A new test method to assess the bacterial deterioration of cementitious materials

The biodegradation of cement-based matrices by agro-industrial effluents is a very complex phenomenon. In this work, a test was developed – the Build-Mat Bio-test (BMB test) – to examine the degradation mechanisms caused by microbial activity on any type of building material. The main objective of this device was to analyze and distinguish between the effects caused by the bacteria and those caused by their metabolites in the deterioration. In this study, the BMB test was used to evaluate the impact on cementitious matrices of the bacterium Escherichia coli, found in liquid manure. The mechanisms and kinetics of deterioration resulting from exposure to the bacterial culture or to the metabolites were compared with those obtained with synthetic organic acids alone. It was notably observed that the bacterial suspension caused more intense deterioration and higher alteration kinetics as compared to the medium without microorganisms and to the synthetic acid solution.     

Modeling the degradation of Portland cement pastes by biogenic organic acids

Reactive transport models can be used to assess the long-term performance of cement-based materials subjected to biodegradation. A bioleaching test (with Aspergillus niger fungi) applied to ordinary Portland cement pastes during 15 months is modeled with HYTEC. Modeling indicates that the biogenic organic acids (acetic, butyric, lactic and oxalic) strongly accelerate hydrate dissolution by acidic hydrolysis whilst their complexation of aluminum has an effect on the secondary gel stability only. The deepest degradation front corresponds to portlandite dissolution and decalcification of calcium silicate hydrates. A complex pattern of sulfate phases dissolution and precipitation takes place in an intermediate zone. The outermost degraded zone consists of alumina and silica gels. The modeling accurateness of calcium leaching, pH evolution and degradation thickness is consistently enhanced whilst considering increase of diffusivity in the degraded zones. Precipitation of calcium oxalate is predicted by modeling but was hindered in the bioleaching reactor.     

Degradation kinetics of recalcitrant organic compounds in a decontamination process with UV/H<Subscript>2</Subscript>O<Subscript>2</Subscript> and UV/H<Subscript>2</Subscript>O<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> processes

In this study, degradation aspects and kinetics of organics in a decontamination process were considered in the degradation experiments of advanced oxidation processes (AOP),i.e., UV, UV/H₂O, and UV/H₂O,/TiO₂ systems. In the oxalic acid degradation with different H₂O₂ concentrations, it was found that oxalic acid was degraded with the first order reaction and the highest degradation rate was observed at 0.1 M of hydrogen peroxide. Degradation rate of oxalic acid was much higher than that of citric acid, irrespective of degradation methods, assuming that degradation aspects are related to chemical structures. Of methods, the TiO₂ mediated photocatalysis showed the highest rate constant for oxalic acid and citric acid degradation. It was clearly showed that advanced oxidation processes were effective means to degrade recalcitrant organic compounds existing in a decontamination process.     

Influence of chemical degradation on mechanical behavior of a petroleum cement paste

Cement paste used in the Oil Industry is generally subjected to chemical degradation due to flow of acid fluids in various situations. The present study focuses on the evolution of thermo-hydro-mechanical (THM) behavior with chemical degradation of petroleum cement paste. Triaxial compression tests with different confining pressures (0, 3, 10 and 20 MPa) are carried out on a standard oil cement paste in sound state and completely degraded state by ammonium nitrate solution under a temperature of 90 °C. The results obtained show that the material in its initial state exhibits a small elastic phase and a strong capacity of compaction. The mechanical behavior depends on the load induced pore water pressure. Because of the increase in porosity caused by chemical degradation, the mechanical strength (cohesion and friction angle) and Young's modulus decrease. The dependence of mechanical strength and Young's modulus on confining pressure is smaller in the chemically degraded cement paste than in the sound one. In fine, the mechanical behavior of the whole material becomes more ductile. As a result, such effects of chemical degradation should be taken into account when modeling such cement paste materials exposed to such chemical degradations.     

Effect of admixtures of lower alcohols on the properties of humic acid salts in dispersed fuel systems

The effect of lower alcohols on the plasticizing, emulsifying, and stabilizing properties of salts of humic acids in coal-water slurries and emulsions was studied. It was found that water-soluble salts of humic acids can be used as additives regulating the physical and chemical properties of dispersed fuel systems (coal slurries and fuel emulsions) that contain lower alcohols. Since humic acid salts are capable of aggregation in aqueous alcohol solutions, their regulatory effect in colloidal fuels can be predicted.     

The physical and chemical characteristics of the shell of air-entrained bubbles in cement paste

Recent research has suggested that the shell of an air-entrained void is important for resisting coalescence between air-voids and diffusion of gas from the surrounding fluid. The current paper describes the physical and chemical properties of an air-void shell during the first 2 h of hydration and chemical characteristics at 60 days. Results from this research suggest that the air-void shells found in air-entrained paste have varied physical properties and the crystalline material of these shells is largely made up of fine cement particles during the first 2 h of hydration. Observations of paste at 60 days of hydration suggest that the shell is made up of calcium silicate hydrate (C-S-H) with a morphology different from that in the bulk paste.     

