Test methods for determining potential alkali-silica reactivity in cements

The ASTM C227 test can be modified to develop performance tests for predicting potential alkali-silica reactivity of both portland and blended portland cements. The two methods of test investigated here differed mainly on the choice of the standard reactive aggregate, one using pyrex and the other a naturally occurring reactive silica. Low water/cement and aggregate/cement ratios were found helpful in accelerating expansion of mortar bars stored at 110F (43C). A 14-day test period was considered by the writers to be adequate for the evaluation of relative alkali-silica reactivity of a cement in the methods developed. Test data in 17 portland cements and 10 blended portland cements are reported to show that for this purpose performance tests may be more suitable than chemical specification limits.     

Methods of determining coke quality

Methods of determining coke quality are compared.     

Group chemical composition of coal batch and reactivity of coke 1. Determining coke reactivity

With a view to finding correlations between coke reactivity and the coal batch employed, methods of determining coke reactivity are considered—in particular, the standard and pulsed methods. The kinetic equation fundamental to all methods of assessing the coke reactivity from the gasification rate constant is presented. The possibility of combining data obtained by different methods of estimating the coke reactivity is established.     

Coal rank and coke reactivity

For a series of cokes prepared under identical carbonizing conditions it was shown that rates of reaction with carbon dioxide/nitrogen mixtures at about 1000°C were generally higher for the cokes prepared from coals of above 30% volatile matter. The reaction rates of cokes prepared from certain Durham coals were generally higher than anticipated. Gasification of cokes prepared from certain Durham coals were generally higher than anticipated. Gasification of the cokes resulted in loss of strength, decrease in apparent density, enlargement of pores and reduction of pore-wall thickness. It appeared that burn-off was primarily associated mineral constituents of the coke ash upon gasification rates was detected. A tentative relation was derived between gasification rates and the ratio of pore-wall thickness to pore diameter of the cokes. In turn, this latter ratio appeared to bear some relation to the oxygen content of the coal. The majority of the parameters studied were measured by established techniques. Porosity was determined by mercury pressure porosimetry and the Quantimet 720 automatic image analysis microscope was employed for structural studies. The accuracy of the measurement of pore and pore-wall dimensions was approximately ± 2%.     

炼焦煤CO2化学反应性与焦炭反应性关系

煤的CO2化学反应性和焦炭的反应性(CRI)都是在高温条件下碳与CO2进行还原反应,其中原料煤性质是主要影响因素。为了讨论二者之间的联系,选取气煤、肥煤、焦煤,1/3焦煤和气肥煤进行单煤反应活性和40 kg实验焦炉捣固炼焦所得焦炭反应性的测定。焦炭反应性的测定无论从样品量、反应时间及操作方法上,都较煤的反应活性复杂且对设备要求高。结果表明:所选煤样的反应活性与对应焦炭反应性之间的相关关系较好,相关系数R可达到0.99。因此在时间或煤样量有限的情况下,可以通过测定煤样反应活性推导CRI。     

Comparative study of methods of determining oil content of sunflower seed

An extraction-gravimetric method (AOCS Official Method Ai 3-75) was compared with 2 instrumental techniques, near-infrared reflec-tance (NIR) spectroscopy and wide-line nuclear magnetic resonance (NMR), for the determination of the oil content of oilseed-type hybrid sunflower seed. Eight sunflower seed samples of varying oil contents, replicated 5 times, were analyzed by the 3 procedures. The overall mean oil contents and standard deviations for the 8 samples were: AOCS method, 44.5% ± 0.33%; NMR, 44.8% ± 0.27%; and NIR, 44.2% ± 0.81%. Analysis of variance of the means of the 3 methods of analysis indicated no difference (p>0.05) in oil content due to the method. However, there was a difference (p>0.001) in total oil content due to replicated analyses of the same sample with the NIR method. With the AOCS and NMR methods, no effect (p>0.05) of replicated analyses of the same sample was found. The NMR method was more precise and repro-ducible than the other 2 methods. Although the NIR mean oil contents were not significantly different from the means of the other 2 methods, the coefficient of variations for all samples were consistently higher for the NIR analyses than for the AOCS and NMR analyses.     

Photometric and titrimetric methods of determining the gallium content in glasses

Translated from Steklo i Keramika, No. 6, pp. 29–30, June, 1993.     

Correlation of reactivity and electrical resistivity of coke

A correlation between the reactivity and electrical resistivity of a series of cokes was determined using cokes prepared from blends of medium- and high-volatile coals. After correcting for the ash yield of the coke and the density of the resistivity specimen, a statistically significant relation between reactivity and resistivity was established. As the resistivity test requires much less time to perform than the reactivity test, it can be considered as an alternative approach to reactivity testing currently performed for quality control purposes.     

New insights into the reactivity of blast-furnace coke

The factors most responsible for the reactivity of metallurgical coke—the structure of the carbon matrix and the catalytic action of the inorganic components—are considered in the light of new data regarding the relation between CRI and the anisotropy of the reflectance ΔR _o and data regarding the variable composition of the mineral components during the high-temperature reaction of CO₂ with coke. New literature data regarding the transformations of coke samples within special metal baskets in a prototype blast furnace are also discussed.     

