纳米TiO2分散性对水泥水化和性能的影响

采用磁力搅拌+超声波分散+聚羧酸高效减水剂方法来提高纳米TiO₂（NT）在水泥净浆中的分散性与稳定性,研究了不同掺量NT对水泥净浆力学性能的影响,通过水化热、热重-差示扫描量热（TG-DSC）分析、压汞（MIP）等测试方法,研究NT对水泥水化性能的影响机理.结果表明：采取磁力搅拌20 min、超声波分散15 min、再磁力搅拌15 min,并辅以聚羧酸高效减水剂,可制得分散稳定的NT悬浮液;当NT掺量为2.0%时,水泥净浆的抗压强度最大,且在相同掺量下,使用悬浮液法制备的水泥净浆力学性能高于干混法;NT可显著缩短水泥水化的诱导期,提高水泥早期水化放热速率,改变CH的结晶度及取向,并优化硬化水泥净浆内部的孔隙结构,提高其力学性能.     

碱镍渣混凝土的制备及性能研究

以碱镍渣混凝土材料为研究对象,研究了碱镍渣混凝土的坍落度和强度,结合场发射扫描电镜(SEM-EDS)和压汞仪微观测试仪器,分析了碱镍渣水泥水化产物的形貌和孔结构。研究结果表明,碱镍渣混凝土的抗压强度发展规律与普通混凝土相似;碱镍渣水泥的主要水化产物是水化硅酸钙(C-S-H)和方解石;随着养护龄期的延长,孔结构被方解石填充,提高了密实度,有助于强度的提高。     

纳米SiO2与VAE复合改性水泥基材料的耐久性能

研究了单掺乙烯-醋酸乙烯酯共聚乳胶粉（VAE）和复掺VAE/纳米SiO₂（NS）对水泥基材料抗氯离子渗透性能、抗硫酸盐侵蚀性能和吸水率的影响,并通过X射线衍射仪、热分析仪、扫描电子显微镜、压汞仪和红外光谱仪等探究了其作用机理.结果表明：单掺VAE和复掺VAE/NS均可提高材料的抗氯离子渗透性能以及抗硫酸盐侵蚀性能,降低其总吸水率,且复掺效果优于单掺;单掺VAE可以改善材料的水化特性,有害孔和多害孔减少了65.3%,但增大了最可几孔径和界面过渡区的钙硅比;复掺VAE/NS可进一步改善材料的水化特性,有害孔和多害孔减少了82.6%,提高了水化硅酸钙（C-S-H）的生成量和聚合度,增强了材料的耐久性能.     

自然通风下教室CO2体积分数的实测与模拟

将某高校教室作为研究对象,实测过渡期室内CO₂体积分数随时间的变化。采用Airpak软件,模拟过渡期自然通风条件下（课间门窗开启）室内空气温度、CO₂体积分数的分布。由实测结果可知：室内CO₂体积分数大多数时间均超过1 000×10^-6,CO₂体积分数上升速率与人员密度成正相关。由模拟结果可知：1.1 m高度截面的温度,随门窗开启时间的延长而下降。教室前后部室内温度的下降速率明显高于人员密集区域。1.1 m高度截面的CO₂体积分数,随门窗开启时间的延长而下降。门窗开启10 min时,教室平均CO₂体积分数为1 073×10^-6。自然通风可有效降低室内CO₂体积分数。     

粉煤灰和炉渣对碱激发镍渣胶凝材料流动度和强度的影响

在NaOH及水玻璃(WG)两种碱激发剂下,研究了粉煤灰及炉渣对碱激发镍渣-粉煤灰-炉渣胶凝材料(ANC-FI)流动度及强度的影响,并通过XRD和IR揭示其机理。结果表明,当粉煤灰及炉渣总掺量为30%(等质量取代镍渣)时,随着炉渣掺量的增加(即粉煤灰掺量降低),ANC-FI的标准稠度用水量增加,凝结时间延长,砂浆流动度降低;ANC-FI抗折强度和抗压强度均随着炉渣掺量的增加呈先增大后减小的趋势,最佳掺量为粉煤灰和炉渣各取代15%的镍渣。     