温度对羧二酸金属皂稳定性的影响

首次采用热重分析法研究了羧二酸钙盐和锌盐在多种温度下的分解动力学,发现脂肪酸金属盐的分解速率常数的数值大约在相同的数量级,但戊二酸盐比琥珀酸盐更稳定。测定了羧二酸金属盐的分解焓、熵和活化自由能,热力学数值显示反应体系是一个放热且不可自发的过程。     

Chloride-free biodegradable organic acid hydrolyzed zinc silicate coating

Partially hydrolyzed ethyl silicate has widely been used as a binder to formulate inorganic zinc silicate paint for anticorrosive coating applications. Hydrochloric acid is used most popularly to catalyze the hydrolysis of ethyl silicate. Although different acids have been tried as catalysts for ethyl silicate hydrolysis, no attempt has been made to make stable paints out of those hydrolyzed silicate binders. In this study, environment benign biodegradable organic acids such as oxalic acid, citric acid, lactic acid and acetic acid were used for the hydrolysis of ethyl silicate and compared with the hydrolysis using conventional hydrochloric acid. The hydrolyzed silicate sols were pigmented further with silica powder and evaluated for their stability. Of the various organic acids catalyst used, only oxalic acid catalyzed sol acted as a stable binder system. The pigmented binder was then mixed with metallic zinc to formulate anticorrosive inorganic zinc silicate paint. The resultant coatings were characterized for various physical, surface, mechanical and chemical resistance properties such as drying, hardness, adhesion (cross hatch) and solvent resistance. Corrosion resistance properties were analyzed by means of salt spray, open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The results revealed that the physical, mechanical, chemical and anticorrosive properties of the coating hydrolyzed with hydrochloric acid and oxalic acid are comparable. Thus, a chloride free biodegradable organic acid hydrolyzed inorganic zinc silicate primer is reported and due to its long term stability same also can be scaled up commercially.     

Fenton试剂氧化降解结晶紫的动力学研究

探讨了Fenton试剂在光照条件下对结晶紫模拟印染废水进行氧化处理的动力学规律,讨论了H2O2初始浓度、FeSO4初始浓度、反应温度及草酸的络合作用对结晶紫氧化降解的影响,确定了最佳降解条件,建立了Fenton试剂氧化降解结晶紫的动力学方程,为光照条件下利用Fenton试剂处理含结晶紫类的印染废水提供了依据.     

Telomer Acids: Monocarboxylic acids with long-chain branching; Their derivatives,properties and potential uses in lubricants

Telomer acids are synthesized by addition of acetic anhydride to α-olefins using managenese (III) acetate as a free radical initiator. The telomerization mechanism comprises initiation, propagation and termination steps. The reaction product consists of a mixture of acids having [xn+2] carbon atoms (n: number of carbon atoms of α-olefin: x:1, 2, 3, 4, ...). The “first telomer” (x=1) is a linear fatty acid. Under appropriate conditions, mainly telomer acid (x:2, 3, 4, ...) are obtained, being α- and γ-branched monocarboxylic acids, characterized by long-chain branches. Telomer acids derived from α-olefins up to n=14 are liquids at room temperature, despite the high molecular weight. Esters of telomer acids show interesting properties in lubricant applications: low pour point, high viscosity index, low viscosity as a function of molecular weight, good thermo-oxidative stability and a remarkably low elastomer swell. In amino amide derivatives, the telomer acid structure gives low viscosity properties, as is, for instance, found in significant viscosity reductions by using telomer acid as coreactant in polyisobutenyl succinic anhydride—tetraethylene pentamine condensation products. Dispersancy properties of these products are retained. Telomer acid metal salts exhibit quite different solubility characteristics and rheological properties than do fatty acid salts. Calcium salts of telomer acids are readily soluble in mineral oil: the rheology of these low viscosity solutions exhibits Newtonian behavior. Solvent-free magnesium salts which are liquid can be obtained. Neutral and overbased calcium salts show pour point depressing activity in paraffinic oils. For overbased calcium salts, decrease of coefficient of friction with increasing temperature has been observed.     

