共查询到20条相似文献,搜索用时 109 毫秒
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1.前言细骨料表面水的变化,不仅影响新拌混凝土的和易性等各种性质,而且对已硬化混凝土的强度和干燥收缩等性质的变化有很大影响,因此对细骨料表面水的控制成为混凝土生产中最重要的项目之一。但是,一般情况骨料都堆放在露天的场 相似文献
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混凝土是一种人造建筑材料。由石骨料、水泥、砂、水及一些外加材料按照一定的比例均匀拌后,经过一定时间的硬化而成。水利施工过程中,混凝土强度的影响因素有很多。包括水泥、水灰比、骨料、施工方法等。水泥的标号和骨料等可以根据设计要求确定,所以,施工过程中,控制水灰比就成了混凝土质量最直接、最关键的影响因素。 相似文献
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传统再生细骨料的需水量大、强度低,较难利用。将废弃混凝土全部破碎成细骨料的全再生细骨料技术能够有效提高再生细骨料的性能。在前期研究的基础上,进行了全再生细骨料的制备及其对混凝土性能影响的研究。研究结果表明,全再生细骨料的制备应包括破碎、筛分和整形工艺;全再生细骨料中小于0.075和0.15mm的细粉对其强度性能有利,不宜去除;考虑到其细粉组成包括石粉,其微粉含量限值可较现有标准有所提高。全再生细骨料相对于传统再生细骨料在性能上有很大改善,胶砂需水量小且强度高,以其配制的C30和C50混凝土性能明显优于传统再生细骨料。全再生细骨料的胶砂需水量等性能仍不如机制砂和河砂,但其胶砂强度却高于机制砂和河砂;以其配制的混凝土抗压强度(特别是高水胶比时)明显高于河砂和机制砂混凝土,但工作性能略低。综合来看,全再生细骨料能够全取代河砂和机制砂用于制备C30和C50混凝土。 相似文献
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《材料导报》2020,(Z1)
本实验研究了不同仿钢纤维掺量(0%、0.2%、0.4%、0.6%)对透水混凝土抗压强度和透水系数的影响,并分析了骨料粒径、细骨料、纤维素等因素对仿钢纤维增强透水混凝土抗压强度和透水性能的影响。研究表明:仿钢纤维能够在一定程度上提高透水混凝土的早期强度;随仿钢纤维掺量的增加,透水混凝土28 d的抗压强度呈先上升后下降趋势,即存在最优掺量;当仿钢纤维掺量增加时,透水混凝土的透水能力先下降后上升;透水混凝土的抗压强度随骨料粒径的增大而降低,透水系数随骨料粒径的增大而明显增大;细骨料会使透水混凝土的早期抗压强度降低,但会提高透水混凝土28 d的抗压强度;随着细骨料取代量的增加,透水混凝土的透水系数先增大后减小;透水混凝土的抗压强度随纤维素掺量的增加而降低,透水系数随纤维素掺量的增加而增大。本研究可为实际透水混凝土施工过程中外掺料的选择提供参考。 相似文献
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《中国新技术新产品》2021,(2)
长寿命耐久性混凝土主要从材料措施、生产措施、浇筑措施、养护措施、监测措施和检验措施6个方面进行控制管理,实现混凝土结构的耐久性目标。在施工过程中对低热型硅酸盐水泥、整形粗骨料、级配优化的细骨料、补偿收缩材料、Ⅰ级粉煤灰和保坍型外加剂等6种优选原材料进行严格管控,对施工配合比、水泥入机温度、细骨料含水率匀质性、混凝土运输时间、混凝土入模温度、混凝土浇筑振捣、保温保湿养护条件和养护期间温控等主要技术参数加强管理,以实现八达岭长城站耐久性混凝土长寿命的目标。 相似文献
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采用快冻法对9种再生混凝土进行了冻融循环试验。分析了经受100次冻融循环后不同取代率下再生粗骨料和再生细骨料对混凝土立方体抗压强度的影响;研究了每25次冻融循环后再生混凝土的棱柱体质量损失率和相对动弹性模量的变化;比较了100次冻融循环作用对不同取代率下再生混凝土抗压承载力的影响。结果表明,再生混凝土抗冻融性能有所下降,且降低幅度随再生骨料取代率的增加而加剧;100次冻融循环后,再生粗骨料取代率为50%,细骨料为天然骨料的再生混凝土,其质量损失率、相对动弹性模量衰减幅度和抗压承载力损失率均与普通混凝土接近,建议再生粗骨料掺量不高于50%的再生混凝土可在寒冷地区推广应用。 相似文献
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骨料作为支撑透水材料空间骨架结构的原料,其形状、粒径范围及分布、种类与品质都对材料强度、透水性及耐久性产生重要的影响。文章从透水混凝土的骨料种类与品质要求为切入点,介绍了应用于透水混凝土中的天然骨料,建筑垃圾、工业固废、人造骨料及生活垃圾底渣等再生骨料与砂基细骨料的基本物理化学特性,重点综述了各类骨料对透水混凝土强度、透水性、耐久性及水质净化等性能影响的研究进展,并进行了简要分析与总结。最后,提出了透水混凝土可以通过对骨料的质量控制来提升其透水时效性与耐久性,指出未来需扩大透水混凝土行业协同处置废弃物的范围与能力。 相似文献
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废弃混凝土再生利用技术的研究进展 总被引:4,自引:1,他引:4
废弃混凝土再生利用对于保护环境、减少资源与能源浪费以及实现可持续发展具有重要意义。从混凝土再生骨料对混凝土性能的影响、混凝土再生骨料的应用、提高再生混凝土性能的方法3个方面介绍了目前国内外废弃混凝土再生利用技术的研究现状。指出除了进一步加大相关试验及基础理论研究外,国家以及相关机构还应在政策、资金等方面进行支持,并建立废弃混凝土再利用的具体实施标准、规范等,最终实现废弃混凝土"零排放"。 相似文献
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再生混凝土的应用,不仅能够解决废弃混凝土处理问题;又能降低因资源过度开采所引起的生态环境破坏,因而具有广阔的发展前景。相比于普通混凝土,再生混凝土的抗压强度、弹性模量以及抗疲劳性能较低,主要与再生骨料多方面因素的影响有关。对近年来再生混凝土力学性能相关研究进展进行了综述,再生骨料总吸水率是降低抗压强度的主要原因,疲劳性能则主要与再生骨料取代率和附着砂浆含量有关。在再生混凝土中掺加矿物掺合料能够改善新、旧双界面从而提高抗压强度和劈裂抗拉强度,掌握多个因素的影响和作用对再生骨料和再生混凝土进一步研究和应用具有重要意义。 相似文献
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Previous research demonstrated that the packing density, water film thickness and paste film thickness have great effects on the performance of a concrete mix. On this basis, it is herein proposed a strategy of adding a powder waste as both paste and aggregate replacements to reduce the cement and aggregate consumptions for sustainable development and to improve the packing densities of both the paste phase and aggregate phase for performance improvement. To evaluate such strategy, 25 concrete mixes incorporating granite polishing waste (GPW) as paste and aggregate