养护条件对可控制渗透性模板使用效果的影响

通过空气渗透性试验、混凝土表层水吸附试验(ISAT),对采用可控制渗透性模板(CPF)的混凝土,在不同条件养护下混凝土表层性能的效果进行了对比分析,试验结果表明不采用可控制渗透性模板(CPF)的普通混凝土面,其抗渗性受养护条件影响很大,而采用可控制渗透性模板(CPF)的混凝土面不论养护条件如何都能对混凝土表层抗渗透性有很大的提高。     

有机硅烷与透水衬里模板对提高混凝土表层渗透性试验研究

有机硅烷与透水衬里模板(CPF)都是通过降低混凝土表层渗透性而提高混凝土耐久性的技术,通过空气渗透性试验与表层水吸附试验(ISAT)分别研究了有机硅烷、透水衬里模板单独使用时,以及有机硅烷与透水衬里模板共同使用时对混凝土表面渗透性的影响,试验表明有机硅烷能有效降低普通混凝土表层水吸附作用但对空气渗透性没有明显影响,透水衬里模板对普通混凝土表层的空气渗透性与水吸附作用都有明显降低作用,有机硅烷和透水衬里模板同时使用能进一步提高混凝土表层上的抗渗透性.     

非织造布模板衬对高性能混凝土养护效果影响的研究

混凝土的保湿养护对干燥地区混凝土结构具有重要意义.透水模板(CPF)通过降低混凝土表层水灰比而提高混凝土耐久性,其中的保湿材料具有保持水分的作用.通过采用MOIST-200B型微波测湿仪检测混凝土贴衬与未贴衬的湿度状况,研究了保湿型非织造布模板衬对混凝土表层的养护作用.同时,采用空气渗透性试验与表层水吸附试验(ISAT)研究了透水衬里模板对混凝土的效果,试验表明透水衬里模板对高性能混凝土表层的空气渗透性与水吸附性的降低作用不明显.     

基于现场条件下混凝土空气渗透性检测CLAM test法和Sch(o)nlin法的应用研究

透水衬里模板(CPF)通过其滤层排除新拌混凝土表层水分和因振捣而富集于混凝土表层的气体来提高混凝土表层强度和抗渗透性。通过混凝土表层水吸附试验(ISAT)评价了透水衬里模板对混凝土抗渗透性的提高作用,并利用文献提供的混凝土表层水吸附试验(ISAT)与压汞法(MIP)之间的关系式分析了采用透水衬里模板后混凝土表层孔结构参数的变化。在对比分析用压力试验机获得的混凝土整体抗压强度与回弹法得到的表层抗压强度后,可以发现透水衬里模板可以提高混凝土的表层抗压强度而不是混凝土的整体抗压强度。     

透水衬里模板改善混凝土表层性能的研究

透水衬里模板(CPF)通过其滤层排除新拌混凝土表层水分和因振捣而富集于混凝土表层的气体来提高混凝土表层强度和抗渗透性。通过混凝土表层水吸附试验(ISAT)评价了透水衬里模板对混凝土抗渗透性的提高作用,并利用文献提供的混凝土表层水吸附试验(ISAT)与压汞法(MIP)之间的关系式分析了采用透水衬里模板后混凝土表层孔结构参数的变化。在对比分析用压力试验机获得的混凝土整体抗压强度与回弹法得到的表层抗压强度后,可以发现透水衬里模板可以提高混凝土的表层抗压强度而不是混凝土的整体抗压强度。     

保湿自养护型混凝土透水模板内衬的性能研究

通过混凝土渗透性试验和湿度检测,研究了新型模板内衬材料对混凝土进行"保湿养护"的作用,试验结果表明"保湿自养护型"透水模板内衬不但为混凝土表层提供了一个"湿养护环境",同时能提高混凝土表层的抗渗透性能。     

透水模板布在南水北调工程扭曲面混凝土施工中的应用

结合南水北调工程某标段倒虹吸渐变扭曲面混凝土成型高质量需求,对比研究了透水模板布对混凝土力学性能及表层渗透性的影响。结果表明,采用透水模板布施工能使混凝土外观显著改善,表面力学性能大幅提高,同时混凝土表层渗透性大幅降低。透水模板布能有效提高混凝土表层性能,进而提高混凝土结构的耐久性。     

混凝土保护层渗透系数测试方法研究

混凝土保护层的渗透性是决定混凝土耐久性的重要因素,对其渗透性检测方法的研究具有重要的工程实际意义.基于达西(Dracy)渗透定律,介绍一种新型的混凝土保护层渗透系数测试方法.该方法利用真空泵在混凝土表层创建负压区,通过控制气体流动方向,依据内部压强差测定混凝土保护层的渗透系数.依据试验数据,建立了简化的数学计算模型,并...     

透水模板布对铁路混凝土性能影响研究

采用透水模板布浇筑大尺寸试验墩,从表面回弹、permit测试、吸水性、电通量等方面对比研究了透水模板布对混凝土力学性能及表层渗透性的影响。结果表明,采用透水模板布施工能使混凝土外观显著改善,表面力学性能大幅提高,同时混凝土表层渗透性大幅降低。透水模板布能有效提高混凝土表层性能,进而提高混凝土结构的耐久性。     

透水模板布对混凝土抗渗性能影响分析

对普通胶合板模板与贴透水模板布模板成型条件下不同水胶比及掺合料所获得的混凝土试件,运用回弹法、快速氯离子渗透法(ASTMC1202)、压汞法以及GEM理论,从宏观和微观两方面研究了透水模板布对混凝土抗渗性能的影响.结果表明:使用透水模板布后,对于不同配合比的混凝土试样,表观质量及密实度得到不同程度改善,回弹强度相应提高;试件表层临界孔径和有害孔数量明显减少,渗透系数降低,表层混凝土微观孔结构得到改善,整体抗渗性能相应增强.     