多壁碳纳米管的氨表面改性及其臭氧催化降解草酸

采用水热方法制备了一系列用浓氨水改性的多壁碳纳米管催化剂,该催化剂的活性通过非均相催化臭氧化降解水溶液中的草酸来进行评价。降解过程符合零级反应动力学模型,且催化剂的表观动力学常数与其表面碱性基团数量以及零电位pH值（pHPZC）呈正相关。为此,可断定用浓氨在水热条件下处理多壁碳纳米管能明显提高催化臭氧降解草酸能力是因为提高了催化剂的表面碱性基团数量和pHPZC。     

Effect of Fatty Acid Unsaturation on Phytosteryl Ester Degradation

This study examined the thermo-oxidative degradation of stigmasterol fatty acids esters. Stigmasterol stearate, oleate, linoleate and linolenate were synthesized by chemical esterification and their purity evaluated by ¹H-NMR and GC–MS. The degradation of stigmasterol esters was examined after heating them at 60 and 180 °C for 1, 2, 4, 8 and 12 h. It was established that stigmasterol esters were prone to thermo-oxidative degradation, with time and temperature affecting the degree of degradation. The unsaturation of fatty acids affected the rate of stigmasteryl ester degradation. The kinetics of StS and StO degradation were similar and the additional double bonds in StL and StLn resulted in their faster decomposition. The esters degraded faster at 180 than at 60 °C. The sterol and fatty acid molecules degraded at different rates, such that the fatty acid moiety deteriorated faster than the sterol at both temperatures, independent of the time of heating and the level of unsaturation.     

Nature of luminescence during galvanostatic anodizing of high purity aluminium

Galvanoluminescence of high purity aluminium was found to have two fundamental origins: one was the luminescence associated with scintillation or with some concommitant side reactions, taking place at the flaws; the other was the luminescence associated with anions included in the films during anodization. The former appeared to be the origin of the luminescence in inorganic electrolytes such as ammonium borate, borax, borax plus boric acid etc; and the latter appeared to be responsible for the luminescense in organic acids and their salts, such as oxalic, citric, tartaric and succinic acids and ammonium tartrate.     

Synthesis,Corrosion Inhibition Performance and Biodegradability of Novel Alkyl Hydroxyethyl Imidazoline Salts

New alkyl hydroxyethyl imidazoline salts were synthesized via a high pressure process with imidazoline and dimethyl carbonate, and their chemical structure were confirmed using mass spectral fragmentation and FTIR spectroscopic analysis. In addition, several quaternary ammonium salts with new counterions (formic acid, acetic acid and lactic acid) were also synthesized by ion exchange reaction of methyl carbonate quaternary ammoniums with the corresponding acids. These new compounds reduced the surface tension of water to a minimum value of approximately 27 mN m^?1 at a concentration of 8.72 × 10^?5 mol L^?1. They also show efficient corrosion inhibition performances and could significantly inhibit the corrosion of mild steel in acid solutions. It was also found that the biological degradation of these imidazoline surfactants was greater than 98 % after 7 days.     

Synthesis of Thumba,Castor and Sal Fatty Ethanolamide-Based Anionic Surfactants

The study involved the preparation and evaluation of anionic surfactants from non-edible oil based thumba (containing unsaturated-rich fatty acids, 80.9 %), castor (containing ricinoleic acid, a hydroxy fatty acid 89.3 %) and sal (containing saturated-rich fatty acids, 56.5 %). The oils extracted from these seeds (using Soxhlet) were reacted with monoethanolamine and diethanolamine to get corresponding fatty mono- and diethanolamides. The ethanolamides were sulfated using chlorosulfonic acid and the sulfated sodium salts were evaluated for surfactant properties namely surface tension, critical micelle concentration (CMC), emulsifying property, wetting, foaming power and calcium tolerance. The properties were compared with sodium dodecyl sulfate (SDS) a well known anionic surfactant. Among the different sulfated sodium salts of ethanolamides, thumba showed superior surfactant properties compared to castor and sal. Sulfated sodium salt of thumba monoethanolamide showed better properties (CMC, 0.035 mmol/L, surface tension 30.2 mN/m and calcium tolerance >1,000 ml, 0.5 % calcium acetate solution) compared to sulfated sodium salts of thumba diethanolamides, followed by sulfated sodium salts of castor monoethanolamide (CMC 0.037 mmol/L, surface tension 35.3 mN/m and calcium tolerance >1,000 ml, 0.5 % calcium acetate solution). Sal being saturated rich was not properly soluble in water and showed poor surfactant properties compared to the other two. Also the sulfated sodium salts of thumba and castor ethanolamides exhibited superior properties compared to SDS.     

