Comparison of Hydration Properties between Cement-GGBS-fly ash Blended Binder and Cement-GGBS-steel slag Blended Binder

The hydration properties of cement-GGBS-fly ash blended binder and cement-GGBS-steel slag blended binder were compared. The experimental results show that the hydration rate of cement-GGBS- steel slag blended binder is higher than that of cement-GGBS-fly ash blended binder within 28 days, but lower than the latter after 28 days. The hydration of cement-GGBS-steel slag blended binder tends to produce more Ca（OH）2 than the hydration of cement-GGBS-fly ash blended binder, especially at late ages. Cement-GGBS- steel slag mortar exhibits higher strength than cement-GGBS-fly ash mortar within 28 days, but at late ages, it exhibits similar compressive strength with eement-GGBS-fly ash mortar and even slightly lower bending strength than cement-GGBS-fly ash mortar. Cement-GGBS-steel slag paste has finer early pore structure but coarser late pore structure than cement-GGBS-fly ash paste. Cement-GGBS-steel slag paste can get satisfied late pore structure and cement-GGBS-steel slag mortar can get satisfied late strength as compared with pure cement paste and pure cement mortar, 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.

Beneficial use of stainless steel EAF slag as composite cement admixture and its heavy metals leaching risk analysis

This study analyzes the feasibility of using stainless steel electric arc furnace （EAF） slag as composite cement admixture and the risk of leaching-out of heavy metals. The results show that the stainless steel EAF slag, mainly made up of Ca2 SiO4, Ca3 Mg （ SiO4 ） 2, some Cr-containing minerals and in small particle size, is easily ground and has cementitious activity. EAF slag, when used as cement admixture, can be added with a maximum percentage of 32%. It can meet the strength requirements of the standard P · C 32.5 cement. When the mixing percentage is decreased to 25 % , the strength of the cement can be increased to that of P · C 42.5 cement. Other main quality indexes of composite cement, such as the setting time and stability, also satisfy standard requirements. The results also show that most of the heavy metals in the stainless steel EAF slag exist in a stable speciation. The concentration of heavy metals that leach out from the stainless steel EAF slag and the composite cement products is far lower than the standard limit of hazardous wastes. The main heavy metal, chromium, exists as less hazardous trivalent chromium. Therefore, the risk of heavy metals leaching out from the stainless steel EAF slag is low. The internal exposure index （IRa） and the external exposure index （Iγ） of the stainless steel EAF slag are both lower than 1.0, satisfying the standard requirements of the state for the radionuclides of building materials. Therefore, stainless steel EAF slag can be safely used as admixture to produce composite cement.

Formulating for Innovative Self-Compacting Concrete with Low Energy Super-Sulfated Cement Used for Sustainability Development

This study proposed a new way to formulate a low energy super-sulfated cement (SSC) which can be used to produce self-compacting concrete (SCC) with high compressive strength and durability in terms of chloride penetration resistance. This innovative SSC, different from the traditional SSC, was purely produced with a ternary mixture of three industrial by-products of ground granulated blast furnace slag, low calcium Class F fly ash and circulating fluidized bed combustion (CFBC) fly ash and was denoted as SFC-SSC (super-sulfated cement made by mixture of slag, Class F fly ash and CFBC fly ash). Experimental results showed that the combination of a fixed amount of 15 wt.% of CFBC fly ash with various ratios of Class F fly ash to slag could be used to produce the hardened SCCs with high 28-day compressive strengths (41.8 - 65.6 MPa). Addition of Class F fly ash led to the resulting SCCs with lowered price and preferable engineering properties, and thus it was considered as state-of-the-art method to drive such type of concrete towards sustainable construction materials.

Cleaner geopolymer prepared by co-activation of gasification coal fly ash and steel slag:durability properties and economic assessment

Geopolymer is a material with high early strength.However,the insufficient durability properties,such as long-term strength,acid-base resistance,freeze-thaw resistance,leaching toxicity,thermal stability,sulfate resistance and carbonation resistance,restrain its practical application.Herein,a longterm stable geopolymer composite with high final strength(ASK1)was synthesized from shell coal gasification fly ash(SFA)and steel slag(SS).Additionally,a geopolymer composite with high early strength(ASK2)was also synthesized for comparison.The results showed that ASK1 exhibited better performance on freezing-thawing resistance,carbonization resistance and heavy metals stabilization compared to the ASK2 at long-term curing.Raising the curing temperature could accelerate the unconfined compressive strength(UCS)development at initial curing ages of 3 to 7 d.Both ASK1 and ASK2 exhibited excellent acid-base and sulfate corrosion resistance.An increase for UCS was seen under KOH solution and MgSO_(4)solution corrosion for ASK1.All leaching concentrations of heavy metals out of the two geopolymers were below the standard threshold,even after 50 freezingthawing cycles.Both ASK1 and ASK2 geopolymer concrete exhibited higher sustainability and economic efficiency than Portland cement concrete.The result of this study not only provides a suitable way for the utilization of industrial solid waste in civil and environmental engineering,but also opens a new approach to improve the long-term stabilities of the geopolymers.

