Study on anhydrite plaster from waste phosphogypsum for use in polymerised flooring composition

The paper deals with an investigation about the production of high strength plaster from the waste phosphogypsum and its use in making flooring tiles. To achieve this objective, phosphogypsum was calcined at 900–1000 °C to anhydrite which was mixed with suitable chemical activators (alkali/alkaline earth hydroxides, sulphates, carbonates) and finely ground (>400 m²/kg Blaine's) to achieve high compressive strength (36–37 MPa). The anhydrite plaster was blended with 2–3% of predetermined quantity of a monomer methyl methacrylate (MMA) with a compatible catalyst, metalic oxide pigments, fly ash or red mud, chopped glass fibres (E-type, 12 mm long) and quartz sand to form flooring tiles by vibration moulding technique followed by high humidity curing, drying, grinding and polishing. The addition of chemical activators increase the rate of dissolution of anhydrite for rapid transformation into hard strong gypsum matrix while the MMA gets polymerised during hydration of anhydrite into polymethyl methacrylate which fills up voids and pores of hydrating anhydrite and thus improves density, strength and durability of the anhydrite plaster against water. The durability of anhydrite plaster by alternate wetting and drying and heating and cooling cycles is reported along with hydration mechanism. The use of phosphogypsum anhydrite for making high strength plaster and flooring tiles is recommended.     

Role of phosphogypsum impurities on strength and microstructure of selenite plaster

The effect of phosphatic, fluoride and organic impurities as present in waste phosphogypsum were studied on the setting time, strength development and microstructure of the selenite gypsum plaster. The results showed that these impurities affect the physical properties of the plaster in a similar fashion as observed in the setting and hardening of the phosphogypsum plaster. The selenite plaster sets fast with a fall in strength. The selenite plaster which normally crystallizes into long interlocking needle shaped crystals has been found to be modified to prismatic, lath, and tabular shaped crystals of variable sizes interspersed with radiating crystals and anhedral to subhedral microcrystallites having irregular boundaries and poor stacking. It is concluded that formation of prismatic and lath-like crystal of different morphology affect the normal setting and strength characteristics of selenite gypsum plaster to a great extent. The effect is more pronounced when soluble phosphatic, fluoride and organic matter were added to the selenite plaster than the sparingly and less soluble compounds intermixed.     

磷石膏制备建筑石膏工艺研究

化学石膏的资源化利用是保护环境、实现可持续发展的重要课题之一。磷石膏是排放量最大的化学石膏,而磷石膏中的可溶性磷和氟是影响建筑石膏性能的主要因素,采用石灰中和法将磷石膏中的可溶性磷和氟变成难溶于水的稳定物质,消除其对建筑石膏性能的影响,同时对磷石膏的煅烧工艺进行研究,并对显微结构进行了观察。结果表明,加入3%生石灰,中和预处理磷石膏,通过150℃煅烧,陈化4d所得建筑石膏性能稳定,改善了磷石膏结构疏松、空隙率大的缺陷,可达到GB9776—88《建筑石膏》优等品要求。     

耐火混凝土用结合剂的发展

阐述了耐火混凝土用结合剂的种类，用途，分析了各种结合剂的现状，认为，高浓度耐火陶瓷泥浆结合剂是耐火混凝土比较理想的结合剂，它不仅有许多优良性能，而且对于节约资源和能源，保护环境，提高经济效益都是有益的。     

粉刷石膏复合外加剂的研制

用石灰等天然非金属矿物材料与有机外加剂制成了新型粉刷石膏复合外加剂,研究了这些外加剂对粉刷石膏听凝结特性,保水性,粘结力及强度的影响。     

新型粉刷石膏改性剂的研制

为更广泛地满足粉刷石膏的应用要求,研制以缓凝、保水、增粘等多种组分合成的新型粉刷石膏改性剂。对不同类型的石膏掺用试验和粉刷石膏强度、保水性的试验研究表明,该改性剂除对石膏有优异的改性作用外,对水泥也有显著的减水、引气作用,适用于内墙抹灰石膏材料的改性。文中介绍了缓凝、保水效果,改性剂的各项技术性能及经济分析。     

