Sulfate Attack on Cement-Stabilized Sand

A 3.5-km (2.2 mi) section of a road in Georgia developed unexpected transverse bumps within 6 months after construction. The source of the bumps appeared to be expansion within the cement-stabilized base course. Laboratory examination of samples from areas showing distress revealed the presence of ettringite, a calcium sulfoaluminate the formation of which can be accompanied by severe expansion. This expansive material was the probable cause of the volume changes causing the transverse bumps. The calcium and alumina needed to form ettringite were available from the portland cement and the stabilized soil's clay minerals. The source of the sulfur was identified as the well water that was mixed with the cement-stabilized base. Sulfate attack of cement-stabilized soils is a relatively infrequent problem, but it is highly destructive when it occurs. Currently, there are no firm criteria for identifying when sulfate attack of a cement-stabilized soil is a potential problem nor are there established methods of preventing the attack.     

Behavior of Cement-Stabilized Fiber-Reinforced Fly Ash-Soil Mixtures

An experimental program was undertaken to study the individual and combined effects of randomly oriented fiber inclusions and cement stabilization on the geotechnical characteristics of fly ash-soil mixtures. An Indian fly ash was mixed with silt and sand in different proportions. The geotechnical characteristics of the raw fly ash-soil specimens and fly ash-soil specimens containing 1% randomly oriented polyester fiber inclusions were investigated. Unconfined compression tests were carried out on fly ash-soil specimens prepared with 3% cement content alone and also with 3% cement and 1% fiber contents, after different periods of curing. The study shows that cement stabilization increases the strength of the raw fly ash-soil specimens. The fiber inclusions increase the strength of the raw fly ash-soil specimens as well as that of the cement-stabilized specimens and change their brittle behavior to ductile behavior. Depending on the type of fly ash-soil mixture and curing period, the increase in strength caused by the combined action of cement and fibers is either more than or nearly equal to the sum of the increase caused by them individually.     

Influence of Portland Cement Type on Unconfined Compressive Strength and Linear Expansion of Cement-Stabilized Phosphogypsum

This technical note summarizes the results of a laboratory-testing program aimed at evaluating the engineering properties of cement-stabilized phosphogypsum mixtures for road base and subbase construction. Phosphogypsum is a solid byproduct of the production of phosphoric acid, a major constituent of many fertilizers that has chemical and radioactive properties may cause environmental problems. For every ton of phosphoric acid produced, approximately 5.0 tons of phosphogypsum are generated. This magnifies the problem of dealing with growing phosphogypsum stockpiles. The research program described herein, covered the physical characterization of phosphogypsum, and tests that uncovered the influence of cement type and content, curing time, and compaction energy on its unconfined compressive strength and expansion. The laboratory results indicate that cement-stabilized phosphogypsum mixtures have potential applications as road base and subbase materials.     

电渗析硫酸钠的试验研究

文章研究了在电渗析硫酸钠过程中,影响电流效率和槽电压的各因素对它们的影响规律,从而找到较好的电渗析条件。     

Sand Control Measures and Sand Drift Fences

Sand drift and sand dune movements are typical logistic problems facing civilian and industrial cities in arid and semiarid countries like Saudi Arabia. Some of these countries are considered active when it comes to sand drift and sand dune movement, due to the high annual sand drift rate. Urban cities have extensive facilities in the middle of these active areas that require good protection and innovative solutions?to this problem. This paper briefly reviews sand movement control measures and highlights sand drift fence design guidelines for the first time.     

Observations on Sand Jets in Air

This note presents the results of an experimental study of circular sand jets in air from three nozzles of diameter of 19.2, 31.1 and 63.8 mm. It was found that the frontal speeds of the sand jets and the steady sand jet velocity accelerate due to gravity with negligible air resistance. The sand velocity does not appear to be affected by sand particle sizes for the three sizes tested. The diameters of sand jets, as they travel downwards, decrease and gradually approach an asymptotic value after a distance of 120 times of the initial jet diameter. The sand concentration in the jet decreases as the distance from the nozzle increases. Waves were observed at the periphery of the sand jet and some preliminary results of wave speed and wavelength are reported.     

硫酸银生产方法的研究

首先介绍了生产硫酸银的各种方法．通过试验对各种方法进行了对比，从中选择出了工艺流程简单、产品质量符合要求的生产方法．同时还介绍了硫酸银在不同温度和酸度的溶液中的溶解度，对提高硫酸银产品产出率很重要．讨论了银在硫酸溶液中的存在形态，不仅具有理论意义，而且对硫酸银生产过程有重要的实际意义．     

Closely Spaced Footings on Geogrid-Reinforced Sand

The results discussed in this paper are based on a total of 74 tests performed on closely spaced strip and square footings on geogrid-reinforced sand. The study was carried out to evaluate the effect of spacing between the footings, size of reinforcement, and continuous and discontinuous reinforcement layers on bearing capacity and tilt of closely spaced footings. The interference effects on bearing capacity and settlement of closely spaced square footings on reinforced sand were almost insignificant in comparison to those on isolated footings on reinforced sand; whereas a significant improvement in the tilt of adjacent square footings has been observed by providing continuous reinforcement layers in the foundation soil under the closely spaced footings. A considerable improvement in bearing capacity, settlement, and tilt of adjacent strip footings has been observed by providing continuous reinforcement layers in the foundation soil under the closely spaced strip footings.     

