Methods for Improving Volume Stability of Steel Slag as Fine Aggregate

Suitable methods for enhancing the volume stability of steel slag utilized as fine aggregate were determined. The effects of steam treatment at 100 ℃ and autoclave treatment under 2.0 MPa on the soundness of steel slag sand were investigated by means of powder ratio, linear expansion, compressive and flexural strength. DTA, EDX, XRD and ethylene glycol methods were employed to analyze both the treated slags and susceptible expansion grains. Experimental results indicate that powder ratio, content of free lime and rate of linear expansion can express the improvement in volume stability of different treated methods. Steam treatment process cannot ultimately prevent specimens from cracking and decrease of strength, but mortar made from autoclave treated slag keeps integration subjected to hot water of 80℃ until 28 d and its strength do not show significant decrement. The hydration of over-burn free lime and periclase phase are the main cause for the disintegration or crack of untreated and steam treated steel slag＇s specimens. Autoclave treatment process is more effective than steam treatment process on enhancement of volume stability of steel slag.

Study on the properties and application of the steel slag special fine aggregate

The physical properties, grading stability and application stability of the steel slag special fine aggregate （diameter≤0. 8mm） at Baosteel were analyzed in this study, and the mechanical and working properties were studied when the aggregate was applied to concrete. The： result shows that the aggregate has special advantages of hardness and wear-resistance, so it can be used as an excellent road surface material. The concrete mixed with the steel slag special fine aggregate exhibits good mechanical properties and working properties,which is safe and reliable.

Numerical Comparative Study on the Effective Replacement Thickness of Traditional Stone Coarse Aggregate or Steel-Slag Aggregate Mixtures in Improved Soft Fine Soils

This study uses Steel Slag Coarse Aggregate (SSCA) as a mixture replacement, preamble material to improve soft soils, which is economic, and has good effect environment. Recently, the development and utilization of by-product, waste and recycle materials must be studied and investigated as a source of improved material for soft soils as, an economic and good effect environmental. The study analyzes effects of both replaced mixtures, (SSCA) or (TSCA) on improved soil bearing capacity and expected settlement after verifying the model. Numerical modeling of the one of real store loaded strip using, PLAXIS, 2D, strain deformation behavior to achieve field visible and measured deformations of untreated soft soil. Numerical studies were devolved to investigate geomechanics parameters improved to compare between using (SSCA) or (TSCA) as, replacement mixture. Results demonstrate that using (SSCA) improved compressibility and strength of shallow soft soil layer significantly than using (TCSA) mixture, while (SSCA) improved strip footing ultimate bearing capacity, (UBC), by 84.4% compared with increase of 20.5% when using (TCSA) mixture at the same thickness. In addition, the study highlights the effective (SSCA) replacement thickness ranges between (0.65 ~ 0.80) footing width.

Effect of Fine Steel Slag Powder on the Early Hydration Process of Portland Cement

Hydration heat evolution, non-evaporative water, setting time and SEM tests were peorormed to investigate the effect of fine steel slag powder on the hydration process of Portland cement and its mechanism. The results show that the effect of fine steel slag powder on the hydration process of Portland cement is closely related to its chemical composition, mineral phases, fineness, etc. Fine steel slag powder retards the hydration of portland cement at early age. The major reason for this phenomenon is the relative high content of MgO , MnO2, P2O5 in steel slag, and MgO solid solved in C3 S contained in steel slag.

Laboratory Evaluation of Fiber-Modified Asphalt Mixtures Incorporating Steel Slag Aggregates

