Influence of coal bottom ash as fine aggregate on fresh properties of concrete

This paper investigates the influence of the use of coal bottom ash as a replacement for natural fine aggregates on the properties of concrete in the fresh state. Tests for water loss through bleeding, and the determination of the setting times and plastic shrinkage, were carried out in order to evaluate the material in the presence of bottom ash. The influence of the porosity of bottom ash on the potential water absorption and water loss of the material, as well as on the water consumption of concretes produced with bottom ash, is also discussed. The results showed that in the fresh state the concretes produced with the bottom ash are susceptible to water loss by bleeding and the higher the percentage of bottom ash used as a natural sand replacement the lower the deformation through plastic shrinkage. The results also showed that the setting time is affected by the presence of bottom ash in the concrete. In conclusion, different forms of bottom ash mix result in concretes with different properties in the fresh state, but the behavioral tendencies are maintained when bottom ash is employed as a replacement for natural aggregates.     

重晶石混凝土施工及质量控制

本文介绍了重晶石混凝土结构施工准备阶段寻找重晶石料源及配合比优化情况,重晶石混凝土的搅拌、运输以及施工特点;施工存在的问题及对策.     

沥青混凝土级配设计中细集料的运用

从石屑、人工砂、天然砂三种细集料室内车辙试验入手,以相同级配条件下的动稳定度试验作为最终评价标准,对三种细集料用于沥青混凝土的可能性进行分析,得出人工砂完全具备用于沥青混凝土路面各项性能要求的结论。     

涡压挤扩细石混凝土锚固支护土体的施工方法

提出且验证了涡压挤扩机理,分析了混凝土介质向土体介质中挤入的力学条件,介绍了涡压挤扩细石混凝土锚固支护土体的设备及施工工艺流程,结果表明,采用涡压挤扩方法实施锚固支护土体的施工工艺在理论上是可行的。     

屋面细石混凝土刚性防水层作法改进

从防止混凝土裂缝和改进细部作法两个方面介绍了提高屋面细石混凝土刚性防水层性能及耐久性的措施 ,重点阐述了分格缝的留设方法和在细部作法中增加混凝土收头的改进作法 ,最后结合具体工程评析了应用效果     

再生混凝土粗骨料质量等级模糊综合评估方法

对再生混凝土骨料质量进行评估是评价其品质是否满足混凝土结构工程性能要求的关键所在。基于模糊综合评估理论,提出了再生混凝土粗骨料质量等级评估方法。采用表观密度、吸水率、洛杉矶损失值、吸附的水泥砂浆含量、氯化物含量与硫酸盐含量6个指标,将再生混凝土粗骨料划分为3个模糊质量等级,对应于优质、合格与不合格3个状态,给出了不同质量等级再生粗骨料的适用环境作用等级与适用工程。采用基于可信度矩阵与频数统计的CMFS法确定各指标的权重,用最优区间型隶属度函数确定各指标的隶属度以实现等级变化的连续性,采用加权平均模糊算子计算评判矩阵,对评判矩阵作归一化处理后以质量等级评分值作为等级评定的唯一标准。用matlab语言编制了评估程序并用大量的算例验证了评估方法的合理性。     

Mix design procedure for recycled aggregate concrete

Conservation of natural resources and preservation of environment is the essence of any development. Use of recycled aggregate concrete (RAC) is one such attempt and is an answer to some of the problems in constructional engineering. The concept of using RAC is now gaining popularity and research in this direction has gained momentum. In this paper, the authors have identified the most suitable method of mix design for RAC, from amongst the available conventional methods of mix design. An influencing parameter is identified and an empirical relation is suggested to modify the influencing parameter. Mix design parameters thus obtained, enable RAC to attain the desired and designed target strength without attempting any trial mixes. The suggested modified procedure, however, demands 10% more cement which is considered quite reasonable and acceptable in view of the inferior quality of recycled aggregate.     

多孔膨胀珍珠岩轻集料混凝土分层离析控制技术的研究

探讨了多孔膨胀珍珠岩轻集料混凝土分层离析产生的原因,采用掺入适量粉煤灰、高效外加剂并对多孔膨胀珍珠岩进行预湿处理等技术措施有效防止了轻集料混凝土的分层离析,配制出了具有优良工作性和匀质性,不离析、低收缩,易于浇筑和开挖的CL5～CL10多孔膨胀珍珠岩低强轻集料混凝土.     