硫酸钡比浊法测定氧化铁中硫酸根

在盐酸介质中,钡离子与硫酸根离子生成难溶的硫酸钡,使溶液混浊,采用乙醇作稳定剂,利用分光光度法计进行比色,可测定氧化铁中硫酸根。该法手续简便、准确性高。     

氧化铌的硫酸溶解机理研究

研究Nb2O5在硫酸中的溶解过程,利用溶解热力学相图,结合前期试验结果确定了氧化铌的溶解产物;通过测定H2SO4-Nb2O4SO4-H2O溶液体系电导率研究了Nb2O5在硫酸中的强化溶解机理。结果表明,溶解产物Nb2O4SO4在溶液中是以稳定的配合形式存在的,稳定常数为572,根据配位溶解理论说明配位促进了Nb2O5在酸中的溶解。     

硫酸铜制备工艺及研究现状

根据原料的不同,分类总结了硫酸铜生产工艺,包括酸浸—结晶、氨浸—结晶、氧化焙烧、溶剂萃取、氧化溶解等,比较了各工艺的优缺点。针对国内硫酸铜产品含砷、钙高,粒度小且分布不均等问题,综述了砷、钙深度脱除方法及硫酸铜结晶优化工艺研究现状。     

脱除硫酸锰溶液中杂质镁的研究

分别采用重结晶法和氟化沉淀法脱除硫酸锰溶液中的杂质镁。用Pitzer热力学模型对二元系MgSO4-H2O、MnSO4-H2O和三元系MgSO4-MnSO4-H2O的溶解度相图进行模拟预测,并结合溶解度相图对三元系的固溶体用重结晶法验证其分配比。同时采用氟化沉淀法进行对比试验。结果表明,由于固定分配比,重结晶法对镁锰分离作用十分有限,而加入MgF2晶种的氟化沉淀除镁新方法能够有效提高氟化沉淀法的效率,在95℃下,加入0.3g氟化镁晶种和250%理论用量的NH4F搅拌1h,能使镁的除去率达到94.3%。     

硫酸化焙烧处理镍钼矿的工艺研究

随着过度的开采,镍、钼、钒富矿越来越少,从含有色金属镍、钼、钒的高碳质页岩中回收镍、钼、钒等有价金属成为目前研究的重点。文章采用硫酸化焙烧法对含镍钼钒等有色金属的高碳质页岩进行了焙烧浸出研究,重点研究了焙烧条件对镍钼钒浸出率的影响,在优化条件下镍钼钒的浸出率分别为65．70％,86．02％,45．30％。     

硫酸锌溶液的萃取工艺研究

P204萃取低浓度硫酸锌溶液中的锌是可行的。为了降低萃取过程消耗,有机相不应进行皂化或萃取过程不能进行中和。在室温、相比A/O=2∶1、混合时间5~10 min、萃取级数5~6级、有机相中P204的体积分数为40%时锌的萃取率约80%,萃取终点pH为1.0左右,负载有机相含锌14~15 g/L。萃取过程中,影响锌电积或锌产品质量的杂质基本上不被萃取或萃取率低。     

锌电积液的密度研究

按照工业生产的条件,测定了不同的锌、酸浓度和不同温度下电积液的密度。通过分析试验数据,找到电积液的密度与锌离子浓度、硫酸浓度以及温度之间的变化规律,并且建立了相应的经验关系式。     

Professions Under Attack.

The "professionalization" of psychology, during and subsequent to World War II, has given rise to some anxiety and antagonism among psychologists, themselves, not to mention senior professions like medicine, law, and the ministry of religion. To a lesser degree, also, the general public, through its elected representatives or its civil servants, has expressed such anxiety or antagonism. This could be documented by reference to a number of comments which have been published in the "American Psychologist" in the last few years. For this column, however, let us concern ourselves with a more general question. It is this: What can be learned from the history of attacks on professions? (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

关于LF／VD炉钢包用铬质引流砂的探讨

结合了引流砂在LF/VD钢包水口的工作原理,重点分析了四种铬质引流砂的物理性能,秆〕隽号#铬质引流砂作为攀长钢炼钢厂一车间LF/VD钢包水口的填充材料,并改进钢包在实际生产中的使用状态,使钢包的自动开浇率得以大幅度提高,从而提高生产效率.     

聚合磷硫酸铁与聚合硫酸铁的动力学及水解形态

研究了用固体投加法制备聚合磷硫酸铁（PFPS）的反应动力学及聚合磷硫酸铁的水解形态,并与聚合硫酸铁（PFS）进行对比,结果表明,PFPS中Fe（b）的含量、稳定性均较PFS有很大提高;随着n（OH）／n（Fe）的增大,Fe（b）含量并非相应增加。采用该工艺合成PFS和PFPS,随n（OH）／n（Fe）变化,PFS中Fe（b）形成机理不同,而PFPS中Fe（b）形成机理变化不大。     

提钒尾液回收硫酸钠、硫酸铵的研究

以某企业现场提钒尾液蒸发浓缩结晶物为原料,采用中温焙烧技术回收其中的硫酸钠、硫酸铵。中温焙烧主要采用闪蒸干燥一回转窑焙烧,使混合结晶物中的硫酸铵分解以获得纯度较高的硫酸钠。结果表明,闪蒸干燥后原料中水分可由20％降至1％;回转窑焙烧温度为400℃、焙烧时间为0．5h时,焙烧产物中硫酸铵含量可降至1％以下。回收所得硫酸钠可作为硫化钠生产原料;所得副产物氨气、二氧化硫和三氧化硫（少量）可制成硫酸铵返回钒氧化物沉淀工序使用。