磷石膏空心砌块的研制

利用磷石膏、粉煤灰和石灰,按一定比例配料,经混合、粉碎、成型等工艺,制成建筑内墙用空心砌块。该砌块具有防火、隔热、质轻、可加工性好等特点,且安装方便,造价低,符合建筑物结构大开间、灵活隔断发展趋势对内墙材料的要求。     

无可见泛碱水泥基瓷砖填缝剂的研制

通过分析泛碱形成的条件,采用添加憎水型胶粉、超细活性掺合料及抑碱树脂有效降低填缝剂的泛碱,研制出无可见泛碱水泥基填缝剂.该填缝剂的最佳配比为:憎水型胶粉掺量1%、超细活性掺合料20%等量取代水泥、抑碱树脂掺量0.2%.按最佳配比配制的填缝剂无可见泛碱,吸水量、强度、收缩等性能指标均符合JC/T 1004-2005标准要求.     

水泥基渗透结晶型防水材料的研制

介绍了渗透结晶型防水材料的制备和性能测试,讨论了催化剂和促凝剂用量对产品性能的影响,重点研究了速凝型产品的抗渗性能。     

Preparation of load-bearing building materials from autoclaved phosphogypsum

Previous studies have been carried out on calcined phosphogypsum (PG) for making the building materials. The present study was focused on autoclaved PG and its use in making load-bearing wall bricks. Autoclaved PG was prepared from original waste PG with steam pre-treatment. The crystalline phase, morphology, and thermal characteristics of original waste PG and autoclaved PG were investigated by XRD, SEM, and SDT. Then bricks of the size of Chinese standard brick were prepared from different types of PG in the PG-fly ash–lime–sand system. Results showed that the compressive strength of bricks from autoclaved PG by lower-pressure steam of 0.12 MPa, 120 °C for 16 h was much higher. The flexural strength and compressive strength of the bricks could reach 4.0 MPa and 15.0 MPa, respectively. The durability of the bricks was investigated by 15 freezing–thawing cycles at temperatures from ?20 °C to 20 °C, and the weight loss was only 0.029% after all of cycles. Hemihydrates (CaSO₄ · 0.5H₂O) were dehydrated products from dihydrates in original PG with lower-pressure steam treatment, and hemihydrates were susceptible to absorbing the humidity and were transformed into densified re-crystallization gypsum (CaSO₄ · 2H₂O) that contributed to the final strength of bricks. Microstructural characteristics of bricks were investigated by XRD and SEM. Tobermorite was the significant hydrated product, which contributed to the strength of bricks. The use of autoclaved PG for making load-bearing wall bricks was recommended instead of conventional burnt clay bricks.     

新型低碳墙体保温膏的制备和性能

以无机粘结剂和少量成膜剂为胶凝材料,以闭孔膨胀珍珠岩、空心陶瓷微珠为保温骨料,以膨润土、OK粉为填料,以氢氧化铝和轻烧粉为阻燃剂,添加少量表面活性剂和聚丙烯纤维,利用有机、无机复合方法和颗粒级配理论,制备一种新型低碳陶瓷墙体保温膏.研究了无机粘结剂与有机成膜剂掺量及配比、闭孔膨胀珍珠岩颗粒级配及表面活性剂掺量对保温膏保温效果和抗折强度的影响.结果表明,优选原料种类和配比,采用适宜技术路线,可制备出低碳环保、隔热保温、抗折强度高,阻燃效果好、抗裂性能优异的新型墙体保温膏.该保温膏导热系数为0.049 W/(m·K),抗折强度为1.2 MPa.     

柠檬酸废渣粉刷石膏的研制

柠檬酸废渣石膏经过处理,可制得性能优良的α型半水石膏;以α型半水石膏料为原料,加入外加剂,可配制出优质的粉刷石膏。这种粉刷石膏产品凝结硬化块,粘结力强,有较好的保温、隔热、吸声性能,体积稳定性好,质地细腻光滑,施工方便,是一种优质的内墙抹灰材料。本文就利用柠檬酸废渣石膏生产粉刷石膏的生产工艺、成本及产品性能进行了研究与分析。     

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.     