谈清水混凝土二次结构细部作法施工质量的提高

依据设计图纸,通过对清水混凝土二次结构各控制点的统筹分析、研究,对整个结构系统利用科学的方法实践,大大提升了其施工质量,为今后同类型工程的施工提供了有力的依据。     

浅谈大面积细石混凝土地面的施工

介绍了地面基土及3：7灰土垫层的夯填施工技术，论述了细石混凝土地面面层的施工方法，提出了施工过程中应控制的几方面内容，以防止细石混凝土路面质量通病的发生。     

Alternative materials for concrete— Mersey silt as fine aggregate

The possible use of Mersey silt as a fine aggregate for concrete has been investigated. Sound concrete with compressive strength up to 45 N mm^?2 has been made. However, the cement content required for typical mixes is higher than with conventional sands and there is no overall cost saving. Current British Standard limits for silt content of aggregates have been examined critically in the light of available data and it is recommended that the requirement for material finer than 75 μm be eased to 5% of the total aggregate weight.     

再生混凝土结构设计研究

结合近年来我国再生混凝土研究与应用成果以及我国首部再生混凝土应用设计规范--上海市工程建设规范DG/TJ08-2018-2007<再生混凝土应用技术规程>,初步探讨了再生混凝土结构设计方法,主要包括再生骨料的质量标准、再生混凝土的技术性能指标和再生混凝土基本构件承载力计算与设计方法等内容.通过<规程>计箅结果与搜集到的大量试验结果进行对比,霞点分析了<规程>中建议的再生混凝土技术性能指标以及基本构件承载力计算公式的精度及安全性.研究结果表明,<规程>中给出的性能指标计算公式总体上与大量试验结果吻合良好,且偏于安全.     

A specific conductance method for quality control in water analysis

A method to aid quality control in water analysis is described. It can be used both to help maintain a high quality of analytical data and to highlight inconsistencies in existing data.The procedure, either computational or graphical, relies on a comparison of measured specific conductance with a specific conductance calculated from the analytical data using an extended version of the Onsager limiting equation.The method is discussed in relation to water analyses typical of limestone catchments. A number of limitations are set forth and the method is shown to be suitable for most waters with a specific conductance in the range 80–350 μs cm^-1, although it can probably be extended to waters with a specific conductance in the range 50–1000 μs cm^-1.     

Feldspar and mica. Key minerals for fine aggregate quality

Research on the aggregate-concrete interaction has proved feldspar and mica to be key minerals for concrete quality. Feldspars are predominant minerals in most Norwegian aggregates. A relation has been found between the strength of cement mortars and the type and condition of the feldspars present. Especially, the degree of feldspar alteration (saussurite, sericite) appears to be a primary factor for mortar strength. Concerning mice, a dependence on the weathering conditions has been demonstrated, naturally occurring mica proving less harmful to concrete properties than mica in crushed aggregates. A geochemical interpretation of this includes changes in cation exchange capacity resulting from alteration and weathering.     

生活垃圾焚烧灰渣代砂混凝土配合比及力学性能试验

对生活垃圾焚烧灰渣代砂作为混凝土细骨料进行了试验研究。从有毒物质浸出、筛分、压碎指标等分析了生活焚烧垃圾灰渣的骨料特性,并对5种水胶比、3种代砂率的生活垃圾焚烧灰渣细骨料混凝土进行了配合比试验及力学性能试验。试验结果表明,生活垃圾焚烧灰渣多孔、吸水率高、压碎指标低,具有一定的潜在水硬性;通过增加减水剂等合理配合比设计,可以配出工作性能满足工程要求的生活垃圾焚烧灰渣细骨料混凝土;生活垃圾焚烧灰渣细骨料混凝土强度要低于同配合比条件的普通天然砂混凝土,尤其是100%代砂率焚烧灰渣混凝土28 d抗压强度仅为普通天然砂混凝土的一半左右,50%代砂率焚烧灰渣混凝土抗压强度更接近普通天然砂混凝土。     

页岩陶粒轻骨料混凝土配合比设计及应用

以广西来宾大桥维修加固工程为例,介绍页岩陶粒轻骨料混凝土原材料选择、配合比设计及施工技术要点;通过试验研究和工程实践,评价页岩陶粒轻骨料混凝土在旧桥改造加固中的应用效果;并为轻骨料混凝土的设计及应用提供依据.     

基于层次分析法的混凝土建模在质控中的应用

针对混凝土质量提出运用层次分析法，分析影响混凝土质量的各种因素，建立实用有效的层次结构模型，并列表采用求根法进行计算，经过一系列的综合分析和一致性检验，最终确定混凝土进行质量控制的重点，为混凝土进行质量控制提供了理论依据和指导。     

由设计谈混凝土结构施工质量控制重点

介绍了建筑物采用混凝土结构的优势,分析了混凝土结构施工中存在的问题,通过对设计规范相应条文的分析,总结了混凝土结构施工中质量控制的重点,以期减少或消灭在混凝土中长期存在的质量通病,建造出优质的建筑物。