Influence of the reactivity of coke on blast-furnace performance

The cold strength M ₂₅₍₄₀₎ and M ₁₀ of the coke determines the gas permeability of the batch bed in the blast furnace down to the viscoplastic zone of the ore and the coke windows in that zone. The hot characteristics CRI and CSR determine the mechanical strength of the coke in the lower part of the furnace batch, in and below the viscoplastic zone, including the furnace well. It is wrong to regard the hot and cold characteristics as alternatives, since they describe different conditions; the significance of each one should be acknowledged. The coke consumption may be reduced with increase in reactivity of the coke, so long as the high initial strength of the coke is maintained. The minimum permissible reactivity of the coke without clogging of the hearth depends on the operating conditions in the specific blast furnace.     

Effect of pore diffusion on reactivity of lump coke

The gasification of fine-grained and lump coke in CO₂ atmosphere was measured in a laboratory reactor. Owing to the effect of pore diffusion, the reactivity of lump coke at 1050 °C was found to be considerably lower than that of fine-grained coke at otherwise the same conditions. The diffusion effect is more significant for cokes produced by a stamping method than for cokes from top charges. To express the gasification of lump coke, a simplified mathematical model considering the effect of pore diffusion on gasification rate was adopted. Kinetic parameters were determined from experiments with fine-grained coke, while effective diffusivity was evaluated from experiments with a single coke particle. The model fits experimental data of lump coke well. The relation between reactivity and textural characteristics was also examined: the correlation between effective diffusivity and the fraction of largest pore volume was found.     

An investigation of oven methods for determining the moisture content of shelled peanuts

Air-oven methods, using ground, sliced, and whele shelled peanuts, were investigated. The use of ground samples was found to be unsatisfactory. Slightly more accurate results were obtained with whole nuts than with sliced nuts. The method of heating 50-g. samples of whole shelled peanuts for 3 hrs. at 130°C. in a foreed-draft oven gave results agreeing closely with those obtained by the Karl Fischer method for samples of low moisture content.     

Comparative analysis of methods of determining the oiling agent content in chemical fibres

A comparative analysis of methods of extracting oiling agent from chemical fibres showed that one extraction in a shaker could be used for all types of fibres investigated. Repeated extraction of the oiling agent using a Soxhlet apparatus can be recommended for all fibres investigated except for polyamide and polypropylene, since other compounds are extracted from these fibres together with the oiling agent. __________ Translated from Khimicheskie Volokna, No. 5, pp. 53–55, September–October, 2007.     

浅析焦炭反应性与高炉冶炼

总结了焦炭反应性与高炉冶炼关系的认知历程,阐述了不同反应性焦炭对高炉冶炼过程的影响以及不同反应性焦炭生产的技术手段和研究现状。通过对不同反应性焦炭与高炉冶炼过程适用性的讨论,提出了应根据高炉的冶炼条件和矿石的还原性能来规定适宜的焦炭反应性。     

复合镀层中纳米SiO2含量的测定方法研究

纳米复合镀层中纳米粉体含量的测定目前主要采用重量法和表面能谱分析法,而这2种方法都存在较大的局限性。提出采用紫外-可见分光光度法测定复合镀层中纳米SiO2的含量。以pH=1的HNO3溶液、NiSO4-HNO3溶液、CuSO4-HNO3溶液、ZnSO4-HNO3分别作为空白液来模拟复合镀层的溶解液。通过试验确定了测定波长,试验发现测定的标准曲线线性都非常理想、采用该法与重量分析法分别测定了待测液中纳米SiO2的含量,并对其误差进行了比较,结果表明该法的准确度高,其平均相对误差(1．05％)远远小于重量分析法,而且更省时。     

Assessment of simple methods of determining the free chloride ion content of cement paste

A range of possible techniques for assessing the “free” chloride ion content of hydrated cement pastes dosed with sodium chloride or calcium chloride have been investigated. The techniques are based on mixing powdered samples with a solvent and measuring the amount of chloride passing into solution. The values obtained have been compared with the chloride ion content of pore solution expressed from parallel specimens. The results indicate that in the range of chloride additions considered several extraction techniques may be used to estimate the free chloride ion content of cement paste; the total chloride content will dictate the most appropriate extraction technique(s) to adopt.     

Surface structure and oxidation reactivity of oil sand coke particles

Fractions of particles of varying mean diameter were isolated from coke obtained from the fluid coking of Athabasca bitumen. Correlations were established between the rate of oxygen sorption and the apparent surface area as measured by carbon dioxide adsorption. The rate of oxygen sorption, r₀, could be related to particle radius, R, by the equation: r₀ ∝ R^{D − 3} over a range of particle size where D is the fractal dimension of the coke. The existence of such correlations may be related to the iterative processes which form the particles.     

炼焦工艺条件对焦炭反应性和反应后强度的影响

通过40 kg焦炉炼焦实验,研究了加热速率、焦饼终温、焖炉时间、入炉煤堆密度及入炉煤细度等对焦炭的CRI(焦炭反应性)、CSR(反应后强度)的影响。结果表明:为保证焦炭成熟和获得较低的CRI值,较高的CSR值,焦饼终温应控制在1000～1050℃范围内。炼焦时焖炉时间应控制在3 h以上。提高入炉煤堆密度,可显著改善焦炭的热性质。入炉煤细度控制在90%左右时,CRI、CSR值较佳。提高加热速率,特别是粘结阶段的升温速率,有利于改善焦炭的热性质。