replacements were tested. The results revealed that the addition of GPW as paste replacement up to 7.5% and as aggregate replacement up to 10% would most effectively increase the packing densities of the paste phase, aggregate phase and whole concrete mix, and thereby increasing the strength of the concrete, despite reduction in cement content. Such increases in packing density would also increase the excess water and excess paste to avoid excessive reductions in the water and paste film thicknesses, which are needed to maintain workability. Last but not least, separate optimization of the paste phase and aggregate phase is an effective way of optimizing the concrete mix design. 相似文献
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For making artificial lightweight aggregate, selected raw materials are fed into a rotary kiln at high temperature. Providing such a high temperature is costly and generally, the process of making artificial lightweight aggregate is not environmentally friendly. The use of natural lightweight aggregate for making lightweight concrete can lead to low-cost construction. The use of a solid waste lightweight aggregate namely oil palm shell (OPS) as coarse aggregate, is not only environmentally friendly but leads to a low-cost material. This study is a comparison between some engineering properties of OPS lightweight concrete and an artificial lightweight (expanded clay) concrete with low water to cement ratio, along with having good workability and without any segregation. The test results show that OPS concrete has better mechanical properties and a higher efficiency factor than expanded clay lightweight concrete. The ceiling strength of expanded clay lightweight concrete occurs at an early age; while it happens in OPS concrete at a later age. The crack pattern of the tested specimens shows that OPS is much stronger than expanded clay. On the other hand, the compressive strength of OPS lightweight concrete is more sensitive to lack of curing. Although OPS lightweight concrete shows twice the amount of drying shrinkage than expanded clay lightweight concrete in the short term, this difference reduces significantly at later ages. 相似文献
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This paper reviews the effect of incorporating recycled aggregates, sourced from construction and demolition waste, on the carbonation behaviour of concrete. It identifies various influencing aspects related to the use of recycled aggregates, such as replacement level, size and origin, as well as the influence of curing conditions, use of chemical admixtures and additions, on carbonation over a long period of time. A statistical analysis on the effect of introducing increasing amounts of recycled aggregates on the carbonation depth and coefficient of accelerated carbonation is presented. This paper also presents the use of existing methodologies to estimate the required accelerated carbonation resistance of a reinforced recycled aggregate concrete exposed to natural carbonation conditions with the use of accelerated carbonation tests. Results show clear increasing carbonation depths with increasing replacement levels when recycled aggregate concrete mixes are made with a similar mix design to that of the control natural aggregate concrete. The relationship between the compressive strength and coefficients of accelerated carbonation is similar between the control concrete and the recycled aggregate concrete mixes. 相似文献