纸面氟石膏空心隔墙板的研究

氟石膏是氟化物生产过程中的副产品,其水化缓慢、凝结能力差,且污染环境。通过实验研究,确定采用粉磨、煅烧及掺加外加剂等方法激发氟石膏水化活性,在此基础上经过一定的成型工艺,研制纸面氟石膏空心隔墙板,该墙板主要由氟石膏、玻璃纤维、外加剂、改性淀粉和护面纸等构成,开辟了氟石膏资源化的新途径。     

氟石膏的改性研究

利用正交设计确定改性氟石膏的最佳配比，实验结果证明，在氟石膏中掺入改性剂，凝结时间和强度指标可到建筑石膏一等品的技术要求，其后期强度不断增长，２８天强度大于４０ＭＰａ。改性氟石膏具有微膨胀性，膨胀率小、膨胀稳定期短，说明其长期安定性是良好的。通过ＤＴＡ和ＸＲＤ的分析，证明改性剂能够加速氟石膏的水化，主要水化产物是二水石膏及少量钙矾石，２８天龄期二水石膏含量大大增加，是原氟石膏的２－３倍。     

氟石膏抹面材料的应用研究

采用物理和化学改性方法对氟石膏进行有效激发,加快氟石膏的水化硬化进程;掺加保水剂、减水剂和防水剂,提高氟石膏抹面材料的综合性能,使其具有工程应用价值.     

氟石膏胶凝材料激发试验研究

添加适量激发剂可以缩短氟石膏胶凝材料凝结时间,较大幅度提高氟石膏水化率,加快氟石膏水化进程。SEM分析结果表明,激发剂可以改变氟石膏硬化体晶体形貌。在激发剂的作用下,氟石膏硬化体中有较多发育完全,以棒状、柱状为主的CaSO4.2H2O和CaSO4.1/2H2O生成。     

氟石膏粉煤灰混凝土的水化特性与抗压强度

用Ｘ射线衍射分析（ＸＲＤ）、扫描电镜与能谱（ＳＥＭ－ＥＤＳ）和压汞法观察了氟石膏粉煤灰胶结材的水化产物和硬化浆体结构，并用这种胶凝材料配制出长期强度高的混凝土。氟石膏粉煤灰胶结材的水化产物为二水石膏、ＣＳＨ凝胶及钙矾石。微晶状的二水石膏和钙矾石与ＣＳＨ凝胶均匀混合，形成致密的硬化浆本结构，使胶结材获得优良的力学性能。     

用工业氟石膏做水泥缓凝剂的试验研究

本文通过总结对工业氮石膏的化学分析与做水泥缓凝剂的实际情况，提供了工业氟石膏的化学万分，相组成及制成水泥的物理力学性能，证明了工业氟石膏做水泥缓凝剂切实可行。     

激发剂对氟石膏适应性的研究

氟石膏在自然环境中水化进程缓慢,历时2年结晶水含量为17.25％,水化率为82％.KAl (SO4)2·12H2O和K2S(4能加快氟石膏的水化进程,随添加量增加和水化时间延长,试样的水化率均出现不同程度增大.早强快硬硫铝酸盐水泥能有效提高氟石膏基材料的绝干抗压强度,随着水泥掺量增加,绝干抗压强度增大:当掺量为20％时,绝干抗压强度为14.5 MPa; KAl (SO4)2·12H2O对氟石膏基材料有良好的适应性,当掺2.78％KAl (SO4)2·12H2O和20％硫铝酸盐水泥时,其绝干抗压强度为22.4 MPa.     

建筑抹面用氟石膏的激发效果研究

采用粉磨处理作为物理改性方法,研究了不同粉磨时间对氟石膏粒度和标准稠度用水量的影响。选取煅烧明矾、硫酸钾和草酸钠作为氟石膏的化学激发剂,分别研究了其对氟石膏水化进程、强度以及硬化体微观形貌的影响,并分析了强度与硬化体微观结构的内在联系。结果表明:粉磨处理30min时,氟石膏过80目标准筛筛余量为6.8%,标准稠度用水量达到最小值30%;掺加煅烧明矾、硫酸钾和草酸钠可不同程度地加快氟石膏的水化进程,其适宜掺量分别确定为0.6%～0.8%、0.4%和0.8%;在适宜掺量下,三种激发剂提高氟石膏强度的大小顺序为:煅烧明矾>硫酸钠>草酸钠;与空白试样相比,掺加激发剂的氟石膏硬化体晶体长径比明显增大。     

