碳酸化钢渣和矿渣作硅酸盐水泥混合材水化性能研究

通过对钢渣碳酸化前后的硅酸盐相提取及水化放热性能和将碳酸化钢渣和矿渣作为混合材的硅酸盐水泥的胶砂强度和水化产物种类的测定,以及对它们微观形貌的观察,研究了碳酸化钢渣对胶凝体系水化性能的影响.结果表明,碳酸化使钢渣中硅酸盐相的含量由47.06％下降至14.38％;碳酸化促进了钢渣的早期水化,抑制其后期水化;在配比相同的条件下,碳酸化钢渣-矿渣-硅酸盐熟料体系试样的3、28d抗压强度较未碳酸化钢渣-矿渣-硅酸盐熟料体系试样的高;碳酸化生成的CaCO3促进了熟料的水化;碳酸化钢渣促进了胶凝体系中AFt的生成,且生成水合碳铝酸钙.     

Modification of steel slag powder by mineral admixture and chemical activators to utilize in cement-based materials

Modification of steel slag powder by mineral admixture and chemical activators to utilize in cement-based materials was studied in this work. The results showed that for cement pastes with steel slag alone, the normal consistency water requirement and compressive strength were decreased significantly. Both of the initial setting time and final setting time were also retarded than that of the control sample. When a compound admixture of ground granulated blast furnace slag (GGBFS) -steel slag powder added the compressive strength was evidently improved. Modification of steel slag powder by “Gypsum-type” and “Sodium-type” chemical activators were further studied. Cement paste with the modified compound admixture by 1.5 % calcium sulfate hemihydrate or sodium sulfate, its 28 days compressive strengths could reach to 75.4 and 76.2 MPa, respectively. X-ray diffraction (XRD) patterns showed that the main hydration products mainly included Ca(OH)₂ and ettringite. It indicated that proper mineral admixture and chemical activators had a positive effect regarding early hydration of steel slag powder, and enhanced forming calcium silicate hydrate(C–S–H) gel and ettringite. This work contributes to understanding of how to sustainably manage wastes and byproduct materials and has the potential to provide several important environmental and economic benefits.     

镍渣机械力化学效应及其对反应活性的影响

为提高镍渣的反应活性,根据机械力化学原理,采用高能球磨技术处理镍渣并采取蒸压工艺制备镍渣制品.通过粒径分析、X射线分析以及扫描电镜分析等手段研究不同高能球磨时间下镍渣的粒径、结构和形貌变化以及镍渣的反应活性变化.结果表明:高能球磨可以进一步细化镍渣,使大颗粒块状粉体破裂、表面粗糙化并提高镍渣的反应活性,长时间球磨可使水化样品诱导期和加速期两个阶段的水化放热量显著增大;高能球磨4 h时镍渣蒸压试块的强度最大,可达24.4 MPa,是未高能球磨时的4.5倍,球磨4 h后蒸压试块水化产物的X射线谱图中出现了硬硅钙石、托勃莫来石和镁水化物等衍射峰.     

The influence of blast-furnace slag hydration products on microcracking of concrete

New hydration products of ground granulated blast-furnace slag are formed during the hydration process of Portland slag cement concrete. Spatial distribution of microcracks in concrete is related also to newly formed slag hydrates. The chemical composition of hydration products is variable and unstable. The Si/Ca ratios rise in hydration products near the unhydrated slag core significantly. There is also a certain increase of Mg and Al content in the central parts of hydration rims. The scope of the paper is to find a relation between slag hydration products and the process of microcracking. The amount of microcracks was reduced in concretes with a lower content of vitreous fraction where the slag basicity was high. Neoformation of hydration products is accompanied by volume changes, which can lead to concrete microcracking.     

Structure characterization of hydration products generated by alkaline activation of granulated blast furnace slag

The hydration mechanism and mineral phase structures by waterglass activation of granulated blast furnace slag (GBFS) are investigated in detail by means of XRD and FTIR. The results show that the network structures of glassy phases are disintegrated and there is not any new material phase formed in the early stage of hydration processes. With evolution of hydration, the polycondensation reaction takes place between [SiO₄]⁴⁻ and [AlO₄]⁵⁻ species and some new mineral phases are produced. A hydration mechanism for the formation of geopolymer by waterglass activation of GBFS is proposed in detail.     

