不同粗细骨料组合下的混凝土耐硫酸腐蚀研究

为比较不同粗细骨料组合对混凝土耐硫酸腐蚀性能的影响,对水灰比为0.45、尺寸为100×200的4种骨料组合（青石+黄砂,青石+大理砂,大理石+黄砂,大理石+大理砂）混凝土试件进行耐硫酸加速腐蚀试验。将混凝土试件浸泡于pH值为0.95左右的硫酸溶液中进行为期194 d的12次跟踪监测,根据检测数据计算得到了混凝土的腐蚀深度,按线性方程斜率从大到小对4种骨料组合混凝土硫酸腐蚀速率进行了排序。结果表明:含有大理石或大理砂骨料的混凝土比含青石和黄砂骨料的混凝土耐硫酸腐蚀性能高;腐蚀层受扰动情况下,腐蚀深度与腐蚀时间呈线性关系;大理石细骨料比大理石粗骨料更有利于减小腐蚀深度。     

陶瓷废弃物代砂制备混凝土的强度特征

陶瓷废弃物经破碎筛分加工制成人工砂,以此作为混凝土的细骨料进行部分或全部取代天然砂,并对制备的混凝土不同龄期的抗压强度、抗折强度等特征进行了试验研究,研究中对不同取代率、灰水比、陶瓷砂处理方式、龄期等因素对陶瓷砂混凝土强度特征进行了系统考察.研究表明,陶瓷废弃物经破碎筛分加工后,可以满足混凝土用砂规范的要求,尤其是加工过程中与部分碎石混合破碎,其人工砂的性能是优异的.可全部取代优质河砂,而纯陶瓷废弃物加工的砂配制的混凝土,其立方体抗压强度和抗折强度值均能达到设计要求,甚至可以超过同等配合比的天然河砂配制的混凝土的强度;陶瓷砂混凝土的强度与天然骨料混凝土的变化规律相似,即随灰水比的增加而提高,随龄期的增长强度不断增加.强度特征的评价为陶瓷砂混凝土的配合比设计提供了有效的依据.     

工业和生活废弃物的利用与混凝土的使用安全

随着天然砂石自然资源的日渐枯竭,工业废弃物、建筑垃圾和污泥等加工后作为人造粗、细集料用于混凝土,掺入水泥中作混合材,以及作为混凝土的掺合料和矿物外加剂,促进了资源再生利用和节能减排工作.加强废弃物的成分研究,规定其有害物质限量,防止利用不当,造成对环境的二次污染,影响混凝土的耐久性与使用寿命,应是当前研究的重点.     

Use of aggregates produced from marble quarry waste in asphalt pavements

More than 95% of asphalt pavement materials (by weight) consist of aggregates. The highway and construction industries consume a huge amount of aggregates annually causing considerable energy and environmental losses. The aggregates are usually produced from neighborhood aggregate quarries or from natural aggregate sources. As a result of the increasing demands for new aggregate quarries, the general texture of earth's surface has been steadily deteriorating, causing environmental concerns. The use of marble wastes from marble quarries as aggregates might help meet the increasing demands and slow down any detrimental effects on the environment. In this study, recycled aggregates produced from homogeneous marble and andesite quarry wastes in Afyonkarahisar–Iscehisar region were compared to two other aggregate specimens currently used in Afyonkarahisar city asphalt pavements. Los Angeles abrasion, aggregate impact value, freezing and thawing, flakiness index and Marshall stability flow tests were carried out on the aggregate specimens. The test results indicate that the physical properties of the aggregates are within specified limits and these waste materials can potentially be used as aggregates in light to medium trafficked asphalt pavement binder layers.     