Vigorous and continued efforts by researchers and engineers have contributed towards maintaining environmental sustainability through the utilization of waste materials in civil engineering applications as an alternative to natural sources.In this study,granite aggregates in asphaltic mixes were replaced by electric arc furnace(EAF)steel slag aggregates with different proportions to identify the best combination in terms of superior performance.Asphalt mixtures showing the best performance were further reinforced with polyvinyl alcohol(PVA),acrylic,and polyester fibers at the dosages of 0.05%,0.15%,and 0.3%by weight of the aggregates.The performance tests of this study were resilient modulus,moisture susceptibility,and indirect tensile fatigue cracking test.The findings of this study revealed that the asphalt mixtures containing coarse steel slag aggregate exhibited the best performance in comparison with the other substitutions.Moreover,the reinforced asphalt mixtures with synthetic fibers at the content of 0.05%exhibited an almost comparable performance to the unreinforced asphalt mixtures.Modifying the asphalt mixtures with PVA,acrylic,and polyester fibers at the proportion of 0.15%have improved the fatigue cracking resistance by 41.13%,29.87%,and 18.97%,respectively.Also,the fiber-modified asphalt mixtures with PVA,acrylic,and polyester have enhanced the fatigue cracking resistance by about 57%,44%,and 39%,respectively.The results of the resilient modulus demonstrated that as the fiber content increase,the resilient modulus of the reinforced asphalt mixtures decreases.Therefore,introducing synthetic fibers at the content of 0.3%has slightly decreased the resilient modulus in comparison with unreinforced mixtures.On the other hand,the results of the mechanisticempirical pavement design showed that the reinforced asphalt mixes with a high content of synthetic fibers have shown lower service life than the control mixes due to the low resilient modulus.On the contrary,based on the laboratory results,the asphalt mixes incorporating PVA,acrylic,and polyester fibers at the proportion of 0.15%have shown the potential to reduce the thickness of the asphalt layer by about 14.9%,11.80%,and 8.70%,respectively.

Preparation of Reactive Powder Concrete Using Fly Ash and Steel Slag Powder

To decrease the cement and SF content of RPC by using ultra-fine fly ash （UFFA） and steel slag powder （SS）, the effect of these mineral admixtures on compressive strength of RPC were investigated. The experimental results indicate that the utilization of UFFA and SS in RPC is feasible and has prominent mechanical performance. The microstructure analysis （SEM and TG-DTG-DSC） demonstrated that the excellent mechanical properties of RPC containing SS and UFFA were mainly attributed to the sequential hydration filling effect of the compound system.

Experimental Research of Concrete with Steel Slag Powder and Zeolite Powder

In order to increase use ratio of steel slag solid waste,the concrete containing steel slag powder and zeolite powder as admixtures was prepared by using the orthogonal test method.The effects of water-binder ratio,sand ratio,steel slag powder content and zeolite powder on working properties,mechanical strength and chloride ion permeability of the concrete was studied.It was found that the early strength of the concrete had a decrease with the mixing of steel slag and zeolite powders,but its later strength approached to pure concrete.Moreover,the physical filling and pozzolanic activity of the admixtures increased the density of the concrete,resulting in the improvement of the durability of the concrete by the migration speed of Cl−reducing.The optimum mix ratio of C40 steel slag powder-zeolite powder concrete is obtained,and which had the slump of 220 mm,the 3 d,7 d and 28 d compressive strengths of 27.8 MPa,37.5 MPa and 48.4 MPa,the 6 h electric flux of 950 C and the diffusion coefficient of 1.65×10−12 m2/s.

Effects of Steel Slag Powder on Workability and Durability of Concrete

The workability and durability of a type of sustainable concrete made with steel slag powder were investigated. The hydrated products of cement paste with ground granulated blast furnace slag（GGBFS） alone or with a combined admixture of GGBFS-steel slag powder were investigated by X-ray diffraction（XRD）. Furthermore, the mechanism of chemically activated steel slag powder was also studied. The experimental results showed that when steel slag powder was added to concrete, the slumps through the same time were lower. The initial and fi nal setting times were slightly retarded. The dry shrinkages were lower, and the abrasion resistance was better. The chemically activated steel slag powder could improve compressive strengths, resistance to chloride permeation and water permeation, as well as carbonization resistance. XRD patterns indicated that the activators enhanced the formation of calcium silicate hydrate（C-S-H） gel and ettringite（AFt）. This research contributes to sustainable disposal of wastes and has the potential to provide several important environmental benefi ts.

The Research for Surface Properties of Steel Slag Powder and High-Temperature Rheological Properties of Asphalt Mortar

In order to evaluate the feasibility of steel slag powder as filler,the coating properties of steel slag and limestone aggregate were compared by water boiling test,the micro morphology difierences between steel slag powder and mineral powder(limestone powder)were compared by scanning electron microscope(SEM),and the high-temperature rheological properties of asphalt mortar with difierent ratio of filler quality to asphalt quality(F/A)and difierent substitution rates of mineral powder(S/F)were studied by dynamic shear rheological test.The results show that the surface microstructure of steel slag powder is more abundant than that of mineral powder,and the adhesion of steel slag to asphalt is better than that of limestone.At the same temperature,the lower the ratio of S/F is,the greater the rutting factor and complex modulus will be.In addition,the complex modulus and rutting factor of the asphalt mortar increase with the increase of F/A,and the filler type and F/A have a negligible efiect on the phase angle.

