再生混凝土集料的研究

再生集料作为废弃混凝土的主要用途,其性能及对混凝土的性能影响程度将决定废弃混凝土的再生利用可能,本文进行了这方面的探索性研究。     

粉煤灰再生集料混凝土的研究

探讨粉煤灰再生集料混凝土的性能。研究表明,利用粉煤灰取代部分再生集料,将显著提高再生集料混凝土的强度,改善表观质量,降低生产成本。建议在利用再生集料制备混凝土时宜掺加合理比例的粉煤灰。     

再生集料混凝土循环利用的试验研究

随着再生集料混凝土技术的成熟知大量应用，今后对于到了使用年限的废弃的再生集料混凝土的处理又将成为一个新的课题。本试验研究了再生集料多次循环利用的可能性。本文通过大量实验证实：用废弃混凝土作为集料来配制再生混凝土是对废弃混凝土利用的最为经济可行的方法，所配制的再生混凝土完全能满足相应施工要求，而且对废弃混凝土可实现真正的循环利用。本试验研究为再生集料混凝土实现真正的资源化循环利用提供了实用的参考数据。     

再生集料透水混凝土的试验研究

为研制一种适合工程实际需要的再生集料透水混凝土,通过对再生集料透水混凝土原材料用量的计算,调整并确定了原材料的用量,得到再生集料透水混凝土的实际应用配合比,试验结果表明:孔隙率为17.5％,透水系数为2.50mm/s,28d抗压强度达35.6MPa.     

路面再生集料混凝土的特性初探

介绍了再生混凝土的概念,针对来源于公路路面的废弃混凝土再生骨料的特点,结合再生骨料和天然骨料基本特性的差异,配制工作性能和强度满足设计要求的再生骨料混凝土,并对天然骨料混凝土和再生骨料混凝土的各项性能进行试验对比分析研究.     

沥青混凝土面层碎石集料的质量控制

从碎石集料生产加工、运输、存放等方面,提出沥青中、上面层碎石集料质量控制的几点要求,最大限度的减小原材料对沥青混凝土面层施工质量及耐久性的影响,进而提高沥青路面使用性能。     

废旧水泥混凝土再生集料技术的探讨

本文概述了再生混凝土对环境的影响以及其在国内外的研究现状和发展,并分析了废旧水泥混凝土再生集料的制备技术,探讨了国内外再生集料生产设备,认为混凝土的再生具有良好的经济性和较大的发展潜力,加大再生技术的研究。     

再生集料用于商品混凝土的研究

用废弃混凝土制成的再生集料代替部分天然集料配制混凝土技术,因其具有明显的环境效益、经济效益,已受到人们的重视。本文以某搅拌站的混凝土下脚料制成的再生集料,用于商品混凝土中,对再生混凝土的有关性能进行研究,并在工程中进行应用。结果表明,再生集料用于商品混凝土不仅能确保工程质量,而且有明显的经济效益。     

再生混凝土集料透水性混凝土性能研究及应用

研究了再生混凝土集料对透水性混凝土物理力学性能和耐久性能的影响;从结构分析角度提出了透水性混凝土在工程应用中的结构形式;结合工程实例介绍了再生集料透水性混凝土的应用效果.     

高品质再生骨料混凝土的力学性能和耐久性试验研究

对高品质再生骨料混凝土的力学性能和耐久性进行了系统的试验研究,主要包括其立方体和棱柱体抗压强度、劈裂抗拉强度、抗折强度、弹性模量以及收缩、徐变、抗氯离子渗透、抗碳化性能和抗冻性能.高品质再生骨料由课题组提出的包含机械磨损(干拌)和水冲洗两个流程的一套高品质再生骨料生产工艺加工得到.试验结果表明,与由普通再生骨料(常规破碎工艺生产的再生骨料)配制的混凝土相比,高品质再生骨料混凝土的力学性能和耐久性均有显著的提高,基本上可以达到与普通混凝土相近的水平.     

高品质再生骨料的生产及基本性能试验研究

为了提高再生骨料的品质,提出了一套高品质再生骨料生产工艺,与目前常规的再生骨料生产工艺相比,增加了机械磨损(干拌)和水冲洗两个流程.测试了利用新工艺生产的再生骨料的基本性能,并与天然骨料和常规再生骨料工艺生产的再生骨料进行了对比.结果发现,与常规工艺生产的再生骨料相比,新工艺生产的再生骨料品质显著提高,主要表现在密度增加、废旧水泥砂浆含量和吸水率降低、坚固性增加等.进一步研究了利用新工艺生产的高品质再生骨料混凝土的抗压强度,发现其与相同条件下普通混凝土差别不大.     

