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     

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.     

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。     

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。     

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.     

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。     

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.     

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。     

Strength and stiffness of compacted crushed concrete aggregate

A comprehensive series of drained triaxial compression tests were performed on crushed concrete aggregate (CCA) moist as compacted. When compared to ordinary natural well-graded gravelly soils, the peak strength and stiffness increase more significantly with dry density, while the effect of the degree of saturation during compaction is much less significant. In a range of confining pressure of 30–600 kPa, the strength and stiffness of well-compacted CCA is similar to, or, in some cases even higher than, typical selected high-class backfill materials (e.g., well-graded gravelly soil of crushed quarry hard rock). The strength and stiffness of CCA with a maximum particle size D_max=37.5 mm obtained from a typical concrete crushing plant are noticeably lower than CCA sieved to D_max=19 mm compacted using the same energy. However, when compacted to the same dry density, the original CCA exhibits the strength and stiffness higher than the sieved CCA. Effects of the strength of original concrete on the strength and stiffness of compacted CCA are insignificant, while the strength and stiffness of compacted CCA are, respectively, noticeably higher than, or similar to, the original concrete aggregate (i.e., natural gravelly soil) compacted using the same energy. All these results indicate that well-compacted CCA can be used as the backfill material for important civil engineering soil structures requiring a high stability while allowing a limited amount of deformation.     

Sodium silicate activated clay brick

The paper discusses the addition of sodium hydroxide to readily available natural materials in Senegal, in order to produce stronger and more durable bricks. The case study involves the Tchieky clays which were mixed with varying amounts of NaOH and heated at temperatures of 40, 80 and 120°C for periods of up to 60 days. The caustic solution could be sodium hydroxide mixed with sodium silicate and water/seawater. In general the maximum strength was reached after 28 days for samples mixed with 8 M NaOH at 40°C. The bricks produced were shown to be durable and relatively inexpensive. The process does not generate pollutants and can use by-products, assisting with environmental problems.      

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.     

Effects of portland composite and composite cements on durability of mortar and permeability of concrete

In this study, the effects of Portland composite and composite cement on the properties of cement paste, durability of mortar and permeability of concrete were investigated. The results were compared with reference mixture of cement paste, mortar and concrete made with Portland cement. The ratio of water to cementitious materials (W/C_m) in cement paste, mortar and concrete mixtures were determined in a way that all the similar mixtures had the same workability. Flexural tensile and compressive strength of mortar samples containing Portland Composite and Composite cement were determined at various ages. In cement paste samples, the shortest and longest setting time was obtained in samples made with Portland and composite cement, respectively. Also, maximum amount of volume expansion was found in the sample made with Portland composite cement. Mortar samples made with Portland composite and composite cement had lower strength values than the reference mortar mixture at early ages but at 28 days and later ages they had higher strength values than the reference mixture. In durability tests, there was no loss of weight and cracks in mortar mixture samples made with Portland composite and composite cement when they were held in microthiol, Na₂SO₄ and MgSO₄ solutions. Also, no water leakage was observed through the concrete samples made with Portland composite and composite cement when they were held under five-bar pressurized water.     

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。     

Strength and durability of concrete incorporating crushed limestone sand

In recent years, there is a growing interest in the use of crushed sand obtained from limestone quarries in some countries where river sand is not widely available. The fines content is usually high in crushed sand which can adversely affect concrete properties. The influence of fines in crushed sand on physical and mechanical properties of concrete has been widely investigated. The results proved that up to 15% of fines content in crushed sand could be used without adversely affecting concrete strength. However, little work has been done so far on the effect of fines in crushed sand on the durability of concrete. This paper examines the influence of limestone fines in crushed sand on concrete properties. Properties include strength, water, gas and chloride-ion permeability and capillary water absorption. Four different cement types were used while maintaining a constant water/cement ratio. The results show that concrete containing 15% of limestone fines as replacement of crushed sand reduces the water permeability and increases the gas and chloride-ion permeability.