Synthesis of nanoparticles from slag and their enhancement effect on hydration properties of CaO/CaSO4-activated slag binder

Developing a low-cost and eco-friendly alternative to cement is of great significance for reducing the CO₂ emissions. CaO/CaSO₄-activated slag binder may only be served as a promising cementitious material when the severe defect in the early strength is overcame. In this study, gel-like nanoparticles with an average size of ～ 328 nm were prepared from the slag through dissolution at room temperature and reprecipitation at 50 °C. Subsequently, synthetic nanoparticles (SNPs) were added as a supplementary additive to enhance the strength of CaO/CaSO₄-activated slag binder. The effects of SNPs on the strength development, hydration kinetics, hydration products, and microstructure of the slag binders were investigated. The results indicated that the addition of moderate SNPs shortened the duration of induction period and improved the reaction rate in the acceleration period of the slag binders. As a result, large amounts of calcium aluminosilicate hydrate (C-A-S-H) gel was generated at early hydration ages. Meanwhile, SNPs increased the polymerization degree of this gel through the nucleation effect. Gel products’ well-filled the pore spaces between slag particles and yielded a compact microstructure, consequently enhancing the binder strength. The sample with adding 1.5 wt% SNPs exhibited the optimum strengths of 7.78 and 39.86 MPa after 1 and 28 days.     

Recycling of steel slag as an alkali activator for blast furnace slag: geopolymer preparation and its application in composite cement

Clean Technologies and Environmental Policy - The recycling–utilization rate of steel slag in China is less than 30%. Steel slag is rich in CaO and can produce the Ca(OH)2 after hydration,...     

Effect of particle size and slag content on the early hydration of interground blended cements

Three blended cements prepared by intergrinding 6–35% slag with clinker and gypsum, and a control portland cement, were sieved to yield 0–10 μm, 10–30 μm, 30–50 μm, and >50 μm subgroups. Clinker/slag/gypsum contents, and oxide compositions of the subgroups differed significantly from the unsieved cements. Fine subgroups always contained more gypsum and had lower slag-to-clinker ratios than coarse subgroups. Heat evolution was investigated up to 48 h using isothermal calorimetry. Contribution of slag to early heat evolution was limited. 0–10 μm particles evolved up to 5–10% of their heat in the first 30 min. Particle size affected the peak rate of heat evolution but not its timing. A linear relationship was observed between heat evolved from 0 to 24 h and from 24 h to 48 h. Median size or slag content of subgroups affected the positions of data points on this line. Heat evolved up to 24 h (or 48 h) was found to be closely related to particle size. Rate of heat development does not appear to be strongly influenced by particle size above ∼30 μm.     

钢渣制备水滑石阻燃剂及其在EVA复合发泡材料中的应用

以钢渣为原料合成了磷酸根型水滑石(P-LDHs),并用十二烷基硫酸钠(SDS)插层P-LDHs得到改性水滑石(SDS-P-LDHs).分别将P-LDHs,SDS-P-LDHs和膨胀石墨、EVA共混,发泡得到EVA复合发泡材料.利用XRD,XRF,FT-IR,SEM,TEM对P-LDHs和SDS-P-LDHs的形貌结构进行表征.结合极限氧指数(LOI),垂直燃烧(UL-94),SEM,TG,拉伸强度、断裂伸长率等测试,讨论了P-LDHs和SDS-P-LDHs用量对EVA复合发泡材料的阻燃性能和力学性能的影响.结果表明,P-LDHs和SDS-P-LDHs的加入显著提高了EVA复合发泡材料的阻燃性能,可起到良好的成炭作用.相比P-LDHs,SDS-P-LDHs与EVA基体相容性更好,当SDS-P-LDHs添加量为30％(质量分数)时,LOI达到27.5％,UL-94达到V-0级别,拉伸强度和断裂伸长率分别为2.27 MPa和251％,体系综合性能达到最佳.     

