Strengthening effects of finely ground fly ash, granulated blast furnace slag, and their combination

The effect of finely ground fly ash (FGFA), finely ground granulated blast furnace slag (FGGBS), and their combination on the compressive strength of concrete was studied. Test results showed that incorporating 20% FGFA or FGGBS can significantly increase the compressive strength of concrete after 3 days. The compressive strength of concrete incorporating the combination of FGFA and FGGBS is higher than both FGFA concrete and FGGBS concrete, and is quantitatively similar to that of silica fume concrete. Scanning electron microscopic analysis showed that, after the incorporation of the combination of FGFA and FGGBS, a great quantity of a stick-like substance exist in the surface of hardened paste being investigated. The electron probe x-ray microanalyzer analysis showed that the stick-like substance was most probably the sheet C-S-H rolled up during specimen preparation for scanning electron microscopic analysis, which may be the mechanism of the strengthening effect of the combination of FGFA and FGGBS.     

Utilization of fly ash and ground granulated blast furnace slag as an alternative silica source in reactive powder concrete

Reactive powder concrete (RPC) is an ultra high strength cement-based material. Cement and silica fume (SF) content of RPC are generally rather high compared to the conventional concrete. The aim of this study is to decrease the cement and SF content of RPC using with fly ash (FA) and/or ground granulated blast furnace slag (GGBFS). The effect of these mineral admixtures on compressive strength of RPC has been investigated under autoclave curing. In the first stage, the effect of autoclave time and SF content on compressive strength was determined. In the second stage, SF was gradually decreased and cement was replaced with FA and/or GGBFS at different proportions. The microstructure was investigated by scanning electron microscope (SEM). Test results indicate that, the utilization of FA and/or GGBFS in RPC is possible without significant mechanical performance loss. SEM micrographs revealed the tobermorite having different morphology.     

Microsilica and ground granulated blast furnace slag effects on hydration temperature

The heat of hydration of cement mixes is of great importance to civil engineers. A testing setup was developed to provide a continuous recording of temperature inside cement mixes by means of a computer, digital voltmeter, and thermo-couples. Four mixes were tested by the suggested testing setup. A plain normal Portland cement (NPC), 90% NPC/10% microsilica, 40% NPC/ 10% microsilica/50% ground granulated blast furnace slag (ggbs), and 50% NPC/50% sand mixes were used. Microsilica reduced the temperature rise in paste and ggbs reduced it even further. Cement content was seen, as expected, to have significant effect on the rise in hydration temperature. Cement replacement materials had also clear effect on the time needed to reach the peak temperature. Microsilica slightly accelerated the arrival time at peak temperature, whereas ggbs significantly delayed it. Moreover, ggbs clearly reduced the differential change in temperature as a function of time compared to the other mixes.     

Investigation of hydraulic activity of ground granulated blast furnace slag in concrete

Ground granulated blast furnace slag (GGBFS), a by-product of the steel manufacturing industry, being used as an effective partial cement replacement material, has already been proven to improve several performance characteristics of concrete. The reactivity of GGBFS has been found to depend on the properties of slag, which vary with the source of slag, type of raw material used, method and the rate of cooling. The present work aims at bringing out a novel relationship between the Hydraulic Index (HI) of slag at 7 and 28 days (HI7 and HI28) and the influencing properties of slag, namely, glass content, fineness and chemical composition by employing multiple regression analysis on 37 slag samples from various sources. HI7 and HI28, thus obtained, have been mapped onto a Slag Activity Index (SAI) plot, giving an indication of the ranges of strength of slag.     