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.

Mechanism of Calcined Phosphogypsum for the Volume Change of Blended Cement

The paper describes an investigation into the volume change of cement mortar specimen at the three kinds of different curing schedules including 20℃and 5% Na2SO4 solution curing, tap water standard curing, 50% RH curing for 90 days. The testing results of hydration heat, chemical shrinking and XRD prove that calcined phosphogypsum has evident excitation effect on the activity of high calcium ash and steel slag. Simultaneously, calcined phosphogypsum has the function of decreasing volume shrinkage to blended cement possessing steel slag and high calcium ash. In sulfate curing, calcined phosphogypsum can avoid the phenomenon of protrude apex of the blended cement.

Utilization of Low-Alkalinity Cementitious Materials in Cemented Paste Backfill of Gold Mine Tailings

The purpose of this paper was to explore the possility of using low alkalinity cementitious materials as binders,in which ground blast furnace slag and fly ash acted as a partial replacement of ordinary Portland cement,and CaSO_(4),Na_(2)SO_(4),and CaO were used as a sulfate activator and alkali activated additives,to solidify gold mine tail-ings for preparation of a green,inexpensive cemented paste backill(CPB).For this target,the effects of cement/tailings ratio,superplasticizer dosage,solid content,tailings fineness on the mechanical properties of the CPB were inves tigated.Additionally,the hydration mechanism of the CPB was analyzed based on X-ray diffraction and scanning electron microscopy results.The results showed that the fuidity of the CPB slurry could be improved by adding polycarboxylic acid superplasticizer.The unconfined compressive strength(UCS)of the CPB specimens was increased with the increase of cement/tailings ratio and solid content.Under the same experi-mental conditions,the 28 d UCS of the CPB specimens was 3.8-4.9 times higher than that of ordinary Portland cement.The softening coefficient of the CPB specimens was increased with the increasing cement/tailings ratio,ranging from 0.83 to 0.92.The shrinkage rate of the CPB specimens was decreased from 0.70%to 0.54%with the increase of cement/tailings ratio from 1:12 to 1:4 The UCS of the full tailings CPB was the highest,followed by the fine tailings CPB specimens,and the UCS of the coarse tailings CPB specimens was the lowest.The low alka-linity binder was proved to be a promising material to improve the engineering performances of the CPB.The optimal mixing ratio is 1:6 cement/tailings ratio,0.15 wt% superplastizer dosage,and 70 wt%solid content.Pre-pared by this mixing ratio,the UCS values of the CPB after 3,7,and 28 d curing ages reached 1.85,5.87,and 9.16 MPa,respectively,which were suitable as CPB for the Zhaoyuan gold mine in terms of strength requirements.

铁尾矿基多固废混凝土抗压性能及微观结构分析

针对铁尾矿堆存困难、综合利用率低和活性低的问题,以铁尾矿钢渣脱硫灰为复合掺合料制备多固废混凝土。通过抗压性能测试,研究复合掺合料掺量、铁尾矿细度对混凝土抗压强度的影响,并利用压汞法(MIP)和背散射电子成像技术(BSE)探究混凝土的微观结构。结果表明:复合掺合料的掺入对混凝土早期抗压强度影响较大,掺量小于20%的混凝土28 d抗压强度与无掺合料组抗压强度基本持平,30%掺量的混凝土抗压强度随铁尾矿比表面积的增大而先增大后减小;掺入复合掺合料和减小铁尾矿细度能够改善混凝土孔结构和提高界面过渡区的密实度。

复合吸波剂增强钢渣-水泥基双层结构吸波材料的制备

利用工业固废资源制备水泥基吸波材料对其资源化利用与城市空间电磁污染的防治具有重要意义。采用钢渣作为制备水泥基材料的主要掺合料,协同石墨粉与碳纤维配制的复合吸波剂制得一种双层结构水泥基吸波材料。通过力学与电学性能测试得到了性能优异的钢渣-水泥基体,探究了复合吸波剂作用下钢渣-水泥基材料的力学电学性能变化规律及其影响机理。基于单层结构设计方法,采用渐进阻抗原则设计了双层结构,制备出吸波性能优异的双层结构水泥基材料。研究表明:钢渣与复合吸波剂的掺入会削弱水泥基材料的力学性能,但可以有效提升其导电能力,进而增强水泥基材料的吸波性能。双层结构能够显著提升水泥基材料的吸波性能,在最优设计参数条件下,两种配方的吸波材料最小反射损失分别达到-29.79 dB与-36.66 dB,并具有1.39 GHz与1.37 GHz的超高有效带宽。本研究对复合吸波剂作用下钢渣-水泥基吸波材料的影响机理进行了深入的阐释,提出的双层结构水吸波材料设计方法具有较好的设计灵活性与多样性,对工程设计和施工具有一定的指导意义。

