大掺量粉煤灰水泥砂浆溶蚀强度变化规律

研究了加速溶蚀下纯水泥和粉煤灰用量分别为50%,70%和90%的混合水泥砂浆强度的变化规律,采用XRD测试技术对溶蚀和未溶蚀硬化浆体化学组成进行分析,结合宏观数据进行了机理解释。结果表明,相对于溶蚀前,纯水泥砂浆试件破坏严重,抗折和抗压溶蚀强度均下降显著;而粉煤灰水泥砂浆,抗折强度略有下降,抗压强度反而有所增长,其中粉煤灰掺量为70%时,砂浆抗溶蚀性能最好;相对于未溶蚀试件,纯水泥砂浆强度损失严重,粉煤灰水泥砂浆强度亦有所降低,但强度损失程度相对较低,其变化规律与粉煤灰用量关联不明显;混合水泥中粉煤灰的二次水化,降低了浆体中氢氧化钙(CH)的量,优化了浆体微结构组成,对溶蚀产生了阻碍缓释作用,提高了砂浆抗溶蚀性能。当粉煤灰用量过高时,浆体中CH严重贫乏,不足以满足粉煤灰二次水化的需求,将限制缓释作用的发挥。     

低温-干湿循环耦合作用下水泥砂浆抗硫酸盐侵蚀试验研究

研究了不同水胶比水泥砂浆试件在低温-干湿循环耦合作用下的抗硫酸盐侵蚀性能。采用0.36与0.5两种水胶比的普通硅酸盐水泥、中抗硫水泥以及矿粉-硅灰复掺的水泥砂浆试件,检测试件标养28d后的孔结构及各试件在5±1℃的3%Na_2SO_4溶液中干湿循环后的强度、质量损失变化情况,并对砂浆低温干湿循环条件下抗硫酸盐侵蚀性能进行评价。结果表明:在5℃低温条件下,0.36水胶比试件抗蚀性高于0.5水胶比试件,抗硫酸盐侵蚀性能随着水胶比的降低而提高;复掺矿粉-硅灰对0.5水胶比水泥砂浆抗硫酸盐干湿循环侵蚀性能产生不利影响,复掺矿粉-硅灰提高了0.36水胶比水泥砂浆的抗硫酸盐干湿循环侵蚀性能。     

水灰比对建筑砂浆抗酸雨性能的影响分析

根据我国南北方酸雨的pH值和离子组成配制了硫酸型模拟酸雨溶液,采用干湿交替周期浸泡的试验方法来研究不同水灰比下酸雨溶液对水泥砂浆试件抗酸性能的影响。试验结果表明:在酸雨侵蚀下,水泥砂浆质量溶蚀百分数与水灰比呈一元线性关系。水灰比为0.6的水泥砂浆抗折强度降低最为明显,而水灰比为0.5的水泥砂浆抗折强度下降最小,合理的水灰比为0.45~0.55。     

矿物掺和料对玄武岩纤维水泥砂浆强度发展的影响

研究了粉煤灰和硅灰对玄武岩纤维增强水泥基材料强度发展规律的影响,分析了粉煤灰和硅灰复掺对水泥砂浆中玄武岩纤维耐腐蚀性的影响.结果表明：玄武岩纤维对水泥基材料的早期抗折强度具有增强作用,后期增强效果下降,甚至会降低基体强度;粉煤灰和硅灰可显著延长玄武岩纤维对水泥砂浆抗折强度增强效果的时效.XRD图谱和显微结构分析表明,粉煤灰和硅灰复掺后降低了水泥基体中Ca(OH)2晶体的含量和玄武岩纤维的腐蚀程度,改善了玄武岩纤维和水泥基体之间的界面性质.     

酸雨对水泥基材料的腐蚀

本文主要阐述了酸雨对砂浆的危害.酸雨的危害主要是由于其中含有的H＋离子,SO4^2-子对混凝土产生腐蚀.通过周期浸泡法,对砂浆试件进行了酸雨侵蚀的模拟,研究其抗压和抗折强度变化.     

