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。     

非水洗预处理磷石膏的研究

磷石膏预处理技术经济性是其建材资源化的关键。分别对非水洗预处理磷石膏作水泥缓凝剂,制备建筑石膏、粉刷石膏以及Ⅱ型无水石膏胶结材进行了研究。结果表明：磷石膏非水洗预处理资源化是可行的。石灰中和磷石膏与煅烧无水石膏可用作水泥缓凝剂;石灰中和球磨预处理在实验室和中试生产线制备出优等品建筑石膏;采用复合缓凝剂、保水剂可配制优等品粉刷石膏;石灰中和球磨预处理,８００℃煅烧,掺入激发剂可制备性能良好的无水石膏     

磷石膏脱水制度与中试生产研究

通过宏观性能试验 ,结合石膏相分析、过饱和度及结晶水测定及DSC、SEM分析 ,对磷石膏的适宜炒制制度以及预处理方式对炒制建筑石膏性能的影响进行了研究 ,介绍了采用生石灰中和预处理磷石膏工业性生产建筑石膏的性能、能耗与经济分析。本文还介绍了煅烧磷石膏胶结材的性能试验结果。实验室研究与生产实践表明 ,磷石膏经石灰中和预处理可制备性能良好的胶结材     

改性磷石膏作水泥缓凝剂的研究

为将磷石膏应用于水泥缓凝剂,采用水洗等方式对磷石膏进行预处理。确定水洗磷石膏的最优用水量和水洗时间。对比研究天然石膏、原状磷石膏和改性磷石膏对硅酸盐水泥凝结时间和强度的影响。通过水化热、XRD和SEM分析改性磷石膏对硅酸盐水泥水化特性的影响机理。结果表明,磷石膏在液固比为4和水洗时间为25 min条件下水洗效果最佳;生石灰单掺以及生石灰和膨润土复掺对磷石膏中可溶性磷和可溶性氟表现出较好的固化效果;水洗改性后磷石膏可有效缩短水泥的凝结时间,提高早期强度,其中生石灰与膨润土按2∶1复掺水洗改性后磷石膏用于硅酸盐水泥,水泥初、终凝时间比使用原状磷石膏时缩短了50%和31%;改性磷石膏制备的水泥早期水化速率正常,水泥固结体结构致密,缺陷较少,早期强度高。     

改性磷石膏用作水泥缓凝剂研究综述

采用水洗法、中和法和煅烧法等对磷石膏进行改性,能在一定程度上降低企业生产成本,并减少环境污染,具有较好的社会效益。改性磷石膏替代天然石膏用作水泥缓凝剂,能减小磷石膏中的有害杂质对水泥的不良影响,并可对水泥的强度产生增强效果。     

磷石膏基建筑腻子的配制与性能研究

磷石膏经石灰中和，球磨或水洗，球磨预处理，可煅烧成优等品建筑石膏。采用改性木薯淀粉胶和有机，无机复合缓凝保水技术，可配制磷石膏建筑腻子。它具有节能，利废，施工性能好，硬化快，粘结强度高的特点，是一种新型绿色建材。文中介绍了磷石膏建筑腻子配制原理，制备工艺及性能。     

磷石膏不同预处理方法的效果比较

通过对比磷石膏最具代表性的3种预处理方法——水洗法、石灰中和法和煅烧法的预处理效果,经过3种预处理方式处理的磷石膏都满足建材制品使用要求,其中石灰中和对去除磷石膏中可溶性磷(P2O5)效果较好;煅烧法对去除磷石膏中可溶性氟(F)的效果较好,相比之下石灰中和法更加经济和适用。     

磷石膏预处理工艺研究

经济、有效的预处理是磷石膏建材资源化的关键。系统研究了水洗、石灰中和、球磨、浮选、筛分以及煅烧等预处理工艺,分析了不同预处理工艺的效果,存在的问题及其可行性。提出了磷石膏建材资源化的预处理原则。磷石膏年利用量超过１０万吨,推荐采用水洗工艺,否则拟采用石灰中和球磨工艺。     

利用工业石膏开发高强度建筑石膏关键技术研究

从工业石膏的自身特性出发,在了解工业石膏不能直接用作建筑石膏原材料的原因后,以磷石膏为例,通过试验得出磷石膏在水洗预处理后可以作为生产建筑石膏的原材料,并介绍了工业石膏生产建筑石膏的工艺以及产品测定结果,为以后的相关工作提供理论依据。     

