the Portland cement as they have appropriate physicochemical properties, and are available at high abundance.The effect of the association of FNS and CR on the mechanical properties of mortar is investigated. Microstructural characterization of these additives are carried out using Scanning Electron Microscopy, X-Ray diffraction and Raman spectroscopy. Formulated mortars contain different mixes of FNS-CR and Portland cement. Specific surface area, workability and setting times of fresh mortars are studied. The mechanical properties are investigated using 3-point bending and compressive tests for curing periods ranging from 2 to 28 days. In the fresh state, the replacement of cement by up to 20 wt.% of FNS-CR does not significantly affect mortar properties. However, at the hardened state, the setting time is increased using FNS-CR. With up to 20% wt.% of FNS-CR incorporation, the mechanical properties are similar or even slightly larger than that of the control mortar.

Definition and Exploration of the Integrated CO2 Mineralization Technological Cycle

This paper is part of a multi-disciplinary research program on development and application of an integrated CO2 mineralization (ICM) framework for development of carbon mineralization as a CO2 mitigation solution. ICM is viewed as a three concentric layer system: technological, industrial integration, and decision-making. The search for viable ICM solutions in a given societal and economic context, which could be posed as an inverse design problem, begins with the identification and characterization of every system component. As an early writing on the development and applicability of the proposed ICM framework, this contribution focuses on ICM's inner technological layer. Several technological pathways, each one defined as a set of processing and transformation steps that connect a feedstock to a specific marketable product, can coexist within this layer. The paper addresses the characterization of one such technological pathway, whose cycle is divided into three successive blocks: feedstock, carbonation and valorization. The proposed concepts are illustrated through the valorization of ferronickel slag from New Caledonia as supplementary cementitious material or cement constituent, a case study that targets the production of “greener” construction materials. The data presented in the paper confirm the feasibility of characterizing the chosen ICM technological pathway, giving credit to the proposition that ICM can be approached as an inverse design problem. While exemplifying the significance of the characterization work necessary for one particular ICM technological pathway, the paper argues that development of ICM requires working on a scale considerably larger than that of standard mineral carbonation process research. Indeed, where grams of carbonated products are sufficient to investigate mineral carbonation processes, kilograms are mandatory to test and validate the use performance of final marketable products. Without precluding the merits of seeking innovative solutions, the authors argue that unit operations and transformation processes whose validity is proven at an industrial scale should be favored for timely development of viable ICM solutions.

Recovery of chromium from ferronickel slag: A comparison of microwave roasting and conventional roasting strategies

A novel strategy for selective recovery of chromium from ferronickel slag via microwave assisted sodium peroxide roasting followed by water leaching was proposed in this study. The experimental results showed that 94.21% of chromium was leached with 64.43% of sodium and 6.13% of silicon, while only 0.06 wt% chromium remained in the leaching residue when the mixture of ferronickel slag and sodium peroxide with the mass ratio of 1 was roasted at 600 °C for 20 min before leaching at 50 °C for 1 h with the liquid-to-solid ratio of 10 mL/g. In comparison with conventional roasting, the microwave roasting showed a much higher efficiency for recovering chromium from ferronickel slag with the recovery of chromium increased by 12.92%, resulting from the enhanced conversion of Cr2O3 in the slag to NaCrO2 and from the looser and more porous structure during the roasting process which was beneficial for subsequent water leaching.

The evaluation of in-site remediation feasibility of Cd-contaminated soils with the addition of typical silicate wastes

In-site remediation is a relatively promising and socially acceptable technique for heavy metal contaminated soils. But the key task is to select cost-effective and environment-friendly amendents for the consideration of practical application. Based on the property of four typical silicate wastes such as straw ash (SA), coal fly ash (CFA), ferronickel slag (FNS) and blast-furnace slag (BFS), effects of four wastes on available Cd content and Cd chemical speciation in amended soils, and physicochemical properties of the amended soils were carried out in the study. The results showed that four wastes were dominately composed of the amorphous phases with OH− ions readily released. When the weight ratio of silicate wastes to artificial Cd-contaminated soils reached 10%, the available Cd contents decreased from 4.12 mg/kg in untreated soils to 1.94, 1.92, 1.45 and 1.53 mg/kg in amended soils by adding SA, CFA, FNS and BFS respectively, after the soils were amended for 30 days. The residual fraction of Cd (R) was 2.54, 2.48, 2.77 and 2.58 times higher in amended soil than that in untreated soil when SA, CFA, FNS and BFS was added, respentively. The soil pH and CEC were improved. The amended soils by adding SA and FNS were looser than those by adding CFA and BFS, and air permeability of the amended soils by SA was better than that by FNS.