激发剂对粉煤灰混凝土的碳化及钢筋锈蚀性能影响

本文对掺激发剂的粉煤灰混凝土进行了抗碳化性能研究,分析了CO2浓度对碳化性能的影响。同时利用GECOR6型钢筋锈蚀率测定仪对其钢筋锈蚀性能进行了电化学研究。结果表明,掺激发剂的粉煤灰混凝土具有良好的抗碳化和抗钢筋锈蚀性能,并且CO2浓度对粉煤灰混凝土碳化影响较大。     

CO2 加氢合成甲醇催化剂的研究进展

CO_2加氢合成甲醇的运用是在现代社会中对CO_2循环利用的重要方式之一。也同样是对环境保护的重要要求。无论是在CO_2的合成反映之中,还是在新型的催化剂的研制过程之中。在环境保护的过程之中,全球变暖的问题的存在,是急需面对的一个重要问题。所以,对CO_2加氢合成甲醇催化剂的研究非常重要。     

等强度条件下碱激发高炉镍渣混凝土与普通硅酸盐水泥混凝土的性能对比

分别以NaOH和水玻璃为激发剂,制备了碱激发高炉镍渣混凝土,在碱激发高炉镍渣混凝土的7 d抗压强度与普通硅酸盐水泥混凝土的28 d抗压强度基本相等的条件下,对比了碱激发高炉镍渣混凝土和普通硅酸盐水泥混凝土的后期（90 d）力学性能、孔结构发展规律和抗氯离子渗透性能的差异。结果表明：碱激发高炉镍渣混凝土的早期（7 d前）强度发展迅速,其中,NaOH激发高炉镍渣混凝土28 d后的强度发展相对缓慢;等强度条件下,碱激发高炉镍渣混凝土的后期抗压强度和劈裂抗拉强度、孔结构和抗氯离子渗透性能均优于普通硅酸盐水泥混凝土,其中,水玻璃激发高炉镍渣混凝土的各项性能最好。     

纳米SiO2和PVA纤维增强水泥基复合材料的断裂性能

通过18组共90根纳米SiO2和聚乙烯醇(PVA)纤维增强水泥基复合材料预制切口小梁试件的三点弯曲断裂试验,以起裂断裂韧度和断裂能作为评价指标,探讨了纳米SiO2掺量、PVA纤维体积分数及石英砂粒径对水泥基复合材料断裂性能的影响.结果 表明:适量的纳米SiO2和PVA纤维可显著改善试件的断裂性能,在未掺纳米SiO2或纳米SiO2掺量为2.0％条件下,随着PVA纤维体积分数的增加,试件的起裂断裂韧度和断裂能均呈现先增后减趋势,且均在PVA纤维体积分数为1.2％时达到最大值.当纳米SiO2掺量小于1.5％时,试件的断裂性能随着纳米SiO2掺量的增加而提高;当纳米SiO2掺量大于1.5％时,纳米SiO2的掺入对试件的断裂性能有不利影响;随着石英砂粒径的减小,试件的断裂性能逐渐降低.     

激发作用下锰矿渣掺合料对混凝土性能的影响

以锰矿渣为掺合料替代30%水泥配制混凝土,并与基准混凝土和掺加矿渣微粉的混凝土进行了性能对比.试验结果表明,锰矿渣可以改善混凝土的工作性能;锰矿渣混凝土的早期抗压、抗折强度较低,但后期强度发展较明显;锰矿渣混凝土的抗冻、抗渗、收缩等长期耐久性能较基准混凝土稍差.加入某激发剂(代号JS)后的锰矿渣混凝土早期抗压强度和抗折强度接近基准混凝土,且可使锰矿渣混凝土的抗冻、抗渗、收缩等长期耐久性能大大提升(略好于基准混凝土).     

