Calcium Carbonate and Ettringite Induced Efflorescence in CAC-Anhydrite Binary Systems

We focused on the efflorescence induced microstructural evolution of ettringite-rich systems prepared with calcium aluminate cement(CAC)and anhydrite.The effects of anhydrite on the visible efflorescence,and the corresponding capillary absorption of CAC-anhydrite mortars were revealed.The composition and microstructure of efflorescence-causing substances were investigated by optical microscope,in-situ Raman spectroscopy,scanning electron microscope,energy dispersive spectrometer,thermogravimetric analysis,and differential scanning calorimetry,at multi-scales.Results indicate that,besides the calcium carbonate,ettringite is another main component of efflorescence-causing substances.Compared with the neat CAC mortars,the addition of anhydrite has a significant effect on the degree of efflorescence by acting on the composition of hydration products and pore structure.In addition,methods are proposed for the prevention of efflorescence of CAC-anhydrite binary system.

Fly Ash-based Geopolymers:Effect of Slag Addition on Efflorescence

Blended fly ash/blast-furnace slag geopolymers are focused on due to their excellent mechanical and chemical resistant properties. We investigated the effect of slag partial substitution for fly ash on the efflorescence of the resulting geopolymers. The efflorescence of geopolymer binders was inspected and evaluated through leaching tests. The efflorescence deposits on surface of the geopolymer binders were analyzed using XRD and SEM-EDS. The results showed that sodium and calcium cations leached from geopolymer binders reacted with the atmospheric CO2 and formed the crystal deposits, gaylussite and calcite, in the forms of granular and angular crystal particles. The slag addition led to a refinement of the pore structure of fly ash-based geopolymers, but an increment in the concentration of alkali leaching. The crystal deposits gradually developed in the pore volume of the binders, and finally exceeded the capacity of pore volume. The extent of efflorescence on the surface of specimens increased with the slag substitution. The visible efflorescence is therefore a result of available alkalis and pore sizes and volumes. Higher concentration of available alkalis and smaller pores （and volume） will lead to more intensive efflorescence.

Deliquescence and Efflorescence Processes of Aerosol Particles Studied by in situ FTIR and Raman Spectroscopy

Deliquescence and efflorescence are the two most important physicochemical processes of aerosol particles. In deliquescence and efflorescence cycles of aerosol particles, many fundamental problems need to be investigated in detail on the molecular level, including ion and molecule interactions in supersaturated aerosols, metastable solid phases that may be formed, and microscopic structures and deliquescence mechanisms of aerosol particles. This paper presents a summary of the progress made in recent investigations of deliquescence and efflorescence processes of aerosol particles by four common spectral techniques, which are known as Raman/electrodynamic balance, Fourier transform infrared/aerosol flow tube, Fourier transform infrared/attenuated total reftection, and confocal Raman on a quartz substrate.

Analysis of Efflorescence of Castables in Walking Beam Reheating Furnace

When the castable refractory linings are installed without drying out sufficiently and exposed to high humidity for a long time,white fibrous or powdery substance appears on the surface,which is called“efflorescence”.The main reason is the cement of castable refractory linings contacts with C02 and moisture in the atmosphere to form calcium carbonate(CaC03).In general,efflorescence takes place more readily in lightweight castable refractories.In the walking beam reheating furnace construction project,there are many white powdery substances in the walking beams,because the construction procedure causes poor ventilation in the surrounding area,and the internal moisture of castable refractory linings cannot be evaporated effectively.In future,the project programming should consider the environmental humidity and surrounding ventilation.

Dry Mix Slag—High-Calcium Fly Ash Binder. Part Two: Durability

This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na2CO3): the soundness, sulfate resistance, alkali-silica reactivity and efflorescence factors are considered. Results of tests show that such mortars are resistant to alkali-silica expansion. Mortars are also sulfate-resistant when the amount of HCFA in the complex binder is within a limit of 10 wt%. The fineness of fly ash determines its’ ability to activate GGBFS hydration, and influence soundness of the binder, early strength development, sulfate resistance and efflorescence behavior. The present article is a continuation of authors’ work, previously published in MSA, Vol. 14, 240-254.

FCH型吸附剂对重金属铬吸附能力的研究

一、前言近年来,国外用纸热值年青煤、风化煤等净化含重金属废水已作了不少工作。利用风化煤作净化废水的吸附剂,国内也有报道,但大多是用有机物作粘结剂,或用风化煤提取腐植酸后制备吸附剂,成本较高。若用工业废物作粘结剂,以风化煤为原料,制成FCH型吸附剂,工艺简单,价格便宜,原料易得,便于推广,有一定的实用意义。经用此吸附剂对郑州电器厂、和郑州电镀厂的含铬电镀废水进行处理,处理后含铬均能低于国家的排放标准。铬有多种氧化态,在镀铬废水中重要是含三价铬和六价铬两种形态,本文主要研究对六价铬的吸附能力。

Optimum Calculation of Coal Pillars in Inclined Weathered Oxidation Zone

In the mining process of coal mine,waterproof coal pillars should be set between the weathered oxidation zone and the first mining face.In order to determine the reasonable upper limit of the first mining face of Hongyi Coal Mine,the waterproof coal pillar needs to be wide enough to resist the lateral hydrostatic pressure of the oxidation zone,and to ensure that the top plate aquifer does not run through the water guide crack zone,while also liberating as much stagnant coal as possible.In this paper,the first coal mine face’s waterproof coal pillar was calculated using conventional and optimized calculation methods,taking into account the dip angle of the coal seam,the height of the water-guide crack zone,and the rock shift influence zone,and finally the upper limit of the first face of Hongyi Coal Mine was determined.

The effect of CTAB on Na_2SO_4 nucleation in mixed Na_2SO_4/CTAB aerosols by FTIR-ATR technology

FTIR-ATR technology is used to study the efflorescence kinetic of Na2SO4 and mixed Na2SO4/CTAB aerosols.As the RH decreased linearly,the v3-SO42 band shifts from 1094 cm1 to 1132 cm1,suggesting the phase transition of Na2SO4 from solution to crystal phase（Ⅲ）.For pure Na2SO4 aerosols,the ERH is 75.1%RH,whereas the efflorescence point of mixed Na2SO4/CTAB aerosols（74.2%） is lower.By further analysis of IR differential spectra,the ratio of Na2SO4 crystals in mixed aerosols is only 62.7%and the heterogeneous nucleation rate of Na2SO4 in Na2SO4/CTAB mixed aerosols is lower than that in pure Na2SO4 aerosols.They showed that CTAB assembled into reversed micelle and part Na2SO4 droplets are in the core to form core-shell structure,and CTAB shell prevents core Na2SO4 solutions from crystallizing.However,the counter ion Br for CTAB reversed micelle can interact with Na＋ ions,which decreases the crystallization rate of free Na2SO4 droplets and ERH is delayed.