Creep and shrinkage of recycled aggregate concrete

This paper presents the results of experimental research into concrete produced by replacing the natural aggregates with recycled aggregates coming from construction waste and concrete work demolitions. The main aim of this work was to determine creep and shrinkage variations experienced in recycled concrete, made by replacing the main fraction of the natural aggregate with a recycled aggregate coming from waste concrete and comparing it to a control concrete. The substitution percentages were 20%, 50% and 100%. Fine natural aggregate was used in all cases and the amount of cement and water–cement ratio remained constant in the mixture. It was possible to state that the evolution of deformation by shrinkage and creep was similar to a conventional concrete, although the results after a period of 180 days showed the influence of the substitution percentage in the recycled aggregates present in the mixture. In the case when 100% coarse natural aggregate was replaced by recycled aggregate there was an increase in the deformations by creep of 51% and by shrinkage of 70% as compared to those experienced by the control concrete.     

Properties of concrete using metallurgical industrial by-products as aggregates

The use of industrial by-products and waste materials in concrete opens a whole new range of possibilities in the reuse of materials in the building industry. In this research study, concretes were made with chemical foundry sand (QFS) and green foundry sand (GFS) as substitution for raw sand. Also Electric arc furnace slag (EAFS) and blast furnace slag (BSF) were used as substitution for coarse raw aggregates in 25%, 50% and 100% of concrete production. Two concrete production stages were carried out. In stages 1 and 2, slump test and compressive and tensile splitting strengths and modulus of elasticity were determined. Due to adequate properties of all concretes found in stage 2, length change (during 56 weeks), sorptivity and high temperature exposure evaluation were also determined. The tests results obtained from concretes produced in stages 1 and 2 were compared with those of conventional concrete (CC) and the adequate use of the by-products for concrete production was verified.     

以废弃陶瓷为骨料生产再生混凝土可行性探讨

通过国内外有关文献的分析与研究,介绍了使用陶瓷废弃物取代天然骨料生产混凝土的发展情况及可行性,分析了用陶瓷废弃物作原料生产再生混凝土的社会效益和经济效益,为我国陶瓷废弃物的处理提供了一条新思路.     

我国混凝土骨料的现状与问题

针对目前我国天然矿石资源短缺、乱采滥挖砂石的现象屡禁不止、砂石质量严重失控的现状,应提高对砂石重要性的认识,引导砂石行业成为保护环境、开发建设用地、充分利用废弃资源的主力军。发展以工业废渣及淤泥、岩石为原料的人造轻骨料,积极开展再生骨料的应用研究工作。     

Use of concrete road recycled aggregates for Roller Compacted Concrete

Construction waste management is a quite important economical and environmental deal for our societies. More than 2 million tons demolition and construction wastes are annually produced only in Wallonia, Southern Region of Belgium; recycling has clearly to be promoted. Roller Compacted Concrete (RCC) is a special dry concrete made of aggregates, water and low quantity of cement, laid down and compacted like a soil, for the construction of massive structures like dams or large horizontal surfaces like road foundations. The topic of this research is the replacement of natural aggregates by concrete road recycled aggregates in the mix design of concrete. Characteristics of aggregates are of prime importance for the quality of the concrete: Los Angeles, water absorption and specific gravity. It has been observed that RCC with natural and concrete road recycled aggregates are similar for solid compactness, while no major influence of cement content – when around 200 kg – may be detected. However, compressive strength is higher for RCC with natural aggregates. This study clearly shows the opportunity of using concrete road recycled aggregates for RCC in basements.     

绿色建造下的泵送混凝土原材料市场资源综述

泵送混凝土原材料的需求量和质量要求越来越高,同时其生产和运输过程中产生的建筑垃圾、碳排放等环境污染问题也日益凸显。目前,河砂、卵石等天然原材料供不应求;以石灰石为原料生产的碎石和机制砂的质量和产量不断提高,但仍有提升空间;老旧淤塞河道中开采的河砂、使用大粒径天然卵石为原料生产的碎卵石和机制砂,其市场认可度尚待提高;水泥、粉煤灰、粒化高炉矿渣粉等原材料在企业转型升级的同时也带来了平原、丘陵、山地等区域的整体供应分布不均问题;聚羧酸型外加剂以其高效、经济、方便等优点普及市场,还可进一步提升与砂石的适应性。     