碳化对碱矿渣水泥石干燥收缩的影响

为研究碳化行为对碱性胶凝材料干燥收缩的影响,以水玻璃或NaOH为碱组分,制备Φ27.5×50mm碱矿渣水泥石试件,并测量Φ27.5×1mm水泥石薄片在干缩条件与碳化条件下的直径变化率,以表征碱矿渣水泥石的干燥收缩与碳化收缩.结果表明:在(20±1)℃,相对湿度(70±5)%的条件下,以NaOH为碱组分的碱矿渣水泥石干燥收缩大于以水玻璃为碱组分的碱矿渣水泥石干燥收缩;碳化使硅酸盐水泥石的收缩增加,但未增加碱矿渣水泥石的收缩;碱当量适当提高有利于减小碱矿渣水泥石的干燥收缩与碳化收缩;以模数为1.2~1.5的水玻璃配制的碱矿渣水泥石干燥收缩与碳化收缩较小.     

碳化对碱矿渣水泥浆体微观结构的影响

针对碱-矿渣水泥水化产物中不存在Ca(OH2)且碳化比较严重的现象,选择水玻璃作为碱组分,采用X-射线衍射(XRD)和可变真空扫描电子电镜(SEM)研究了碱-矿渣水泥浆体的碳化产物和微观形貌,结合氮吸附方法分析了碳化对碱-矿渣水泥浆体孔结构的影响.结果表明:碱-矿渣水泥浆体碳化导致的孔隙溶液Ca2+浓度降低由水化硅酸钙(C-S-H)凝胶脱钙补偿,碳化生成的碳酸钙主要以方解石的形式存在;碳化后,C-S-H凝胶的钙硅比降低,浆体的比表面积增大,平均孔径降低,而累积孔体积的变化与水玻璃的模数有关.     

3%与20% CO2体积分数下混凝土加速碳化试验研究

选取CO2体积分数为3%和20%进行加速碳化试验,比较分析了2种情况下单掺粉煤灰、矿粉混凝土及二者复掺混凝土碳化深度及碳化速率系数随碳化龄期的变化规律.结果表明:在3%CO2体积分数下进行加速碳化试验,不但能较好地反映普通混凝土的自然碳化规律,而且能对水胶比相同矿物掺合料不同的混凝土碳化性能进行有效区分,但试验时需要适当延长碳化龄期;采用20%CO2体积分数进行加速碳化试验,并不能有效区分水胶比相同矿物掺合料不同的混凝土的碳化性能.     

碳化对碱矿渣水泥石孔结构的影响

以水玻璃(WG)和氢氧化钠(NH)为碱组分配制碱矿渣水泥石（AASS）,采用氮吸附方法分析了这两种碱矿渣水泥石碳化前后的孔结构,并与硅酸盐水泥石（PC）作对比.结果表明：碳化前,以水玻璃为碱组分的矿渣水泥石比表面积最大,平均孔径最小,累积孔体积最大,最可几孔径最小;以氢氧化钠为碱组分的碱矿渣水泥石比表面积最小,平均孔径最大,累积孔体积最小,最可几孔径最大;而硅酸盐水泥石的比表面积、平均孔径、累积孔体积及最可几孔径均介于上述两者之间.碳化后,上述3种水泥石平均孔径、最可几孔径均减小;碱矿渣水泥石比表面积增大,硅酸盐水泥石比表面积减小.     

Effect of green roof on ambient CO2 concentration

Plants can improve air quality by removing pollutants. The air purification capability of plants has been receiving increasing attention because of the rapid deterioration of the environment. However, research on evaluating quantitatively the effect of plants on the environmental pollutant concentrations is still scarce. This paper studies the effect of a green roof on the ambient CO₂ concentration as an example to assess the benefit of urban greening. The study comprises three parts: (1) Field measurement of the difference of CO₂ concentration at a location in the middle of the plants in a small plot of green roof and one in the surrounding area, (2) Experiments to measure the plant’s CO₂ absorption velocity and emission rate using a sealed glass chamber; and (3) Computer simulation of the CO₂ concentration distribution around a green roof using the measured CO₂ absorption velocity and emission rate to quantify the effects of the green roof on the ambient CO₂ concentration.     