Preparation of High Activity Admixture from Steel Slag,Phosphate Slag and Limestone Powder

The problem of low disposal and utilization rate of bulk industrial solid waste needs to be solved.In this paper,a high-activity admixture composed of steel slag-phosphate slag-limestone powder was proposed for most of the solid waste with low activity and a negative impact on concrete workability,combining the characteristics of each solid waste.The paper demonstrates the feasibility and explains the principle of the composite system in terms of water requirement of standard consistency,setting time,workability,and mechanical properties,combined with the composition of the phases,hydration temperature,and microscopic morphology.The results showed that the steel slag:phosphate slag:limestone=5:2:3 gave the highest activity of the composite system,over 92%.Besides,the composite system had no significant effect on water demand and setting time compared to cement,and it could significantly increase the 7 and 28 d activity of the system.The composite system delayed the exothermic hydration of the cement and reduced the exothermic heat but had no effect on the hydration products.Therefore,the research in this paper dramatically improved the solid waste dissipation in concrete,reduced the amount of cement in concrete and positively responded to the national slogan of carbon neutral and peaking.

Study on rapid stabilization of steel slag powder

Dry ball milling and wet ball milling were used to treat converter slag with particle size < 10 mm and the converter slag powder was stabilized by H_2O only and H_2O coupled with CO_2.respectively.Results showed that when CO_2 &H_2O was used,the free-calcium oxide(f-CaO) content in converter slag decreased significantly and after an-hour treatment the f-CaO content was reduced to 3%;however,when only treated by H_2O without CO_2, f-CaO needed 3-hour stabilization to decrease its content to 3%.When f-CaO in converter slag powder was treated by CO_2 &H_2O,its main reaction products were CaCO_3 and then Ca(OH)_2;however,when only H_2O was used, the f-CaO content decreased gently and the main products were Ca(OH)_2.

Recycling of industrial waste and performance of steel slag green concrete

Workability and mechanical properties of steel slag green concrete with different types of steel slag and different dosages of admixtures were investigated. The effectiveness of steel slag powder on suppressing alkali aggregate reaction(AAR) expansion was assessed using the method of ASTM C441 and accelerated test method. Experimental results show that mechanical properties can be improved further due to the synergistic effect and mutual activation when compound mineral admixtures with steel slag powder and blast-furnace slag powder are mixed into concrete. In addition,about 50% decrease in expansion rate of mortar bars with mineral admixtures can be achieved in AAR tests. Mineral admixtures with steel slag powder as partial replacement for Portland cement in concrete is an effective means for controlling expansion due to AAR.

Challenges in the use of stainless steel slag

Stainless steel melting shops of Outokumpu Group are located in Finland,Sweden and England(UK). In all of the countries the European Union legislation is the same,but in practice the plants face different technical,economical and administrative challenges in developing sustainable treatments and use of by-products. Due to availability of good natural construction materials,the use of slag and other industrial by-products has been quite small in Northern Europe.Blast furnace slag has been completely utilized,while slag from stainless steel processes has earlier been regarded as waste.Steering of the metallurgical melt phase,slag cooling,treatment and metal recovery processes are the main technical challenges for increasing the sustainable use of stainless steel slag. Moreover,product properties have to fulfill standards and customer requirements.Dry or water-cooled EAF slag aggregates are typically used in road construction.Outokumpu has developed light mineral slag aggregates which are cooled in rapid water process.During this process,a specific structure and mineralogy is formed in the slag and leaching from the material decreases.In many regulatory discussions,it seems that there is not enough relevant scientific data from harmful compounds.Limit values are based only on laboratory tests and model estimations,not on the material use itself or real nature.A risk-based approach is needed when environmental acceptance is not clear.Limit values based on content are not applicable because environmental or health risks depend on the release or leaching of substances from the material.This is the case especially with metals.

