Paving blocks made with recycled concrete aggregate and crushed clay brick

Clay brick generated from construction sites is usually delivered to landfills for disposal. With the limited landfill space in Hong Kong, there is an immediate need to explore the possible use of crushed clay brick as a new civil engineering material. In Hong Kong, government specifications promote the use of paving blocks made with 70–100% recycled concrete aggregate in order to facilitate the recycling of construction and demolition (C&D) waste. This paper presents a recent study at the Hong Kong Polytechnic University on the investigation of blending recycled concrete aggregate and crushed clay brick as aggregates in the production of paving blocks.The results indicated that the incorporation of crushed clay brick reduced the density, compressive strength and tensile strength of the paving blocks. Due to the high water absorption of crushed clay brick particles, the water absorption of the resulting paving blocks were higher than that of the paving blocks that did not incorporate crushed clay brick. Although it was found that crushed clay brick impaired the quality of the resulting paving blocks to a certain extent, the paving blocks using 50% crushed clay brick met the minimum requirements specified by AS/NZS 4455 and ETWB of Hong Kong (Grade B) for pedestrian areas. Furthermore, it was feasible to produce paving blocks prepared with 25% crushed clay brick that satisfied the compressive strength requirement for paving blocks (Grade B) prescribed by ETWB of Hong Kong for trafficked area.     

用废粘土砖集料配制砌块的试验

本文通过试验 ,证明了以废粘土砖集料代替大部分轻质陶粒生产填充砌块、用废粘土砖集料和高掺量粉煤灰配制承重砌块是可行的 ,寻求了一种既能利用建筑和工业废料又能降低生产的原材料成本的新路子     

Concrete with recycled concrete aggregate and crushed clay bricks

In the last two decades, a variety of recycling methods for construction and demolition wastes (CDW) have been developed. For instance, as one of the major components in CDW, concrete rubble has been used to replace natural aggregate after being treated. This is known as recycled concrete aggregate (RCA). The property and use of RCA for structural or non-structural concrete have been extensively studied and numerous findings have been adopted in engineering practice to produce sustainable concrete. Concrete rubble, however, is inevitably mixed with other wastes such as crushed clay bricks (CCB). The level of inclusion varies depending on the original construction materials of demolished buildings. The differing properties of CCB from RCA will affect the mix design as well as the physical and mechanical properties of the resulting new concrete when the inclusion level exceeds a certain limit. Separating CCB from RCA presents an operational difficulty in practice and also has huge cost implications. Therefore, it is important to study the effect of CCB with various inclusion levels on the properties of fresh and hardened concrete. This paper reports on a study conducted to investigate the physical and mechanical properties of recycled concrete with high inclusion levels of RCA and CCB and to explore the potential or the limitation of this type of mixed recycled aggregate in primary concrete structures.     

防水砂浆粘结剂用于改善古城墙砖耐久性的研究

古城墙作为一种建筑形式,凝结着人类科技和文化艺术的成果,保留了历史和传统的文化。针对西安市古城墙砖上部的剥蚀和下部的侵蚀,结合JL-FS防水砂浆粘结剂开展了试验研究。找到了一种防护效果好,且便于大规模施工的防护材料。     

废弃黏土砖再生骨料对混凝土性能的影响研究

配制了4组不同水泥用量的黏土砖再生骨料混凝土,通过试验测试和分析了4组混凝土物理、力学和变形方面基本性能的变化规律.试验结果表明.在骨料用量和水灰比不变的情况下,水泥用量的增加,可以在一定程度上提高黏土砖再生骨料混凝土强度、弹性模量和导热系数,降低其干表观密度、吸水率、干燥收缩率和泊松比.适当选择骨料和设计配合比,黏土砖再生骨料混凝土可以用于保温轻骨料混凝土和结构保温轻骨料混凝土制品.     

