Durability of Seawater Mixed Concrete with Different Replacement Ratio of BFS （Blast Furnace Slag） and FA （Fly Ash）

Using seawater in concrete can be considered as one of the sustainable approaches in construction industry not only to save the freshwater resource but also to promote the use of abandoned seawater resource, especially in the construction at the uninhabited area close to the sea where the procurement of fresh water is difficult. In this study, durability against chloride attack of seawater mixed concrete with different replacement ratio of BFS （blast furnace slag） and FA （fly ash） is discussed and the life time until the occurrence of corrosion crack is evaluated. The results show that： （1） Chloride penetration rate of seawater mixed specimens with BFS and FA is lower than that of freshwater mixed OPC （ordinary Portland cement） specimens; （2） Oxygen permeability of seawater mixed specimens with BFS and FA is almost the same or lower than that of freshwater mixed OPC specimens; （3） Total life time （corrosion incubation period and propagation period） of seawater mixed specimens with BFS and FA is almost the same or only slightly shorter than that of freshwater mixed OPC specimens. From the results, it was confirmed that the usage of seawater in concrete mixing is feasible in concrete with the appropriate BFS and FA replacement ratio.

Comparative Studies on Microstructure and Mechanical Properties of Granulated Blast Furnace Slag and Fly Ash Reinforced AA 2024 Composites

Composites are most promising materials of recent interest. Metal matrix composites (MMCs) possess significantly improved properties compared to unreinforced alloys. There has been an increasing interest in composites containing low density and low cost reinforcements. In view of the generation of large quantities of solid waste by products like fly ash and slags, the present expensive manner in which it is discarded, new methods for treating and using these solid wastes are required. Hence, composites with fly ash and granulated blast furnace (GBF) slag as reinforcements are likely to overcome the cost barrier for wide spread applications in automotive and small engine applications. In the present investigation, AA 2024 alloy-5 wt% fly ash and GBF slag composites separately were made by stir casting route. Phase identification and structural characterization were carried out on fly ash and GBF slag by X-ray diffraction studies. Scanning electron microscopy with energy dispersive X-ray spectroscopy EDS was used for microstructure analysis. The hardness and compression tests were carried out on all these alloy and composites. The SEM studies reveal that there was a uniform distribution of fly ash and GBF slag particles in the matrix phase and also very good bonding existed between the matrix and reinforcement. Improved hardness and mechanical properties were observed for both the composites compared to alloy;this increase is higher for Al-fly ash composite than Al-GBF slag composite.

Tests on Alkali-Activated Slag Foamed Concrete with Various Water-Binder Ratios and Substitution Levels of Fly Ash

To provide basic data for the reasonable mixing design of the alkali-activated (AA) foamed concrete as a thermal insulation material for a floor heating system, 9 concrete mixes with a targeted dry density less than 400 kg/m3 were tested. Ground granulated blast-furnace slag (GGBS) as a source material was activated by the following two types of alkali activators: 10% Ca(OH)2 and 4% Mg(NO3)2, and 2.5% Ca(OH)2 and 6.5% Na2SiO3. The main test parameters were water-to-binder (W/B) ratio and the substitution level (RFA) of fly ash (FA) for GGBS. Test results revealed that the dry density of AA GGBS foamed concrete was independent of the W/B ratio an RFA, whereas the compressive strength increased with the decrease in W/B ratio and with the increase in RFA up to 15%, beyond which it decreased. With the increase in the W/B ratio, the amount of macro capillaries and artificial air pores increased, which resulted in the decrease of compressive strength. The magnitude of the environmental loads of the AA GGBS foamed concrete is independent of the W/B ratio and RFA. The largest reduction percentage was found in the photochemical oxidation potential, being more than 99%. The reduction percentage was 87% - 93% for the global warming potential, 81% - 84% for abiotic depletion, 79% - 84% for acidification potential, 77% - 85% for eutrophication potential, and 73% - 83% for human toxicity potential. Ultimately, this study proved that the developed AA GGBS foamed concrete has a considerable promise as a sustainable construction material for nonstructural element.