再生粗骨料的微观特征及基本性能研究

作为建筑垃圾主要组成之一的废弃混凝土,可以通过回收处理变为再生混凝土骨料,部分或全部代替天然骨料而再次应用到建筑工程中。通过扫描电子显微技术,对破碎后的骨料表面的微观状态进行了观察分析,得到了再生骨料表观特征以及微裂缝分布情况。同时依照JGJ 52-2006《普通混凝土用砂、石质量及检验方法标准》对再生粗骨料进行了基本性能测试,并与天然粗骨料的基本性能进行对比。通过实验,得出了再生粗骨料具有表观密度小、吸水率与含水率高、压碎指标值较高、针片状含量小的特点。还对实验结果进行了分析,为制备再生混凝土提供了依据。     

自燃煤矸石集料预处理对混凝土工作性及强度影响

自燃煤矸石集料的多孔性能决定了其吸水特性,其附加水及预湿时间对混凝土性能影响较大。通过对自燃煤矸砂+天然碎石、天然河砂+自燃煤矸石两种组合集料配制的混凝土进行试验研究,揭示附加水及预湿时间的变化对混凝土拌合物工作性及硬化强度的影响。结果表明:自燃煤矸砂按饱和吸水率的60%、自燃煤矸石按吸水率的80%加入附加水,拌合物可获得预拌混凝土大流动性的配制要求。自燃煤矸砂、煤矸石随着附加水的递增,混凝土7,28 d抗压和劈拉强度皆呈下降的趋势,抗压强度下降幅度较大;自燃煤矸石粗集料预湿时间越长其强度增长越好,但当预湿时间大于1 h,变化幅度很小。而自燃煤矸砂随预湿时间的递增,强度呈递减趋势。     

Bulk engineering and durability properties of washed glass sand concrete

The paper reports the results of an experimental programme aimed at examining the performance of Portland-cement concrete produced with washed glass sand (WGS), as natural sand substitute- by mass. The effects of up to 50% WGS on fresh, engineering and durability related properties have been established and its suitability for use in a range of normal-grade concrete production assessed. WGS characteristics results showed that the post-container glass waste can be crushed to provide WGS of physical properties that satisfy the current requirements set in appropriate standards for natural sand for concrete. The density and water absorption of WGS was found to be lower than natural sand. The results for fresh concrete showed a reduction in workability of concrete with increase WGS proportion beyond 20% in the mix, although slump measurements remained within the allowable margin of ±25 mm. The mixes with high proportions of WGS were found to be less cohesive. Studies of hardened concrete properties, comprising bulk engineering properties (compressive cube and cylinder strength, flexural strength, modulus of elasticity, drying shrinkage) and durability (near surface absorption, alkali silica reaction) showed similar performance for concrete produced with natural aggregates and up to 15% WGS.     

Recycling of scale and steel chips waste as a partial replacement of sand in concrete

Modification of concrete properties by the addition of appropriate materials is a popular field of concrete research. This study is focusing on the use of selected waste of iron and steel industry (steel chips and scale) as a partial replacement for sand in the production of concrete. In this research study, concretes were made with steel chips scale (ScC) and (SchC) as substitution for raw sand. Sand was replaced by these waste in different proportions (25%, 50%, 75%, and 100%) by weight of sand.The aim of this study is to investigate the compressive strength and absorption properties for gamma radiation of concrete with steel chips and scale waste as a partial replacement for sand. The tests results obtained from concretes produced with scale and steel chips were compared with those in conventional concrete (CC-0).The experimental results indicate that, the addition of these waste to concrete enhances the absorption of gamma radiation without impairing other technical features of the investigated concrete. The data shows, that the concrete mixed with steel chips have better strength than conventional concrete, while in the case of concrete mixed with scale in excess of 25%, the strength become deteriorated. The linear attenuation coefficient of gamma radiation of concrete with a mixture of scale and steel chips with 75% and 100% was very good while the rest have good and satisfying radiation properties. Consequently, concrete prepared from the iron and steel industry solid waste containing steel chips and scale could be preferred for buildings as shielding concretes against gamma radiation. In this research the thickness of the concrete shield which can be used instead of the conventional concrete was also calculated.     