Combined effect of two sustainable technologies: Self-compacting concrete (SCC) and controlled permeability formwork (CPF)

The work presented in this paper aims at contributing to sustainable construction through enhancement of durability of concrete structures. Full size precast elements were cast with both self-compacting concrete (SCC) and conventional vibrated concrete (CC) using controlled permeability formwork (CPF). SCC is known to impart a more homogeneous and finer microstructure, compared to conventional concrete, therefore leading to more durable reinforced and pre-stressed concrete structures. CPF enables, in fresh concrete, drainage of excess water and air besides retaining binder particles at the concrete surface, leading to a blow-hole free surface and enhanced quality of the outer layers. The research program developed was designed to compare performance of two different CPF systems and also assess the combined effect of using CPF on SCC compared to CC.     

电渗结合透水模板成型混凝土表观质量试验

基于电渗均匀快速的排水特性,建立了电渗滤水试验模型,阐述电压加载初始时点、电压值、电渗历时及电极间距对混凝土成型效果的影响,并研究了结合透水模板垫层来改善电渗混凝土成型外观的方法.结果表明:电渗结合透水模板工艺排水可形成致密无孔洞混凝土表面,显著降低混凝土渗水透气性能,且可提高混凝土表面强度.     

真空脱水工艺改善混凝土抗冲磨性能试验研究

采用透水模板衬与真空脱水工艺相结合的方法浇注低水灰比混凝土,探讨以中高强度配比的真空成型混凝土达到高强混凝土抗冲磨性能的可行性.试验结果表明： 降低水泥的比表面积可提高低水胶比混凝土的真空脱水率,进而提高混凝土抗冲磨性能;采用透水模板衬和真空脱水工艺相结合的方法,可使配制强度为C50的真空成型混凝土抗冲磨性能达到或超出配制强度为C70的非真空高强混凝土,由此可减少单方混凝土胶凝材料用量,有利于减少混凝土的收缩.真空脱水工艺提高混凝土抗冲磨性能的机理在于其明显降低了混凝土孔隙率,靠近表层的混凝土最可几孔径、临界孔径和平均孔径均明显减小,孔结构得到明显优化.     

透水模板改善混凝土性能试验

对比分析了2种透水模板(CPF)的主要物理性能;结合宏观、微观试验,探讨了透水模板改善混凝土性能的机理与效果.结果表明:透水模板能有效降低混凝土浇注时的表面水灰比,提高混凝土的表面密实度,改善混凝土的孔隙分布和表观质量,提高混凝土抗渗性和耐久性.     

透水模板布对海工混凝土性能影响研究

研究了国产透水模板布与进口透水模板布在重复使用过程中对海工混凝土外观质量、表面强度、抗压强度和抗渗透性能的影响.研究表明:透水模板布随使用次数的增多,混凝土的外观质量、表面强度、抗压强度和抗渗透性能会有不同程度的降低.国产QS透水模板布在前两次使用时性能与两种进口透水模板布相当,部分性能优于进口产品,但第3次使用时效果不如丹麦透水模板布.     

Evaluation of concrete mixes and mineral additions when used with controlled permeable formwork (CPF)

The influence of concrete mixes and commonly used mineral additions and their effects on the near surface performance of vertically cast concrete against controlled permeable formwork (CPF) are the focus of this study. Three grades of concrete (C25, C30 and C45) and mineral additives including GGBS and PFA have been tested for surface performance in situ with CPF. The various loadings were chosen to represent the minimum and maximum levels seen in standard industry practice. The range of tests used to characterise the near surface performance include subjective assessment of surface quality, surface hardness and surface tensile strength. Permeability studies of the liners after casting indicate that no excessive embedding of fine particles occurred irrespective of constituents used. Surface quality was dramatically improved in each case and changes to surface colour through densification were quantified. Near surface performance studies indicated a significant improvement for all systems studied.     

An Investigation into the critical factors affecting the performance of composite controlled permeable formwork liners: Part I – Drainage medium

The critical elements associated with a CPF drainage medium and their associated effects on the near surface performance of vertically cast concrete slabs are the focus of this study. A range of board absorption levels, textured features and texture depth are investigated using a Taguchi orthogonal array approach. A permeable polypropylene filter layer was used in conjunction with the various drainage mediums. Statistical software was utilised to determine significant variables as a function of the near surface performance. The range of tests used to characterise the surface performance of the various drainage mediums include surface roughness, surface hardness, surface tensile strength and water absorption. Results are compared to a control sample which was cast against impermeable plywood formwork. All drainage medium permutations showed similar evidence of water/cement ratio reduction at the near surface region of the concrete slab. Surface quality was analysed using quantitative methods and showed significant improvements for all systems over the control. The results for the systems studied indicate that the features of a drainage medium are not critical to the functionality of a CPF liner to reduce the near surface w/c ratio. In fact, it is indicated that the absence of a drainage medium has the same enhancement in near surface concrete slab properties as that of a complex structure when compared to the control sample.     

掺活化湿排粉煤灰混凝土性能试验研究

本文采用石灰预处理工艺处理低等级湿排粉煤灰作混凝土的掺合料,发现其配制的混凝土强度超过同掺量的普通二级干灰配制的混凝土强度。通过研究掺活化湿排粉煤灰的混凝土的抗冻性能、收缩性能、抗氯离子渗透性能,发现其耐久性能良好。处理后的粉煤灰可作为优质的混凝土掺合料。