氟石膏在水泥生产中的应用

氟石膏是化工行业排放的工业废料,开发利用氟石膏代替天然石膏作水泥缓凝剂,既可节约天然石膏资源和降低水泥成本,又可综合利用工业废渣,解决堆放氟石膏造成的生态环境污染问题。江都未来水泥有限责任公司在氟石膏的使用上做了大量的试验,并成功地投入生产,取得了     

氟石膏的应用现状与分析

阐述了石膏的组成,介绍了两种处理氟石膏呈酸性的方法,着重讨论了国内氟石膏的研究情况,提出了氟石膏的特点,指出氟石膏中有毒氟化物含量极低,对人体危害很小,且利用氟石膏废渣生产建筑材料是安全可行的。     

氟石膏基自流平地面材料的研制

以化工生产排出的氟石膏废渣为主要原料,通过掺加激发剂、减水剂、保水剂、掺合料、骨料等进行改性处理,研制成功了一种流动性好、平整度高、凝结快速、强度高、耐水性好的自流平地面材料,变废为宝,不仅环境效益和经济效益显著,而且为氟石膏废渣的资源化利用开辟了一条新途径。     

F－型粉刷石膏及其在工程中的应用

本文介绍了氟石膏材料的化学组成、放射性水平及外加剂对其强度的影响。并对制得的Ｆ型粉刷石膏的凝结时间、耐水、耐热强度，抗裂、抗冻、低温硬化及与基面的粘结性能进行了分析；为降低成本，探讨了掺合料、骨料对产品性能的影响。文中介绍了Ｆ型粉刷石膏的应用情况     

钢渣-矿渣-氟石膏基胶结材固结铜尾矿性能

水泥作为传统尾矿固结材料造成尾矿充填成本居高不下,而钢渣和氟石膏等工业废渣利用率不高,因此采用其制备钢渣矿渣氟石膏基胶结材来替代水泥,需要对其固结尾矿性能进行研究。通过对不同时间尾矿固结浆体的泌水量及流动度、不同水化龄期抗压强度变化趋势研究,发现钢渣矿渣氟石膏基明显优于P·O 42.5级水泥和中国2种常用尾矿固结剂,其尾矿固结体浸出液3d后的PH值均在9.0以下,远低于这3种高碱性尾矿固结材料,浸出液氟离子浓度极低,对环境影响小。SEM分析也显示掺钢渣矿渣氟石膏基胶结材的尾矿固结体具有较为密实的微观结构。     

A computational study on effects of fire location on smoke movement in a road tunnel

In this work, a numerical model of tunnel fire is developed and aimed to investigate the influence of cross-sectional fire locations on critical velocity and smoke flow characteristic. It is shown that the critical velocity for a fire next to the wall is obviously higher than that for a fire in the middle or on the left/right lane. The ratio is estimated to be 1.12. The predictions of critical velocity from ‘small-fire’ models show a good agreement with that for a fire in the middle or on the left/right lane from CFD. The tunnel height at the fire location is proposed to be instead of the hydraulic tunnel height in the ‘big-fire’ model of Wu and Bakar for a fire next to the wall. The smoke moves backward in a tongue like form as the ventilation velocity is lower than the critical velocity. The back-layering length of a fire in the middle is shown to be approximate twice than that on the left/right lane under the same ventilation velocity, although they share the same critical velocity. Whereas a relatively short back-layering length for a fire next to the wall under the velocity of 2.6 and 2.7 m/s. In addition, a snaky high-temperature profile on the top wall at the initial downstream is observed for a fire on the left lane and next to the wall, and finally a steady and layered smoke flow. The likely cause of this phenomenon is subsequently explained in this study.     

Ventilation performance prediction for buildings: Model assessment

Designing ventilation systems for buildings requires a suitable tool to assess the system performance. This investigation assessed seven types of models (analytical, empirical, small-scale experimental, full-scale experimental, multizone network, zonal, and CFD) for predicting ventilation performance in buildings, which can be different in details according to the model type. The analytical model can give an overall assessment of a ventilation system if the flow could be approximated to obtain an analytical solution. The empirical model is similar to the analytical model in terms of its capacities but is developed with a database. The small-scale model can be useful to examine complex ventilation problems if flow similarity can be maintained between the scaled model and reality. The full-scale model is the most reliable in predicting ventilation performance, but is expensive and time consuming. The multizone model is a useful tool for ventilation design in a whole building, but cannot provide detailed flow information in a room. The zonal model can be useful when a user has prior knowledge of the flow in a room. The CFD model provides the most detailed information about ventilation performance and is the most sophisticated. However, the model needs to be validated by corresponding experimental data and the user should have solid knowledge of fluid mechanics and numerical technique. Thus, the choice for an appropriate model is problem-dependent.     