Adjusting the melting and crystallization behaviors of ferronickel slag via partially replacing of SiO2 by B2O3 for mineral wool production

Utilization of ferronickel slag as a raw material for mineral wool production not only conserves natural resources, but also achieves the sustainable development for the ferronickel industry. In order to utilize the ferronickel slag more efficiently, the melting and crystallization behaviors of the slag with the partial replacement of SiO2 by B2O3 were investigated in this paper. The results show that the initial and complete melting temperatures decreased with B2O3 substitution for SiO2, which indicates that the addition of B2O3 can reduce the energy consumption during the melting process. The incubation time of the slag in the Time Temperature Transformation (TTT) diagram increased, whereas the initial crystallization temperature in the Continuous Cooling Transformation (CCT) diagram decreased when SiO2 was substituted by B2O3. In addition, the main crystalline phases precipitated in the slags were columnar MgSiO3 and Mg2SiO4. The weakening of crystallization ability caused by the substitution of B2O3 for SiO2 will be beneficial for the improvement of fiber quality when the ferronickel slag is used as a raw material for mineral wool production.

Immobilization of hazardous ferronickel slag treated using ternary limestone calcined clay cement

This study aims to develop the limestone calcined clay (LC3) as a low-carbon treatment to immobilize waste ferronickel slag (FNS) containing heavy metals. The results indicate that the ordinary portland cement (OPC) and limestone calcined clay cement (LC3) adequately immobilized the Chromium (Cr), with the leaching results of 0.10–0.30 mg/L. The LC3 cement provided superior Mn immobilization (lower than 5 mg/L) compared to OPC. Calcium aluminum silicate hydrate (C-A-S-H) and ettringite (AFt) were the two main hydrated products of LC3 that ensure the capacity to encapsulate metals. The LC3 specimens had the lower porosity between 50 and 10,000 nm compared to that of OPC. The Embodied Energy (EE) and Embodied Carbon Emissions (ECO2e) of per m3 LC3 remarkably decreased by 38.21% and 44.77%.

Factors affecting co-valorization of fayalitic and ferronickel slags for the production of alkali activated materials

The first objective of this experimental study is the assessment of the alkali activation potential of two types of fayalitic slags, an as-received one (FS) and the one obtained after plasma treatment (FSP) of the initial FS, for the production of alkali activated materials (AAMs). Furthermore, the second objective is the elucidation of the co-valorization potential of FS and FSP slags when mixed with ferronickel (FeNi) slag (LS). The alkaline activating solution used was a mixture of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The effect of various operating parameters, such as H2O/Na2O and SiO2/Na2O ratios present in the activating solution, curing temperature, curing period and ageing period on the compressive strength, density, water adsorption, porosity and toxicity of the produced AAMs was explored. The structural integrity of selected AAMs was investigated after firing specimens for 6 h at temperature up to 500 °C, immersion in distilled water and acidic solution or subjection to freeze-thaw cycles for a period of 7 or 30 days. The results of this study show that FS- and FSP-based AAMs acquire compressive strength of 44.8 MPa and 27.2 MPa, respectively. When FS and FSP were mixed with LS at 50:50%wt ratios the compressive strength of the produced specimens increased to 64.3 MPa and 45.8 MPa, respectively. Furthermore, selected AAMs produced after co-valorisation of slags retained sufficient compressive strength after firing at 500 °C, 45–68 MPa, and exhibited very low toxicity. These findings prove the alkali activation potential of fayalitic slags as well as their co-valorization with ferronickel slag for the production of AAMs, an approach which is in line with the principles of zero-waste and circular economy.