Effects of Quicklime and Iron Tailings as Modifier on Composition and Properties of Steel Slag

Steel slag had lower activity and much lower hydration rate than cement. Quicklime and iron tailings were designed as modification agent to adjust the composition and properties of high temperature steel slag. The results show that quicklime as modifier can greatly increase the content of cementitious minerals in modified steel slag and also promote the decomposition of RO phases and transformation of MgO in RO phase to f-MgO. After high temper- ature modification with compound modifier of quicklime and iron tailings, steel slag shows the main mineral phases of C3S, C2F and MgFe2O4. The activity index of modified steel slag at 28 days reaches 95.5% when the steel slag is modified by 15% of the compound modifier with the ratio of quicklime to iron tailings equal to 2 ： 1 at 1 350 ℃. Mo- reover, the sample with the modified steel slag exhibits the dense structure of hydration paste and the main hydration products of C-S-H gels and Ca（OH）2 crystals.

钢渣粉和粉煤灰对硫铝酸盐水泥砂浆性能的影响试验研究

硫铝酸盐水泥(SAC)具有速凝早强、抗渗性好和耐化学腐蚀等优点,广泛应用于快速抢修、水利水电、地下管网和海洋工程等环境中;但是高昂的使用成本限制了SAC的进一步发展和应用。利用工业废弃物少量取代SAC,可在改善水泥性能的同时降低材料成本。研究了钢渣和粉煤灰对硫铝酸盐水泥砂浆(SACM)的工作性能、力学强度和抗渗性能的影响,并通过SEM和XRD分析了微观结构和水化产物。结果表明:钢渣掺量30%时,砂浆的终凝时间仅70 min,相比纯SACM缩短了28.5%;粉煤灰因“滚珠效应”显著提高了砂浆的扩展度;2种掺合料提高了SACM的吸水率;因为活性低,钢渣和粉煤灰均在不同程度上不利于砂浆的力学性能和抗渗性能。单掺10%钢渣的砂浆能最大程度保持纯SACM的基本性能,且凝结时间更短;该组砂浆综合性能最优,具有一定环保和经济价值。

钢渣-粉煤灰-脱硫石膏胶凝协同作用研究

以抗压强度作为主要指标研究了粉煤灰、钢渣和脱硫石膏三种工业固废的协同胶凝效应,并采用XRD和SEM分析手段对复合胶凝试块的矿物组成和微观形貌进行分析以明确其协同作用机理。研究表明:不同胶凝体系的协同效应依次为三元体系、二元体系和一元体系。XRD分析发现,三元体系胶凝试块具有更明显的硅铝酸盐水化产物衍射峰,并且多出了钙矾石的衍射峰。SEM分析表明,三元体系胶凝试块呈现针杆状的钙矾石晶体与水化硅酸钙凝胶交错生长,形成致密网络状结构的微观形貌。

粉煤灰-矿渣-水泥复合胶凝材料强度和水化性能

研究了不同细度和不同掺量的矿渣和粉煤灰对粉煤灰-矿渣-水泥(FSC)复合胶凝材料强度的影响.借助激光衍射粒度仪测定了矿渣和粉煤灰的粒径.测定了FSC复合胶凝材料的水化热,分析了其水化进程.结果表明:矿渣细度对FSC复合胶凝材料强度影响较大,矿渣越细,FSC复合胶凝材料强度越高;通过优化矿渣、粉煤灰的颗粒级配,可发挥出它们的"叠加效应";当粉煤灰和矿渣总掺量(质量分数)为50%,而矿渣掺量在33%以上时,可配置出52.5R复合水泥.

