共查询到19条相似文献,搜索用时 125 毫秒
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由于纳米微晶纤维素(nanocrystalline cellulose,NCC)具有高模量、极高长径比和大比表面积等特性,近几年来NCC在水泥基材料中的应用成为了研究前沿和热点。虽然NCC在水泥基材料中的应用研究还处于初级阶段,但却为改善水泥基材料性能提供了一个新的研究方向。本文综述了近几年国内外对NCC在水泥基材料中的应用研究,主要介绍了NCC在水泥基材料中的存在形式,及其对水泥基材料的流变性、水化、力学性能和耐久性的影响。最后,分析了NCC在研究中存在的问题,并对NCC今后的研究方向给出了可行性建议。 相似文献
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氧化石墨烯(GO)因其出色的性能在改善水泥基材料微观结构、力学性能上均有很好的应用前景。然而,GO的增强效果很大程度上取决于其在水泥基体中的分散性。总结了近年来GO在水泥基材料中的研究成果,重点综述了GO的分散方式、分散机理以及相应的力学性能改善机理;对比了不同GO分散方式的优缺点,分析了GO分散前后对水泥基材料微观结构和力学性能的影响;提出了目前研究存在的问题,并对未来研究趋势进行展望;旨在为后续GO在水泥基材料中的稳定应用提供参考,以促进制备高效功能化的GO水泥基复合增强材料。 相似文献
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《材料导报》2020,(16)
煤矸石经过适宜温度煅烧、粉磨后可制备活性混合材。但由于煤矸石的组成较为复杂,煅烧后其颜色变化较大,在水泥基材料中大掺量应用会影响水泥基材料的色泽。若能制备出与水泥基材料色差较小的煅烧煤矸石活性粉体材料,则对煤矸石在水泥工业中的应用有着重要意义。本工作研究了制备工艺对煅烧煤矸石活性粉体材料颜色的影响;基于PS软件中红、绿、蓝(R、G、B)三个通道的颜色值量化表征了煅烧煤矸石活性粉体材料的颜色;分析了粒状煤矸石制备活性粉体材料颜色转变的机理。结果表明:热活化时,煤矸石颗粒越小、热活化保温时间越长、煅烧环境中氧气越充足,制得的煅烧煤矸石活性粉体材料颜色越红,其红色值(R值)也越高。煤矸石中炭和菱铁矿的氧化程度是影响煅烧煤矸石活性粉体材料颜色的主要原因。当黑色的炭脱除较充分、菱铁矿被氧化为赤铁矿时材料颜色较红,而炭脱除不充分、菱铁矿被氧化为磁铁矿时材料颜色较黑。 相似文献
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水泥基材料是目前使用量最大的建筑材料,在实际应用过程中,水泥基材料会出现损坏,达不到预期的性能要求.水泥水化产物中存在大量结晶的Ca(OH)2,影响各种水泥水化产物之间的粘结性,造成水泥基材料性能的降低.如何增强水泥基材料的性能成了国内外研究的热点,需要找到能够有效改善水泥基材料性能的方法.查阅国内外相关文献发现,将粉煤灰、硅灰、纳米SiO2(因三种材料的主要组分为SiO2,以下统称为硅基材料)或矿渣掺入到水泥基材料中,因其具有火山灰反应,并能起到填充作用,可明显提高水泥基材料的性能.掺合料的加入可降低水泥基材料中Ca(OH)2含量,减小其晶粒尺寸,使C-S-H凝胶的数量增多,改善水泥基材料的孔隙率,提高其性能.粉煤灰和矿渣成分中有部分玻璃态物质,能减少水泥浆体用水量,增加和易性;具有较低的火山灰性,适量掺入能降低水泥浆体的水化速度;含有粉煤灰或矿渣的水泥基材料早期强度较低,后期强度较高.硅灰与纳米SiO2的火山灰活性较高,能促进水化,适量掺入能够使水泥基材料早期强度大幅提高,但后期强度发展较慢;同时也会增大水泥基材料早期收缩,增加其结构开裂的风险.不同掺合料复掺后能产生协同增强效应,可获得性能优异的复掺改性水泥基材料.本文主要介绍了硅基材料和矿渣在水泥基材料中的应用,从反应机理、水化热、强度、孔隙率等方面来阐述其在水泥基材料中的研究现状和相关成果.对目前研究中存在的相关问题进行了分析总结,以期为制备性能优异的水泥基材料提供一定的参考. 相似文献
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Currently, ground granulated blast-furnace slag cements use in cement-based materials is being increasing because perform well in marine and other aggressive environments. However, mortars and concretes made of this type of cement exhibit high carbonation rates, particularly in badly cured cement-based materials and when high blast-furnace slag contents are used. Concrete reinforcement remains passive but can be corroded if the pore solution pH drops as a result of the carbonation process promoting the reinforced concrete structure failure during its service life. Results show the very sensitive response to wet-curing time of slag mortars with regard to the natural carbonation resistance. Then, a minimum period of 3–7 days of wet curing is required in order to guarantee the usual projected service life in reinforced concrete structures. In this work, estimation models of carbonation depth and carbon dioxide diffusion coefficient in ground granulated blast-furnace slag mortars as a function of the curing period and the amount of ground granulated blast-furnace slag are proposed. This information will be useful to material and civil engineers in designing cement-based materials and planning the required curing time depending on their ground granulated blast-furnace slag content. 相似文献
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This study investigates the properties of cement-based composites with addition of various rock wool wastes. The rock wool wastes are an insulating material. This study used rock wool waste with a cylindrical size distribution ranging from 17 to 250 μm, 30% of which is less than 150 μm. Rock wool waste can be used as a suitable substitute for coarse and fine aggregates, saving on the cost of natural aggregates and minimizing the environmental impact of solid waste disposal. In addition, because the composition of rock wool waste is similar to other pozzolan materials such as fly ash, ground granulated blast-furnace slag (GGBS), and silica fume, it can be considered as a supplementary cementitious material. Experimental results show that