Dry Mix Slag—High-Calcium Fly Ash Binder. Part One: Hydration and Mechanical Properties

High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace slag (GGBFS). Substitution of 10% - 30% of GGBFS by HCFA and premixing of 1% - 3% Na2CO3 to this dry binary binder was discovered to give mortar compression strength of 10 - 30 to 30 - 45 MPa at 7 and 28 days when moist cured at ambient temperature. High-calcium fly ash produced from low-temperature combustion of fuel, like in circulating fluidized bed technology, reacts with water readily and is itself a good hardening activator for GGBFS, so introduction of Na2CO3 into such mix has no noticeable effect on the mortar strength. However, low-temperature HCFA has higher water demand, and the strength of mortar is compromised by this factor. As of today, our research is still ongoing, and we expect to publish more data on different aspects of durability of proposed GGBFS-HCFA binder later.

Dry Mix Slag—High-Calcium Fly Ash Binder. Part Two: Durability

This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na2CO3): the soundness, sulfate resistance, alkali-silica reactivity and efflorescence factors are considered. Results of tests show that such mortars are resistant to alkali-silica expansion. Mortars are also sulfate-resistant when the amount of HCFA in the complex binder is within a limit of 10 wt%. The fineness of fly ash determines its’ ability to activate GGBFS hydration, and influence soundness of the binder, early strength development, sulfate resistance and efflorescence behavior. The present article is a continuation of authors’ work, previously published in MSA, Vol. 14, 240-254.

Effect of content of Al_2O_3 and MgO on crystallization of blast furnace slag during fiber formation

The simulation of blast furnace slag was prepared by pure chemical reagents.Test methods like DSC,XRD and SEM were used to study the effect of Al2O3 and MgO content on crystallization of blast furnace slag during fiber formation.The results show that as Al2O3 and MgO contents in the sample changed,blast furnace slag was crystallized at the average temperature below 1232 K.When the ratio of Mg/Al in the samples is 0.6 calculated by Kissinger equation,crystallization activation energy is at the maximum value and the system is in the most stable condition.The sample crystallization phases are mainly calcium akermanite(2CaO?MgO?2SiO2)and gehlenite(2CaO?Al2O3?SiO2).Secondary crystallization phases are anorthite(CaAl2Si2O8),wollastonite minerals(WOLLA)and pyroxene minerals(cPyrA).Meanwhile,the principal crystallization phases of the samples are different types and have different contents,and the microstructures of the sample sections are different due to the difference between MgO/Al2O3 ratio.

Basicity for blast furnace-type slag containing B_2O_3 and high MgO

There is quite abundant resource of ludwigite ore in Liaoning Province of China. Content of MgO in the slag of pyrometallurgical separation of boron from iron is much higher than that in the ordinary slags. Through the equilibrium partition ratio of sulfur L S between the metal and the slag in an atmosphere of CO N 2, the acidic coefficients for B 2O 3 and the basic coefficients for MgO were estimated. The basic formulae were given for the blast furnace type slag containing B 2O 3 and high MgO.

Clayey soil stabilization using alkali-activated volcanic ash and slag

Lime and Portland cement are the most widely used binders in soil stabilization projects.However,due to the high carbon emission in cement production,research on soil stabilization by the use of more environmentally-friendly binders with lower carbon footprint has attracted much attention in recent years.This research investigated the potential of using alkali-activated ground granulated blast furnace slag(GGBS)and volcanic ash(VA)as green binders in clayey soil stabilization projects,which has not been studied before.The effects of different combinations of VA with GGBS,various liquid/solid ratios,different curing conditions,and different curing periods(i.e.7 d,28 d and 90 d)were investigated.Compressive strength and durability of specimens against wet-dry and freeze-thaw cycles were then studied through the use of mechanical and microstructural tests.The results demonstrated that the coexistence of GGBS and VA in geopolymerization process was more effective due to the synergic formation of N-A-S-H and C-(A)-S-H gels.Moreover,although VA needs heat curing to become activated and develop strength,its partial replacement with GGBS made the binder suitable for application at ambient temperature and resulted in a remarkably superior resistance against wet-dry and freeze-thaw cycles.The carbon embodied of the mixtures was also evaluated,and the results confirmed the low carbon footprints of the alkali-activated mixtures.Finally,it was concluded that the alkali-activated GGBS/VA could be promisingly used in clayey soil stabilization projects instead of conventional binders.

The Ionization Theory of Desulphurization of the Panzhihua Blast Furnace Slag

With the proper choice of the ion species present in the Panzhihua blast furnace slag, the sulphur partition ratio was calculated based on the ionization theory of the slag. It can be concluded that TiO_2 reacts as an acidtc oxide and the Panzhihua ore or concentrate cannot be treated as a semi-self-fluxing ore.