钢渣粉煤灰复掺对水泥性能的影响

运用正交设计实验方法研究了钢渣粉煤灰的复掺比例、细度及石膏的种类等对复合水泥性能的影响,并对其组成进行了优化设计。结果表明,在矿渣掺量一定时,粉煤灰(FA)的细度是影响其强度的关键因素,其次为钢渣粉煤灰的复配比例,而钢渣(SS)的细度及石膏的种类对其影响较小。经过优选后的配比为:钢渣和粉煤灰的配合比为21∶9,钢渣细度为447 m2/kg,粉煤灰细度为400 m2/kg,石膏为3份天然二水石膏混合2份脱硫石膏。

不锈钢钢渣用作水泥混合材及其安全性分析

研究了不锈钢钢渣作为水泥混合材的可行性及安全性.结果表明:不锈钢钢渣主要矿物组成为硅酸二钙和镁硅钙石,还有少量的含铬矿物,具有一定的胶凝活性,易磨性较好;掺入适量的不锈钢钢渣可以配制出符合标准要求的复合水泥,当不锈钢钢渣掺量(质量分数)为32%时,可以生产32.5复合水泥,掺量为25%时,可以生产42.5复合水泥;不锈钢钢渣中重金属主要以稳定态存在,其浸出浓度远低于危险废物鉴别标准限值,也低于铬渣用作水泥混和材国家标准限值,且铬主要以3价态存在;不锈钢钢渣的放射性内、外辐照指数均低于1.0,满足作为建筑材料的放射性国家标准要求;不锈钢钢渣作为水泥混合材安全、可行.

基于XRD与FTIR的碱钢渣胶凝材料复合激发机理研究

以Na_2SiO_3、NaOH和Ca(OH)_2制备碱溶液,然后利用碱溶液对钢渣进行活化处理。分别研究Na_2SiO_3用量、NaOH用量和Ca(OH)_2用量对碱钢渣胶凝材料的力学性能影响,获得最优力学性能的碱钢渣胶凝材料。采用XRD,FTIR和SEM对最优力学性能的碱钢渣胶凝材料进行表征。结果表明,当NaOH用量为4.50g、Na2SiO_3用量为11.25g和Ca(OH)_2用量为6.75g时,碱钢渣胶凝材料的力学性能最优。Na_2SiO_3对碱钢渣胶凝材料的7d抗压强度影响显著,NaOH对碱钢渣胶凝材料的3d抗压强度影响显著,Ca(OH)2对碱钢渣胶凝材料的28d抗压强度影响显著。Na_2SiO_3,NaOH和Ca(OH)_2碱性物质的加入促使钢渣形成稳定的C-S-H凝胶与沸石类相。

钢渣作为混合材在复合水泥中的应用

对钢渣作为一种混合材在复合水泥中的综合利用进行了研究,并通过X线衍射(XRD)、扫描电镜(SEM)、水化热测试、孔结构测试等现代物相检测手段,揭示钢渣复合水泥微观结构与宏观性能之间的内在联系。结果表明:钢渣能显著降低水泥的水化热,降低水泥的标准稠度用水量;钢渣水泥浆体线膨胀率很小,均没有超过0.1%,体积稳定性良好;一定掺量混合材能有效降低浆体孔隙率,改善孔径分布,提高浆体致密度;复合掺加20%钢渣、10%粉煤灰时,水泥的28 d抗折、抗压强度分别达到了8.3、48.9 MPa;钢渣和粉煤灰复合掺加有利于水泥强度发展。

碱矿渣复合水泥固化模拟放射性焚烧灰

用偏高岭土、沸石及聚合物乳胶粉改性的碱矿渣复合水泥进行了模拟放射性焚烧灰固化处置研究。结果表明:模拟放射性焚烧灰包容量为40%时,水泥固化体性能满足国标GB14569.1—93要求。Cs+的第42d浸出率(GB7023—86,25℃)最低为1.32×10-4cm/d,累积浸出分数仅为0.041cm。28d抗压强度最低为45.6MPa,且后期强度增长依然较高。碱矿渣复合水泥凝结迅速,克服了焚烧灰中某些成分对水化造成的不利影响。偏高岭土、沸石之间存在协同效应,显著提高固化体的抗压强度,同时改善对核素离子的固化能力。乳胶粉在固化体内形成三维网状结构,改善固化体韧性及抗冲击性,引入的微小气泡优化孔结构、提高耐久性,但导致抗压强度下降,掺量以5%为宜。

粉煤灰矿渣复合水泥试验研究及其应用

通过试验研究了粉磨方式、细度、复合组分比例及添加剂对粉煤灰、矿渣、石灰石与少量熟料组成的复合水泥性能的影响 .研究结果表明 :当以上三组分比例适当时 ,通过添加剂的有效作用 ,采取合理的粉磨工艺和制度 ,在熟料掺量 5 0 %时可以配制出 6 2 5R或 6 2 5复合水泥 ,熟料掺量 4 0 %可以配制出 6 2 5或 5 2 5R复合水泥 ,熟料掺量 30 %可以配制出 5 2 5或 4 2 5R复合水泥 .同时 。