共查询到18条相似文献,搜索用时 93 毫秒
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本文研究了高效减水剂的作用机理及其对混凝土性能的影响,试验采用新型高效减水剂R1100配制大流动性高强混凝土,结果表明高效减水剂能使混凝土减水15-25%,节约水泥10%左右,强度达到120%以上,适合配制大流动高强度混凝土。 相似文献
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为了解决高强度等级混凝土在拌制过程中存在的黏度高、流速慢问题,以甲基烯丙基聚氧乙烯醚、甲基丙烯酸丁酯、丙烯酸、甲基丙烯酸为主要原材料,通过自由基聚合方法合成一种降黏型聚羧酸减水剂,研究了酸醚比、酯醚比、乳化剂用量等试验因素对减水剂性能影响.试验结果表明:减水剂最佳合成工艺为酸醚比为3.5,酯醚比为1.5,AA:MAA用量比例为2,反应温度为35~45℃,乳化剂用量为体系质量的0.4%,混凝土试验结果显示该产品具备良好降黏性能,能够有效降低混凝土塑性黏度. 相似文献
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探讨了混凝土技术的新进展,展示了如何利用新技术和新组分材料(聚合物、纤维、添加剂等)使混凝土的性能得到改进。本文重点论述了高强混凝土的力学性能的最新进展,同时也讨论了强度提高和韧性增强的机理。 相似文献
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本文通过精心设计的一系列试验,对于影响高粉灰陶粒砼强度的主要因素进行研究,给出制备CL40的高强粉煤灰陶粒混凝土的配合比及其配制方法。 相似文献
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由于集料与水泥石变形的不一致,导致混凝土内部结构缺陷几率增大.因此,强度超过150MPa的超高强水泥基材料,如无宏观缺陷水泥基材料(MDF)、活性粉末混凝土(RPC)及工程粘性材料(ECC)等制备时必须剔除粗集料.本文在不剔除粗集料的情况下,采用普通工艺和常规材料,制得了365天龄期时抗压强度为178.3MPa,坍落度210mm的超高强高性能混凝土,同龄期、同配比下的砂浆强度达到178.2MPa,净浆强度达到179.5MPa,混凝土、砂浆及水泥石强度均超过所用粗集料的母岩强度.以此为基础,分析了混凝土各组成结构的微观结构及微观力学特征,探讨了不剔除粗集料的情况下,制备超高强混凝土的理论基础. 相似文献
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Yuvaraj P A Ramachra Murthy Nagesh R Iyer S.K. Sekar Pijush Samui 《计算机、材料和连续体(英文)》2014,41(3):193-214
This paper presents fracture mechanics based Artificial Neural Network (ANN) model to predict the fracture characteristics of high strength and ultra high strength concrete beams. Fracture characteristics include fracture energy (Gf), critical stress intensity factor (KIC) and critical crack tip opening displacement (CTODc). Failure load of the beam (Pmax) is also predicated by using ANN model. Characterization of mix and testing of beams of high strength and ultra strength concrete have been described. Methodologies for evaluation of fracture energy, critical stress intensity factor and critical crack tip opening displacement have been outlined. Back-propagation training technique has been employed for updating the weights of each layer based on the error in the network output. Levenberg- Marquardt algorithm has been used for feed-forward back-propagation. Four ANN models have been developed by using MATLAB software for training and prediction of fracture parameters and failure load. ANN has been trained with about 70% of the total 87 data sets and tested with about 30% of the total data sets. It is observed from the studies that the predicted values of Pmax, Gf, failure load, KIc and CTODc are in good agreement with those of the experimental values. 相似文献
