The effect of slaked lime,anhydrous gypsum and limestone powder on properties of blast furnace slag cement mortar and concrete

Basic properties of blast furnace slag cement mortar and concrete are investigated by adding inorganic activators. The result of this research concludes that slag cement mixed with suitable activator agents such as lime, gypsum and limestone powder could accelerate the compressive strength and tighten pore structure at early age. The addition of activator into mortar and concrete containing slag cement produces superior properties, reduced shrinkage and less carbonation compared to mortar and concrete containing slag cement without the addition of activator. Consequently, there are possibilities for manufacturing blast furnace slag cement, which could compensate the weak properties at early curing age. When compared with ordinary Portland cement, this cement has superior characteristics for long curing age.     

Influence of dry and wet curing conditions on compressive strength of silica fume concrete

This paper reports a part of an ongoing laboratory investigation in which the compressive strength of silica fume concrete is studied under dry and wet curing conditions. In the study, a total of 48 concretes, including control Portland cement concrete and silica fume concrete, were produced with four different water–cement ratios (0.3, 0.4, 0.5, 0.6), three different cement dosages (350, 400, 450 kg/m³) and three partial silica fume replacement ratios (10%, 15%, 20%). A hyperplastisizer was used in concrete at various quantities to provide and keep a constant workability. Three cubic samples produced from fresh concrete were demoulded after a day; then, they were cured at 20±2 °C with 65% relative humidity (RH), and three other cubic samples were cured at 20±2 °C with 100% RH until the samples were used for compressive strength measurement at 28 days. The comparison was made on the basis of compressive strength between silica fume concrete and control Portland cement concrete. Silica fume concretes were also compared among themselves. The comparisons showed that compressive strength of silica fume concrete cured at 65% RH was influenced more than that of Portland cement concrete. It was found that the compressive strength of silica fume concrete cured at 65% RH was, at average, 13% lower than that of silica fume concrete cured at 100% RH. The increase in the water–cementitious material ratios makes the concrete more sensitive to dry curing conditions. The influence of dry curing conditions on silica fume concrete was marked as the replacement ratio of silica fume increased.     

Effects of portland composite and composite cements on durability of mortar and permeability of concrete

In this study, the effects of Portland composite and composite cement on the properties of cement paste, durability of mortar and permeability of concrete were investigated. The results were compared with reference mixture of cement paste, mortar and concrete made with Portland cement. The ratio of water to cementitious materials (W/C_m) in cement paste, mortar and concrete mixtures were determined in a way that all the similar mixtures had the same workability. Flexural tensile and compressive strength of mortar samples containing Portland Composite and Composite cement were determined at various ages. In cement paste samples, the shortest and longest setting time was obtained in samples made with Portland and composite cement, respectively. Also, maximum amount of volume expansion was found in the sample made with Portland composite cement. Mortar samples made with Portland composite and composite cement had lower strength values than the reference mortar mixture at early ages but at 28 days and later ages they had higher strength values than the reference mixture. In durability tests, there was no loss of weight and cracks in mortar mixture samples made with Portland composite and composite cement when they were held in microthiol, Na₂SO₄ and MgSO₄ solutions. Also, no water leakage was observed through the concrete samples made with Portland composite and composite cement when they were held under five-bar pressurized water.     

石雷泡沫混凝土的性生能研究

以脱硫石膏为基材,通过添加矿渣、水泥和自制添加剂改性,外掺少量生石灰、促凝剂和发泡剂制备不同密度等级的石膏泡沫混凝土.研究了不同外加剂掺量对胶凝材料初、终凝时间和力学性能的影响,测试了石膏泡沫混凝土的导热系数,阐述了产品的热工性能.测试结果表明,产品的强度高、导热系数低,综合性能优良,有利于工业副产石膏的资源化利用和提高节能减排水平.     