Potential application of acid jarosite wastes as the main component of construction materials

The purpose of this work was threefold: (1) To test quite new method of materials preparation only from the mixture of hazardous or polluting industrial wastes: of high acid jarosite processing waste (JW) of Zn-industry, alkaline Al-surface cleaning waste (ASCW) as neutralizer of its acidity and dump ferrous slag (DFS) as a binder of neutralized JW. (2) To study the structural formation processes of new substances. (3) To bind the heavy metals contained in JW to come up with new environment-friendly construction materials. XRD and SEM were used to monitor the hardening process, which was controlled by the changes of uniaxial strength and of linear deformation. Using small additions of Portland cement or lime, the strength of jarosite-treated materials can be increased. All these materials can be used in general civil engineering applications, as bases or sub-bases of roads, airfields and dams, replacing natural crushed stones, gravel, sand, and so on, and in the production of bricks, tiles and other products. The materials' enhanced strength is attributed to the new formation of amorphous gel, since the presence of small quantity of crystal hydrate forms cannot explain the strength of the samples.     

废弃混凝土再生利用探讨

随着我国建筑业迅猛发展,我国每年产生的废弃混凝土的量巨大并呈逐年上升的趋势。该文探讨了废弃混凝土再生利用的途径,设计了适应我国目前发展现状的再生骨料的生产工艺流程,并从环境效益和社会效益方面对废弃混凝土再生利用以及其再生利用产生的经济效益方面进行了分析,文章的分析表明废弃混凝土的再生利用一方面可以减轻废弃混凝土对环境的污染,节省其作为垃圾排放的清运和处理费用,另一方面可以充分利用废弃混凝土这种可再生资源,保护自然资源和人类的生存环境,有利于实施可持续发展战略。本文的研究表明废弃混凝土的再生利用具有很好的环保效益、社会效益和经济效益。     

石灰石粉掺量对混凝土性能影响的试验研究

水泥混凝土是目前土木工程建设中最为广泛的材料,它是以水泥为黏结剂,集料为填充物的混合材料,而其中砂石集料的作用往往被忽视,石灰石粉作为砂石集料中的细颗粒成分,作为混凝土的填充使用,不仅使混凝土的级配更合理,而且会影响混凝土的物理力学性能和耐久性。通过研究了石灰石粉作为混凝土掺合料对混凝土工作性能、力学性能、耐久性等的影响和改善,使石灰石粉的作用得到认可,为混凝土材料的发展提供依据,具有很好的经济效益和社会效益。     

Mechanical properties modeling of recycled aggregate concrete

The variability observed in the composition of construction and demolition (C&D) waste is a problem that inhibits the use of recycled aggregates in concrete production. To contribute in this field, a research was carried out varying water/cement ratio and substitution percent of natural aggregates by recycled aggregates. The experimental program used samples of main Brazilian C&D waste sources, which are concrete, mortar and red ceramic bricks as well as tiles. Results of concrete compressive strength and elastic modulus were statistically analyzed and modeled. The study shows that for both concrete properties, recycled coarse aggregate was more influential than recycled fine aggregate. However, the use of fine recycled red ceramic increased concrete strength. Coarse recycled red ceramic aggregate and fine recycled concrete aggregate exercised the largest and the smallest influence, respectively, in concrete properties.     

再生粗骨料对混凝土坍落度和抗压强度的影响

简述了哈尔滨市城市建筑垃圾的产生量和利用度,研究粗骨料的主要指标;采用再生粗骨料20%、30%、50%、70%、100%等质量代替天然碎石骨料配制了C30混凝土,研究了再生粗骨料对混凝土工作性和抗压强度的影响。研究结果表明:在水胶比相同时,混凝土坍落度下降,28d强度降低;若要保持混凝土坍落度基本相同,需采用增加用水量或增大减水剂的方式进行调整。     

机制砂和细砂在高性能混凝土中的研究

针对安徽省建筑用砂的特点,采用细河砂与机制砂混掺,配制C30高性能混凝土,通过正交试验优化混凝土配合比。试验结果表明,用60%的机制砂与40%的天然细砂作为细骨料,能够满足高性能混凝土的各项技术指标要求,与天然中砂相比,其力学性能和耐久性能更为理想。