关于混凝土抗渗性试验方法的研究

混凝土的渗透性是决定耐久性的一个重要因素,本文分析了水渗透、气体渗透和氯离子渗透三种不同的渗透性测试方法的优缺点和使用范围。并提出了混凝土渗透性今后有待进一步研究的问题。     

配套轿车轮胎的性能测试

介绍配套轿车轮胎开发过程中,从轮胎单体性能到轮胎整车性能所需的测试项目、设备及方法等。耐久性能包括常规耐久性能、老化耐久性能、结构耐久性能和整车加速耐久性能,安全性能包括强度性能、脱圈阻力、实车脱圈阻力、保持性能、制动性能、横向抓着性能、高速稳定性和耐鼓包性能,动力学性能包括刚度特性、六分力、操纵稳定性以及噪声、振动和声振粗糙度,经济性包括滚动阻力性能和耐磨性能等。指出建立完备的测试系统是配套轮胎开发的基础。     

季冻区高速铁路路基改良填料冻融性能研究

针对季冻区高速铁路路基填料冻融性能问题,将水泥和水泥粉煤灰掺入级配碎石作为改良措施。为了研究水泥和水泥粉煤灰改良碎石填料的抗冻融耐久性能,对填料的水稳定性、冻融变形特性和冻融耐久性进行试验,分析改良剂的种类、掺量以及养护龄期等因素的对路基填料性能的影响规律。研究结果表明：水泥改良填料相较于水泥粉煤灰改良填料有较高的无侧限抗压强度;填料单向冻胀量随着水泥掺量的增加而降低,掺入粉煤灰后会提高填料的冻胀率;水泥粉煤灰改良填料在28 d养护后水稳定性性能较水泥改良填料更佳优异,抗冻融性能则会低于水泥改良填料。     

预应力混凝土试件碳化试验及碳化深度预测模型研究

进行了碳化环境下预应力混凝土试件弯曲受拉和直接受压的耐久性试验研究,阐述了碳化作用对预应力混凝土结构的损伤机理。引进拉、压应力状态影响函数χσ,以反映碳化深度和应力状态及应力水平的关系。分别假定Fick第Ⅰ定律中的碳化时间指数α为0.50或为变量,由此建立了多因素影响下的预应力混凝土结构碳化深度预测模型,且采用一次可靠性方法(FORM)对碳化深度预测模型进行了分析。研究结果表明,拉、压应力分别可加快和减缓混凝土结构的碳化速度,χσ反映了碳化速率的变化趋势。最优的碳化时间指数α=0.48,若近似取α=0.50,计算结果也是足够准确的,由此印证了Fick第Ⅰ定律的正确性,而且采用FORM计算预应力混凝土结构碳化深度的离散程度是可靠的。     

混凝土耐久寿命预测的研究方法综述

混凝土耐久寿命的预测是混凝土耐久性研究的一项重要课题,本文综合介绍了目前国内外有关混凝土耐久寿命预测的重要理论方法与实践,并简要论述了各种研究方法的优缺点.     

Review of recent developments in cement composites reinforced with fibers and nanomaterials

The quest for high-performance construction materials is led by the development and application of new reinforcement materials for cement composites. Concrete reinforcement with fibers has a long history. Nowadays, many new fibers associated with high performance and possessing eco-environmental characteristics, such as basalt fibers and plant fibers, have received much attention from researchers. In addition, nanomaterials are considered as a core material in the modification of cement composites, specifically in the enhancement of the strength and durability of composites. This paper provides an overview of the recent research progress on cement composites reinforced with fibers and nanomaterials. The influences of fibers and nanomaterials on the fresh and hardened properties of cement composites are summarized. Moreover, future trends in the application of these fibers or of nanomaterial-reinforced cement composites are proposed.     

粉煤灰在清江隔河岩工程中的应用

本文根据清江隔河岩工程粉煤灰混凝土试验资料及施工情况,并参考有关资料,对掺粉煤灰的利弊进行了分析,结果表明在大体积混凝土中掺粉煤灰技术上是可行的,经济社会效益显著,对其不足之处只要采取适当的措施是可以克服的。     

A Stress Singularity Approach for the Prediction of Fatigue Crack Initiation in Adhesive Bonds. Part 2: Experimental

Using the epoxy-aluminum wedge specimens defined and analyzed in Part 1, we measure the number of cycles required to initiate an interfacial fatigue crack near the apex, where the stress field is predicted to be singular. The eigenvalue, λ, and the generalized stress intensity factor, Q, are varied via the wedge angle, and via the beam deflection, respectively. Crack initiation is detected using a strain gage bonded near the tip of the wedge.

Following the methodology developed in Part 1, the fatigue data are then used to construct a fatigue initiation criterion characteristic of the bimaterial interface. This criterion is a 3-D surface, with the ordinate representing the generalized stress intensity factor and the two horizontal axes representing the number of cycles to initiation and the eigenvalue, respectively. Three key assumptions of the model are found to be satisfied in the specimens tested herein: (1) geometric imperfections at the apex are smaller than the singular region, (2) the plastic zones near the apex are also smaller than the singular region, and (3) the locus of initiation is near interfacial.

Finally, a thermomechanical analysis indicates that the residual thermal stresses generated during the fabrication process make a significant contribution to the critical stress intensity factor. With high T_g adhesives and under unfavorable conditions (high modulus, high CTE, poor adhesion), we predict that the residual stresses alone could be sufficient to cause debond initiation.     

涤纶低弹丝纬编针织产品性能的研究

对编织的八种Coolnise涤纶低弹丝纬编针织面料的热湿舒适性、顶破强力、耐磨性和透气性进行了测试,分析了纱线种类和织物结构对热湿舒适性和物理机械性能的影响。     

新型碱矿渣混凝土技术

抗渗、抗冻及抗化学侵蚀试验表明,新型碱矿渣混凝土具有优异的耐久性能。新型碱矿渣混凝土由于配制技术易为一般混凝土技术人员接受和掌握,且原材料广泛,成本低廉,因此研究和开发具有广阔前景。