几种水泥基材料的渗透率及其超临界碳化的应用

孔隙度和渗透率是水泥基等多孔材料的重要指标,是水泥基材料内部离子迁移多物理场耦合预测模型中的关键材料参数。针对水泥基材料超亚临界碳化预测模型的质量控制方程,采用稳态法试验分析得到了液体渗透率、氮气渗透率、固有渗透率,采用体积法得到了材料孔隙度和含水饱和度,试件包括水泥砂浆、混凝土、水泥瓦、纤维水泥板等材料。其中水泥砂浆和混凝土材料固有渗透率分别为0.001mD和0.0001mD数量级,其他试件为0.01mD数量级;而混凝土的固有渗透率最低为9e-4mD。木纤维等纤维材料的掺加,将大幅增加材料的孔隙度和渗透率。最后使用得到的各项渗透率、孔隙度、含水饱和度,对水泥砂浆和水泥瓦的超亚临界碳化试验进行了多物理场耦合模拟,模拟结果与试验吻合较好。     

Properties and interfacial microstructure of cement-based materials with composite micro-grains

Silica fume, fly ash and nano-fiber mineral materials （NR powder） are employed to incorporate into cement-based materials. According to the grain grading mathematical model of cement-based materials, two packing systems, namely, spherical grading system and nano-fiber reinforced system were designed. Properties and interfacial microstructure of the two systems were studied according to secondary interface theory. It was shown that nano-fiber mineral materials can improve the grain grading of the admixture, increase the density of the system, improve the microstructure of the interface and the hardened paste, and enhance the uniformity of cement-based materials mixed with composite micro-grains and greatly increase their wearable rigidity and flexure strength. In this paper, two kinds of interface models, including spherical grain model and nano-fiber reinforced interface model of the cement-based materials mixed with composite micro-grains, were brought forward.     

Model of Coherent Interface Formation in Cement-Based Composites Containing Polyblend of Polyvinyl Alcohol and Methylcellulose

The texture of interfacial zone between cement paste and quartz in the cement-based composites containing polyvinyl alcohol (PVA) ,methylceUulose (MC) and their polyblend in an amount of 10 wt % with respect to cement, as well as the texture of dehydrated bodies of PVA , MC , and the polyblend solutions, were inves-tigated with SEM. The network texture of the dehydrated polyblend is confirmed by comparing the texture of dehy-drated bodies of PVA and MC. The network texture has restrained the movement of polyblend molecules in the ce-ment mortar but is helpful to forming a coherent interface between cement paste and quartz. The key factor of form-ing the coherent inteoCace is not the neutralization reaction between H ^ from hydrolysis of quartz and OH ^- from hydration of cement, but the electrostatic attraction and the chemical reaction between polar groups on the polyblend molecule and cations and anions from hydrolysis of quartz and hydration of cement, respectively. The model of the coherent interface formation is that excessive [ HSiO3 ]^ - and [ SiO3 ]^2- an/ons are bonded tgzh the hydrated cations such as Ca^2 and Al^3 , which is confumed by the gel containing Ca and Si on the quartz surface.     

Influence of fly ash fineness and shape on the porosity and permeability of blended cement pastes

The effects of the fineness and shape of fly ash on the porosity and air permeability of cement pastes were investigated. Pulverized coal combustion (PCC) fly ash and fluidized bed coal combustion (FBC) fly ash classified into three different finenesses were used. River sand with particle size distribution similar to that of fly ash was also used for comparison. Portland cement was replaced with fly ash and ground sand at the dosages of 0, 20wt%, and 40wt%. A water-to-binder ratio (w/b) of 0.35 was used thr...     

Effect of coal gangue with different kaolin contents on compressive strength and pore size of blended cement paste

The effects of activated coal gangue on compressive strength, porosity and pore size distribution of hardened cement pastes were investigated. Activated coal gangue with two different kaolin contents, one higher and one lower, were used to partially replace Portland cement at 0%, 10%, and 30% by weight. The water to binder ratio（w/b） of 0.5 was used for all the blended cement paste mixes. Experimental results indicate that the blended cement of activated coal gangue mortar with higher kaolin mineral content has a higher compressive strength than that with lower kaolin mineral content. The porosity and pore size of blended cement mortar were significantly affected by the replacement of activated coal gangue.     

石材废渣粉对纤维砂浆新拌性能控制因素的影响研究

掺入石材废渣粉可以改善纤维砂浆或纤维混凝土的力学性能,但同时显著降低其新拌性能.为探索掺入石材废渣粉置换等体积标准砂的聚丙烯纤维砂浆新拌性能的控制因素,测量了20组不同水灰比、不同石材废渣粉置换量下纤维砂浆的流速、扩展度、粘聚性、粘附性和填充密度,计算出平均液层厚度和平均泥浆层厚度.结果显示平均液层厚度和平均泥浆层厚度...     