氯化钡对高延性碱矿渣复合材料力学性能的影响

通过开展单轴拉伸与抗压力学性能试验,系统探究了BaCl₂对高延性碱矿渣复合材料（HDASC）力学性能的影响.结果表明：当BaCl₂掺量为3.0%时,HDASC的凝结时间延长至109 min;HDASC的初裂强度、抗拉强度及抗压强度随着BaCl₂掺量的增加逐渐降低,尤其是BaCl₂掺量为3.0%时,HDASC强度的下降率高达50.0%,但其拉伸应变基本维持在6.24%~9.66%的高延性区间;BaCl₂的掺入使得HDASC的水化程度逐渐降低、孔隙数目增多,降低了基体的密实度,削弱了纤维与基体的黏结.     

Driving CO2 reduction by Integrating Transport and Urban Design strategies

Can the climate problem be framed as an urban development and transport problem where CO₂ reduction is understood as a co-benefit of good development and transport?The third largest source of greenhouse emissions in Australia is transport, and road transport accounts for 88% of transport emissions. A move towards sustainable urbanism, matched with the use of sustainable technologies (vehicle and fuels), is critical to arrest the increased dependence on fossil fuels and the escalating air-pollution at both the local and global scales. An approach towards sustainable urbanism, besides requiring a strong emphasis on land use and transport integration, demands the attainment of a certain level of urbanity through place-making. The DDD of sustainable urbanism (density, diversity, and design) forwarded by Cervero, when combined with Schipper’s ASIF identity to estimate the components of travel that yield emissions (Schipper, Marie,& Gorham, 2000) and the more recent ASIF2 paradigm (avoid, shift, improve and finance) (Dalkmann & Brannigan, 2007) to address changes in these components that reduce emissions, provide a coherent framework for the development of a sustainable green town: Bentley Technology Precinct, located in the car-oriented city of Perth. The success of the outcome is measured by undertaking an audit for place-making, VKT and CO₂ reductions. Findings are presented from the Master Class on ‘Cities - Green or Red? Transport and Urban Design in the context of climate change’, held at Perth in August 2009.     

CO2 transport by urban plumes in the upper Spanish plateau

CO₂ transport from two cities, Valladolid, over 20 km away and Palencia, over 40 km away from a rural site is analysed through three years of detrended CO₂ concentrations obtained near the surface. Meteorological data were obtained from a RASS sodar. Directional analysis by histogram of concentrations above the 95th percentile revealed three differing sectors, one associated to a rural origin and two linked to both cities. Modes indicated anticyclonic turning during plume travel, confirmed by the daily evolution of the wind direction. At night, the Valladolid concentration median was 6 ppm above the Palencia median, which was 2 ppm higher than the rural sector median. Monthly evolution of daily maxima evidenced the Valladolid plume influence in spring and September, whereas the Palencia plume was noticeable in October and November. Skewness analysis showed almost symmetric distributions in the Valladolid plume and right skewed distributions in the Palencia and rural sectors. This result was attributed to the different mixing of both plumes. Vertical gradients of wind speed, direction and potential temperature were also calculated, and evidenced a stratified structure of the lower atmosphere at night and an almost uniform layer during the day. Finally, the median gradient Richardson number showed the highest values, occasionally above 0.8 for the Valladolid sector, implying lower mixing with the environment in the Valladolid plume than in the Palencia plume.     

Capture of CO2 from flue gas via multiwalled carbon nanotubes

Carbon nanotubes (CNTs) were modified by 3-aminopropyl-triethoxysilane (APTS) solution and were tested for its CO₂ adsorption potential at multiple temperatures (20-100 °C). The physicochemical properties of CNTs were changed after the modification, which makes CNTs adsorb more CO₂ gases. The adsorption capacities of CO₂ via CNTs and CNTs(APTS) decreased with temperature indicating the exothermic nature of adsorption process and increased with water content in air at 0-7%. The mechanism of CO₂ adsorption on CNTs and CNTs(APTS) appears mainly attributable to physical force regardless of temperature change, which makes regeneration of spent CNTs at a relatively low temperature become feasible. The CNTs(APTS) have good adsorption performance of CO₂ at 20 °C as compared to many types of modified carbon or silica adsorbents documented in the literature. This suggests that the CNTs(APTS) are promising low-temperature adsorbents for CO₂ capture from flue gas.