Influence of organic admixtures on the rheological behaviour of cement pastes

The rheological properties of cementitious pastes used to proportion Self-Consolidating Concretes (SCC) have been examined, in particular, the influence of High range water reducing admixture (HRWRA) with that of Viscosity Modifying Admixtures (VMAs) have been compared. HRWRAs are known to have dispersing effects on the cement particles through steric and/or electrostatic repulsion, while the effects of VMAs are expected to stabilise the paste by increasing the viscosity of the aqueous solution. Both transient and steady state rheological behaviour of the cementitious pastes proportioned with different dosages of HWRA and VMA were considered. Experimental results show that the influence of VMAs on rheological properties is actually minor compared to that of HRWRAs. These results are discussed in the framework of rheology of concentrated suspensions.     

Influence of mineral admixtures on the alkali-aggregate reaction

Different mineral admixtures were used as cement replacements to study the alkali-aggregate reaction between quartzite and cement paste. The experimental program included expansion measurement of the mortar-bar specimens, observation of the microstructure, and analysis of the gel composition. Two Portland cements with different alkali contents were used to prepare mortar bars containing different amounts of natural pozzolan, fly-ash, and slag. Three natural pozzolans with different alkali contents were also utilized to assess the effect of their alkalies on the mortar expansion. The results indicate that not all gels are equally expansive and that mineral admixtures change the composition of the gel. The double layer theory is used to explain the expansion results of the mortar bars containing different levels and types of mineral admixtures. As this theory predicts, the experimental results show a strong negative correlation between expansion and the charge fraction of bivalent cations in the gel.     

Improved chloride binding stability for hydration products of calcium aluminates by phosphorus modification

Improved chloride binding stability for calcium aluminate cements is proposed by the doping of phosphorus. Phosphorus-modified aluminates clinker has an improved chloride binding stability compared to pristine aluminates, ordinary Portland cement and sulfur-modified calcium aluminates, as verified by experimental observation. The existence of the newly found phosphorus-modified Friedel's salt (PFS) accounts for the excellent chloride binding stability, which was understood by density functional theory calculations. Local density of states of the valence band minimum is predominantly localized around P atoms in the PFS, but evenly distributed in the Friedel's salt (FS). The frontier band energy of the partial density of states on Cl and O elements in the PFS is lower than that in the FS by 0.21 and 0.05 eV, respectively. This makes the PFS more stable than the FS salt to ionic attack.     

Interactions of polymers and organic admixtures on portland cement hydration

Interaction of polymers and other organic admixtures on Portland cement hydration is reviewed. This has been compiled in a systematic way. First hydration of Portland cement is described in short. Later, interaction with 4 important components of Portland cement is discussed. Finally interphase effects in polymer modified hydraulic cement are discussed. It is concluded that polymers and organic admixtures interact with the components of Portland cement when they come in contact with water. This interaction is due to ionic binding, causing cross-links which inhibit the film formation property of polymers and influence considerably the crystallisation process during the hardening of concrete. Some low molecular weight organic substances also have a considerable influence on Portland cement during its reaction with water.     

有机接枝改性凹凸棒石对磷吸附性能的影响

有机接枝可以改善凹凸棒石粉末在吸附中的流失现象,但同时接枝反应也会影响凹凸棒石对磷的吸附效率。为了降低这一影响,对改性凹凸棒石进行接枝试验,研究不同接枝工艺对接枝产物吸附除磷效果的影响。结果表明,当丙烯酰胺、N,N′-亚甲基双丙烯酰胺、碳酸氢钠、改性凹凸棒石的质量分别为0.7、0.04、1、1 g,无水乙醇、5%过硫酸钾和水的用量分别为5、1和7 mL时,有机接枝凹凸棒石吸附剂除磷率能达到92%,是未接枝时的93.8%,吸附容量达到4.6 mg/g。     

复合反应器中高浓度有机废水对硝化作用的影响

选用悬浮球形填料作为复合生物反应器的填料,研究有机物去除和硝化作用。研究显示,将进水COD质量浓度从400 mg/L逐渐增加到2 000 mg/L,进水NH3-N质量浓度维持在30 mg/L~45 mg/L运行20天,随着COD质量浓度的逐渐增高,NH3-N的去除率从82%左右降低到-25.9%,硝化反应能力呈逐渐减小的总体趋势。     