Effect of w(MgO)/w(Al_(2)O_(3)) ratio and basicity on microstructure and metallurgical properties of blast furnace slag

The CaO–SiO_(2)–Al_(2)O_(3)–MgO system is the main component unit in the slag formation process in blast furnace smelting.Its structural changes directly affect the high-temperature metallurgical properties of slag.Molecular dynamics simulations were thus conducted to analyze the microstructure changes of the quaternary slag system under different basicities and w(MgO)/w(Al_(2)O_(3))ratios.The changes in w(MgO)/w(Al_(2)O_(3))ratio and basicity could affect the stability of each ion-oxygen.Increasing the basicity and w(MgO)/w(Al_(2)O_(3))ratio,the average coordination number of O surrounding Si atom only changed a little and remained approximately 4,indicating that Si exists as a stable structure of the[SiO4]4−tetrahedron in the slag structure,while the average coordination number of O surrounding Al atom changed greatly from 4 to 6,which indicated that the Al existence form could be transformed from[AlO_(4)]^(5−) tetrahedron to[AlO_(5)]^(7−) pentahedron and[AlO_(6)]^(9−) octahedron.Also,the diffusion rate of ions was accelerated with the increase in w(MgO)/w(Al_(2)O_(3))ratio and basicity.Moreover,the self-diffusion coefficients of each ion were obtained,and the magnitudes were observed to be in the following order:Mg^(2+)>Ca^(2+)>Al^(3+)>Si^(4+).The calculation and analysis of the slag viscosity and activation energy of viscous flow under different basicities and w(MgO)/w(Al_(2)O_(3))ratios revealed that the metallurgical properties of slag at high temperature depend on the flow-unit diffusivity and the microstructure stability,simultaneously,the basicity should be controlled between 1.0 and 1.2,and the w(MgO)/w(Al_(2)O_(3))ratio could be controlled between 0.45 and 0.55.

Effect of Glass Powder on Chloride Ion Transport and Alkali-aggregate Reaction Expansion of Lightweight Aggregate Concrete

The effects of glass powder on the strength development, chloride permeability and potential alkali-aggregate reaction expansion of lightweight aggregate concrete were investigated. Ground blast furnace slag, coal fly ash and silica fume were used as reference materials. The re- placement of cement with 25% glass powder slightly decreases the strengthes at ？ and 28 d, but shows no effect on 90 d＇s. Silica fume is very effective in improving both the strength and chloride penetration resistance, while ground glass powder is much more effective than blast furnace slag and fly ash in improving chloride penetration resistance of the concrete. When expanded shale or clay is used as coarse aggregate, the concrete containing glass powder does not exhibit deleterious expansion even if alkali-reactive sand is used as fine aggregate of the concrete.

Characteristics of the stabilized/solidified municipal solid wastes incineration fly ash and the leaching behavior of Cr and Pb

Fly ash is a hazardous byproduct of municipal solid wastes incineration （MSWI）. An alkali activated blast fumace slag-based cementifious material was used to stabilize/solidify the fly ash at experimental level. The characteristics of the stabilized/solidified fly ash, including metal leachability, mineralogical characteristics and the distributions of metals in matrices, were tested by toxic characteristic leaching procedure （TCLP）, X-ray diffrac- tion （XRD） and scanning electron microscopy-energy dispersive spectrometer （SEM-EDS） respectively. Contin- uous acid extraction was utilized to extract metal ions and characterize their leaching behavior. The stabilization/ solidification procedure for MSWI fly ash demonstrates a strong fixing capacity for the metals by the formation of C- S-H phase, hydrated calcium aluminosilicate and ettringite. The stabilized/solidified fly ash shows a dense and homogeneous microstructure. Cr is mainly solidified in hydrated calcium aluminosilicate, C-S-H and ettringite phase through physical encapsulation, precipitation, adsorption or substitution mechanisms, and Pb is mainly solidified in C-S-H phase and absorbed in the Si-O structure.

