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71.
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. 相似文献
72.
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. 相似文献
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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。 相似文献
76.
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。 相似文献
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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. 相似文献
80.
研制了基于局域共振的阻尼材料和纳米涂料两款减振降噪材料,实测结果表明,与常规的减振降噪材料相比,在变电站的噪声频段这两款材料具有良好的降噪特性,可尝试在变电站项目中开展工程应用。 相似文献