Porosity of recycled concrete with substitution of recycled concrete aggregate: An experimental study

In this paper, we present the experimental analysis of samples of recycled concrete (RC) with replacement of natural aggregate (NA) by recycled aggregate originating from concrete (RCA). The results of the tests of mechanical properties of RC were used for comparison with tests of mercury intrusion porosimetry (MIP), in which the distribution of the theoretical pore radius, critical pore ratio, the surface area of the concrete, threshold ratio and average pore radius were studied at ages of 7, 28 and 90 days. The results showed some variation in the properties of the RC with respect to ordinary concrete. Porosity increases considerably when NA is replaced by RCA. Additionally, a reduction in the mechanical properties of the RC is seen compared with ordinary concrete when porosity increases.     

Temperature and pressure effects on supercritical CO2 extraction of tomato seed oil

Tomato seed oil was extracted with supercritical carbon dioxide in a semibatch-flow extractor within the temperature range 313–343 K and the pressure range 10.8–24.5MPa. The extraction rates increased with pressure, but decreased with temperature increase because of the variation in solvent density and resultant differences in oil solubility. The fatty acid composition of the extracted oil was similar to that of soybean oil.     

余热利用系统多目标优化模型及应用

以炭黑生产中的余热利用系统为背景建立了余热利用系统多目标优化规划数学模型;阐述了模型的求解方法;给出了实例分析。     

预应力工程中的OVM锚固体系

ＯＶＭ锚固体系是我国第一种采用二片四开式，锚碇１８６０ＭＰａ级低松弛钢绞线的预应力锚固体系。本文介绍其基本性能，与其他系列锚具的组合以及它在斜拉桥主索上的应用。     

Eight-year exploration of shrinkage in high-performance concrete

In this paper, an experimental and analytical exploration on the effect of water-binder ratio (w/b), silica fume and age on autogenous, carbonation, drying and total shrinkage of high-performance concrete (HPC) is outlined. Eight types of HPC were studied. Carbonation, internal relative humidity (RH) and strength were studied on specimens from the same batch of HPC that was used in the studies of shrinkage. The results indicate fairly good correlation between carbonation, shrinkage, w/b and RH. The type and amount of silica fume affected shrinkage.     

C50 级混凝土冬季施工技术探讨

介绍了应用在预应力砼Ｔ型梁的Ｃ５０级砼的冬季施工配制措施，并给出了－１０℃条件下的砼有效配合比及冬季４５℃±５℃蒸汽养生法措施。     

废电解液除杂制取硫酸铜和粗镍

介绍了废电解液除杂制取硫酸铜和粗镍的主要工艺条件及试验结果。在废电解液中加入CH80调节pH值到一定范围后,再加入CH64将电解液中Fe2+等杂质除去,铁的去除率可达到94%～98%。然后向滤液中加入CH80调节pH值沉淀铜。过滤后的滤饼用H2SO4溶解后再结晶,可得到CuSO4·5H2O晶体。滤液中加入Na2CO3沉淀镍,过滤后的滤饼即为粗镍(NiCO3)。铜和镍的回收率分别达96%和90%。该流程简单,投资少,效益高,环境保护好,在工业上有较广的应用前景。     

A thermochemical concept-based equation to estimate waste combustion enthalpy from elemental composition

Waste combustion is an interesting alternative for waste management and energy recovery. Knowledge of the waste higher heating value (HHV) is important for judging it’s worth as fuel. This work introduces a new equation, based on thermochemical concepts, to calculate HHV from elemental composition. This equation is expressed in terms of mass percentages on a dry basis of carbon (%C), hydrogen (%H), oxygen (%O), nitrogen (%N), and sulfur (%S); the HHV is computed in MJ/kg. The equation is as follows: HHV=(1−(%H₂O/100))(−0.3708(%C)−1.1124(%H)+0.1391(%O)−0.3178(%N)−0.1391(%S)). The thermochemical concept on which this expression is based involves a wide applicability. This equation neglects the inorganic carbon, hence it is not very adequate when there is a significant concentration of it. The predictions from this approach were contrasted against those proceeding from equations currently used in combustion technology, and also against bomb calorimeter data. The new equation is clearly competitive with respect to other formulations, and it can be very helpful for presenting a waste HHV value based on different derivation suppositions.     

结构粘结剂的试验研究

粘结剂是粘钢加固技术的关键材料,通过对粘结剂的试验研究,得到了粘结剂的拉压试验曲线与材料力学指标以及粘附于各种标号混凝土时,粘结层的抗剪强度;并且还进行了粘结剂的短期流变试验。     

特大型地下厂房岩壁梁锚杆和混凝土施工技术及质量控制

岩壁梁是一种新型结构，为通过一定深度的锚杆将钢筋混凝土梁固定在地下厂房两侧的岩壁上，而吊车荷载则通过锚杆和钢筋混凝土与岩石接触面的摩擦力传到岩体上，形成岩壁梁和岩体共同受力的结构。岩壁梁是地下厂房施工和运行的核心建筑物，岩壁梁锚杆和混凝土的施工质量是直接关系到岩壁梁成败的关键，所以施工技术和施工质量均要求极高，是地下厂房系统施工的重点和难点。本文介绍了瀑布沟水电站地下厂房岩壁梁锚杆和混凝土施工的关键技术及质量控制经验，可供同类工程借鉴参考。