Reverse leaching of magnesium from ferronickel slag using alkali solvent NaOH

A research based on magnesium extraction of ferronickel slag waste processed by reverse leaching using sodium hydroxide (NaOH) solutions has been carried out. The ferronickel slag has the main compositions of magnesium silicate and iron silicate. The early procedure of the research was the preparation of ferronickel slag grinding using a ball mill until it gets a size of –200 mesh. Secondly, the calcination of ferronickel slags to remove crystal water and increase the size of the porosity so that it would facilitate the leaching process. The next procedure was reverse leaching using sodium hydroxide (NaOH) to dissolve silica. By dissolving the silica, it was expected that the contents of elements such as magnesium and iron would increase in the residue. The variations in this ferronickel slag leaching research were leaching time, solvent concentration and leaching temperature. The reverse leaching of ferronickel slag was carried out with a time variation of 15 to 240 minutes, the temperature of 30 °C, 70 °C, and 100 °C and NaOH concentrations are 9 M, 10 M, and 11 M. The XRD (X-ray diffraction) analysis, (XRF X-ray fluorescence) analysis, SEM (Scanning Electron Microscope) analysis, and ICP-OES (Inductively Coupled Plasma) analysis were used to observe the initial characteristics of the ferronickel slag and the results after the leaching process. The characterization result towards ferronickel slag samples by XRD analysis shows that the compositions of the dominant compounds are forsterite (Mg 2 SiO 4 ), enstatite (MgSiO 3 ) and fayalite (Fe 2 SiO 4 ). Moreover, the result is also supported by XRF analysis and SEM mapping analysis. The quantitative analysis of XRF shows that ferronickel slag contains 45.69 % of SiO 2 , 29.32 % of MgO and 16.5 % of Fe 2 O 3 . The results of the SEM mapping analysis show that Mg, Si, Fe and O bond together that indicates the presence of magnesium silicate and iron silicate. The highest percentage of magnesium extraction is 73.10 % under experimental temperature conditions of 100 °C for 240 minutes, 10 M of solvent concentration and 300 rpm of stirring speed. Increasing percentage of magnesium extraction is caused by the dissolution of silica in the leaching process. The dissolution of silica is proved by the existence of magnesium hydroxide and iron(II) hydroxide in the residue that is shown by the XRD analysis. It resulted in the MgO content in the residue increase significantly to 42.8 % as shown by the XRF analysis. Moreover, the SEM mapping analysis shows that Mg and O bond together that indicated the presence of MgO. It also can be determined that MgO is dominant

페로니켈슬래그 및 플라이애시를 결합재로 사용한 삼성분계 시멘트의 수화 특성 및 기초물성에 관한 연구

본 연구는 철과 니켈의 합금강 제조공정에서 발생하는 산업부산물인 페로니켈슬래그를 혼입하여 기존 결합재와의 화학 반응 및 성능을 확인하였다. 플라이애시와 페로니켈슬래그를 활용하여 시멘트 대비 치환율 30 %까지 삼성분계 치환을 하고 배합하여 실험을 통해 기초 물성 및 특징을 평가하였다. 실험 결과에 따르면 페로니켈슬래그를 혼입할 시 포졸란 반응이 기여하여 밀실한 내부 공극 및 수화물이 형성되었고, 수화열과 건조 수축 감소 효과도 나타났다. 압축강도는 초기 재령 28일까지 다소 저조한 강도발현을 나타냈으나, 365일 장기재령으로 갈수록 강도 증가가 나타났다. 추후 최적 배합을 도출하여 용도에 맞게 활용할 경우 시멘트 결합재로서의 활용 가능성이 기대된다.

Compressive Strength, Chloride Ion Penetrability, and Carbonation Characteristic of Concrete with Mixed Slag Aggregate.