复合侵蚀条件下水泥砂浆的耐蚀性能研究

在地下水富含硫酸盐的地区,结构混凝土不仅受到硫酸盐的侵蚀,而且会常常面临干湿循环-硫酸盐-CO2复合侵蚀。在试验室条件下研究了碳化侵蚀、干湿循环-硫酸盐侵蚀以及干湿循环-硫酸盐-CO2复合侵蚀的情况下水泥砂浆的耐蚀性能。试验结果表明:在干湿循环-硫酸盐侵蚀条件下砂浆试样强度呈现先增后降的趋势;硫酸盐-干湿循环-CO2环境对水泥砂浆的侵蚀最为严重;三种试验制度对砂浆试件侵蚀影响大小按龄期分为两个阶段;在干湿循环-硫酸盐侵蚀条件下产生的物质为Na2SO4晶体和钙矾石,在硫酸盐-干湿循环-CO2侵蚀条件下产生的物质为Ca CO3和Na2SO4晶体。     

粉煤灰加气混凝土的耐久性研究

研究了不同环境条件对粉煤灰加气混凝土耐久性的影响,认为碳化、冻融循环和干湿循环是引起粉煤灰加气混凝土长期性能劣化的主要原因。粉煤灰加气混凝土抗冻融循环能力较差,在碳化和干湿循环作用下,抗压、抗拉和抗折强度有不断降低的趋势;无论自然碳化还是人工碳化,碳化后的粉煤灰加气混凝土试件的抗压强度与未碳化试件的相比均有不同程度的降低,碳化系数小于1。     

掺合料对水泥砂浆抗折性能的影响北大核心

研究了偏高岭土、粉煤灰、矿粉、硅灰等矿物掺合料种类以及掺入方式对水泥砂浆抗折性能的影响规律,采用XRD分析了硬化水泥浆体的水化产物。结果表明:单掺情况下,偏高岭土对水泥砂浆抗折强度的增强作用最明显,掺量为15%时,28、56 d水泥砂浆抗折强度分别提高了12.2%、36.1%;复掺情况下,偏高领土与粉煤灰和矿粉复掺的效果最好,28、56 d水泥砂浆抗折强度分别提高了16.4%、28.6%。掺入不同矿物掺合料时,水泥水化产物种类无明显区别,主要晶相组成为Ca(OH)_2、AFt;偏高岭土-矿粉-粉煤灰复掺,复合效应显现,提高了水化产物中钙矾石生成量,降低了水泥水化析出的Ca(OH)_2含量,能显著提高水泥砂浆的抗折强度。     

掺合料对水泥砂浆抗折性能的影响

研究了偏高岭土、粉煤灰、矿粉、硅灰等矿物掺合料种类以及掺入方式对水泥砂浆抗折性能的影响规律,采用XRD分析了硬化水泥浆体的水化产物。结果表明:单掺情况下,偏高岭土对水泥砂浆抗折强度的增强作用最明显,掺量为15%时,28、56 d水泥砂浆抗折强度分别提高了12.2%、36.1%;复掺情况下,偏高领土与粉煤灰和矿粉复掺的效果最好,28、56 d水泥砂浆抗折强度分别提高了16.4%、28.6%。掺入不同矿物掺合料时,水泥水化产物种类无明显区别,主要晶相组成为Ca(OH)_2、AFt;偏高岭土-矿粉-粉煤灰复掺,复合效应显现,提高了水化产物中钙矾石生成量,降低了水泥水化析出的Ca(OH)_2含量,能显著提高水泥砂浆的抗折强度。     

掺粉煤灰混凝土耐城市污水侵蚀性能的研究

根据上海城市污水实际组分,配制高浓度人工污水作为腐蚀介质,采用应力腐蚀和干湿交替循环快速腐蚀试验方法,对掺粉煤灰的Ｃ３５,Ｃ５０混凝土及水泥砂浆进行侵蚀试验。研究表明,混凝土中掺入粉煤灰后,在人工污水中的荷载作用下应力腐蚀、强度损失、膨胀率及钢筋阻锈性能均有显著改善。     

聚硅铁混凝去除腐殖酸的研究

考察了聚硅铁(PSF)对腐殖酸(HA)的去除效果及影响因素,并与聚合硫酸铁(PFS)、硫酸铁[Fe_2(SO_4)_3]进行了比较.结果表明,当5相似文献   

天津城市供水系统中卤乙酸含量的研究

考察了天津市城市供水系统中卤乙酸的含量及其变化规律.结果表明,各自来水厂的出厂水及管网水中的二氯乙酸和三氯乙酸含量均远远低于<生活饮用水卫生标准>(GB 5749-2006)规定的限值;自原水进入自来水厂至最终到达用户自来水龙头的整个过程,水中的二氯乙酸和三氯乙酸含量呈快速上升--保持平稳--快速下降的变化趋势,其中滤后水中的卤乙酸含量最接近或达到峰值;采用预氯化工艺会促进卤乙酸的生成,水温与卤乙酸的生成呈正相关.     

