浅谈制浆和混凝土搅拌机

水泥浆通常作为预应力孔道的灌浆材料,是防止预应力筋锈蚀和部分传递预应力的一种常用建筑材料,一般采用水泥浆搅拌机现场拌制。在我们工程实践中,由于工地条件有限,经常会遇到一些施工单位为了省事,要求用混凝土搅拌机替代专用制浆设备而进行制浆     

延长自组织InAs／GaAs量子点发光波长的研究进展

在近几年的InAs／GaAs自组织量子点的研究中，如何荻得1．3～1．55μm。长波长量子点材料是一个很热门的课题。本文综述了各种延长自组织InAs／GaAs量子点发光波长的方法，并提出了实用化的最佳途径。     

格栅式水泥搅拌桩支护在西涌泵站的应用

简介水泥搅拌桩的支护机理,以西涌泵站为例介绍采用格栅式水泥搅拌桩作支护结构的设计及计算方法,指出该技术能较好地解决软湿粘性土地区枢纽深基础开挖问题.     

铁铝酸盐复合膨胀水泥化学预应力机理及其应用研究

本文阐述铁铝酸盐自应力混凝土的主要物理力学特征.研究了限制膨胀应变与配筋率之间的定量函数关系.通过正交试验和方差分析,确定了复合外加剂对其性能的影响.针对其在自应力管中的应用,提出多层中空圆柱理论计算模型,按弹性理论计算出自应力管初始应力分布规律.对比以前的线性理论计算误差,给出相应的修正系数.本文对类似的自应力混凝土,具有普遍的指导意义.     

HEC influence on cement hydration measured by conductometry

Cellulose ethers are of universal use in factory-made mortars, though their influences on mortar properties at a molecular scale are poorly understood. Recent studies dealt with the influence of hydroxyethylmethyl cellulose (HEMC) and hydroxypropylmethyl cellulose (HPMC) molecular parameters on cement hydration. It was concluded that the degree of substitution is the most relevant factor on cement hydration kinetics, contrary to the molecular weight. Nevertheless, the major role played by the substitution degree has not been verified for other types of cellulose ethers such as hydroxyethyl cellulose (HEC), which generally possesses a higher hydration retarding capacity compared to HPMC and HEMC. In this frame, a study of the impact of HEC molecular parameters on cement hydration was performed. A negligible influence of the molecular weight was observed. Moreover, the results emphasize that the hydroxyethyl group content mainly determines the delay of cement hydration.     

丁苯橡胶对水泥水化过程及水泥石微观结构的影响

用多种实验手段研究了在普通硅酸盐水泥中掺入丁苯橡胶乳液对水泥水化过程的影响，并用扫描电镜分析了掺入丁苯橡胶后水泥石微观结构形态的改变，从而探讨了丁苯橡胶改善水泥石物理力学性能的机理。     

Impedance spectroscopy study of hardened Portland cement paste

In this paper, the differential impedance analysis (DIA) has been applied to the study of the dielectric properties of hardened Portland cement paste. Two time constants are found in the impedance spectra obtained in the frequency region form 100 kHz to 15 MHz. One time constant has been attributed to the solid matrix and the other one to the liquid phase filling the pores. The effect of the cement paste-electrodes interface has been quantified using two different experimental set-ups. Measurements using direct contact between electrodes and cement paste have been compared with measurements using an air gap technique in which the specimen “floats” between the electrodes. The two referred time constants have been found in both types of measurements. The influence of drying on the dielectric parameters is also studied.     

改性MgO膨胀剂对水泥浆体流动度和膨胀性能的影响

为了改善MgO膨胀剂(MgO expansive agent,简称MEA)对混凝土流动性的不利影响和延缓氧化镁混凝土的膨胀时间,采用十八碳不饱和脂肪酸对MEA进行表面改性,测试了改性MEA的活性指数、孔结构和水化热等特性,并通过测定掺改性MEA的水泥浆体的流动度和膨胀性能来评价其改性效果。结果表明:MEA经过表面改性后,其活性指数增大,孔结构被细化,水化放热时间有所延迟;改性MEA可明显降低MEA水泥浆体的流动度经时损失,并有效地延缓MEA水泥浆体的膨胀时间,提高其后期膨胀量。研究成果可为表面改性MEA在大体积混凝土中的应用提供参考。     

谈谈水泥土挡墙的合理计算

阐述了水泥土挡墙在工程基坑支护中的作用,并结合工程实例,对水泥土挡墙的合理计算模型进行了探讨。