高性能胶凝材料的发展历程及研究进展

针对目前混凝土掺合科、外加荆的使用情况及所存在的问题,通过研究分析国内外大量的文献,对高性能胶凝材料进行了研究,提出了高性能混凝土用胶凝材料的生产体系和发展方向,大大提高了工业废渣的利用率,简化了混凝土?亮 的配制、生产方法.     

Rheology of warm mix asphalt binders with aged binders

This study addresses the rheological investigation of properties of warm mix asphalt (WMA) binders containing long-term aged binders. The recycled binders with the additives were produced using two (i.e., zeolite Aspha-min® and wax Sasobit®) of the available warm asphalt processes. The main rheological factors selected in this study were relationships between loading and response as a function of time, temperature and frequency using a Bohlin Dynamic Shear Rheometer II. The results indicated that the addition of Sasobit® into recycled binders played an important role in determination of the binder properties evaluated in this study. The use of lower performance grade (PG) as a virgin binder (PG 58-28 in this study) was critical on offsetting the change of rheological binder properties due to the warm additives and the aged binders.     

Recovery of nano-calcium fluoride and ammonium bisulphate from phosphogypsum waste

ABSTRACT

The production of phosphoric acid generates an enormous amount of phosphogypsum with emission of toxic fluorine acid gas. To remedy these environmental problems, a novel and a simple procedure permits converting phosphogypsum waste by recycled fluorine acid into valuable products. The obtained results confirm the efficiency of this procedure, which synthesises at room temperature the calcium fluoride in the form of nano-crystalline powder and the ammonium bisulphate salt from the exact stoichiometric proportions of phosphogypsum, hydrofluoric acid and ammonia. The total conversion of phosphogypsum is achieved after reaction time equal to one hour and a half. Generally, this novel procedure offers not only a solution for reducing phosphogypsum waste and fluorine gas emission, but also gives rise to valuable products, useful to industry and agriculture.     

胶凝材料复合早强剂开发及混合料浆配比优化

利用矿山周边矿渣、磷石膏、废石等固废开发早强胶凝材料用于矿山充填,可降低采矿成本,且实现固废资源化利用。首先基于试验材料物化分析,对胶凝材料复合早强剂进行开发;然后通过正交试验对多固废混合充填料浆进行试配,利用遗传规划获得最优配比。结果表明,复合早强剂可有效提高充填体早期强度,最优配比为芒硝1%～2%、NaOH 1%～1.5%、NaCl 1.5%;充填料浆最优配比为废砂比1:9、胶砂比1:5,料浆浓度80%;此时3d强度为2.04MPa,7d强度为4.19MPa,坍落度为28.6cm,分层度为0.75cm,强度和管输特性满足要求且成本最低。     

磷石膏应用现状分析

磷石膏具有重要的应用价值,文章对磷石膏在建材、化工产品、农业生产等诸多方面的应用进行了综述.同时,磷石膏中存在磷酸盐、氟化物、有机物等多种微量杂质,对石膏产品具有负面影响,直接限制了磷石膏的应用.文章重点讨论了各种杂质组分对石膏产品性能的影响以及目前国内外主要采用的解决方法.     

Laboratory evaluation of antioxidants for asphalt binders

A laboratory study was carried to investigate whether certain antioxidants could be used to reduce age-hardening in asphalt binders. Several additives including: Vitamin E, Irganox 1010, Irgafos P-EPQ, carbon black, hydrated lime, and DLTDP/furfural, were evaluated. The modified asphalt binders were subjected to two accelerated oxidative aging regimes in the laboratory. Short-term oxidative aging of the binders was simulated using a rolling thin film oven while long-term aging was performed using a pressure aging vessel. The effects of aging on the binders were evaluated based on changes in rheological properties of asphalt binders undergoing oxidative aging. Binders modified with a combination of furfural and DLTDP was found to posses the lowest aging index. The antioxidant-treated binders exhibited improved performance at both high and low pavement temperatures.     

纸面石膏板生产技术更新

论述了纸面石膏板生产技术更新，包括石膏研磨煅烧技术，发泡和成型技术，石膏板干燥技术，采用这些新技术能提高纸面石膏板的档次和质量，节省能耗，降低成本，减少投资，改善生产环境，文中论述的生产技术代表了20世纪90年代纸面石膏板生产的先进水平。