LM立磨用于矿渣粉磨的生产实践

介绍瑞昌水泥公司利用辊式立磨进行矿渣混合料粉磨的生产工艺及生产实践。重点通过减少系统漏风、稳定料床压差等措施,保证系统运行的稳定性;同时,依靠加强生产管理,优化系统工艺参数,在保证产品质量指标的前提下,使系统产量较设计值有较大幅度提高,电耗明显下降,取得了较好的经济效益,并积累了辊式立磨系统应用经验。     

粒化高炉矿渣粉的生产及应用

目前,矿渣粉的制备,国外普遍采用立式磨+选粉机组成圈流系统的生产工艺,国内除极个别企业采用该工艺外,多数为小型球磨机,开流系统。立式磨生产的主要特点是单机产量高、能耗低,但一次性投资较大,国内一般企业难以承受。而小型球磨机开路生产又存在单机产量低、能耗高、产品细度不易控制等缺陷,故难以承担起大批量生产的重任。不过,球磨机的优势是技术成熟,运转可靠,操作简单。对此,我们经过全面分析,结合自身实际情况,选择了南京水泥设计研究院开发的Φ3.0m×11m两仓球磨机和XWXK19高效组合式选粉机,组成圈流生产系统,建成了年产10万t矿…     

Characterization of granulated and pelletized blast furnace slag

The objective of this study is the characterization of slags from different sources by their chemical composition, glass content, rate and total heat of hydration and compressive strength development with a view to establish a relationship between some of their properties and compressive strength. Binders incorporating 50 per cent slag present the same classification derived from total heat evolved as from slag activity indexes.     

Crystallisation behaviour of blast furnace slag modified by adding fly ash

Crystallisation of molten blast furnace (BF) slag can increase its viscosity, which can in turn affect the quality of slag fibres. Fly ash was added to BF slag to control its crystallisation and modify its chemical composition. FactSage simulation and analyses using X-ray diffraction (XRD), scanning electron microscope-backscattered electrons (SEM-BSE) coupled to an energy dispersive spectrometer (EDS), and single hot thermocouple technique (SHTT) were performed to explore the crystallisation behaviour of the modified BF slag. The relationship between temperature, mineral precipitation, and added fly ash content was investigated. The minerals contained in the modified BF were melilite, anorthite, clinopyroxene, and spinel. Variation in the fly ash content did not change the composition of the precipitate, but changed its content and the crystallisation temperature of the minerals, which affects the initial crystallisation temperature of the modified BF slag. It decreased as fly ash content increased, and was influenced by the crystallisation of melilite when the added fly ash content was between 5% and 20%. When the added fly ash content increased to 25%, the initial crystallisation temperature was influenced by the precipitation of anorthite. The initial crystallisation temperatures obtained by FactSage simulation, XRD analysis, and SHTT experiments differed due to kinetic effects. The modified BF slag with a fly ash content of 15% is considered suitable for manufacturing of slag fibres due to its low initial crystallisation temperature and cost.     

Selective dissolution of hydrated blast furnace slag cements

Methods for determining the content of blast furnace slag (BFS) in blended cements composed of BFS and OPC have been briefly reviewed. A variety of dissolution procedures were investigated and the results compared critically. Extractions with methanol-salicyclic and/or acetic acid show that these solvents attack the BFS but fail to dissolve certain components of the cement which have been identified by X-ray diffraction. A recent method involving EDTA solvent extraction appeared more promising and additional work was undertaken to verify and improve it. The method was used to determine BFS content of blended cements hydrated for periods up to 12 months.     

Hydration and properties of novel blended cements based on cement kiln dust and blast furnace slag

The aim of the present paper is to address the key technical issues pertaining to the utilization of cement kiln dust (CKD) as an activator for ground granulated blast furnace slag (GGBFS) to create nonconventional cementitious binders for concrete. The relatively high alkaline content of CKD is the predominant factor preventing its recycling in cement manufacture. However, it was observed that depending on the water-soluble alkali and sulfate compounds, CKD could provide the environment necessary to activate latent hydraulic materials such as GGBFS. Binary blends containing slag and CKDs from different sources were characterized and compared in terms of the rates of heat evolution and strength development, hydration products, and time of initial setting. A study of the effects of the influencing factors in terms of soluble alkali content, particle size, and free lime content was undertaken. The results confirm the dependence of the dissolution rate of slag on the alkalinity of the reacting system, and the importance of the optimum lime content on the rate of strength gain.     