阿利特-硫铝酸钡钙水泥混凝土的试配及力学性能的研究

根据混凝土的配合比设计及试验室现场操作,配制出工作性良好的阿利特-硫铝酸钡钙水泥混凝土。采用对比试验研究的方法,研究了不同水灰比对该水泥混凝土抗压强度的影响,并将其与相同配合比的普通混凝土的力学性能进行比较。试验结果表明:两种混凝土的抗压强度均随水灰比的增大而减小;相同配比下,该水泥混凝土的抗压强度比同龄期的普通混凝土有了明显的改善,尤其早期抗压强度,1 d强度提高了50%~65%。微观结构分析发现:阿利特-硫铝酸钡钙水泥混凝土中水化产物的粒径分布均匀,界面粘结状况较好,结构较为致密。     

钛石膏作水泥缓凝剂研究

介绍了钛石膏中的杂质组成与形态,以及用钛石膏作水泥缓凝剂时,杂质对水泥性能的影响。研究结果表明,钛石膏中杂质主要为Fe(OH)3、FeSO4和Al(OH)3。杂质对水泥性能影响不大,不经预处理作水泥缓凝剂,其性能与采用天然石膏的水泥相当。     

阿利特-硫铝酸钡钙水泥混凝土的试配及力学性能的研究

根据混凝土的配合比设计及试验室现场操作,配制出工作性良好的阿利特-硫铝酸钡钙水泥混凝土.采用对比试验研究的方法,研究了不同水灰比对该水泥混凝土抗压强度的影响,并将其与相同配合比的普通混凝土的力学性能进行比较.试验结果表明:两种混凝土的抗压强度均随水灰比的增大而减小;相同配合比下,该水泥混凝土的抗压强度比同龄期的普通混凝土有了明显的改善,尤其早期抗压强度,1d强度提高了50%～65%.微观结构分析发现:阿利特-硫铝酸钡钙水泥混凝土中水化产物的粒径分布均匀,界面粘结状况较好,结构较为致密.     

脱硫石膏泡沫凝土砌块的性能研究

以脱硫石膏为主要材料,通过添加水泥、矿渣粉、自制添加剂改性,外掺少量CaO、促凝剂和发泡剂制备出了不同密度等级的脱硫石膏泡沫混凝土砌块。研究了不同外加剂掺量对胶凝材料初终凝时间和力学性能的影响;利用导热系数测定仪测试了石膏泡沫混凝土的导热系数;对脱硫石膏基胶凝材料水化产物机理进行了分析。研究表明：脱硫石膏泡沫混凝土砌块与其他类型砌块相比具有强度高、耐抽陛好、导热系数低等优良性能。     

21世纪初期水泥混凝土的发展趋势

结合国内外水泥和混凝土发展现状,论述了21世纪初期硅酸盐水泥混凝土发展的主要特征,分析了水泥混凝土的发展趋势,介绍了几种有发展前景的硅酸盐水泥和混凝土,说明了水泥混凝土使用数量的发展规律,提出了几点关于水泥混凝土发展方向的结论.目前水泥性能改善的重点是"绿色化"和"耐久性"方面;混凝土的发展趋势为:高强化、高性能化、绿色化、高技术化.水泥消耗量的发展是有一定规律的,当经济和科技发展到一定阶段,人均水泥消耗量不再随人均国民生产总值的增长而增长.     

Effect of cement type on the resistance of concrete against chloride penetration

In chloride containing environment, chloride permeability of concrete is an important parameter affecting the service life of concrete structures. The primary objective of this experimental study was to study the effect of cement types on the resistance of concrete against chloride penetration for given compressive strength classes. These cements included two different types of granulated blast-furnace slag cement (CEM III/A 32.5N and CEM III/A 42.5N), a sulfate resisting cement (SRC 32.5), and a Portland cement blended with fly ash; all of which compared to an ordinary Portland cement (CEM I 42.5R). For each binder type, four concretes at different strength classes were produced and as a result 20 mixtures were obtained. Rapid chloride ion penetration tests according to ASTM C 1202 were conducted. In addition, electrical resistivity and capillary water absorption tests were carried out. In order to characterize the concrete quality, compressive strength of the specimens were also obtained. The test results clearly demonstrated that the blast-furnace slag cements have the highest resistance against chloride penetration, while the pure Portland cement and sulfate resisting cement have the lowest resistance. Concretes produced with the sulfate resisting cement had substantially higher capillary sorption compared to other mixtures. Test results confirmed the strong relationship between the chloride permeability and electrical resistivity.     

