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21.
The polymer-cement composite is an immiscible band having modified morphology. Polymer phase improves the toughness of brittle cement and has a reinforcing effect, and interactions between cement components and polymers provide stability. In this study, polymer latex [poly(methyl methacrylate), PMMA] – cement paste was prepared with different weight proportions of polymer content. The main scientific objective of this report has been the analysis and the prediction of high strength with the aim of understanding the interactions of PMMA polymer with Portland cement after hydration reaction of cement pastes and curing the specimens for 28 days. The samples were studied by Fourier transform infrared (FT-IR) spectroscopy. The results are critically examined. It is shown that bands support the interaction of PMMA with cement in the composite. 相似文献
22.
Qianping Ran Ponisseril Somasundaran Changwen Miao Jiaping Liu Shishan Wu Jian Shen 《Journal of Dispersion Science and Technology》2013,34(6):790-798
Comb polymers are commonly used as dispersants to stabilize highly concentrated cement suspensions. The effectiveness of such polymeric additives to stabilize these suspensions is determined to a large extent by the amount adsorbed. In this study we investigated the adsorption characteristics of various comb dispersant containing different graft densities on surfaces of cement particle. The effect of inorganic salts on their adsorption was also examined in order to elucidate their adsorption mechanism. The results show that the adsorption of comb polymer dispersants on cement surface conforms approximately to Langmuir's adsorption isotherm and the characteristic plateau A s and adsorption free energy ΔGads are largely dependent on the anionic group content of the comb polymers. The A s and ΔGads increase with increasing anionic group content. This information suggests that the adsorption of comb polymers on cement surfaces is dominated by electrostatic interaction between COO-groups on the comb polymers and the positive surface of the cement. This conclusion is supported by effects of inorganics such as calcium and sulfate ions, and diffuse reflectance FTIR spectroscopy. The implication of results for tuning polymers for the required performance in cement manufacture should be noted. 相似文献
23.
Yingyot Poo‐arporn Surachai Thachepan Rungtiva Palangsuntikul 《Journal of synchrotron radiation》2015,22(1):86-90
Evidence of internal sulfate attack in field exposure was demonstrated by the damaged interior wall of a three‐year‐old house situated in Nakhon Ratchasima Province, Thailand. Partial distension of the mortar was clearly observed together with an expansion of a black substance. Removal of the black substance revealed a dense black layer. This layer was only found in the vicinity of the damaged area, suggesting that this black material is possibly involved in the wall cracking. By employing synchrotron‐based X‐ray photoelectron spectroscopy (XPS) and X‐ray absorption near‐edge structure (XANES) techniques, the unknown sample was chemically identified. The S 2p and O 1s XPS results mutually indicated the existence of sulfate species in the materials collected from the damaged area. The XANES results indicated the presence of ferrous (II) sulfate, confirming sulfate‐induced expansion and cracking. The sulfate attack in the present case appeared to physically affect the structure whereas the chemical integrity at the molecular level of the calcium silicate hydrate phase was retained since there was a lack of spectroscopic evidence for calcium sulfate. It was speculated that internal sulfate probably originated from the contaminated aggregates used during the construction. The current findings would be beneficial for understanding the sulfate‐attack mechanism as well as for future prevention against sulfate attack during construction. 相似文献
24.
Hua Chyn Lee Kah Weng Siew Maksudur R.Khan Sim Yee Chin Jolius Gimbun Chin Kui Cheng 《天然气化学杂志》2014,(5):645-656
The paper reports the development of cement clinker-supported nickel (with metal loadings of 5 wt%, 10 wt%, 15 wt% and 20 wt%) catalysts for glycerol dry (CO2) reforming reaction. XRF results showed that CaO constituted 62.0% of cement clinker. The physicochemical characterization of the catalysts revealed 32-folds increment of BET surface area (SBET) with the addition of nickel metal into the cement clinker, which was also corroborated by FESEM images. Significantly, XRD results suggested different types of Ni oxides formation with Ni loading, whilst Ca3SiO5 and Ca2Al0.67Mn0.33FeO5 were the main crystallite species for pure cement clinker. Temperature-programmed reduction analysis yielded three domains of H2 reduction peaks, viz. centered at approximately 750 K referred to as type-Ⅰ peaks, another peaks at 820 K denoted as type-Ⅱ peaks and the highest reduction peaks, type-Ⅲ recorded at above 1000 K. 20 wt% Ni was found to be the best loading with the highest XG and H2 yield, whilst the lowest methanation activity. Syngas with lower H2/CO ratios (0.6 to 1.5) were readily produced from glycerol dry reforming at CO2-to-Glycerol feed ratio (CGR) of unity. Nonetheless, carbon deposit comprised of whisker type (Cv) and graphitic-like type (Cc) species were found to be in majority on 20 wt%Ni/CC catalysts. 相似文献
25.