Use of three-dimensional excitation and emission matrix fluorescence spectroscopy for predicting the disinfection by-product formation potential of reclaimed water

This study was undertaken to demonstrate the feasibility of using three-dimensional excitation-emission matrix (3DEEM) fluorescence spectroscopy for the determination of chlorination disinfection by-product (DBP) precursors and the disinfection by-product formation potential (DBPFP) of reclaimed water samples. Two major DBP precursors were examined in this study, including humic acid (HA) and fulvic acid (FA). The 3DEEM fluorescence results obtained from various reclaimed water samples indicated that the reclaimed water samples were rich in fulvic acid-like substances that were associated with two main peaks (Ex/Em = 235-245/420-440 nm, and Ex/Em = 330-340/410-430 nm) in the fluorescence spectrum. The results also illustrated that the wavelength location of peak fluorescence intensity of a reclaimed water sample was independent of the influent water quality and the wastewater treatment process used in the reclamation plant. As a result, the peak fluorescence intensity and the wavelength location of the peak were used to identify the species of DBP precursors and their concentrations in the reclaimed water sample. Four regression models were then developed to relate the peak fluorescence intensity of the water sample to its DBPFP, including the formation potential of trihalomethane (THMFP) and the formation potential of haloacetic acid (HAAFP). The regression models were verified using the measured DBPFP results of a series of reclaimed water samples. It was found that the regression modeling results matched the measured DBPFP values well, with prediction errors below 10%. Therefore, the use of 3DEEM fluorescence spectroscopy together with the developed regression models in this study can provide a reliable and rapid tool for monitoring the quality of reclaimed water. Using this method, water quality could be monitored online, without utilizing the lengthy conventional DBPFP measurement.     

Formation of disinfection by-products in indoor swimming pool water: the contribution from filling water natural organic matter and swimmer body fluids

The contribution and role of different precursors in the formation of three class of disinfection by-products (DBPs) [trihalomethanes (THMs), haloacetic acids (HAAs), and halonitromethanes (HNMs)] in swimming pool waters were examined using filling waters obtained from five drinking water treatment plant (WTP) effluents and three body fluid analogs (BFAs). BFAs exerted higher chlorine demands as compared to natural organic matter (NOM) in filling waters. BFAs exhibited higher HAA formation potentials than THM formation potentials, while the opposite was observed for the filling water NOM. There was no appreciable difference in the HNM formation potentials of BFAs and filling water NOM. Different components in the BFAs tested exhibited different degree and type of DBP formation. Citric acid had significantly higher THM and HAA yields than other BFA components. The effect of temperature was greater on THM formation, whereas the effect of contact time had more impact on HAA formation. Experiments with filling waters collected from WTP effluents at three different times showed more variability in HAA than THM formation at the WTPs studied.     

十六醇/十六酸/十二酸三元复合相变体系研究

采用步冷曲线法测定了不同质量比的十六醇(H)/十六酸(PA)二元体系的相变温度,绘制了该体系的t-x相图;在其最低共熔点附近引入十二酸(LA)组成三元体系,同样测定了该三元体系在不同质量比下的相变温度,得到了其t-x相图.采用差示扫描量热仪(DSC)和傅里叶变换红外光谱(FTIR)对上述二元和三元体系中低共熔物的热性能和稳定性进行表征.结果表明:不同质量比的H-PA二元体系均能形成共熔物,H与PA的质量比分别为6:4和7:3时引入LA的三元体系能形成最低共熔物;H,PA,LA这三者的质量分数之比分别为30:20:50和35:15:50的三元体系,其相变焓和相变温度分别为179.63,177.87 J/g及26.5,27.0℃,连续相变过程无分层现象,1200次热循环后热稳定性好.     

Determination of EDTA species in water by square-wave voltammetry using a chitosan-coated glassy carbon electrode

The electrochemical behavior of Fe(EDTA)(-/2-) on a chitosan-coated glassy carbon electrode (GCE) and the determining method of the EDTA species in water samples by square-wave voltammetry (SWV) have been investigated. Fe(EDTA)(-) can be adsorbed on the positively charged chitosan membrane assembled on a GCE and be reduced at a potential of -0.095V vs. Ag/AgCl. On the chitosan-coated GCE, the cathodic stripping peak current is proportional to the concentration of EDTA after the operating parameters of SWV were optimized. The measuring range of EDTA was from 2.0x10(-6) to 8.0x10(-5)mol/L with a correlation coefficient of r=0.998 and a detection limit of 2.0x10(-7)mol/L. The relative standard deviation was less than 6.4% (n=5) and the recovery was in the range of 98-105% for the determination of practical samples. The result was consistent with that from the HPLC method.     