复掺混合材水泥流变性及其与高效减水剂相容性的研究

根据工厂实际情况设计混合材正交配比水平,通过Marsh时间和水泥净浆流动度实验,比较复掺矿渣、粉煤灰、石灰石对水泥流变性的影响,发现粉煤灰对浆体流变性的影响最大;并从中挑选流变性较好的几组试样,测试其与高效减水剂的相容性,得出最佳配比.即当掺入0.6%的萘系高效减水剂时,最佳复掺混合材配比为矿渣21%,粉煤灰3%,石灰...     

Influence of calcium concentration in the washing liquor on detergency performance of linear alkylbenzene sulfonate

The effect of the concentration of linear alkylbenzene sulfonate (LAS) on soil removal efficiency at various water hardnesses was studied. The present investigation indicates that: (i) For each LAS concentration, a calcium ion concentration interval exists, defined by 0.78<(Log(LAS)/Log(Ca))<0.85, where the detergency reaches a maximum; (ii) 24 h after having been prepared, the solutions present either clear solutions (water appearance), milky solutions (without precipitate in the bottom of the bottle), or clear solutions with precipitate in the bottom of the bottle. The milky solutions correspond to the defined interval. The solutions where the relationship LAS/Ca is defined are located, surprisingly in a precise zone of the LAS-calcium solubility diagram. The study has been carried out with and without ionic strength buffering, and the addition of electrolyte moves the maximum detergency performance interval to higher calcium concentrations.     

Influence of chitosan derivatization on its physicochemical characteristics and its use as enzyme support

Chitosan was derivatized by two methodologies for analyzing their effect on chitosan physicochemical characteristics and its applicability as carrier for Bacillus circulans β‐galactosidase immobilization. Glutaraldehyde (GA) and epichlorohydrin (EPI) were used for crosslinking and activation of chitosan, producing the corresponding supports (C‐GA and C‐EPI‐EPI) after a one‐step and a two‐step process, respectively. The spherical shape and mean diameter of chitosan particles was not significantly affected by polymer derivatization, while Fourier transform infrared analysis showed that in both cases, chitosan polymer was chemically modified. TGA analysis indicated that C‐EPI‐EPI was the most thermally stable. The high degree of activation of C‐EPI‐EPI (586 μmol of aldehydes/g) resulted in the highest loss of activity during immobilization; hence a support with 100 μmol of aldehydes/g was produced (C‐EPI‐EPI₁₀₀). The highest expressed activity (89.3 IU/g) was obtained with the enzyme immobilized in C‐GA, while the biocatalyst with highest thermal stability at 60°C was obtained with C‐EPI‐EPI₁₀₀ (half‐life was 84‐fold higher than the one of the soluble enzyme). The best compromise between biocatalyst expressed activity and thermal stability corresponded to β‐galactosidase immobilized in C‐EPI‐EPI₁₀₀. According to this study, chitosan derivatized with EPI is a thermally stable carrier appropriate for producing highly stable immobilized B. circulans β‐galactosidase. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40171.     

Dependence of oil stability index of fatty compounds on their structure and concentration and presence of metals

During storage and use, vegetable oil-derived industrial products such as biodiesel and biodegradable lubricants can be subjected to conditions that promote oxidation of their unsaturated components. The materials arising during oxidation and subsequent degradation can seriously impair the quality and performance of such products. Therefore, oxidative stability is a significant issue facing these vegetable oil-derived products, and enhanced understanding of the influence of various components of vegetable oils and storage parameters is necessary. In this work, the oil stability index (OSI) was used for assessing oxidation of monoalkyl esters of FA by varying several parameters. Neat fatty compounds and prepared mixtures thereof were studied for assessing the influence of compound structure and concentration. Small amounts of more highly unsaturated compounds had a disproportionately strong effect on oxidative stability. The recently developed concept of bis-allylic equivalents correlated more closely than the iodine value with the OSI times of mixtures of fatty esters. The OSI times of free acids were shorter than those of the corresponding alkyl esters. The presence of copper, iron, and nickel also reduced oxidative stability, but their effect was less than the presence of more highly unsaturated fatty compounds. Of these metals, copper had the strongest catalytic effect on OSI time. OSI may be an alternative to long-term storage tests for determining the influence of extraneous materials such as metals on oxidative stability.     