添加外加剂降低a高强石膏膨胀率的研究

本文分析研究了强石膏加入生石灰可显著降低其膨胀率，同时添加辅助剂，可保持高强石膏原有的特性不变，为开拓石膏建筑制品提供帮助。     

Study on lime–fly ash–phosphogypsum binder

In this study a new type of lime–fly ash–phosphogypsum binder was prepared to improve the performances of lime–fly ash binder which was a typical semi-rigid road base material binder in China. The modified lime powder had much higher activity than ordinary quick lime or slaked lime powder, it was the best alkali activator to prepare lime–fly ash–phosphogypsum binder. The optimum formulation of this binder was consisted of 8–12% modified lime, 18–23% phosphogypsum and 65–74% fly ash. The parallel experiments shown that lime–fly ash–phosphogypsum binder had higher strength than ordinary lime, cement, and lime–fly ash stabilized soils road base materials, granular soils stabilized with this binder had higher later strength than that of lime–fly ash or cement stabilizing granular soil, it had higher early strength and steady strength development. The phosphogypsum hastened the pozzuolana reactions between the lime and fly ash, it reacted with lime and fly ash also, this reaction formed some AFt and the formation of AFt brought on a slight expansivity which could compensate the shrinkage of the binder. The pore structure of this binder was finer than that of the lime–fly ash, so the strength and performances of the road base material stabilized with lime–phosphogypsum–fly ash binder was much higher than those of the lime–fly ash road base material.     

石灰改性磷石膏的工程性质研究

磷石膏改性后力学性质会大为改善,可用于多种类型的填方工程.文章分析了磷石膏的化学组分.提出了石灰含量与最优含水率的线性关系;试验表明石灰可以降低磷石膏的压缩性质,提高磷石膏的抗剪性能中.还分析了石灰改性磷石膏性质变化的化学机理,以及加入石灰的环境保护作用,综合比较提出了的石灰含量的变化对磷石膏工程性质的影响.     

Development of alpha plaster from phosphogypsum for cementitious binders

Efforts have been made to make high strength alpha plaster from phosphogypsum, a by-product of phosphoric acid industry. Phosphogypsum was autoclaved in slurry form (phosphogypsum 50% + water 50%, by wt.) in the laboratory at different steam pressures for different durations in presence of chemical admixtures. It was found that with small quantity of chemical admixture (sodium succinate/potassium citrate/sodium sulphate), alpha plaster of high strength can be produced. The optimum pressure and duration of autoclaving was found to be as 35 psi and 2.0 h, respectively. The alpha plaster was examined for making cementitious binders by admixing hydrated lime, fly ash, granulated blast furnace slag, marble dust and chemical additives with alpha plaster. Data showed that cementitious binder of compressive strength of 22.0 and 30 MPa (at 28 days of curing at 40° and 50 °C) and low water absorption was produced. DTA and SEM studies of the binder showed formation of CSH, ettringite and C₄AH₁₃ as main cementitious products to give strength.     

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.     

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.     

Environment hazard mitigation of waste gypsum and chalk: Use in construction materials

The rapid urbanization and industrialization have resulted in the production of various types of solid, liquid and gaseous wastes which pose serious problems to the environment. The disposal and use of solid industrial wastes like phosphogypsum, fluorogypsum, fly ash, slag, and lime sludge, is significant in view of their availability and potential applications. The paper deals with studies on select wastes like phosphogypsum and chalk for use in value-added building materials. The engineering properties and techno-economics of materials like gypsum plasters, cementitious binders, boards/blocks, masonry cement and flooring tiles produced from phosphogypsum and lime have been detailed. The production and use of building materials from such wastes will protect the environment from degradation.     

Effect of pozzolanic admixtures on mechanical,thermal and hygric properties of lime plasters

Compressive and bending strength, thermal conductivity, specific heat capacity, water sorptivity, moisture diffusivity, water vapor diffusion coefficient, sorption isotherms, and linear thermal and hygric expansion coefficients of three lime plasters with pozzolanic admixtures are determined in the paper. Comparative measurements with common lime plaster are done as well. On the basis of the experiments performed, it can be concluded that all the three analyzed lime-pozzolana plasters are suitable for an application in reconstruction of historical buildings. While their mechanical properties are significantly better compared to the reference lime plaster, their thermal and hygric properties are mostly similar or slightly improved. The only parameter that is found to be worse than for the common lime plaster is the linear hygric expansion coefficient but its worsening can be matched by the improved mechanical properties.     

磷石膏中磷的分析及对性能影响研究

可溶磷是磷石膏中主要有害杂质。研究了不同形态可溶磷、共晶磷对磷石膏性能的影响 ,测定了磷石膏中磷、可溶磷及共晶磷含量 ,用扫描电镜及光电子能谱研究了可溶磷的存在形式及其分布。结果表明 :可溶磷主要分布在磷石膏晶体表面 ,其含量随磷石膏粒度增加而增加 ;共晶磷则随磷石膏粒度增加而减少。可溶磷、共晶磷降低硬化体强度。当磷石膏胶结材水化时 ,不同形态磷转化为难溶盐 ,覆盖在二水石膏晶体表面 ,阻碍其溶解与水化 ,使其缓凝。石灰中和磷石膏可降低磷影响 ,是提高磷石膏性能的一种合理方法。