Incorporation of a nanotechnology-based additive in cementitious products for clay stabilisation

The mechanical performances and water retention characteristics of clays,stabilised by partial substitution of cement with by-products and inclusion of a nanotechnology-based additive called RoadCem(RC),are studied in this research.The unconfined compression tests and one-dimensional oedometer swelling were performed after 7 d of curing to understand the influence of addition of 1%of RC material in the stabilised soils with the cement partially replaced by 49%,59%and 69%of ground granulated blast furnace slag(GBBS)or pulverised fuel ash(PFA).The moisture retention capacity of the stabilised clays was also explored using the soil-water retention curve(SWRC)from the measured suctions.Results confirmed an obvious effect of the use of RC with the obtained strength and swell properties of the stabilised clays suitable for road application at 50%replacement of cement.This outcome is associated with the in-depth and penetrating hydration of the cementitious materials by the RC and water which results in the production of needle-like matrix with interlocking filaments e a phenomenon referred to as the‘wrapping’effect.On the other hand,the SWRC used to describe the water holding capacity and corresponding swell mechanism of clays stabilised by a proportion of RC showed a satisfactory response.The moisture retention of the RC-modified clays was initially higher but reduced subsequently as the saturation level increased with decreasing suction.This phenomenon confirmed that clays stabilised by including the RC are water-proof in nature,thus ensuring reduced porosity and suction even at reduced water content.Overall,the stabilised clays with the combination of cement,GGBS and RC showed a better performance compared to those with the PFA included.

铁尾矿-矿渣基地聚合物的制备及其性能

我国铁尾矿产生量较高,但利用率仍较低,为了高附加值资源化利用铁尾矿,将铁尾矿、高炉矿渣与粉煤灰混合后作为硅铝原料,通过机械粉磨和碱性激发剂来激发其反应活性,制备地聚合物胶凝材料。探讨了高炉矿渣与铁尾矿的配比、碱激发剂水玻璃的掺量对地聚合物试样抗压强度的影响,分析了地聚合物胶凝材料形成机理。结果表明:将铁尾矿和高炉矿渣采用机械粉磨活化时,粉磨时间超过60 min后其比表面积提高幅度变小,综合考虑原料活性和成本,机械粉磨时间定为60 min。当粉煤灰掺量为10%、高炉矿渣与铁尾矿的配比为5∶3、碱性激发剂水玻璃掺量为10%时,所制得的地聚合物试样3、7、28 d龄期的抗压强度分别为10.7、18.9、32.9 MPa。地聚合物试样在养护过程中,随着养护时间的延长,试样的结构越来越致密,尤其是28 d龄期的试样结构更加致密,生成的凝胶产物填充在原料颗粒之间的空隙,并将未反应的原料颗粒包裹,与相邻的凝胶产物相互胶结,形成一整体,从而有利于试样抗压强度的提高。

利用粉煤灰和高炉渣制备发泡陶瓷材料

这是一篇陶瓷及复合材料领域的论文。以粉煤灰和高炉渣为主要原料,外加碳化硅(SiC)为高温发泡剂,硼酸钠(Na_(2)B_(2)O_(7))为助熔剂,采用高温烧结法制备发泡陶瓷材料。主要研究了原料配比、SiC添加量及Na_(2)B_(2)O_(7)添加量对发泡陶瓷的气泡结构、体积密度、吸水率、抗压强度及导热系数的影响。实验结果表明:当粉煤灰含量为70%,高炉渣含量为30%,并额外添加0.3%SiC粉末和5%Na_(2)B_(2)O_(7),在烧成温度1100℃下保温40 min时,发泡陶瓷具有较佳的综合性能,其体积密度为0.516 g/cm^(3),吸水率为3.82%,抗压强度为3.62 MPa,导热系数为0.094 W/(m·K)。且该条件下样品的主要物相包括石英相(SiO_(2))、钙长石(CaAl_(2)Si_(2)O_(8))和辉石相(Ca(Mg,Al,Fe)Si_(2)O_(6)),大量晶体的析出促进了材料强度的提升。本研究为粉煤灰和高炉渣等工业固体废弃物转成高附加值的建筑保温材料提供一种新方法。

水工混凝土掺合料特性及石灰石粉水化机理研究

利用扫描电镜、X射线衍射、压汞等材料分析手段,系统研究了石灰石粉、粉煤灰、磨细矿渣三种水工混凝土常用掺合料的矿物组成、表面特性,以及二元、三元胶凝材料体系的水化机理。结果表明,石灰石粉颗粒表面粗糙,促进水泥早期水化,微弱参与反应并生成水化碳铝酸钙,但不具有火山灰活性,石粉对水泥石中孔径在20~100 nm范围的孔隙影响较大,提高石粉掺量,该范围的孔隙增多,硬化浆体孔结构变差。粉煤灰中含有大量的球形颗粒,颗粒表面致密光滑,含有大量玻璃体,将粉煤灰与石粉复合双掺,粉煤灰的火山灰效应能够优化浆体孔结构。