Influence of shrinkage-reducing admixtures on the reduction of plastic shrinkage cracking in concrete

Fresh concrete exposed to high evaporation rates is prone to plastic shrinkage cracking, especially in structures with large surface area/volume ratios. The present work shows that the reduction of the surface tension of the mixing water is an effective way for decreasing such cracking. In this study, conventional and high strength concretes with superplasticizers and shrinkage reducing admixtures (SRAs) were exposed to drying in the plastic state. Continuous monitoring of the surface displacement facilitated the identification of the different stages of plastic shrinkage cracking. Measurements of capillary pressure, settlement, internal temperature and evaporation rate were also made. The results show the effectiveness of SRAs in reducing plastic shrinkage cracking, even in high strength concrete. This is attributed to the reduction in the evaporation rate, delay of the peak capillary pressure due to the development of menisci in the pores and lower settlement.     

Influence of photoirradation on reduction of hexavalent chromium by zero-valent iron in the presence of organic acids

Reduction of hexavalent chromium (Cr(VI)) by zero-valent iron (Fe⁰) was investigated systematically in the present study. No change in Cr(VI) concentration occurs using untreated Fe⁰ powders even after a long contact time. The Fe⁰ powders treated with acid washing shows a weak activity and a poor long-term performance to reduction of Cr(VI). The activity and long-term performance of treated Fe⁰ powders is not effectively improved in the presence of citric acid. In contrast, introduction of photoirradiation not only dramatically increases the reduction rate of Cr(VI) in the presence of citric acid but also effectively stabilizes the activity of Fe⁰ powders and films. Such enhancement should be attributed to photoreductive dissolution of the oxide layer on Fe⁰ surface. For this newly developed system, effective reduction of Cr(VI) is favored at low pH values and oxalic and tartaric acid are also effective as complex reagents.     

不同品种及掺量混凝材对GB—ISO强度的影响

０前言水泥新标准GB１７５—１９９９已于２００１年４月１日正式实施。该标准中强度检验方法采用了GB／T１７６７１—１９９９《水泥胶砂强度检验方法（ISO法）》（以下简称ISO法）。实验证明,采用ISO法检测的抗压强度值比用GB１７７—８５（以下简称GB法）检测的抗压强度值平均低一个标号。为了提高ISO法水泥强度,探索适应新标准的水泥生产用混合材品种及掺量,促进水泥产品结构调整和产品质量的提高,我公司进行了不同混合材品种在不同掺量下的GB—ISO强度对比试验,本文就有关试验情况作一介绍。１试验用混合材及其性能（…     

Influence of soil phosphorus and manure on phosphorus leaching in Swedish topsoils

In Sweden, subsurface transport of phosphorus (P) from agricultural soils represents the primary pathway of concern for surface water quality. However, there are mixed findings linking P in leachate with soil P and limited understanding of the interactive effects of applied P sources and soil test P on P leaching potential. Identifying soils that are susceptible to P leaching when manure is applied is critical to management strategies that reduce P loadings to water bodies. Intact soil columns (20 cm deep) from five long-term fertilization trials across Sweden were used in leaching experiments with simulated rainfall to explore the interactive effects of dairy cow (Bos taurus L.) manure application, soil test P and cropping system. Strong relationships were observed between ammonium lactate-extractable P in soil and dissolved reactive P (DRP) concentrations in leachate, although regression slopes varied across soils. For three soils, application of manure (equal to 21–30 kg P ha^?1) to the soil columns significantly increased DRP leaching losses. The increase in DRP concentration was correlated to soil test P, but with wide variations between the three soils. For two soils leachate P concentrations after manure addition were independent of soil P status. Despite variable trends in P leaching across the different soils, P concentrations in leachate were always moderate from soils at fertilization rates equivalent to P removal with harvest. Results clearly stress the importance of long-term P balance to limit P leaching losses from Swedish agricultural soils.     