Adsorption intrinsic kinetics and isotherms of lead ions on steel slag

Batch experiments were carried out to investigate the kinetics of adsorption of lead ions by steel slag on the basis of the external diffusion, intra-particle diffusion and adsorption reaction model (pseudo-first-order, pseudo-second-order). The results showed that the controlling step for the adsorption kinetics changed with the varying experimental parameters. When the particle size of steel slag was larger than 120 mesh, intra-particle diffusion of Pb²⁺ was the controlling step, and when the initial concentration of Pb²⁺ was less than 150 mg L^?1 or the shaking rate was lower than 150 rpm, external diffusion of Pb²⁺ was promoted. Contrary to the former experimental conditions the adsorption reaction was the controlling step, and the adsorption followed second-order kinetics, with an adsorption rate constant of 13.26 g mg^?1 min^?1. The adsorption isotherm of Pb²⁺ with steel slag followed the Langmuir model, with a correlation coefficient of 0.99.     

Combined effect of chemical nature and fineness of mineral powders on Portland cement hydration

This paper focuses on the influence of the chemical nature and the fineness of the fillers on the hydration process and on the compressive strength development. Four different types of fillers are considered in combination with Portland cement: quartzite filler, alumina filler, limestone filler, and silica fume. The study deals with blended mortars having a 0.45 water to powder (cement and filler) ratio with a 10% substitution of cement by filler. Quartzite fillers do not seem to accelerate the hydration process in a significant way. No positive effect is noticed on the strength development either. The presence of a fine inert alumina powder increases the rate of early hydration of Portland cement. The greater the fineness, the faster the rate of hydration heat development. This reactivity leads to an increase in the compressive strength at early age for mortar containing the finest alumina powders. In case of coarse alumina powder, no acceleration effect is obtained. Finely ground limestone (calcite) fillers promote heterogeneous nucleation of hydrates which significantly accelerates hydration. At early age, this also results in an increased mortar compressive strength in comparison with the control mortar. From the obtained results, it is clear that both chemical natures as well as fineness are important with regard to the accelerating effect of the hydration process. With increasing fineness, the accelerating effect increases. For powders with comparable fineness, it is clear that limestone powder has a more significant accelerating effect than silica fume and alumina filler. Quartzite filler seems to have no significant effect.     

钢渣混凝土压敏性研究及机理分析

为了确定钢渣混凝土是否具有感知应力的功能,研究了钢渣混凝土在不同荷载条件下的电阻变化规律,即压敏性.通过模拟试验测试了不同加载速率、循环加载、突然加载和卸载等加载条件下钢渣混凝土的压敏性.结果表明,随着钢渣掺量的增加,钢渣混凝土的压敏效应更加明显;压力较小时,电阻率随压力增大而迅速降低;压力增大到一定程度后,电阻率下降十分缓慢;压力达到极限荷载时,电阻率迅速升高;在循环加载情况下,第一次加载循环时钢渣混凝土电阻变化率高于第二次加载循环时的变化率.钢渣混凝土成本很低,制备方法简单,与碳纤维增强水泥一样具有良好的压敏性,因此具有较好的应用前景.     

Synthesis of zeolite from steel slag and its application as a support of nano-sized TiO2 photocatalyst

Steel slag, commercial waste material containing silica and alumina which are the chemical components elements of zeolite, was used as a source for synthesis of FAU zeolite (Y-zeolite, X-zeolite). Through acid-treatment to remove CaO species from steel slag and hydrothermal treatment, well-crystallized Na type FAU zeolite was obtained. Furthermore the synthesized FAU zeolite was applied as a support of photocatalyst. It was found that hydrophobic surface property of zeolite enhances photocatalytic activity for decomposition of organic pollutants and the zeolite synthesized from steel slag would be applicable as promising support of TiO₂ photocatalyst.     

轴向压力作用下钢渣混凝土的压敏性研究

在不同加载速率、突然加载和卸载以及三向约束等加载条件下,钢渣混凝土具有良好的导电性和压敏性;随着钢渣掺量的增加,钢渣混凝土的压敏效应更加明显;施加压力较小时,电阻率随压力增大而迅速降低;压力增大到一定程度后,电阻率下降十分缓慢;压力达到极限荷载时,电阻率迅速升高;受到三向约束时,钢渣混凝土仍然具有压敏特性,相对于单轴受?其压力敏感性较低.     