Effect of steel slag aggregate and bitumen emulsion types on the performance of microsurfacing mixture

Microsurfacing has recently been accepted widely as an effective method for preventive maintenance of pavements.Microsurfacing is a mixture of cationic polymer-modified bitumen emulsion,100%manufactured well-graded fine aggregate,mineral filler,water,and chemical additives.In this research,in order to evaluate the performance of steel slag in microsurfacing mixture,two types of bitumen emulsions(cationic quick setting and cationic slow setting)were used together with three types of mixtures in which 100%siliceous aggregate was used as a control mixture and then steel slag was replaced by 61%and 100%aggregate of control mixture.The performance of the samples was evaluated by experiments included wet cohesion test,wet track abrasion test,and loaded wheel test,according to international slurry surfacing association(ISSA)A143 guideline and ASTM D6372 standard.The results of tests showed that steel slag aggregate has proper compatibility with both of bitumen emulsion types judged by its desirable physical,chemical,and mechanical properties.The alkali characteristic of the steel slag leads to a stronger adhesion of these materials to acidic bitumen and cause prevented the stripping in the vicinity of water in comparison to the control mixture.Also,steel slag-containing mixtures displayed a more appropriate behavior in terms of rutting and stripping distresses.

Effect of Silica Fume on Mechanical Properties of Concrete Incorporating Steel Slag Powder

This study investigated the effect of silica fume(SF) on mechanical properties of concrete incorporating steel slag powder(SSP). The compressive strength and splitting strength tests of concrete with different content of SF(0%, 4%, 8% and 12%) and of SSP(0%, 10%, 20%, 30% and 40%) were carried out, and the test results were analyzed and fitted. Obtained results showed that the brittleness, compressive strength and compressive strength discreteness of concrete increased due to the incorporation of SF. SSP weakened the compressive strength of concrete, which reduced within 10% when the content of SSP was less than 20%. SF and SSP showed synergistic hydration effect when they were mixed, and the optimal group was SF8 SSP30, whose compressive strength was close to that of plain concrete, and whose brittleness as well as discreteness of compressive strength were lower relatively. With the content of SSF and of SSP as variables, the tension-compression ratio and compressive strength of concrete can be well estimated by surface fitting.

钢渣复合矿粉对不同养护条件下混凝土性能的影响

为了探讨利用钢渣和矿渣制备复合掺合料的可行性,按质量比3∶7将钢渣与矿渣进行共同粉磨,制备复合矿粉,研究了复合矿粉对不同养护制度下混凝土的工作性和力学性能的影响,并对水化产物进行了表征。结果表明,复合矿粉使混凝土1 h的坍落度损失下降了6.9%,表现出了较好的保坍效果;在20℃标准养护和60℃蒸汽养护下,掺复合矿粉混凝土的立方抗压和轴向抗压强度与对照组相比均有所提高,但掺复合矿粉混凝土的劈裂抗拉强度均略低于对照组。微观分析发现,复合矿粉的掺入,使得生成的水化硅酸钙氧硅比降低,聚合度增加;水泥石总孔隙率由26.34%下降到23.99%;促进生成更多的水化产物。研究表明,在矿粉中掺入适量的钢渣粉制备复合矿粉具有较高的可行性,是同时实现钢渣和矿渣资源化利用的有效途径。