partially replacing natural aggregates with rock wool wastes improves the compressive strength, splitting tensile strength, abrasion resistance, absorption, resistance to potential alkali reactivity, resistivity, and chloride-ion penetration of cement-based composites. These improved properties are the result of the dense structure achieved by the filling effect of pozzolanic product. Pozzolanic strength activity index (PSAI) results and scanning electron microscope (SEM) observations confirm these findings. Therefore, rock wool wastes can act as either a cementitious material or inert filler in cement-based composites, depending on the particle size. The critical size appears to be 75 μm. 相似文献
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A mixture of converter slag and coal cinder as adsorbent for the removal of phosphorous and other pollutants was studied in the paper. The maximum P adsorption capacity, pH of solution, contact time and initial phosphate concentration were evaluated in batch experiments for the two materials firstly. The data of P sorption were best fitted to Langumir equation, and the maximum adsorption capacities of converter slag and coal cinder were 2.417 and 0.398 mg P/g, respectively. The pH of solutions with converter slag and coal cinder changed dramatically with time and closed to 8 in 8 h, and the influence of initial pH on phosphate removal by coal cinder was more significant than by converter slag. Phosphate removal rate by converter slag decreased with increase of initial phosphate concentrations. Subsequently, two flow-through columns (Column 1#, Vconverter slag:Vcoal cinder = 1:5; Column 2#, Vconverter slag:Vcoal cinder = 1:3) were operated for the removal of phosphorous and other pollutants from the effluents of a vermifilter for nearly eleven months. Results indicated the average removal efficiency of total phosphorus, dissolved phosphorus, COD and NH4+–N by Column 1# were 44%, 56%, 31% and 67%, and by Column 2# were 42%, 54%, 24% and 57%, respectively. Column 1# had higher removal efficiency for P and other pollutants. 相似文献
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《Cement and Concrete Composites》2000,22(2):97-113
An understanding of the performance of portland cement-based materials requires knowledge at the microstructural level. Developments in the instrumentation of several techniques have led to improved understanding of the composition, morphology, and spatial distribution of the various products of cement hydration. In particular, our understanding of the nature of the nearly amorphous calcium silicate hydrate (C–S–H) phases – which are the principal binding phases in all portland cement-based systems – has been advanced by developments in solid-state NMR spectroscopy and analytical TEM. This paper presents an overview of the nature of the hydration products formed in hardened portland cement-based systems. It starts with the most straightforward cementitious calcium silicate systems, C3S and β-C2S, and then considers ordinary portland cement and blends of portland cement with silica fume, ground granulated iron blast-furnace slag, and finally alkali hydroxide-activated slag cements. 相似文献
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掺珍珠岩水泥石孔分形维数及其与孔结构、强度的关系 总被引:1,自引:0,他引:1
通过压汞法测试不同龄期掺0-40%珍珠岩掺合料水泥石的孔结构参数,利用分形理论的相关知识研究这些水化物的孔体积分形特征,计算它们的孔分形维数D=3.3~3.5,分析并探讨该水泥石孔分形维数与孔结构参数、抗压强度之间的关系.结果表明水泥石孔分形维数与孔隙率、孔径、孔表面积有密切的关系,随着孔分形维数增大,孔隙率提高,孔径扩大、孔表面积增大,孔结构就越劣化,对应的材料抗压强度下降.因此孔体积分形维数可用于综合评定材料的孔结构特性. 相似文献
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水泥基材料的收缩开裂已经成为其破坏的一个主要原因,受到国内外关注,碳纳米管(CNTs)作为一种纳米纤维状材料,可能可以抑制水泥基材料收缩。本文将CNTs放入水中,经过超声处理分散后,形成CNTs分散液,设置不同的CNTs掺量将其掺入到水泥基材料中,通过波纹管实验及圆环试验对该种新型复合材料的自收缩及抗裂性能进行研究。结果表明:CNTs的掺入可以很大程度上抑制水泥基材料的自收缩,最高降低率可到40%以上,且明显提高了水泥基材料的抗裂性能。水灰比的增加会提高CNTs对水泥基材料收缩的抑制效果。当CNTs的掺量为0.1wt%时,可以获得最优效果。同时,CNTs的掺入不仅对水泥基材料自收缩有抑制作用,一定程度上也会抑制水泥基材料的干燥收缩。通过将CNTs掺入到建筑结构关键部分的水泥基材料中,可以提高建筑安全系数。 相似文献