The shortage of natural aggregates has recently emerged as a serious problem owing to the tremendous growth of the concrete industry. Consequently, the social interest in identifying aggregate materials as alternatives to natural aggregates has increased. In South Korea’s growing steel industry, a large amount of steel slag is generated and discarded every year, thereby causing environmental pollution. In previous studies, steel slag, such as blast furnace slag (BFS), has been used as substitutes for concrete aggregates; however, few studies have been conducted on concrete containing both BFS and Ferronickel slag (FNS) as the fine aggregate. In this study, the compressive strength, chloride ion penetrability, and carbonation characteristic of concrete with both FNS and BFS were investigated. The mixed slag fine aggregate (MSFA) was used to replace 0, 25%, 50%, 75%, and 100% of the natural fine aggregate volume. From the test results, the highest compressive strength after 56 days was observed for the B/F100 sample. The 56 days chloride ion penetrability of the B/F75, and B/F100 samples with the MSFA contents of 75% and 100% were low level, approximately 34%, and 54% lower than that of the plain sample, respectively. In addition, the carbonation depth of the samples decreased with the increase in replacement ratio of MSFA.

Effect of B2O3 on the properties of ferronickel melt and mineral wool

To utilize both ferronickel slag and its sensible heat, the melting and viscosity-temperature behaviors of the B2O3 modified slags were studied first. Results show that the initial melting temperature reduces from 1612 K (1339 °C) to 1534 K (1261 °C), and the complete melting temperatures decreases from 1744 K (1471 °C) to 1696 K (1423 °C) with the increase of B2O3 from 3 to 9 wt%. However, the temperature span of the viscosity ranging in 0.5–2.5 Pa s increases from 10 K (°C) to 39 K (°C) with increasing B2O3. Then, the characterizations of the slag fibers prepared by the modified slags suggest that the addition of B2O3 decreases the mean diameter of the slag fibers from 5.6 ± 0.45 μm to 3.4 ± 0.27 μm, whereas increases their tensile strength from 1724 ± 80 MPa to 2114 ± 136 MPa. Moreover, both the glass transition temperature (Tg) and crystallization temperature (Tc) are delayed by the addition of B2O3 since boron works as network former in the slag melt structure.

Promoting spinel formation and growth for preparation of refractory materials from ferronickel slag

AbstractThe study provides a method for improving the quality of the refractory material prepared from ferronickel slag by promoting the spinel formation and growth in the slag which was sintered with sintered magnesia and chromium oxide in a broad sintering temperature range from 1200°C to 1500°C. According to the thermodynamic analysis, except for forsterite due to the addition of sintered magnesia, a number of high‐melting point spinel phases can also be formed in the presence of chromium oxide and this trend becomes more apparent with increasing sintering temperature, along with declined presence of low‐melting point clinopyroxene, mainly enstatite. This expectation was verified by conversion of a part of the original phase of ferronickel slag, olivine, to two main spinel phases, including magnesium aluminate spinel and donathite which was produced by the replacement of nontoxic Cr3+ ions with Fe3+ ions in the octahedral vacancies of magnesium chromate spinel. The formation and growth of these spinel phases were promoted by elevating temperature from 1200°C to 1500°C, which accelerated the transition of initially generated enstatite to a glassy phase, in favor of densification. The formation and growth of spinel during sintering contributed to high refractoriness and compressive strength of the resulting refractory materials

Sustainable use of ferronickel slag in cementitious composites and the effect on chloride penetration resistance

Sufficient utilizations of ferronickel slag (FNS), an industrial waste discharged from nickel smelting and stainless-steel production process, are essential under the background of sustainability development. In this work, the replacement of ordinary Portland cement by FNS and its influence on chloride penetration are systematically investigated. A range of measurements including RCPT, corrosion current, natural diffusion, pore structure and X-ray diffraction was carried out. The results show that the concrete pore structure can be refined with an appropriate dosage (up to 30%) of FNS, whereby a higher resistance to reinforcement corrosion and a reduction of electrical conductivity are found. With the inclusion of FNS the chloride binding capacity of cement pastes is enhanced and the binding behavior can be expressed by the Langmuir isotherm. The addition of FNS leads to a higher amount of amorphous C-S-H phases. The formation of hydrotalcite-like phases and the higher C-S-H content account for the enhanced chloride binding of FNS pastes.