Microwave-assisted beneficiation of recycled concrete aggregates

The presence of mortar has been reported as the main factor causing the lower quality of recycled concrete aggregates (RCA) when compared to natural aggregates (NA). A novel microwave-assisted technique to increase the quality of RCA by partially removing the mortar adhering to RCA particles and breaking up the lumps of mortar present in RCA is introduced in this paper. The technique takes advantage of the difference in the electromagnetic properties of the adhering mortar and natural aggregates to generate high thermal stresses within the mortar, especially at the interface with the embedded natural aggregates, to cause delamination. The stresses generated also result in the breaking up of the lumps of mortar into smaller pieces. The results of an experimental study conducted to investigate the capability of the microwave-assisted RCA beneficiation technique and to compare its efficiency with other beneficiation methods proposed in available literature are presented. Moreover, the effects of incorporating various amounts of un-treated and microwave-treated coarse RCA on the mechanical properties of concrete are investigated. The temperature distribution and stresses developed in RCA when subjected to microwave heating during the beneficiation process are numerically calculated for a better understanding of the processes involved.     

混凝土路面砖生产的质量控制

本文分析了影响混凝土路面砖生产的质量因素,总结归纳了路面砖生产的质量控制要点,介绍了彩色饰面混凝土在路面砖中的生产应用.     

沥青混凝土生产质量控制研究

分析了沥青混凝土生产中常见的质量问题,从沥青混凝土设计、搅拌设备调试、成品料温度控制、填料比例控制等方面,阐述了沥青混凝土生产质量的控制措施,有利于提高沥青路面的工程质量。     

Roller compacted concrete with contaminated recycled aggregates

Recycling waste building materials from construction and demolition (C&D) sites is increasingly investigated for economical and environmental reasons. Roller compacted concrete (RCC) is a special dry concrete mix; laid down and compacted like a soil, it is especially used for the construction of massive structures like dams or large horizontal surfaces like road foundation. In this paper, natural concrete slabs were cured in water, sea water, chloride solutions or sulphate solutions and then crushed to obtain virgin and contaminated (polluted) recycled aggregates. The aim of this research is the total replacement (100% coarse and fine) of natural aggregates (NA) by recycled concrete aggregates (RA) in the composition of a roller compacted concrete. The natural and recycled aggregates are characterised and compared. The mechanical properties and durability performances of concrete with contaminated RA are analysed. The experimental results showed that the polluted RA are much richer in chlorides than in sulphates and are leached if they are soaked in water. Significant differences were observed between the properties of original and new concrete and the results demonstrated the need of taking these contaminations into account.     

再生混凝土的耐久性及控制措施研究

对再生骨料进行加强处理对提高再生混凝土的各种性能具有现实意义。现有的再生骨料强化处理措施在耐久性上具有一定的局限性。对再生混凝土的抗渗性、抗冻融性、抗碳化、氯离子渗透性、硫酸盐侵蚀、耐磨性进行了分析,并提出了减小水灰比、掺加粉煤灰、采用二次搅拌工艺、减小再生骨料最大粒径、采用半饱和面干状态等改善再生混凝土耐久性的措施。     

Identification of frost-susceptible recycled concrete aggregates for durability of concrete

Demolished concretes to be recycled show great diversity in property with regard to residual potential of resistance to the environmental effects such as frost action, when they are used in a new concrete as aggregate. There seems to exist no appropriate test method fitting specific characteristics of the recycled concrete aggregates with respect to the fair judgement of their unbound state frost durability. This fact rises another important prejudice against performance of recycled concrete aggregates compared to virgin alternatives. This study deals with reliable identification of frost susceptibility of recycled concrete aggregates. An unbound frost durability test with a mild pre-drying procedure (at 50 °C) was performed on recycled concrete aggregates originated from both air-entrained and non-air-entrained type of source concretes. The procedure distinctly identified the non-durable recycled coarse aggregates in parallel to freezing and thawing durability results of the concretes incorporating identical aggregates. Sulfate soundness test gave misleading results in judgement of the unbound state frost durability due to the highly disruptive physicochemical effect of the method on the recycled concrete aggregates, regardless of the air void characteristics of the materials.     

Influence of recycled concrete aggregates on strength properties of concrete

Many structures in the middle-east’s Gulf region are now either reaching the end of their design life or were not constructed according to the specifications. Demolition or maintenance work on such structures results in large amount of concrete rubbles. Recycling concrete wastes will lead to reduction in valuable landfill space and savings in natural resources. The objective of this study is to investigate the strength of concrete made with recycled concrete coarse aggregate. The variables that are considered in the study include the source of the recycled concrete and target concrete strength. The toughness and soundness test results on the recycled coarse aggregate showed higher percentage loss than natural aggregate, but remained within the acceptable limits. The compressive and splitting tensile strengths of concrete made with recycled coarse aggregate depend on the mix proportions. In general, the strength of recycled concrete can be 10–25% lower than that of conventional concrete made with natural coarse aggregate.     

混凝土再生骨料强化试验研究

利用废弃混凝土制备的再生骨料配制混凝土在发达国家已引起高度重视。结合我国实际情况，用4种不同的浆兴对再生骨料进行了强化试验，对试验结果进行了分析。强化试验表明，水泥外掺Kim粉浆液强化再生骨料效果理想。