高强混凝土制备研究

本文用普通原材料成功制备了８０ＭＰａ以上高强混凝土，研究了各种因素对混凝土的影响关系，探讨了解决坍落度损失的方法。     

降低高强混凝土黏度的减水剂制备与机理研究

根据分子结构设计原理,以马来酸酐与异戊烯醇聚氧乙烯聚氧丙烯醚大单体为主要反应原料,以甲基烯丙基磺酸钠为链转移剂,合成一款减水剂.采用凝胶渗透色谱、红外光谱、核磁氢谱等测试手段获得了合成产物的分子量及分子量分布等结构参数信息,同时比较了该减水剂与普通减水剂在表面张力、对水泥颗粒吸附行为、Zeta电位、水泥净浆流动性、水泥净浆流变性能及新拌混凝土应用性能方面的差异.性能评价结果表明,该减水剂具有良好的降黏效果,本工作还分析了其降黏作用机理.     

高强钢管高强混凝土徐变特性试验研究

高强钢管高强混凝土的应用越来越广泛,但目前对于其徐变特性的试验研究较少.该文对15根不同含钢率的高强钢管高强混凝土轴压短柱进行了365 d的收缩和徐变测试,并将试验结果与常用的徐变预测模型MC90、ACI209和MC2010等进行了对比.试验结果表明:高强钢管高强混凝土的徐变系数远小于素混凝土,当加载365 d后,素混...     

参高效减水剂混凝土性能的研究

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。     

高强箍筋约束高强混凝土轴心受压力学性能试验研究

通过31 根高强螺旋箍筋约束高强混凝土方形截面柱的轴心受压试验,对该类型柱的破坏形态、应力-应变关系曲线等进行了研究,分析了箍筋强度、箍筋间距、箍筋形式及截面尺寸对其性能的影响。结果表明：采用高强箍筋约束是防止高强混凝土应力-应变曲线陡然下降的有效措施;箍筋间距较小、强度较高、形式较复杂的约束混凝土试件,其应力-应变曲线的下降段较为平缓,显示出良好的延性性能;体积配箍率对约束混凝土强度和延性提高程度的影响要明显大于箍筋强度,当ρ_v · f_yv相近时,高配箍率低强度箍筋试件的性能要好于低配箍率高强度箍筋试件;约束混凝土达到峰值强度时,高强箍筋并未屈服,其强度的富裕量可保证约束混凝土试件在达到极限破坏状态之前具有良好的延性性能。在该文试验的基础上,结合国内外试验数据,通过回归分析提出了高强箍筋约束高强混凝土峰值强度和极限应变的计算公式。     

高强混凝土在建筑工程中的应用

开发新型优质高强混凝土,满足结构设计要求,减轻结构自重、简化施工工艺,降低施工成本,改变传统的低强度等,已成为建筑施工科学研究发展方向之一。文中对高强混凝土在建筑工程中的应用做了论述。     

高强混凝土在建筑施工中的应用

文中结合实践对建筑施工中如何使用高强混凝土做了论述。     

公路桥梁高强轻质混凝土配合比研究

为了促进高强轻质混凝土(HSLC)在公路桥梁上的理论研究和实际应用,文章在总结有关资料的基础上,对HSLC配制方法进行了全面系统的介绍和分析。针对预应力HSLC梁桥在施工配合比方面存在的一些实际问题进行了初步讨论,提出了几点改进措施。     

钢纤维增韧高强混凝土的制备及性能研究

以高轻度骨料混凝土为基础,通过引入不同体积比(0％,1％,2％和3％(体积分数))的钢纤维对混凝土进行改性研究,通过对流动性、抗压抗折、冲击压缩等性能分析,研究了钢纤维掺量对混凝土基体的影响.结果表明,钢纤维掺入后,高强混凝土的流动度逐渐降低,从198 mm降至144 mm;随着钢纤维含量的增加,高强混凝土的抗压强度和...     

高强混凝土的增强机理

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。     

高强度灰铸铁的研究进展

介绍了高强度灰铸铁的研究发展状况及其意义,分析了高强度薄壁灰铸铁所需的成分组织及提高灰铸铁强度的一些措施。     

Al-Zn-Mg-Cu系超高强铝合金的研究进展

评述了国内外超高强铝合金的研究及应用概况,介绍了Zn、Mg、Cu等主要元素与Zr、Sc、Li、Ag、Be及稀土等微量元素对Al-Zn-Mg-Cu系超高强铝合金组织与性能的影响,介绍了Al-Zn-Mg-Cu系合金制备技术、热处理工艺及其最新进展,讨论了超高强铝合金主要强化机制以及微观组织与性能之间的关系.针对超高强铝合金现存的问题,提出了今后研究开发的方向.     

Multivariate Adaptive Regression Splines Model to Predict Fracture Characteristics of High Strength and Ultra High Strength Concrete Beams

This paper presents Multivariate Adaptive Regression Splines (MARS) 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). This paper also presents the details of development of MARS model to predict failure load (Pmax) of high strength concrete (HSC) and ultra high strength concrete (UHSC) beam specimens. 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. MARS model has been developed by establishing a relationship between a set of predicators and dependent variables. MARS is based on a divide and conquers strategy partitioning the training data sets into separate regions; each gets its own regression line. Four MARS models have been developed by using MATLAB software for training and prediction of fracture parameters and failure load.MARS 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, KIC and CTODC are in good agreement with those of the experimental values.     