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以CuCl、CuCl_2为催化剂,bipy为配体,2-溴丙酸甲酯为引发剂,通过原子转移自由基聚合的方法,采用二甲基亚砜(DMSO)和H_2O混合溶剂取代单一溶剂,合成了大分子引发剂POEGMA-Br;POEGMA-Br引发甲基丙烯酸叔丁酯聚合后水解,最终得到了PDI可控(PDI1.25)的嵌段聚羧酸POEGMA-b-PMAA。核磁共振氢谱与凝胶渗透色谱证明所得POEGMA-b-PMAA序列结构完全可控。将该嵌段聚羧酸用于水泥基材料分散,该聚合物能有效吸附于水泥颗粒上并减小团聚体尺寸,说明POEGMA-b-PMAA能分散水泥颗粒并改善水泥基材料的工作性。 相似文献
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以异戊烯醇聚氧乙烯醚(TPEG?2400)、丙烯酸(AA)、丙烯酸羟乙酯(HEA)及氨基封端的聚乙二醇(H2 N?PEG?NH2)为主要原材料合成了一种微交联型(抗泥、保坍、减水)聚羧酸减水剂M42.探究了酸醚比、丙烯酸羟乙酯(HEA)的用量、抗泥单体氨基封端的聚乙二醇的用量对聚羧酸减水剂的影响.并通过红外光谱分析证实分子结构,采用红外光谱和热失重(TG)分析了M42在蒙脱土的表面吸附,采用XRD分析了蒙脱土对M42层间吸附的影响.最后,评价了M42对含蒙脱土的水泥净浆流动度、混凝土损失及抗压强度的影响.结果表明:当酸醚比为2.0,HEA和氨基封端的聚乙二醇的用量分别为大单体用量的2.9%和4.4%时,该产品同时具备抗泥、保坍及减水效果,综合性能优于市场同类产品. 相似文献
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为改善橡胶混凝土的强度,本工作选用尿素和NaHSO3两种改性剂对橡胶颗粒进行氨化与磺化改性。借助傅里叶红外光谱仪验证引入的极性亲水基团,利用水接触角试验仪分析改性橡胶的亲水性能,通过粘接强度试验和抗压强度试验研究改性橡胶对橡胶混凝土强度的提升效果,用扫描电子显微镜(SEM)表征橡胶混凝土的微观破坏形貌。结果表明:氨化改性在橡胶颗粒表面引入羰基和氨基等,磺化改性在橡胶颗粒表面引入羟基和磺酸基等;与普通组相比,氨化与磺化改性后,改性橡胶-水接触角分别降低31°、35°,改性橡胶与水泥净浆的粘接强度分别提升44%、53%,改性橡胶混凝土的抗压强度在不同橡胶粒径与掺量条件下均得到提升;SEM结果表明极性亲水基团的引入能较好地提升橡胶颗粒与胶凝材料的粘接性能,有利于改善两者结合界面薄弱的问题,增强橡胶混凝土的整体强度。 相似文献
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This paper presents the advanced analytical methodologies such as Double- G and Double - K models for fracture analysis of concrete specimens made up of high strength concrete (HSC, HSC1) and ultra high strength concrete. Brief details about characterization and experimentation of HSC, HSC1 and UHSC have been provided. Double-G model is based on energy concept and couples the Griffith's brittle fracture theory with the bridging softening property of concrete. The double-K fracture model is based on stress intensity factor approach. Various fracture parameters such as cohesive fracture toughness (KIcc), unstable fracture toughness (KIcun) and initiation fracture toughness (KIcini) have been evaluated based on linear elastic fracture mechanics and nonlinear fracture mechanics principles. Double-G and double-K method uses the secant compliance at the peak point of measured P-CMOD curves for determining the effective crack length. Bi-linear tension softening model has been employed to account for cohesive stresses ahead of the crack tip. From the studies, it is observed that the fracture parameters obtained by using double - G and double - K models are in good agreement with each other. Crack extension resistance has been estimated by using the fracture parameters obtained through double - K model. It is observed that the values of the crack extension resistance at the critical unstable point are almost equal to the values of the unstable fracture toughness KIcun of the materials. The computed fracture parameters will be useful for crack growth study, remaining life and residual strength evaluation of concrete structural components. 相似文献