高贝利特水泥混凝土性能

与硅酸盐水泥混凝土比较,研究了高贝利特水泥混凝土不同龄期的抗压强度,抗拉强度和抗拉弹性模量;高贝利特水泥混凝土的抗冻性、抗渗性和抗硫酸镁侵蚀性能。结果表明,高贝利特水泥混凝土7d龄期的抗压强度低,90d龄期的抗压强度是硅酸盐水泥混凝土的117．6％;28d龄期高贝利特水泥混凝土的抗拉强度和抗拉弹性模量分别是硅酸盐水泥混凝土的116．6％和94．8％;高贝利特水泥混凝土的抗冻性与硅酸盐水泥混凝土基本相同;抗渗和抗硫酸镬侵蚀性能优。高贝利特水泥混凝土早期强度低,后期强度增长率大,抗拉强度高,弹性模量低。高贝利特水泥混凝土的耐久性和后期力学性能优于硅酸盐水泥混凝土。     

石膏掺量对硅酸盐和硫铝酸盐水泥复合体系性能的影响

硅酸盐水泥与硫铝酸盐水泥复合后水泥的矿物组成变得多而复杂,这种复合体系水泥的水化硬化过程是一个多元复杂体系的多种矿物的水化硬化过程。将硫铝酸盐水泥熟料、硅酸盐水泥、无水石膏以合适的比例混合,通过试验和分析,制得早期强度相近、28d强度接近或超过纯硫铝酸盐水泥的复合胶凝体系,得出石膏的最佳掺量。     

阿利特-硫铝酸钡钙水泥混凝土抗渗性能的研究

在与相同配合比的普通硅酸盐水泥混凝土的对比试验中,采用抗渗试验和孔结构分析的方法,研究了阿利特-硫铝酸钡钙水泥混凝土的抗渗性能与水灰比的关系.结果表明,阿利特-硫铝酸钡钙水泥混凝土的相对抗渗系数与水灰比的关系与普通硅酸盐水泥混凝土类似,即随着水灰比的增大而增大;在相同配比和养护龄期条件下,该水泥混凝土的抗渗件能明显优于普通混凝土;阿利特-硫铝酸钡钙水泥混凝土中水化产物的粒径分布均匀,界面粘结状况较好,结构较为致密.     

正交试验极差分析在脱硫石膏综合利用研究中的应用

为研究燃煤电厂脱硫石膏(CaSO₄·2H₂O)的综合利用,以硅酸盐水泥掺量(因素A)、高铝水泥掺量(因素B)、脱硫石膏掺量(因素C)为三因素,各因素选取三水平进行L₉(3⁴)正交试验,以粉煤灰作为辅助调整组分,配成胶凝材料,制作40mm×40mm×160mm胶砂试件,检测试件3d、14d、28d膨胀量及强度,研究脱硫石膏掺量对水泥石的膨胀及强度影响。结果表明,脱硫石膏能不同程度对水泥石强度造成影响;脱硫石膏与高铝水泥掺量和占胶凝材料总量不宜大于20%,且脱硫石膏掺量小于高铝水泥掺量时对水泥石强度影响较小。     