再生细骨料在建筑砂浆中的应用研究

利用建筑垃圾制备再生细骨料,再利用再生细骨料制备再生砂浆是目前建筑垃圾作为原材料进行循环再利用研究的主方向之一。通过对再生细骨料和再生砂浆的概念、生产、性能以及再生砂浆的技术优势和施工要点等进行研究,建议加强对再生砂浆的系统运用,以发挥其最大的社会价值。     

废黏土砖骨料与粉煤灰对GRC性能影响研究

为了再生利用废砖土砖,以及改善GRC的性能,采用50℃热水加速老化的方法,研究了废黏土砖取代天然砂、粉煤灰取代普通硅酸盐水泥对GRC抗折性能及耐久性能的影响,并采用XRD、FTIR和SEM的手段分析了其微结构的变化,结果表明:废砖取代GRC中天然砂可提高其抗折强度和耐久性,即,不但从胶凝材料角度可改善GRC的强度和耐久性,而且从骨料角度也可改善GRC的强度和耐久性。废砖以30%的取代率取代天然砂后,较之粉煤灰以20%取代率取代水泥后对GRC的耐久性改善作用要大;废砖以30%取代天然砂,同时粉煤灰以20%取代水泥后对GRC的耐久性改善效果较之二者单独取代时好;以废砖取代天然砂、粉煤灰取代水泥,既可改善GRC性能又可节约水泥、节约不可再生的天然砂资源、具有良好的环境效益和社会效益。     

Feasible use of recycled concrete aggregates and crushed clay brick as unbound road sub-base

A study was recently conducted at the Hong Kong Polytechnic University to investigate the possibility of using recycled concrete aggregates and crushed clay brick as aggregates in unbound subbase materials. The results showed that the use of 100% recycled concrete aggregates increased the optimum moisture content and decreased the maximum dry density of the subbase materials compared to those of natural subbase materials. Moreover, the replacement of recycled concrete aggregates by crushed clay brick further increased the optimum moisture content and decreased the maximum dry density. This was mainly attributed to the lower particle density and higher water absorption of crushed clay brick compared to those of recycled concrete aggregates. The CBR values (unsoaked and soaked) of the subbase materials prepared with 100% recycled concrete aggregates were lower than those of natural subbase materials. The CBR values further decreased as the replacement level of recycled concrete aggregates by crushed clay brick increased. Nevertheless, the soaked CBR values for all recycled subbases were greater than 30%, which is a minimum strength requirement in Hong Kong. Furthermore, the recorded percentage swells for all subbases were less than 0.13% which can be considered negligible.     

Experimental study of crushed aggregate shape

Aggregate shape is a key parameter that influences mixtures properties. This paper accounts for a closely controlled experimental program aimed at clarifying the variation of aggregate shape with two parameters, gyratory crusher setting and feed grading. The results show that crusher setting has a significant influence on the flakiness index of produced elementary size fractions, which is not the case for spread size fractions. Moreover, a variation of the proportions of feed fraction constituents has no significant influence on the flakiness index of produced aggregates, whereas a variation of the spreading or size of the feed fraction has. Regarding the shape characteristics of particles, it has been observed that the dimensions of a particle were not related, but flat particles are elongated, and vice versa. Finally, it has been observed that flakiness index varies conversely with the size of produced aggregate.     

聚丙烯酸酯修补砂浆耐久性的研究

聚丙烯酸酯修补砂浆是一种用途广泛的混凝土结构修补材料,其耐久性对修补工程的修复效果起到关键作用.依据标准试验方法,分别测试聚丙烯酸酯修补砂浆的收缩性、抗氯离子渗透性和抗冻性,提出测试聚合物砂浆抗裂性的试验方法,并按此试验方法测试其抗裂性.试验结果表明,掺入5％粉煤灰和5％超细矿粉的聚丙烯酸酯修补砂浆具有良好的耐久性能.     

黏土砖微粉的应用研究

介绍了一种建筑垃圾处理过程中大量黏土砖的资源化利用方法.将建筑垃圾筛分、分选、破碎后得到黏土砖颗粒,利用球磨设备将黏土砖颗粒粉磨半小时后得到微粉,在砂浆、砌块等采用干硬性混凝土为原料的生产中作为掺合料代替部分水泥,通过采用醇胺类激发剂激发黏土砖微粉的活性,提高其后期强度,可提高建筑垃圾的资源化利用率,并降低产品的生产成...     

细集料对砂浆抗渗性能的影响

1　前　言水泥防水砂浆作为刚性防水材料 ,在防渗、堵漏工程中应用广泛。水泥防水砂浆的品种很多 ,抗渗性能也有所不同 ,但其组成材料不外乎为水泥、细集料和改性材料。细集料主要起骨架作用 ,本文研究表明砂子的细度模数大小对防水砂浆抗渗性能有着不同的影响。2　原材料(1)砂子 :选用细砂、中砂、粗砂 ,其技术数据详见表 1。(2 )水泥 :选用 42 5Ｒ普通硅酸盐水泥 ,其主要性能指标见表 2。表 1　细度模数不同的河砂性能对比规格 细度模数μｆ含泥量/ %泥块含量/ %堆积密度/ (ｋｇ/ｍ3 )紧密密度/ (ｋｇ/ｍ3 )空隙率/ %累计筛余 / %筛孔尺寸…     