基于ICP-MS研究转炉钢渣微粉吸附镍和铅的动力学机理

随着工业化的发展,水体和土壤中的重金属污染日益严重。其中,重金属镍是一种常见的致敏性金属,会引起人体过敏发炎,甚至会引发癌症;血液中铅浓度的超标会危害人的神经系统、心血管系统和生殖系统,造成终身性的危害。因此,治理镍和铅重金属污染具有十分重要的意义。钢渣是炼钢过程中产生的一种副产物,其存在难以利用与附加值低的问题。同时加之管理制度的不健全,导致大量钢渣露天堆放,对土地资源、地下水源,以及空气质量造成严重影响。钢渣微粉具有比表面积大、多孔、化学活性高等特性,被广泛利用,可以成为吸附材料。本文以转炉钢渣微粉为研究对象,利用激光粒度仪、电感耦合等离子体质谱仪、比表面积与孔隙度吸附仪、X射线荧光光谱仪等测试转炉钢渣微粉的基本性质,重点研究转炉钢渣微粉添加量、重金属初始浓度、溶液pH和吸附时间对转炉钢渣微粉吸附Ni^(2+)、Pb^(2+)的效果,结合吸附动力学与吸附等温线理论揭示转炉钢渣微粉对Ni^(2+)、Pb^(2+)的吸附作用机理,为处理镍、铅重金属污染和工业废水处理提供技术支持与理论依据。结果表明:当转炉钢渣微粉添加量大于12.5 g·L^(-1)、重金属初始浓度小于100 mg·L^(-1)、溶液pH大于3和吸附时间大于120 min时,转炉钢渣微粉对Ni^(2+)、Pb^(2+)的吸附效果良好,即基本达到90%。转炉钢渣微粉对Ni^(2+)、Pb^(2+)的吸附符合准二级动力学模型,吸附速率由边界扩散和颗粒内扩散共同控制,吸附过程以化学吸附为主。转炉钢渣微粉的结构具有多孔性为物理吸附Ni^(2+)、Pb^(2+)提供吸附空间,转炉钢渣微粉的化学成分不仅具有碱性与Ni^(2+)、Pb^(2+)形成络合产物,而且水化过程中CaO与SiO_(2)生成C—S—H凝胶,对Ni^(2+)、Pb^(2+)形成络合吸附与硅酸盐体系包裹。转炉钢渣微粉对Ni^(2+)、Pb^(2+)吸附可能存在多层吸附。吸附Ni^(2+)、Pb^(2+)的过程为优惠吸附,吸附容易进行,其理论最大吸附量分别为18.785和17.002 mg·g^(-1)。

三元矿物掺和料胶砂试件性能研究

为解决煤矸石及钢渣作为单一掺和料强度不足的问题,以煤矸石、钢渣和矿粉为原材料制备复合掺和料水泥砂浆。研究不同配合比下掺和料对水泥砂浆抗压强度的影响,并利用X射线衍射(XRD)、热重-差热分析(TG-DTA)、扫描电镜(SEM)等手段分析不同体系试块的水化机理和微观结构。结果表明,单掺煤矸石、钢渣均表现出较低的活性,而矿粉具有良好的反应活性;三元掺和料中煤矸石-矿粉-钢渣复掺比例为1∶7∶2时,试块的抗压强度最高,28 d抗压强度可以达55.26 MPa。在三元掺和料体系中,煤矸石、矿粉和钢渣可以相互促进水化,增多水化产物,加深水化程度,三者具有一定的耦合作用,具有制备三元矿物掺和料的潜力。

水泥和钢渣粉协同固化高含水率疏浚泥的力学性能研究

研究了钢渣粉的掺入方式(内掺、外掺)和掺量(0、5%、10%、15%)对水泥固化高含水率疏浚泥力学性能的影响。结果表明:当水泥掺量一定时,随着钢渣粉外掺量的增加,固化疏浚泥的3、7、14、28、90 d无侧限抗压强度均先增大后减小,14 d峰值应力和峰值应变也呈先增大后减小的趋势,钢渣粉的最佳外掺量为10%;对于纯水泥固化疏浚泥,其变形系数随着水泥掺量的增加而增大,抵抗变形的能力降低;外掺适量钢渣粉降低了固化疏浚泥的变形系数,提高了固化疏浚泥抵抗变形的能力;钢渣粉内掺取代部分水泥降低了固化疏浚泥的无侧限抗压强度,建议钢渣粉采用外掺方式。

钢-PVA混杂纤维高性能混凝土抗渗性能试验研究

为探究钢纤维掺量、聚乙烯醇(PVA)纤维掺量和矿粉掺量对钢-PVA混杂纤维高性能混凝土(HFHPC)抗渗性能的影响,本文开展了钢-PVA HFHPC抗渗性能试验,并对试验结果进行了极差分析、方差分析和回归分析。结果表明:对HFHPC抗渗性能的影响程度从高到低依次为钢纤维、矿粉和PVA纤维。在试验水平范围内,得出混凝土试件抗渗性能最佳水平组合:钢纤维体积掺量1.0%、PVA纤维体积掺量0.7%、矿粉质量取代率20%。当钢纤维掺量超1.0%时,HFHPC抗渗性能略有下降,但仍高于基准素混凝土。最后采用多元回归分析,建立了HFHPC渗透系数与钢纤维、PVA纤维和矿粉的预测模型。