Properties and microstructures of full graded concrete containing varied impurity aggregate

We investigated mechanical properties of concretes made with impurity aggregates of different combinations. Besides the mechanisms were explored by EDS, CT, and hardness testing. The results showed that fully rust-stained and surface rust-stained sandstone aggregate had significant adverse impact on the compressive strength of concrete while sandstone aggregate had a much more obvious impact on the ultimate tension of concrete. Concrete crack was more prone to expand along surfaces and the micro-hardness of interfacial transition zone of different aggregates was ranked in decreasing trend as sandstone, slate, SR sandstone, marble, and FR sandstone. The cluster growth of long needle-like ettringite crystal and strong preferential growth trend of Ca(OH)₂ crystals would result in wider interfacial transition zone range of concretes made with fully rust-stained sandstone and marble aggregate, respectively. Therefore, the impurity aggregate content should be strictly controlled during aggregate selection.     

Effect of Al in slag blended cement paste under sulfate attack

Unilateral sulfate attack of cementitious materials containing 40% slag with different water to binder ratios was investigated. The results showed that the degradation of slag blended cement pastes was nearly from the corners of paste surface with cracking and spallings, water-to-binder(w/b) ratio made a significant sense to the damage that low w/b ratio led to little weight loss, less cracking and spalling damage and vice versa. Microstructural experimental results demonstrated that in the three different stages of sulfate attack, degradation of pastes was primarily associated with the migration behavior and bonding configuration of aluminum, in the early ages Al was mostly present in C-(A)-S-H, and thus, the damage of pastes hardly appeared while at later ones Al had been largely transferred from C-(A)-S-H into AFt, leading to expansive damage.     

变形翼微系统阵列的协调跟踪控制研究

研究了变形翼的微系统阵列的协调跟踪控制问题.为了增强微系统阵列的协调运动能力,设计了虚拟模型跟踪控制方法.针对在外部干扰作用下的微系统阵列,研究了分布式鲁棒跟踪控制律设计方法,得到线性矩阵不等式形式的控制律参数求解条件,解算方便.理论分析与仿真结果表明:所设计的控制律能够在有外部干扰的情况下,使系统渐近跟踪期望的形状,并具有协调控制能力,使变形翼在跟踪控制的过程中保持形状平滑.     

水泥基材料电特性的研究进展

水泥基材料的电特性与材料的结构和性能密切相关．回顾了水泥基材料电特性的研究历史，介绍了国内外水泥基材料电特性的研究方法及进展，并指出了当前水泥基材料电特性研究的特点和急需解决的问题．     

耐磨蚀混凝土修补材料与施工工艺

本文结合工程实际研制的耐磨蚀混凝土修补材料，具有良好的强度、变形及耐磨蚀性能，同时提出了提高新老混凝土界面粘结强度的施工方法。在增强耐磨机制中，强调控制水泥基材料水化产物水稳定性是保证混凝土具有较高耐磨蚀能力的有效途径的观点，为比较和选择耐磨蚀修补材料提供了又一个依据。     

掺延迟性补偿收缩剂混凝土的特性研究

白云岩经适当温度煅烧并加入辅助剂后，得到由早期补偿收缩组分LE(Lime，Early)和后期补偿收缩组分ML(Magnesia，Later)组成的复合型补偿收缩剂NF-M。通过对砂浆强度、自由收缩变形和混凝土在不同养护条件下自身体积变形的测试，综合评价了MgO与NF-M补偿收缩剂的性能。结果表明，掺NF-M砂浆和混凝土的早期补偿收缩率较大，且具有优异的后期补偿收缩能力，而其力学性能降低并不明显，可以有效的提高混凝土的抗裂能力。同时还对NF-M的煅烧温度、细度和掺或不掺粉煤灰对NF-M补偿收缩性能的影响进行了初步的探讨。     

相转变材料用于混凝土温度自控的探讨

介绍了相转变材料PCM的类型及其热能贮存和温度控制的特点；说明了混凝土温度自动控制的必要性和可行性；分析了PCM应用于混凝土温度自动控制的可行性及PCM的选择，并展望了其发展前景。     

面板混凝土补偿收缩与纤维增强的阻裂试验研究

本文采用在混凝土中掺入补偿收缩剂和有机纤维复合改性的方式,通过试验得到改性后面板混凝土的力学强度、干缩变形以及自身体积变形性能等;结果表明,纤维和补偿收缩剂复合改性技术可以显著地降低混凝土的收缩变形,提高抗裂性能.     

Characterization of pozzolanic reaction and its effect on the C-S-H Gel in fly Ash-cement paste

High resolution solid-state ²⁹Si MAS NMR, combined with XRD, SEM and FTIR were used to characterize the pozzolanic activity of FA, type of main pozzolanic reaction products, and the effect of pozzolanic reaction on the C-S-H microstructure in fly ash-cement (FC) paste. The experimental results indicate that in the hydrated FC paste with 30% dosage of FA at 3 d, FA partially participated in the pozzolanic reaction, while, at 120 d, FA largely reacts. During the hydration of FC paste at laboratory temperature, the pozzolanic reaction products are C-S-H gel rather than zeolitic gel. Moreover, after the covalent bonds of Si-O-Si, Si-O-Al and Al-O-Al in the structure of FA are broken, monosilicates Si-OH and Al-OH groups form, these chemical species can connect C-S-H dimers, thus producing more Al-free C-S-H and aluminous C-S-H than in the plain cement paste. The increased content of Al for Si substitution in the bridging tetrahedra of C-S-H may decrease the stability of C-S-H, which results in a rather obvious loss in the mechanical strength of hardened FC paste.