煤灰混凝土小型空心砌块

混凝土小型空心砌块(包括轻集料混凝土小型空心砌块)是我国墙体材料改革中要大力发展的一种新型墙体材料,也是替代粘土砖的理想材料。粉煤灰混凝土小型空心砌块有承重砌块和框架结构     

再生混凝土的初步探讨

再生混凝土是一种解决供需矛盾的很有效的方法,它是将废弃的旧混凝土破碎成再生骨料,经筛分级配后用作水泥混凝土骨料配制出来的一种新型混凝土。再生混凝土材料对比普通混凝土材料而言,性能上虽略显不足,但仍然有着很广阔的应用空间。通过研究和改良的再生混凝土会完全替代普通混凝土。     

混凝土节能复合砖在建筑节能中的应用

混凝土节能复合砖是一种新型节能墙体材料,用于砌筑节能建筑的外墙,外墙热桥部位的混凝土构件采取保温措施,从而使山东省地区的外墙热工性能达到我国65%的节能要求。文章主要介绍了混凝土节能复合砖的构造组成、墙体的保温性能、砌筑方式和热桥部位的处理措施等。     

艺术压花混凝土施工技术

艺术压花混凝土是直接在传统混凝土材料上现场制作的彩色地面装饰混凝土,可以做出多种图案装饰效果,是替代砖、石铺设路面的一种新型装饰产品。本文结合工程实践,主要介绍施工方法。     

混凝土小型空心砌块多层住宅施工的质量控制措施

混凝土小型空心砌块是一种替代实心粘土砖的新型墙体材料。近年来在工程建设中得到了越来越多的应用。本文结合工程实例探讨了如何提高混凝土小型空心砌块多层住宅施工质量的方法和途径     

怎样正确使用混凝土多孔砖

混凝土多孔砖是近几年开发的一种新型墙体材料,它的推广有助于节约能源,保护土地资源,是一种非常良好的烧结粘土砖替代材料。文章就该墙体材料的性能特点、工艺流程、施工要点及在阜阳市工程质量监督中所发现的质量问题进行了介绍。     

《承重混凝土多孔砖》国家标准编制说明

1概述 混凝土小型空心砌块是一种新型墙体材料,经过20多年的迅猛发展,已成为替代粘土实心砖的理想产品之一.作为一种新的建筑结构体系,已被人们所广泛认同.但由于它不同于我国传统的砖混结构,给建筑设计、施工及推广应用带来了诸多不便.为适应我国传统的设计和施工方式,近几年一种新型的墙体材料产品--混凝土多孔砖得以快速发展.     

探讨混凝土小型空心砌块房屋施工的质量控制

近年来，随着我国建筑业的快速发展，混凝土小型空心砌块作为一种替代实心粘土砖的新型墙体材料，在工程建设中得到了广泛的应用，本文针对如何提高混凝土小型空心砌块房屋施工质量的控制进行讨论。     

不锈钢-混凝土-钢双臂管等效截面计算

不锈钢-混凝土-钢中空夹层组合管作为一种新型构件,可用作水下输送管道、框架柱、桥墩柱等。这种新型结构形式充分的利用了钢与混凝土两种材料的优势。本文借鉴钢-混凝土组合结构构件的基本假定,利用等效截面换算法将有效宽度内圆环形截面等效成工字型截面,简化了计算过程及复杂性,并为组合截面研究提供计算依据。     

混凝土小型空心砌块专用砂浆现状及存在的问题

混凝土小型空心砌块由于具有诸多优点,是替代实心粘土砖的一种主要材料.但混凝土小型空心砌块房屋易裂,影响了这种新型墙体材料更好的推广应用.其中产生裂缝的主要原因之一是砌筑砂浆问题.本文介绍了混凝土小型空心砌块专用砂浆国内外研究现状,解释了混凝土小型空心砌块专用砌筑砂浆存在的一些问题.     

Comparisons of the mechanical properties of timber,steel and concrete sleepers

In this research, the mechanical behaviour of steel, timber and concrete sleepers is investigated and compared by conducting several laboratory and field tests. The main sleeper design parameters including rail seat loads, sleeper-ballast contact pressures and sleeper bending capacities are considered in this investigation. New formulae for the calculation of sleeper design parameters are developed for steel, timber and concrete sleepers. Results indicate that the new formulae can improve the accuracy of current practices in the analysis and design of sleepers. Comparisons of the mechanical properties of steel, timber and concrete sleepers indicate the optimum sleeper type based on railway structural and operational conditions.     

磷矿渣轨枕混凝土力学性能的试验研究

采用对比试验方法,系统研究了磷矿渣比表面积和掺量对轨枕混凝土力学性能的影响,并分析了磷矿渣的作用机理,结果表明:蒸汽养护条件下,适当粒度和掺量的磷矿渣可以有效改善轨枕混凝土的力学性能,从而为磷矿渣混凝土轨枕的实际应用打下良好基础。     

先张法预应力轨枕裂纹产生原因及解决方案

对混凝土轨枕裂纹产生的原因进行了模型计算分析,从钢构、过程控制等方面进行了探讨,同时提出可行性解决方案,从而减少轨枕外部和内部裂纹,以提高混凝土轨枕的耐久性。     

A new approach for evaluating lateral resistance of railway ballast associated with extended sleeper spacing