煤矸石、页岩砖厂粉尘的治理

粉尘的漂尘粒度一般在0．2～200μm之间,煤矸石粉尘中,游离二氧化硅含量一般在30％～40％之间,砖厂工人经常生活在这样粉尘浓度较高的环境中,容易引起肺组织产生广泛的纤维性变化和形成矽肺结节。砖瓦行业为了防止矽肺病的发生,在破碎、原料运输、搅拌等工艺过程,采用有效的方法,防止粉尘的产生和扩散,从而改善工人的工作环境,以提高人们“以防为主,防治结合”的自觉性。     

再生骨料混凝土耐久性研究

研究了用于砌块的再生骨料混凝土在抗硫酸盐侵蚀和抗碳化能力方面的性能,研究表明,利用废混凝土再生骨料生产混凝土砌块时,产品性能可满足现行标准要求。     

Mechanical properties of brick aggregate concrete

This paper presents the results of a research program carried out at University of Aveiro, Portugal to evaluate the properties of concrete made with crushed bricks replacing natural aggregates. Two types of brick were investigated. The bricks were crushed in order to obtain a usable aggregate. The properties investigated were the workability and the density of fresh concrete, and the compressive strength, tensile splitting strength, modulus of elasticity and stress–strain behaviour of hardened concrete. Replacement ratios of natural aggregates by 15% and 30% were investigated as well as water/cement ratios of 0.45 and 0.5. Strength indexes were used to assess the effectiveness of aggregate replacement. The results of concrete produced with recycled aggregates were compared with a reference concrete produced with natural limestone aggregates currently used in Portugal. Observed results indicate that ceramic residuals could be used as partial replacement of natural aggregates in concrete without reduction of concrete properties for 15% replacement and with reductions up to 20% for 30% replacement. The type and the manufacturing process of bricks seem to influence the properties of the resulting concrete. The properties and aesthetics of concrete with bricks indicate the possibility of using this type of concrete in precast applications.     

再生混凝土的耐久性能研究

主要从抗碳化、抗冻、抗氯离子渗透三个方面归纳总结了再生混凝土耐久性能方面的一些最新研究成果和一些改善再生混凝土耐久性能的措施与方法,并且指出有必要对再生混凝土在复合因素作用下的耐久性能进行研究,以填补再生混凝土耐久性研究的空白。     

轻骨料混凝土的耐久性研究

指出混凝土的力学性能和耐久性能制约着混凝土结构的使用功能和安全性。研究了轻骨料混凝土的抗渗与抵抗冻融循环等耐久性能,试验结果表明,轻骨料混凝土的抗渗性能和耐冻融循环性能均优于同强度等级的普通混凝土。     

Statistical methods of aggregate durability evaluation

The advent of microcumputers and access to sophisticated statistical software packages allows the researcher unprecendented opportunities to evaluate his data. In aggregate research, it allows the comparison of basic aggregate properties with empirical tests often used in specifications of aggregate quality. Recent research by the author resulted in some thirty five test results (variables) for one hundred samples of aggregates used for concrete and bituminous mix applications in Ontario. The large amount of data invited statistical treatment. In addition to the usual univariate statistics such as mean, standard deviation, variance, linear regression and correlation, multivariate statistical techniques were used to study the inter-dependence of aggregate properties and tests. These included stepwise regression and factor analysis. The results indicate that some of the simpler properties of rock, such as specific gravity, absorption, adsorption abrasion, impact resistance, and freezing-thawing tests are interrelated, and can be used in empirical mathematical relationships to predict the behaviour of the aggregate in service. Other simulation tests, such as the sulphate soundness and Los Angeles abrasion tests routinely employed in North America bear no relationship to aggregate properties and should therefore be discontinued. The paper describes how the statistical techniques can improve the quality evaluation methods and criteria applied to aggregates anywhere in the world.     

混凝土透水砖透水持久性的研究

通过人工模拟降雨现场试验，研究使用2年后的砂砾料垫层结构透水砖的透水性能变化和可用程度。发现其透水性能虽有所下降，但仍能满足使用要求。透水砖表面瞬时透水性变化很大，砂砾料垫层的透水性变化较小。在正常使用条件下，透水砖的透水性维持时间较长。