Hydration studies of calcium sulfoaluminate cements blended with fly ash

The main objective of this work is to study the hydration and properties of calcium sulfoaluminate cement pastes blended with fly ash (FA) and the corresponding mortars at different hydration ages. Laboratory X-ray powder diffraction, rheological studies, thermal analysis, porosimetry and compressive strength measurements were performed. The analysis of the diffraction data by Rietveld method allowed quantifying crystalline phases and overall amorphous contents. The studied parameters were: i) FA content, 0, 15 and 30 wt.%; and ii) water addition, water-to-CSA mass ratio (w/CSA = 0.50 and 0.65), and water-to-binder mass ratio (w/b = 0.50). Finally, compressive strengths after 6 months of 0 and 15 wt.% FA [w/CSA = 0.50] mortars were similar: 73 ± 2 and 72 ± 3 MPa, respectively. This is justified by the filler effect of the FA as no strong evidences of reactivity of FA with CSA were observed. These results support the partial substitution of CSA cements with FA with the economic and environmental benefits.     

粒化高炉矿渣的水化机理探讨

以上海梅山钢铁公司的矿渣为研究对象,探讨粒化高炉矿渣在无激发剂存在的条件下的水化机理,并建立矿渣水化反应过程的化学模型。为矿渣的大规模、无害化、资源化和高附加值利用奠定理论基础。研究表明:在没有化学激发剂存在的条件下,梅山矿渣的水化产物是水化硅酸钙C2SH(C)、水化硅酸钙2CaO·SiO·(2￣4)HO和钙铝黄长石22Ca2Al(Al,Si)2O7。初期的水化过程是矿渣中的Ca2 等网络改变体阳离子与水中的H之间的置换,随着这种置换反应的进 行,溶液中的pH值不断升高,当pH高到一定程度时,矿渣颗粒表面上的HSiO4的溶解度将提高,溶解了的各种形态4的硅酸离子和溶液中的Ca2 、OH反应生成水化硅酸钙凝胶。     

对比水泥对矿渣粉活性指数检测结果的影响研究

活性指数是评价粒化高炉矿渣粉性能的重要指标。采用不同对比水泥对矿渣粉活性指数进行了检测。结果表明,不同对比水泥对活性指数试验结果影响很大。本研究可为对比水泥生产及选用提供参考。     

粒化高炉矿渣微粉的生产和应用

1 粒化高炉矿渣的利用众所周知粒化高炉矿渣（以下简称矿渣）是高炉炼铁的副产品,经水淬急冷处理,其颜色呈白色、浅灰色或黑色等。我国水泥行业近50年来一直用其作混合材,生产多品种硅酸盐水泥。尤其是矿渣硅酸盐水泥（以下简称矿渣水泥）,其矿渣掺量可达20％～70％。但至今,全国每年仍有几千万吨矿渣处于低效利用状况,其原因主要有以下几方面。1.1关于矿渣质量的评价水泥厂通常根据矿渣的颜色,凭经验判别其易磨程度,且仅对矿渣进行化学全分析,根据GB/T203-94计算其质量系数M作等级判别依据（M=     

对比水泥对矿渣粉活性指数检测结果的影响研究

活性指数是评价粒化高炉矿渣粉性能的重要指标。采用不同对比水泥对矿渣粉活性指数进行了检测。结果表明,不同对比水泥对活性指数试验结果影响很大。本研究可为对比水泥生产及选用提供参考。     

Tensile and fiber dispersion performance of ECC (engineered cementitious composites) produced with ground granulated blast furnace slag

An engineered cementitious composite (ECC) produced with ground granulated blast furnace slag was developed for the purpose of achieving moderately high composite strength while maintaining high ductility, represented by strain-hardening behavior in uniaxial tension. In the material development, single fiber pullout tests and matrix fracture tests were performed, followed by micromechanical analyses to properly select the range of mixture proportion. Subsequent direct tensile tests were employed to assess the strain-hardening behavior of the composite, which exhibited high ductility and strength with the addition of slag. High ductility is most likely due to enhanced workability and fiber dispersion performance which is attributed to the oxidized grain surface of slag, as verified by fiber dispersion tests. These results suggest that, within the limited slag dosage employed in the present study, the contribution of slag to fiber dispersion outweighs the side-effect of decreased potential for saturated multiple cracking, including a slight increase in matrix fracture toughness and fiber/matrix bond strength.     