Recently, attempts have been made to replace wooden sleepers with concrete sleepers with expanded sleeper spacing, especially on conventional railway lines. By extending sleeper spacing in the replacement process, the number of sleepers required is lower. A reduction in the number of sleepers can reduce replacement costs. Behind this attempt to change materials and spacing is the generally held notion the lateral resistance of a ballast is unchanged after the change in the sleeper spacing, whether it is a wooden or a concrete sleeper. However, the changes in the interference degrees of adjacent sleepers and in the rail weight supported by each sleeper are expected to affect the lateral resistance of the ballast. They can change the lateral stability of ballasted tracks in a more complicated fashion than the simple effect of a reduced number of sleepers. However, the current standard design does not consider the combined effects of these changes on the lateral resistance of a ballast. Accordingly, the design of ballasted tracks with extended sleeper spacing cannot be optimized.Therefore, the aim of this study was to investigate the lateral resistance characteristics of a ballast as associated with changes in the sleeper spacing of conventional railway lines. First, single-sleeper pullout tests were conducted on models based on various sleeper spacing conditions to evaluate the lateral resistance of the ballast. The effect of the rail weight on the lateral resistance of the ballast was determined from the test results. An increased frictional resistance at the sleeper bottom was considered to contribute to an increase in the lateral resistance; thus, the friction angle between the ballast and sleeper bottom was used to evaluate the degree of increase. Subsequently, track panel pullout tests were conducted by simulating an expansion of the sleeper spacing. Based on the test results, the effect of the interference between adjacent sleepers on the lateral resistance per sleeper was investigated. The obtained results were quantitatively modeled as a function by using the sleeper width as a parameter (as normalized by the sleeper spacing). Finally, a new approach was proposed for estimating the lateral resistance of a ballast which considered the change in the sleeper spacing for conventional railway lines. The method considered the combined effects of change in the interference of adjacent sleepers and in the rail weight supported by each sleeper on the lateral resistance. Based on the results calculated by the proposed method, practical applications were examined by determining the extent to which the sleeper spacing could be increased without reducing the lateral resistance of the ballast when replacing wooden sleepers with concrete sleepers. It was demonstrated that the proposed method could improve the estimation accuracy of the lateral resistance of a ballast track with extended sleeper spacing.     

高强混凝土轨枕中掺加粉煤灰的试验研究

本文采用正交设计的方法,对粉煤灰在高强预应力混凝土轨枕中的应用进行了试验研究。采用粉煤灰和高效减水剂双掺法,探讨了粉煤灰掺量对混凝土出模和28d抗压,抗折以及疲劳,抗裂性能的影响,评价了粉煤灰在预应力混凝土轨枕中的应用价值。     

磨细矿粉与复合掺和料 在 CRTS 双块式无砟轨道混凝土轨枕中的对比试验应用

研究了分别由复合掺和料、磨细矿粉配制成的CRTS双块式无砟轨道混凝土轨枕在自然养护条件下的力学性能和耐久性能,结果表明:掺加复合掺和料的双块枕混凝土早期强度较基准混凝土提高27%,后期强度较基准混凝土提高15%,耐久性能较基准混凝土有很大程度的提高;掺加磨细矿粉的双块枕混凝土早期强度虽然有所降低,但依然能够满足双块枕混凝土脱模强度的要求,后期强度较基准混凝土可以提高5%,同时磨细矿粉的掺入也可以明显改善双块枕的耐久性能。考虑到复合掺和料成本是磨细矿粉的6倍多,选择磨细矿粉配制双块枕混凝土是较为经济的选择。     

掺粉煤灰高强混凝土轨枕的性能研究

用对比试验方法,系统研究了掺粉煤灰高强预应力混凝土轨枕的各项性能,并分析了粉煤灰的的作用机理,结果表明:蒸汽养护条件下,优质粉煤灰应用于高强混凝土轨枕中,可以有效改善普通高强混凝土的中长期力学性能,降低构件内部温度,提高抗渗性、抗裂性,减少表面缺陷,从而提高了预应力混凝土轨枕的耐久性.     

轨枕制造过程中裂纹产生的原因及控制措施

介绍了预应力混凝土轨枕制造过程裂纹特点,并就轨枕制造过程裂纹产生的原因作了分析,从选用水泥品种、外加剂、掺加料、控制混凝土的浇筑、预应力钢筋定长和放张等方面提出了控制裂纹产生的措施,以提高构件的抗裂性能和刚度。     

上海地铁隧道内整体道床混凝土长轨枕断裂原因分析及预防措施的研究

本文通过对上海地铁二号线整体道床混凝土长轨枕断裂的内在原因的分析研究,确定整体道床下空洞致轨枕支撑情况的改变是造成轨枕断裂的主因。轨枕离缝、钢轨接头震动荷载及地下水侵蚀是间接引起和加速断裂的辅因,并提出了预防轨枕断裂的建议。     

Experimental and parametrical investigation of pre-stressed ultrahigh-performance fiber-reinforced concrete railway sleepers

In this study, ultrahigh-performance fiber-reinforced concrete (UHPFRC) used in a type B70 concrete sleeper is investigated experimentally and parametrically. The main parameters investigated are the steel fiber volume fractions (0%, 0.5%, 1%, and 1.5%). Under European standards, 35 UHPFRC sleepers are subjected to static bending tests at the center and rail seat sections, and the screw on the fastening system is pulled out. The first cracking load, failure load, failure mode, crack propagation, load–deflection curve, load–crack width, and failure load from these tests are measured and compared with those of a control sleeper manufactured using normal concrete C50. The accuracy of the parametric study is verified experimentally. Subsequently, the results of the study are applied to UHPFRC sleepers with different concrete volumes to investigate the effects of the properties of UHPFRC on their performance. Experimental and parametric study results show that the behavior of UHPFRC sleepers improves significantly when the amount of steel fiber in the mix is increased. Sleepers manufactured using UHPFRC with a steel fiber volume fraction of 1% and a concrete volume less than 25% that of standard sleeper B70 can be used under the same loads and requirements, which contributes positively to the cost and surrounding environment.