常用杀菌剂与有机磷的相容性研究

对杀菌剂优氯净、1427、有机溴、活性溴和ClO2与有机磷PBTCA,ATMP,HEDP,EDTMPS和HPA的相容性在实验室进行了研究。实验结果表明,氧化型杀菌剂对有机磷有分解作用,其影响顺序为优氯净>有机溴>ClO2>活性溴,亚甲基型有机磷药剂几乎不抗优氯净的分解,分解率达80%左右;非氧化型杀菌剂1427对PBTCA和HPA有一定的分解率,对其他有机磷影响不大。氧化型杀菌剂能使有机磷的缓蚀性能增加,但降低有机磷除PBTCA外的阻垢效果;非氧化型杀菌剂1427对有机磷的缓蚀和阻垢效果几乎无影响。     

几种外加剂对硫铝酸盐水泥性能的影响

研究了高浓高效减水剂FDN、缓凝剂H3803和四种早强促凝组分(Li2CO3，NaNO2，Al2SO4和Na2SO4)对硫铝酸盐水泥标准稠度、凝结时间以及抗压强度的影响。结果表明，高效减水剂FDN与硫铝酸盐水泥相容性很好，减水效果明显；硼酸对硫铝酸盐水泥的缓凝效果不稳定，但通过复掺早强促凝组分能改善其缓凝效果和早期强度，且适量的硼酸能提高水泥浆的后期强度。碳酸锂对硫铝酸盐水泥有显著的促凝作用，但对后期强度不利。     

Influence of the addition of different radiopacifiers and bioactive nano-hydroxyapatite on physicochemical and biological properties of calcium silicate based endodontic ceramic

The purpose of this study was to investigate the influence of different radiopacifiers on the physicochemical and biological properties of novel calcium silicate based endodontic ceramic enriched with bioactive nano-particulated hydroxyapatite – ECHA. Namely, ECHA was used as a basis for mixing with the following radiopacifiers: strontium fluoride (SrF₂), zirconium dioxide (ZrO₂) and bismuth oxide (Bi₂O₃). For comparison, Portland cement (PC) and mineral trioxide aggregate (MTA) were used. The following physicochemical characteristics were examined: the radiopacity, setting time, compressive strength, porosity, wettability and pH value. The biocompatibility of the cements was assessed by crystal violet, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and cell adhesion assays. The highest radiopacity was obtained for the ECHA + Bi₂O₃ mixture and MTA that were statistically significant in comparison to other materials (p < 0.05). Both initial and final setting times as well as compressive strengths were statistically lower for experimental cements than for PC and MTA (p < 0.05). The lowest total porosity was observed in the ECHA + ZrO₂ group when compared with the other two experimental cements (p < 0.05), but not when compared with PC and MTA (p > 0.05). Experimental cements exhibited statistically higher contact angles of glycerol than PC and MTA (p < 0.05). For blood plasma, a statistical difference was found only between ECHA + Bi₂O₃ and PC (p < 0.05). All investigated materials had alkalization ability. Cell viability assays revealed that the extracts of tested cements did not exhibit cytotoxic effect on L929 cells. Scanning electron microscopy had shown a high degree of cell proliferation and adhesion of cells from apical papilla on experimental cements’ surfaces. Novel endodontic ceramics with nano-hydroxyapatite addition have satisfactory biological and physicochemical properties when compared to MTA and PC controls. Considerable lower setting time of experimental cements might present a huge advantage of these synthesized materials in clinical practice. SrF₂ presents a novel promising radiopacifying agent for dental cements manufacturing.     

Microstructure and compatibility of PVDF/PS blends in the presence of PVA

This research refers to a compatibility study of binary and ternary PVDF blends with PS and PVA by means of the determination of the polymer polymer interaction parameter χ₁₂ calculated from melting point depression analysis of the blends. In addition, a PVDF spherulite growth rate study was conducted in the binary and ternary blends with PS and/or PVA. The nucleation factor is determined by applying the Lauritzen–Hoffman theory. The results obtained show PVA to be capable of compatibilizing PVDF/PS systems when present in concentrations of 30 vol%.