粉磨对锰矿渣中锰提取的促进作用

锰矿渣作为工业固废一直得不到有效利用,危害环境。以四川阿坝某电解锰厂的锰矿渣为原料,采用二次酸浸方法对矿渣中锰元素的提取进行研究,采用X射线荧光光谱(XRF)和原子吸收光谱(AAS)检测技术分别检测固体粉渣和滤清液中锰元素的含量,探讨锰矿渣的粉磨与酸浸条件等因素对二次酸浸锰渣和滤液中锰元素含量的影响。结果表明:原矿渣经7、15 h粉磨后有效促进了矿渣中锰元素的提取,相对没有粉磨的原矿渣锰元素的提取效率分别提高了41. 3%和77. 9%。     

高温固相法制备钒掺杂含钛高炉渣光催化抗菌材料

采用高温固相法,掺杂不同质量分数的V2O5,在800℃煅烧2h合成了钒掺杂的含钛高炉渣催化剂(vanadium oxide modified titanium bearing blast furnace slag,VTBBFS)。用X射线衍射、扫描电子显微镜和紫外-可见漫反射光谱仪对钒掺杂的含钛高炉渣催化剂进行了表征,确定其具有钙钛矿结构;粉体的颗粒形态均为不规则块状,800℃煅烧后出现了团聚现象;在紫外区域具有强光吸收能力,并发生红移。以白色念珠菌为实验菌种考察钒掺杂的含钛高炉渣催化剂抗真菌能力。结果表明,V2O5掺杂量为10%时,催化剂具有较强的抗白色念珠菌能力,在普通光照下杀菌率可达到100%。     

基于均匀设计方法研究不锈钢焊条的脱渣性

为了定量地分析药皮辅料对焊条工艺性能的影响,利用中国数学会均匀设计分会推荐的UST4.0软件安排配方试验并处理数据,研究了不锈钢焊条的脱渣性.试验中,将10种辅料怍为自变量,焊缝的脱渣性作为目标函数.通过数理统计给出了每种药皮辅料影响焊缝脱渣性的趋势图,并建立了10种药皮辅料及其交互作用对应干脱渣性的数学模型.研究表明:金红石、钛白粉、电解锰、钛铁和白泥对焊缝脱渣性的影响都为正相关;冰晶石和萤石对焊缝脱渣性的影响为负相关;绝大多数药皮辅料对焊缝脱渣性的影响呈交互作用的形式.     

改进双采率统计方法的探讨

本文分析了现行双采率统计的产品品种法和产品标准法存在的缺陷 ,提出了在双采率统计中应注重经济因素的原则。并探讨了双采率统计的经济规模法理论 ,给出了运用这种方法的具体统计步骤。针对不同统计对象的较大差异性 ,采取以其经济规模作为权重因子进行整合的方法 ,具有较大的应用范围和价值 ,可用以弥补和改进为数众多的统计方法的缺陷。     

Effect of ground granulate blast-furnace slag on corrosion performance of steel embedded in concrete

Corrosion of steel in concrete is one of the major causes of premature deterioration of reinforced concrete structures, leading to structural failure. To prevent the failure of concrete structures because of corrosion, impermeable and high performance concretes should be produced various mineral admixtures. In this study, plain and reinforced concrete members are produced with mineral admixtures replacing cement. Ground granulated blast-furnace slag (GGBFS) has replaced cement as mineral admixture at the ratios of 0%, 25% and 50%. The related tests have been conducted at the ages of 28 and 90, after exposing these produced plain and reinforced concrete members to two different curing conditions. The unit weight, ultrasonic pulse velocity, splitting tensile and compressive strength tests are conducted on plain concrete members. Half-cell potential and accelerated corrosion tests are also conducted on reinforced concrete members. According to the test results, it is concluded that the curing age and type are important and corrosion resistant concrete can be produced by using GGBFS mineral admixture at the ratio of 25%.