水泥混凝土的发展简史

结合国内外水泥、混凝土、混凝土外加剂发展情况及相关文献,回顾了硅酸盐水泥、水泥混凝土、混凝土外加剂、混凝土研究发展的主要历程,指出了水泥混凝土的发展渊源和简况。     

Development of calcium sulfate–ggbs–Portland cement binders

Binders manufactured using a blend of gypsum, ground granulated blast furnace slag and Portland cements are technically viable and possess considerable environmental and economic advantages when compared to binders manufactured using Portland cement alone. As such, the evaluation of binders made from these materials offers a promising research focus in the quest to produce technically sound, environmental and economical binders for specialist uses as an alternative to traditional concrete binders of higher carbon footprint. The aim of the test programme was to investigate the viability of a series of binders designed to fulfil particular user needs while having significantly decreased carbon footprints.Two distinct series of binders were designed; the dominant ingredient in the first was calcium sulfate while in the second it was ggbs. Potential applications for both series of binders were considered and the strength development of each binder was analysed. In addition, the effect of water on the gypsum-based binders was analysed, as was the sulfate resistance of the ggbs-based binder.The results of the laboratory tests carried out were varied. For the calcium sulfate-based binders, those manufactured using anhydrite II as the dominant ingredient were found to achieve highest strengths. However these binders were found to be particularly susceptible to moisture-induced deterioration. For the ggbs-based binders, it was found that the early strength development was improved by the addition of small quantities of anhydrite II and gypsum. The strengths and sulfate resistance at later ages remained unaffected. These binders may have significant potential in situations where early strength development is a requirement.     

The pozzolanic properties of paper sludge waste

The use of paper de-inking sludge in pozzolanic material manufacture permits a disposable residue to be included in the cycle of the materials. A study on the reuse of paper de-inking sludge, undertaken in Spain, shows its potential as raw material for yielding a product with pozzolanic activity.

This study establishes that an optimal condition for transforming paper de-inking sludge into a pozzolanic addition is achieved at 700 °C maintained for 2 h. Under these conditions, the organic matter disappears and the calcined sludge becomes active by transforming kaolinite into metakaolinite. The calcined product exhibits high pozzolanic activity.

The present paper also analyses mechanical, physical and chemical properties of a blended cement containing 90% (in mass) standard Portland cement (CEM I-52,5N) and 10% of the pozzolanic addition obtained from controlled calcination of paper de-inking sludge (for 2 h at 700 °C). When the blended cement is compared with a cement containing 100% standard Portland cement, the following conclusions can be mentioned: a significant gain in compressive strength from 7 days on, a sooner initial setting time, as well as a reduction in SO₃ percentage. In any case, the new blended cement complies with requirements set out in Spanish/European standard UNE EN 197-1-Part 1.     

石灰石做次要附加组分的物理和化学作用

在硅酸盐水泥中填加少量的石灰石至今已有30多年的历史。石灰石作为次要附加组分给水泥生产商带来了经济和技术效益。虽然其在世界范围内得到了广泛认可,但对石灰石在水泥与混凝土中的实际作用一直没有清楚的认识,影响了其推广使用。加拿大32年使用石灰石作为硅酸盐水泥次要附加组分的经验,显示了其实际的物理和化学作用。     

Radon emanation from concrete and the influence of using flyash in cement

In the Netherlands both Portland cement and blast furnace cement (slags from blast furnaces with about 30% Portland cement) are used for concrete.Radon exhalation measurements were carried out on concrete blocks made with these two types of cement and blocks with 15, 25 and 35% of the cement substituted by three different types of flyash.The results show that substituting part of the cement by flyash has no drastic effect on the exhalation rate. For concrete with Portland cement the exhalation rate decreases using flyash with an average radium content. With blast furanace cement a slight increase may be expected. The exhalation of concrete is greater than the sum of the exhalation values of the constituting components. The water in the pores the concrete plays an essential role in the emanation processs.     

泡沫混凝土弹性模量的测试方法探讨

为获得密度为800 kg/m3的泡沫混凝土的弹性模量数据,设计了一种振弦式应变计测试的方法,并采用该方法测试了采用普通水泥和双快水泥配制的两种泡沫混凝土的应力应变,绘制了变化曲线,计算了弹性模量.采用普通水泥配制的泡沫混凝土,7 d的弹性模量在200～300MPa之间,采用双快水泥配制的泡沫混凝土,2 h的弹性模量在350～500MPa之间.测试表明该方法操作方便、速度快、测试结果离散性小、数值符合泡沫混凝土的特点和强度水平.