高强湿喷混凝土强度降低的原因探析与改进

采用湿喷工艺研究了高强喷射混凝土,发现设计的C50喷射混凝土强度严重降低,通过X射线衍射(XRD)、扫描电子显微镜(SEM)、水泥浆水化程度(Degree of hydration)试验分析了强度严重降低的原因。结果表明:喷射成型对混凝土的水化产物种类和净浆的水化程度影响甚微,但对混凝土的密实度及水化产物的形貌影响较大。喷射混凝土密实度不够、材料间粘接不牢固导致喷射混凝土的微观结构疏松,是造成喷射混凝土强度严重降低的主要原因。改进验证试验表明,对高强喷射混凝土来说,喷射施工质量控制对于混凝土强度至关重要,材料体系应适应喷射施工设备与工艺。高强湿喷混凝土 (C50及以上)宜采取0.8～0.9 MPa的风压;喷射时需连续一次垂直喷射,不得出现间断或脉冲;倒筒时间宜控制在10 s以内;水胶比选取0.32～0.36,混凝土砂率控制在50%～70%。改进后的喷射高强混凝土28 d强度可达63.6 MPa。     

高强铝合金的研究现状及进展

阐述了高强铝合金的微观结构及其与性能之间的关系,从材料自身和热处理工艺两方面介绍了强韧化制度,并介绍了当前比较成熟的制备Al-Zn-Mg-Cu系合金的新技术、喷射成形及金属基复合材料的制备,就今后的研究开发提出了一些建议.     

高力学强度水凝胶的研究进展

传统的水凝胶由于力学强度差而大大限制了其应用。近年来,从分子水平上改进水凝胶内部微结构提高水凝胶力学强度的方法越来越受到关注。文中综述了提高水凝胶力学强度的各种有效方法,期望研究者们能够在这些方法的基础上进一步深入探讨并扩展其应用领域。     

超高强铝合金中杂质元素的研究现状

综述了超高强铝合金中Fe、Si等杂质元素的存在形式以及对合金组织、拉伸力学性能、断裂韧性和抗腐蚀性能的影响,总结了Fe、Si等杂质元素的控制标准,概述了通过熔体净化、添加稀土元素、采用粉末冶金等新型制备工艺减小杂质元素影响的研究进展.     

Structural Performance of Precast and Cast-in-situ Ultra High Strength Concrete Sandwich Panel

This paper investigates the flexural performance of a sandwich panel made up of ultra high strength concrete (UHSC) as top and bottom skin and cold formed steel as sandwich. A novel sandwich panel has been designed such a way that bottom skin of UHSC is of precast in nature and top skin of UHSC is cast-insitu and cold formed steel (profiled sheet) as sandwich. The connection between top skin of UHSC and cold formed steel is made with self tapping screws. Flexural performance of UHSC sandwich panel has been tested under flexural loading and it is found that the post peak response of the panel is significant in terms of more energy absorption. It is observed that the final failure of the specimen is occurred by forming a dominant crack on the bottom face of the skin apart formation of many multiple cracks with increase of load. Numerical investigations have been carried out by simulating the experimental conditions and found that the response obtained through simulation is in good agreement with the corresponding experimental values. From the studies, it can be concluded that UHSC steel sandwich panels can be employed for structural and non structural applications.     

高强度螺栓断裂原因分析

表面磷化处理的高强度螺栓在装配时发生断裂。对断裂螺栓进行宏观和微观检验、化学成分分析、金相检验、能谱分析和力学性能分析。结果表明：该螺栓的裂纹表面有氧化物且存在与螺栓表面相似的磷化物,裂纹处没有脱碳现象,说明裂纹在磷化处理前已存在,判断该裂纹是淬火裂纹。螺栓的断裂是由淬火裂纹造成的。     

Effect of Loading Rate on Fracture Energy of High‐Strength Concrete

Abstract: This research deals with the sensitivity of several types of performance‐designed high‐strength concrete to the loading rate. Variations in the composition of the concrete produce the desired performance, for instance having null shrinkage or being able to be pumped at elevated heights without segregation, but they also produce variations in the fracture properties that are reported in this paper. We performed tests at five loading rates spanning six orders of magnitude in the displacement rate, from 1.74 × 10^?5 mm s^?1 to 17.4 mm s^?1. Load‐displacement curves show that their peak is higher as the displacement rate increases, whereas the corresponding displacement is almost constant. Fracture energy also increases, but only for loading rates higher than 0.01 mm s^?1. We use a formula based on a cohesive law with a viscous term [Anales de Mecánica de la Fractura 25 (2008) 793–797] to study the results. The correlation of the formula to the experimental results is good and it allows us to obtain the theoretical value for the fracture energy under strictly static conditions. In addition, both the fracture energy and the characteristic length of the concretes used in the study diminish as the compressive strength of their aggregates increases.