Accelerated tests of hardened cement pastes alteration by organic acids: analysis of the pH effect

Effluents, such as liquid manure and silage effluents, stored in silos often made of concrete, contain organic acids that are chemically very aggressive for the cement-based matrix. The pH of liquid manure is comprised between 6 and 8, and the pH of silage effluent is about 4.There has already been much research done on manure's effect on concrete using aggressive solutions with a pH of or inferior to 4, in order to accelerate alteration kinetics. These studies aimed at simulating liquid manure and silage effluent, equally.The goal of this article is to validate the use of solutions with a pH of 4 to implement accelerated studies on alterations occurring to structures exposed to the acidic part of liquid manure.In this study, the alteration mechanisms of the cement-based matrix produced by two solutions of organic acids with pH of 4 and 6 were compared.At the end of the experiment, carried out on ordinary Portland cement and slag cement pastes, the kinetics of alteration of the cement pastes immersed in the solution with a pH of 4 was ninefold higher than in the solution with a pH of 6.The chemical and mineralogical modifications of the paste were analyzed by electron microprobe, XRD and BSE mode observations.It was shown that the alteration mechanisms of the paste are sensibly identical for both solutions: almost complete decalcification, the disappearance of the crystallized or amorphous hydrated phases and the probable formation of a silica gel containing aluminum and iron, mainly. The differences in alteration mechanisms between the two solutions are minor and mainly concern the stability of the anhydrous phases: C₄AF and slag grains.     

ALTERING THE PROPERTIES OF HEAVY CLAYS BY THE USE OF ELECTROLYTES1

Some heavy clays otherwise adaptable to industrial use have poor working properties. The possibility of altering these properties beneficially, by the addition of electrolytes to the clays, was investigated. The effects of acids and bases, or those salts which when hydrolyzed, reacted as acids or bases, gave the most promise. Physical properties were determined in the laboratory, on three clays in the green and fired states, without electrolytes and with hydrochloric acid, tannic acid, sodium carbonate, and calcium chloride. Some plant tests were also made, particularly on drying. It was found that the addition of electrolytes improved the properties of some clays, the electrolyte and amount required being individual with each clay.     

Identification of viscoelastic C-S-H behavior in mature cement paste by FFT-based homogenization method

A powerful and robust numerical homogenization method based on fast Fourier transform (FFT) is formulated to identify the viscoelastic behavior of calcium silicate hydrates (C-S-H) in hardened cement paste from its heterogeneous composition. The identification is contingent upon the linearity of the creep law. To characterize cement paste microstructure, the model developed by Bentz at the National Institute of Standards and Technology, which has the resolution of 1 μm, is adopted. Model B3 for concrete creep is adapted to characterize the creep of C-S-H in cement paste. It is found that the adaptation requires increasing the exponent of power law asymptote of creep compliance. This modification means that the rate of attenuation of creep with time is lower in C-S-H than in cement paste, and is explained by differences in stress redistribution. In cement paste, the stress is gradually transferred from the creeping C-S-H to the non-creeping components. The viscoelastic properties of C-S-H at the resolution of 1 μm were identified from creep experiments on cement pastes 2 and 30 years old, having the water-cement ratio of 0.5. The irreversible part of C-S-H creep, obtained from these old specimens at almost saturated state, is found to be negligible unless the specimens undergo drying and resaturation prior to the creep test.     

季铵盐萃取草酸的机理

季铵盐可以直接从氰化浸出液中萃取金，但反萃困难. 酸性硫脲通空气体系能有效反萃季铵盐中的氰化金，向反萃液中添加草酸可以显著提高金的反萃效率. 实验发现在反萃过程中，草酸会被萃取进入有机相. 本文通过3个萃取模型分别拟合草酸的萃取反应并用红外光谱法研究了萃取机理，结果表明，季铵盐萃取草酸的机理主要为中性缔合，草酸的COOH基团与季铵盐的极性端作用，形成1:1型氢键萃合物，表观平衡常数2.12，还有少部分草酸以失去一个氢离子的二聚体形式与Cl–发生阴离子交换，与季铵阳离子形成1:2型离子对萃合物，表观平衡常数0.0031.     

Influence of Processing Additives on the Quality and Stability of Dried Papaya Obtained by Osmotic Dehydration and Conventional Air Drying

The combination of osmotic dehydration and hot air drying (OD/HA) is an industrial alternative to papaya production, but tissue softening and color loss are technological problems. The objective of this work was to study, during OD/HA processing of papaya (Formosa cultivar), the influence of organic acids (citric and lactic), calcium salts (lactate and chloride), and the enzyme pectinmethylesterase (PME) on the texture, color, and sensory characteristics of the product. The stability of the products treated with lactic acid/calcium chloride, PME/calcium chloride, and the standard sample (without additives) was evaluated at 25 and 35°C for up to 100 days, analyzing vitamin C and color degradation. Light microscopy analysis performed at the beginning of stability study showed that the additives better preserved the cell structure. The use of lactic acid/calcium chloride maintained the color of the dried papaya, but the additives did not have an effect on vitamin C degradation. The variations in the chromaticity parameters (b* and a*) were adjusted to zero- and first-order kinetic models, respectively, with Q ₁₀ values ranging between 0.88 and 2.30 and R ² ～ 0.90. The combination of lactic acid/calcium chloride resulted in higher sensory acceptance and color stability of dried papaya during storage.