Fitness-oriented multi-objective optimisation for infrastructures rehabilitations

A new multi-objective decision support system (MODSS) is developed for rehabilitation planning of public infrastructures. The method is generic and provides decision-makers a set of optimal rehabilitation tradeoffs over a desired analysis period. Two main objective functions are handled simultaneously, namely cost and performance, in addition to a set of bounding constraints. The method is based on a new fitness-oriented technique where problem knowledge is taken into account. In order to analyse cost and performance together, a normalisation technique of both objectives is achieved through an innovative time-value concept for both cost and condition states. The proposed method is based on life-cycle costing (LCC) methodology using a dynamic Markov chain to represent the deterioration mechanism and genetic algorithm is used to find the optimal rehabilitation profile. A case study is presented with a comparison between the traditional Markov decision process (MDP) and the newly developed method. The MODSS results in a lower LCC and is found practical in providing a complete maintenance and rehabilitation plan over a required study period. It is proven that the developed multi-objective optimisation is an effective tool in analysing real-life situations involving conflicting goals. Also, weighted sum method could be easily implemented and its outcome is sufficient given that many external factors might alter the decision-makers choice irrespectively of the optimisation method that is used. Furthermore, genetic algorithm is proven useful in the optimisation process in overcoming the computational difficulties associated with large combinatorial problems. The new method is beneficial to researchers and practitioners as it provides a major step towards a broad infrastructure management system.     

Application of model based predictive control for water-based floor heating in low energy residential buildings

A model based predictive control method is applied in order to determine the optimal supply fluid temperature in the case of concrete embedded water-based floor heating in low energy residential buildings. The aim of the control is to keep the indoor temperature within a defined comfort interval. The forthcoming supply fluid temperature is obtained through a numerical optimisation based on a prediction of the upcoming heat demand. The elementary response function, which is the basis for the method, is obtained from a numerical control volume model, and as an alternative, from a simplified 2-node lumped model. The accuracy of the results obtained from the simplified model is surprisingly good in comparison to the detailed numerical model. The control method is applied for a single room for which a perfect prognosis of the heat demand exists. The results show a fairly steady optimised supply fluid temperature.     

混凝土斜拉桥施工控制中的优化问题研究

在混凝土斜拉桥施工控制中,结构体系不断变化,求解规模大,影响因素多,使得计算模型复杂。针对该问题,建立多目标、多约束的优化模型,并在目标函数中,增加了决策者的期望值,构造新的评价函数,利用凝聚函数优化方法求解该问题。传统的优化算法通过降维或者构造评价函数,减少目标函数个数,仍在原有约束条件下进行求解,凝聚函数法通过同时对多个目标和多个约束条件进行凝聚,将多目标、多约束问题转化为单目标、单约束优化问题,减小解题规模,该优化方法是对传统计算方法的补充,最后阐述了该方法在实际工程中的应用。     

A Theoretical Model of Major Fire Spread in a Tunnel

A model of major fire spread in a tunnel is described. It employs the concepts of non-linear dynamical systems theory and identifies the onset of instability with major fire spread in a tunnel. In particular, the model associates the existence of a fold bifurcation with dramatic fire spread from an initial fire to a ‘target object’. The purpose is to identify the thermo-physical and geometrical conditions which lead to instability and sudden fire spread. Flame impingement on the target object is assumed not to exist; fire spread is assumed to be by spontaneous ignition only. The case considered assumes the existence of a longitudinal forced ventilation and predicts the critical heat release rate needed for a fire to spread from an initial fire to an item with a given assumed shape. The target object may be taken to approximate a vehicle. The illustrative case approximating fire spread from an initial fire to a heavy goods vehicle (HGV) within the Channel Tunnel is presented; it is not restricted to this case, however. The model is identified with the name FIRE-SPRINT A3, which is an acronym of Fire Spread in Tunnels, Model A, Version 3. It is a development of an earlier model, FIRE-SPRINT A2. The current model takes greater account of thermal radiation than was done in the earlier work and also assumes a more extensive flame volume for a downstream flame section.