26.
This paper experimentally investigates the influence of carbon nanotubes (CNTs) on phase composition, microstructure deterioration, thermal behavior, and residual mechanical strengths of cementitious composites exposed to elevated temperatures. Cement mortars with small dosages of CNTs, 0.05% and 0.2% by weight of cement, were prepared and then heated at 25 °C, 150 °C, 200 °C, 450 °C, and 600 °C for two hours before being tested. The results show positive impact of the CNTs on the hydration process of cement mortar at room temperature and at higher temperatures up to 200 °C. Decomposition of the hydration products is obvious at 450 °C, whereas sever deterioration in the microstructure occurs at 600 °C. The nano reinforcement and bridging effect of the CNTs are obvious up to 450 °C. Thermal behavior characterization shows that CNTs incorporation enhances the thermal conductivity of the unheated and heat-treated mortar specimens. The decomposition of the hydration products needs more heat in the presence of CNTs. Finally, presence of CNTs significantly enhances the residual compressive and flexural strengths of heated mortar specimens for all studied temperatures. 相似文献
27.
28.
Ibrahim I. A. ElSersy H. H. Abadir M. F. 《Journal of Thermal Analysis and Calorimetry》2004,76(3):713-718
Thermal analysis was first used to investigate the pattern of dissociation of hydrated ordinary Portland cement. Portlandite
(Ca(OH)2) decomposes at about 500°C. This was confirmed by kinetic calculations. Thermal analysis was then performed to establish
the effect of varying the cement content on the percent mass loss associated with the decomposition of Ca(OH)2 in cement mortar cured for 28 days. An increasing relation was obtained. Standard concrete cubes were then prepared with
cement contents ranging from 200 to 450 kg m-3. The loss in mass on heating, up to 750°C, of concrete samples cured for 28 days was then related to the cement content in
concrete. The relation obtained was tested for concrete cubes of known cement content and found to be in better agreement
than the results obtained by conventional chemical analysis. This method can be used for an approximate determination of the
cement content in concrete.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
29.
Comparison of Bottom-up Filling in Electroless Plating with an Addition of PEG,PPG and EPE 总被引:1,自引:0,他引:1
The bottom‐up filling capabilities of electroless copper plating bath with an addition of additives, such as polyethylene glycol (PEG), polypropylene glycol (PPG) and triblock copolymers of PEG and PPG with ethylene oxide terminal blocks termed EPE, were investigated by the cross‐sectional scanning electron microscopy (SEM) observation of sub‐micrometer trenches. Though three additives had inhibition for electroless copper deposition, the suppression degrees of three additives were different. EPE‐2000 had the strongest suppression for electroless copper deposition, and the suppression of PEG‐2000 was the weakest. The bottom‐up filling capability of electroless copper was investigated in a plating bath containing different additives with the concentration of 2.0 mg/L. The cross‐sectional SEM observation indicated the trenches with the width of 280 nm and the depth of 475 nm were all completely filled by the plating bath with an addition of EPE‐2000, but the trenches were not completely filled by the plating bath with an addition of PEG‐2000 or PPG‐2000, and some voids appeared. Linear sweep voltammetry measurement indicated that three additives all inhibited the cathodic reduction reaction and the anodic oxidation reaction, and the inhibition of EPE‐2000 was the strongest among three additives, which agreed with that of the deposition rate of electroless copper. Significant differences in surface roughness of deposited copper film were observed by UV‐visible near‐infrared for different suppressors, and the bright and smooth of deposited copper film were in accordance with the inhibition of three additives. 相似文献
30.
根据水泥市场需求信息,运用自适应模糊推理系统对水泥产品结构需求进行系统建模,应用并行遗传算法对模型求解,得到了来年的最优水泥产品结构需求计划,为水泥企业的生产规划及其经济效益的提高提供了重要的参考价值. 相似文献