Modeling dichloroacetic acid formation from the reaction of monochloramine with natural organic matter

A kinetic model was developed to predict dichloroacetic acid (DCAA) formation in chloraminated systems. Equations describing DCAA formation were incorporated into an established comprehensive monochloramine-natural organic matter (NOM) reaction model. DCAA formation was theorized to be proportional to the amount of NOM oxidized by monochloramine and described by a single dimensionless DCAA formation coefficient, theta(DCAA) (M(DCAA)/M(DOC(ox)). The applicability of the model to describe DCAA formation in the presence of six different NOM sources was evaluated. DCAA formation could be described by considering a single NOM source-specific value for theta(DCAA) over a wide range of experimental conditions (i.e., pH, NOM, free ammonia, and monochloramine concentrations). DCAA formation appears to be directly proportional to the amount of active chlorine (monochloramine and free chlorine) that reacted with the NOM under these experimental conditions. Values of theta(DCAA) for all six NOM sources, determined by nonlinear regression analysis, varied from 6.51 x 10(-3) to 1.15 x 10(-2) and were linearly correlated with specific ultraviolet absorbance at 280 nm (SUVA(280)). The ability to model monochloramine loss and DCAA formation in the presence of NOM provides insight into disinfection by-product (DBP) formation pathways under chloramination conditions. The subsequent model and correlations to SUVA has the potential to aid the water treatment industry as a tool in developing strategies that minimize DBP formation while maintaining the microbial integrity of the water distribution system.     

氟碳表面活性剂环境风险控制措施初探

统计分析了山西省大中型石油化工企业数量以及2007-2011年全省油类火灾发生的时间、地点,由此估算出泡沫灭火剂储备量及含氟碳表面活性剂(主要是C8类氟碳表面活性剂)的用量。从中分析氟碳表面活性剂排入大气中、直接进入土壤、直接流入河流和通过下水道进入污水处理厂对环境造成的污染风险。介绍国际发达国家相关处理措施,提出我国消防领域解决控制氟碳表面活性剂的建议:一是大力开发和选用环境友好型泡沫灭火剂,把对环境的影响降至最低;二是积极应对,加强管理,妥善回收处理消防灭火剂使用后的残液;三是鼓励污水处理厂开发能降解氟碳表面活性剂的处理工艺,最终达到降低此类风险对人类的危害;四是提出研制新型泡沫灭火剂的思路。     

两江重庆段沉积物中腐殖酸特性及其对荧蒽的吸附

从长江、嘉陵江(简称两江)重庆段的5个表层沉积物样品(JL1、JL2、YZ1、YZ2、YZ3)中提取腐殖酸,对其进行了化学组成分析和结构特性表征.结果表明,各样点的腐殖酸中元素含量比值(H/C值、O/C值、C/N值等)存在一定的差异.JL1、YZ3和YZ1样品中的腐殖酸具有较高的O/C值和H/C值,呈现明显的脂肪特性,而YZ2样品的芳香性特征相对明显;各样点腐殖酸的C/N值＞10,表明受藻类污染的潜势较低.傅里叶红外图谱结果表明,各样点腐殖酸的官能团结构组成相似度较高,均含有羧基、羟基、羰基等活性官能团,但官能团的含量存在差异.借助荧光光谱分析,进行腐殖酸对荧蒽的吸附特性试验以及吸附等温线修正Freundlich模型模拟,修正吸附系数(Kf')的大小顺序为:YZ2＞ JL2＞ YZ1＞YZ3＞ JL1,且吸附能力与腐殖酸的极性强弱、元素含量、活性官能团特征等具有一定的相关性;在连续多步解吸附试验中,相对于加标荧蒽的吸附量,各样点的解吸率为40.3％ ～74.8％.     

聚羧酸系高效减水剂酯化反应动力学的研究

研究了甲基聚氧化乙烯与丙烯酸在不同的催化剂的条件下的酯化反应,探讨了酯化的动力学,并建立了动力学方程。试验表明,最佳的酯化催化剂为对甲苯磺酸。