热养护对大体积混凝土不同活性矿物掺合料早期水化性能的影响

研究了大体积混凝土中粉煤灰和矿粉在热养护条件下对水泥早期抗压强度的影响,并通过水化热、XRD以及TGA等技术手段阐述了水化反应过程。结果表明:常温时,粉煤灰和矿粉加入均会大幅度降低早期强度;热养护时,粉煤灰-水泥体系的早期强度仍远低于空白组;但随着矿粉用量的增加和热养护温度的升高,体系早期强度与空白组的差距逐渐减小;50℃养护时,矿粉-水泥体系的早期强度高于空白组。这说明在热激发条件下,粉煤灰的早期火山灰反应仍然有限,但矿粉的早期水化活性显著提高,通过火山灰反应和自水化反应完成水化产物的积累。

复合矿物掺合料颗粒级配优化及多级球磨串联制备技术

复合矿物掺合料多由混合粉磨工艺制得,无法调控各组分粒径,存在过粉磨和欠粉磨问题,导致产品需水量高或活性低。分别粉磨工艺可以实现各组分粒径的分别调控,但设备投资大、改造成本高、对场地空间要求高,未在传统生产企业推广应用。因此本文研究了矿渣、粉煤灰粒度搭配对复合矿物掺合料性能的影响,利用嵩基新材料公司磨机数量多的特点,通过多台球磨串联、分段喂料等工艺分别控制矿粉和粉煤灰粒径,调控各磨机喂料量制备了不同活性指数的复合矿物掺合料。喂料量为37.5 t/h时,该制备技术的电耗和碳排放分别为40.5 kWh/t和48.6 kg/t,复合矿物掺合料7 d活性指数达71.1%,综合效益相对最佳。降低喂料量至28.8 t/h,复合矿物掺合料的7 d活性指数可由40.0 t/h时的68.4%提高至74.8%,但电耗和碳排放较高。

Behavior of liquid passing through deadman:influence of slag/iron ratio and unburned pulverized coal

The ability of a blast furnace hearth liquid(iron and slag)passing through deadman characterizes the activity of the blast furnace hearth.To explore the influence of various factors on the static holdup rate of liquid in the process of passing through the deadman,a physical transport model of liquid passing through the deadman was firstly established.Then,a self-designed experimental device was used to simulate the process,and the influences of slag/iron ratios(250–450 kg/t)and unburned coal content(0%–9%)on the static holdup rate were studied.The experimental results indicate that with the slag/iron ratio increasing,the behavior of liquid passing through the coke packed bed gets much more difficult,and the static holdup rate increases.As the content of unburned pulverized coal(UPC)increases,the static holdup rate decreases first and then rises.This is caused by the dual effects of UPC.On the one hand,UPC can promote the carburizing reaction of unsaturated molten iron,thereby improving the fluidity of molten iron and reducing the static holdup rate.On the other hand,when the content of UPC rises to a certain level,it will be regarded as a kind of solid particle which will increase the liquid viscosity,causing an increase in the static holdup rate.Moreover,the liquid and coke will present interfacial chemical reactions when the liquid flows through the coke packed bed.And the Si-containing iron droplets at the slag–coke interface,generated by the reaction of SiO_(2)with C in the coke,can improve the interface wettability by reducing the interface wetting angle and increase the basicity of slag by consuming SiO_(2),thus improving the fluidity of the liquid and reducing the static holdup rate.

磷石膏协同多元固废制备矿山充填材料

为解决磷石膏利用率低、对环境危害大与低成本矿山充填材料研制的问题,本文以粉煤灰、钢渣、高炉矿渣为胶凝材料组分,协同磷石膏制备一种新型的磷石膏基矿山充填材料。通过抗压强度、流动度、凝结时间、浸出毒性和微观试验研究了充填材料的工程与环境特性。结果表明:所研制的矿山充填材料的抗压强度、流动度、凝结时间均能满足规范,达到工程应用需求;在养护28 d后,充填材料的重金属元素的浸出浓度都可以满足地下水Ⅲ级标准的要求,不会污染环境和危害人体健康。当钢渣和高炉矿渣的掺量逐渐增加时,抗压强度逐渐升高,流动度和凝结时间逐渐降低;充填材料中主要的水化产物是钙矾石和C—(A)—S—H凝胶,两者都为充填材料提供了主要的强度,且C—(A)—S—H凝胶可以包裹住重金属离子。