石粉对水泥湿堆积密度和混凝土性能的影响

石灰岩机制砂的用量越来越大,相应地,它的副产物石灰岩石粉也越来越多。如果不能合理地将石粉加以利用,势必给环境造成很大的负担。以石粉做矿物掺合料取代水泥为研究目的,对比了在0%、10%、15%、20%时的比例等质量取代水泥,对混凝土工作性能、抗压强度和抗渗性能的影响,得出石粉取代水泥的比例为10%左右时,对混凝土的性能有较好的改善作用。通过测其石粉和水泥混合后的湿堆积密度,得出石粉的质量比为10%时,二者的密实度最大。表明石粉做掺合料时,可通过二者混合后密实度的变化来判断二者的最佳比例。     

石膏与硬石膏对蒸养水泥石结构和性能的影响

运用液相分离技术、化学分析、离子发射光谱、ＳＥＭ、ＤＳＣ和压汞测孔等手段,着重研究了石膏与硬石膏对蒸养水泥石结构和性能的影响。结果表明：加有硬石膏的水泥浆体或水泥石孔溶液中的ＳＯ２－４浓度任何时候都明显高于加入二水石膏的浆体;而ＯＨ－浓度在蒸养前硬石膏浆体较高,蒸养后则低于石膏浆体。在蒸养水泥中,以硬石膏代替二水石膏,可使钙矾石数量增加,结晶粗大,分布均匀,且大多远离固相表面;同时使Ｃ－Ｓ－Ｈ（ｇｅｌ）尺寸变小,水泥石的结构致密,总孔隙率和最可几孔径减小,强度大幅度提高。作者认为：控制水泥石结构形成的主要因素是水泥石液相中的ＳＯ２－４和ＯＨ－浓度,增加水泥石液相中ＳＯ２－４浓度,同时适当降低ＯＨ－浓度,可改善钙矾石形成条件和水泥石的结构,从而提高水泥石强度。     

传统无机材料的现状及新材料的发展趋势

介绍了我国传统无机非金属材料 (水泥、陶瓷、玻璃 )的现状和存在的问题 .指出了今后发展传统无机材料应走的道路 .阐述了高技术陶瓷———一种新型无机非金属材料的特点、作用及其应用领域 .论述了纳米材料的研究现状及其所取得的最新成果并对未来新材料的发展趋势作了展望 .     

非线性随机模型估计及应用

讨论了非线性随机模型估计的求解问题，分为方差σ^2已知和方差未知2种情况。方差σ^2已知的非线性随机模型估计适用于测量平差以及一切有规范规定的实验科学的数据处理；方差σ^2未知的非线性随机模型估计适用于没有规范的约束的社会统计学的统计推断。文中附有算例阐述具有同值子样由于σ2已知和未知的2种情况的数据处理结果。σ     

初始干密度对天然砂砾改良红粘土回弹模量的影响及预估模型

以掺天然砂砾改良的红粘土为研究对象,采用室内承载板法测定回弹模量,通过不同初始干密度下的回弹模量试验,深入研究了天然砂砾改良红粘土的回弹模量随初始干密度的变化规律,建立了不同初始干密度下回弹模量的预估模型。试验结果表明:在同一天然砂砾掺量下,随着初始干密度的提高,红粘土的回弹模量逐渐增大。当初始干密度由低向最大干密度增大时,回弹模量增长速度较快,当初始干密度超过最大干密度继续增大时,回弹模量增长速度变缓;在同一初始干密度下,当天然砂砾掺量从0增至30%时,回弹模量的增长幅度较小,当天然砂砾掺量超过30%而继续增长时,回弹模量增长幅度较大;初始干密度由1.6 g·cm^-3增长至2.0 g·cm^-3时,回弹模量增长值随天然砂砾掺量的增加而逐渐增大。分别建立了回弹模量随初始干密度及天然砂砾掺量变化的预估模型,通过补充试验,验证了预估模型的准确性。     

气动系统长气管建模与分析

由于气体的可压缩性,气压信号在长气管中的传递特性表现为非线性,这种非线性给系统设计和应用带来困难。从工程应用的角度出发,难过实验对气动系统中长气管的主要特征－气压信号的延迟进行了研究,根据长气管的物理特点建立了动力模型及数学模型,并对模型参数进行了辨识和分析,还根据流体力学的理论探讨了管内流体的状态,最后通过对数学模型的仿真和实验研究进行了比较,两者具有较好的一致性。     

基于Matlab平台实现二维复杂地质模型多边形网格建模及重力异常正演计算

对已知地质模型进行重力异常正演计算是利用重力场数据对地下介质的密度异常信息进行解释的重要手段。针对三维复杂地质体的建模困难且不便,而且多数三维线性地质体可以近似看作二维地质体以实现快速方便处理的情况,对二维地质体进行多边形网格建模,并利用Matlab平台编写了适用于复杂二维地质模型的重力异常计算的软件系统。该软件系统对模型设定简单、运算速度快。选择华北地区的剖面使用目前业内广为使用的IGMAS正演软件和文中的软件系统进行了对比试验,结果显示两种方法计算的重力异常结果相当。     

道路交通动态OD矩阵预测方法的研究

对现有的动态OD预测方法进行了研究比较,在此基础上提出了一种统计学方法采估算动态交通需求的参数.该方法是基于Bayesian定理的推论得到的,并运用了综合数据和经验数据.与诸如Kalman滤波法和最小二乘法等方法相比,该技术会使得OD分配比例的预测更加精确.如何将这些预测精确地转化为路段流量的预报则需要更进一步的研究.     

高密度聚乙烯过程动态建模与仿真的策略

介绍了高密度聚乙烯ＨＤＰＥ生产过程和用于过程动态模拟与仿真的数学模型的特点。针对ＨＤＰＥ过程,提出了机理＋经验＋神经网络技术的建模策略和方法。给出了数学模型的求解方法。实践证明,研究建立的模型可靠、精确和快速,能满足ＨＤＰＥ过程动态模拟与仿真的需要。     

集成双极晶体管基区表面电流的准二维模型及其参数的提取

考虑到少子准费米能级沿基区表面的非均匀分布,建立了集成双极晶体管基区表面电流的准二维模型。利用栅控晶体管作为测试结构,提取出了主要的基区表面参数。