高强水泥混凝土在沈阳西湖大桥施工中的运用

高强水泥混凝土正迅速得到发展，其配制特点和规律，有待充分认识。目前，尚无统一规范，仅就施工中出现的课题加以探讨。

嘉陵江南屏大桥机制砂高强水泥混凝土的配制技术

根据重庆地区缺少天然中砂，但广泛分布着适于生产机制砂岩石的现状，可通过控制原材料的质量，尽量采用重庆本地区材料来优化配合比配置适用于重庆市合川区嘉陵江南屏太桥的高强水泥混凝土，并采用掺加聚羧酸高效减水剂和矿粉来提高水泥混凝土性能。

超高大直径柱一次性浇筑工程施工技术

通过对某工程高强超高大直径柱一次性浇筑水泥混凝土施工技术的研究,明确了此类结构施工的控制重点、难点及解决措施,指出了粗直径钢筋定位控制的重要性并给出了实用的控制措施。提供了一种优化柱内拉筋配置从而为泵管入柱底提供通道的新方法。为类似的含有同类现场现浇构件的施工提供了有益的借鉴。

Flexural behaviors of steel reinforced ECC/concrete composite beams

An engineered cementitious composite （ECC） is introduced to partially substitute concrete in the tension zone of a reinforced concrete beam to form an ECC/reinforced concrete （RC） composite beam, which can increase the ductility and crack resisting ability of the beam. Based on the assumption of the plane remaining plane and the simplified constitutive models of materials, the stress and strain distributions along the depth of the composite beam in different loading stages are comprehensively investigated to obtain calculation methods of the load-carrying capacities for different stages. Also, a simplified formula for the ultimate load carrying capacity is proposed according to the Chinese code for the design of concrete structures. The relationship between the moment and curvature for the composite beam is also proposed together with a simplified calculation method for ductility of the ECC/RC composite beam. Finally, the calculation method is demonstrated with the test results of a composite beam. Comparison results show that the calculation results have good consistency with the test results, proving that the proposed calculation methods are reliable with a certain theoretical significance and reference value.

Properties of Belite-Rich Portland Cement and Concrete in China

Performances of belite-rich Portland cement, or HBC （high belite cement）, and the resultant concrete are introduced by comparing with that of alite based PC （Portland cement） and concrete. The comparison study of cement properties indicates that HBC possesses the properties of less water demand for normal consistency, better compatibility with water reducer, higher later age strength after 28-day under standard curing temperature of 20 ℃, unique strength gain under elevated curing temperatures of 38-70 ℃, lower hydration heat evolution and temperature rise, lower drying shrinkage and excellent resistance to sulphate attack. These results have been demonstrated by the comparison performance evaluation of concretes prepared by HBC and PC in terms of workability, physical mechanical properties and durability when making high performance high strength concrete and massive concrete.

Creep of Concrete in Contemporary Code-Type Models

The paper presents and compares the conventional models for creep in cement concrete included in the ACI （American Concrete Institute） guide, Eurocode 2 andfib （International Federation for Structural Concrete） Model Code 2010. For the presentation and comparison of the creep models, creep coefficients are developed. The main factors affecting the prediction of creep in concrete are outlined, comparing the influence of concrete grade, environmental conditions, member size and loading conditions. Most of the conventional models currently used for creep in cement concrete develop the code-type procedures and are calibrated for normal- and high-strength concretes. They enable a more accurate analysis and better assessment of the time-dependent deformation of concrete structures at the design stage. Their complexity is significantly reduced and a range of influencing parameters are excluded from the models for simplicity and easy adaptation. The comparison of the models shows that thefib Model Code 2010 model is more consistent and calibrated to avoid shortcomings in the previous models.

Computer-aided design of the effects of Cr_2O_3 nanoparticles on split tensile strength and water permeability of high strength concrete

In the present paper, two models based on artificial neural networks and genetic programming for predicting split tensile strength and percentage of water absorption of concretes containing Cr2O3 nanoparticles have been developed at different ages of curing. For purpose of building these models, training and testing using experimental results for 144 specimens produced with 16 different mixture proportions were conducted. The data used in the multilayer feed forward neural networks models and input variables of genetic programming models are arranged in a format of 8 input parameters that cover the cement content, nanoparticle content, aggregate type, water content, the amount of superplasticizer, the type of curing medium, age of curing and number of testing try. According to these input parameters, in the neural networks and genetic programming models the split tensile strength and percentage of water absorption values of concretes containing Cr2O3 nanoparticles were predicted. The training and testing results in the neural network and genetic programming models have shown that every two models have strong potential for predicting the split tensile strength and percentage of water absorption values of concretes containing Cr2O3 nanoparticles. It has been found that NN and GEP models will be valid within the ranges of variables. In neural networks model, as the training and testing ended when minimum error norm of network was gained, the best results were obtained and in genetic programming model, when 4 genes were selected to construct the model, the best results were acquired. Although neural network has predicted better results, genetic programming is able to predict reasonable values with a simpler method rather than neural network.