Influence of additions of coal fly ash and quartz on hydrothermal solidification of blast furnace slag

Blast furnace water-cooled slag (BFWS) has been solidified hydrothermally with tobermorite formation. The experimental results showed that the addition of fly ash and quartz was favorable to the formation of tobermorite, and the strength development of solidified body depended on both of the tobermorite formation and filling degree of formed tobermorite in the spaces between BFWS particles. The fly ash added appeared to have a higher reactivity than the quartz used during the initial hydrothermal processing due to the higher solubility of glassy phase in fly ash. The tobermorite formation seemed to be very sensitive to the fly ash content, e.g., the addition of fly ash 10-20 mass% was favorable to tobermorite formation, while the excessive addition of fly ash (> 20 mass%) appeared to impede the tobermorite formation. The excessive addition of quartz was also shown to exert a negative effect on the tobermorite formation, which causes strength deduction.     

利用锰渣、矿渣、石灰石制备复合水泥

针对目前矿渣等高活性混合材资源的紧张,实验进行了锰渣、石灰石部分取代矿渣制备复合水泥的试验研究。研究表明,当石灰石粉掺量固定为10%时,相同水泥比例下,随着锰渣和矿渣比例的增加,胶砂试块3d强度增加,28d强度有所下降;当加入复合激发剂后复合混合材总掺量为60%,锰渣和矿渣质量比为4:1时,仍能配制合格的P.C32.5标号水泥。     

The evolution of strength and crystalline phases for alkali-activated ground blast furnace slag and fly ash-based geopolymers

The increase in strength and evolution of crystalline phases in inorganic polymer cement, made by the alkali activation of slag, Class C and Class F fly ashes, was followed using compressive strength test and synchrotron X-ray diffraction. In order to increase the crystallinity of the product the reactions were carried out at 80 °C. We found that hydrotalcite formed in both the alkali-activated slag cements and the fly ash-based geopolymers. Hydroxycancrinite, one member of the ABC-6 family of zeolites, was found only in the fly ash geopolymers. Assuming that the predominantly amorphous geopolymer formed under ambient conditions relates to the crystalline phases found when the mixture is cured at high temperature, we propose that the structure of this zeolitic precursor formed in Na-based high alkaline environment can be regarded as a disordered form of the basic building unit of the ABC-6 group of zeolites which includes poly-types such as hydroxycancrinite, hydroxysodalite and chabazite-Na.     

Immobilization of chromium (VI) evaluated by binding isotherms for ground granulated blast furnace slag and ordinary Portland cement

The interaction mechanisms of the Cr(VI) ion in presence of GGBFS and OPC were evaluated by chromium binding isotherms and by pore solution analysis. The chromium in the final leaching solution was measured and the solid samples were investigated by SEM and by XRD. GGBFS was more efficient than OPC in fixing Cr ions at lower initial concentrations. However, from an initial Cr(VI) concentration of 2000 and 5000 mg/L, OPC was more efficient.

For an initial Cr(VI) concentration of 50 000 mg/L, around 145 mg Cr/g was fixed by OPC and only 8 and 55 mg Cr/g were fixed by GGBFS in alkaline and water-based immersion solutions, respectively. The Cr-bearing phases identified by XRD and SEM are: CaCrO₄ and CaCrO₄·2H₂O, C–S–H and calcium aluminate phases. The pore solution chemistry indicates that a value around 92% of chromium was retained by GGBFS and 87% by OPC.