稻壳灰粒径对水泥砂浆的碱硅酸反应风险影响

固废资源化是实现可持续发展的重要内容.稻壳灰的火山灰活性高,有望作为辅助性胶凝材料用于水泥砂浆或混凝土,但其中K₂O和Na₂O含量较大,需探明不同粒径稻壳灰的掺入可能带来的碱硅酸反应风险.现有研究表明,粉煤灰的火山灰活性能抑制碱硅酸反应,已得到广泛应用.对比起见,设置了基准组、掺4种粒径粉煤灰组和稻壳灰组,在分别测试其抗压、抗折强度的基础上,测试膨胀率,通过SEM和EDS测试了掺粒径为5μm的稻壳灰试件和未掺稻壳灰试件的微观形貌和元素组成.试验结果表明：稻壳灰或粉煤灰的掺入均可以提高砂浆的力学性能,稻壳灰粒径越小提高的程度越大,中值粒径为5μm的稻壳灰可以使砂浆28 d抗压强度提高50.6%,抗压强度提高64.7%,效果均好于粉煤灰;稻壳灰的粒径不超15μm时,对砂浆的膨胀率可起到显著的抑制作用,且抑制效果优于粉煤灰,5μm的稻壳灰能使14 d膨胀率减小90%,并使骨料表现为无害,而8～20μm粉煤灰均仅减小60%左右的14 d膨胀率,骨料仍表现为有害;稻壳灰的火山灰活性不仅能生成低Ca/Si比的C-S-H凝胶,降低碱含量,还能使砂浆致密性提...     

砂岩骨料的碱活性检测与抑制试验

用岩相法、砂浆棒快速法、溶胶-凝胶膨胀法和混凝土棱柱体法,联合研究了砂岩骨料的碱硅酸反应(ASR)活性,评价了粉煤灰对该砂岩ASR膨胀的抑制效果.试验结果一致表明了该砂岩骨料具有潜在的ASR活性,其碱活性主要来自于玉髓状微晶石英和波状消光石英.采用20%的Ⅰ级粉煤灰替代水泥,可以把这种砂岩的ASR膨胀量控制在非碱活性范围之内.     

矿物掺合料对机制砂水泥基自流平砂浆性能的影响

试验选用普通硅酸盐水泥、硫铝酸盐水泥与半水石膏的三元胶凝体系,选用机制砂作为细集料,制备全机制砂水泥基自流平砂浆.选用粉煤灰、石粉与硅灰作为矿物掺合料,并研究矿物掺合料对全机制砂制水泥基自流平砂浆流动度、抗压抗折强度与尺寸变化率的影响.研究结果表明:矿物掺合料的火山灰效应对自流平砂浆力学性能的发展产生积极影响,自流平砂...     

洛河流域安山玢岩碱骨料反应试验研究

碱骨料反应是影响水工混凝土耐久性的重要因素之一.分别采用砂浆棒快速法和碳酸盐骨料碱活性检验法对洛河流域安山玢岩骨料碱活性进行试验研究.采用砂浆棒快速法,取3组安山玢岩骨料试件进行碱活性试验,分析安山玢岩骨料在3,7,14,28 d 4个不同龄期的膨胀率变化,试验结果未能确定安山玢岩骨料碱活性,需采用碳酸盐骨料碱活性检验法进一步试验研究;采用碳酸盐骨料碱活性检验法,取18组安山玢岩骨料试件进行碱活性试验,并分析安山玢岩骨料在3,7,14,28,56,84 d 6个不同龄期的膨胀率变化,编号X-6组试件和编号Z-5组试件84 d龄期的膨胀率均大于0.1%,依据《水工混凝土试验规程》(SL 352—2006)判定,洛河流域安山玢岩骨料具有潜在碱活性.综上试验结果表明,洛河流域安山玢岩具有一定的潜在碱活性危害.     

再生微粉配制细砂改善ECC力学性能研究

作为一种纤维增强水泥基复合材料,ECC的力学性能受到很多因素影响。因而可以通过很多手段对其力学性能进行改良,对水泥砂浆基材进行改性是提升ECC力学性能的一个重要手段,而改良细骨料级配是容易被忽视的有效措施。本试验利用废弃混凝土再生微粉与普通砂制备均匀级配细砂,用该细砂配制的ECC砂浆,与普通砂（过1.25mm筛）配制的ECC砂浆进行力学性能比较。结果表明：均匀级配细砂ECC砂浆的直拉、抗弯性能均比普通砂ECC砂浆有明显提高。研究有助于拓展再生超细骨料的应用领域.     

再生细骨料与天然砂碱骨料反应特点比较

通过快速碱一硅酸方法测定了再生细骨料和天然砂碱骨料反应（ASR）膨胀值,并分析比较了两种细骨料碱骨料反应的特点和原因,发现再生细骨料具有不同于天然砂的碱骨料反应特点．     

SiO2/CaSiO3复合粉体对水泥基材料早期性能的影响

目的为探讨SiO2／CaSiO3复合粉体对水泥基材料早期性能的影响．方法采用400目、800目的天然硅灰石分别与浓盐酸反应制备了两种细度的SiO2／CaSiO3复合粉体，测试其在水泥基材料中的火山灰活性及3d龄期的抗压强度和抗拉强度．结果在5％～15％掺量内，掺复合粉体的砂浆3d抗压、抗拉强度均高于空白砂浆，掺DSV大的复合粉体砂浆强度高于掺DSV小的复合粉体砂浆强度．结论本实验制备的SiO2／CaSiO3复合粉体具有较高的活性，可提高砂浆的早期强度；应优选DSV较大的天然硅灰石为原料制备SiO2／CaSiO3复合粉体．     

碱激发矿粉海水珊瑚骨料混凝土力学性能研究

以矿粉为原材料,通过碱激发的方式制备胶凝材料,拌以海水和珊瑚骨料制备碱激发矿粉海水珊瑚骨料混凝土.首先通过碱激发矿粉海水珊瑚砂浆试验确定了合理的水胶比.进而通过改变珊瑚骨料相对于普通骨料的替代量,发现碱激发矿粉混凝土强度随普通骨料替代量的增加而不断降低.基于此,提出了提高混凝土的砂率、增大浆体对骨料的包裹作用,以提高碱激发全珊瑚骨料混凝土的强度.本文确定砂率为60%,提出了碱激发矿粉海水珊瑚骨料混凝土的合理配合比,并进行了基本力学性能试验.结果表明,由于海水与珊瑚骨料的早强作用,该新型混凝土7 d的抗压强度与抗拉强度均达到28 d的70%以上.且轴心抗压强度与立方体抗压强度的比明显高于普通混凝土.     

水泥与偏高岭土地聚物砂浆碱骨料反应对比研究

为减少环境污染,近年来对碱激发胶凝材料的研究逐渐增加,而目前研究大多集中在地质聚合物机理方面,较少涉及其碱骨料反应。本文试图探究高温高碱环境下,碱激发胶凝材料砂浆与传统水泥砂浆碱骨料反应的不同,以推进碱激发胶凝材料的工程应用。通过测量试件不同龄期长度变化,研究掺不同骨料的水泥砂浆和偏高岭土基地聚物砂浆在高温高碱溶液中的变形行为,同时采用XRD、SEM等微观手段分析二者不同龄期产物的组成和微观结构。研究结果表明：地聚物与水泥的碱骨料反应历程存在明显区别,地聚物中不会发生严重的碱骨料反应,工程中能使用碱活性强的骨料;地聚物浆体最终形成(类)沸石结构,其笼式结构能吸附和固溶大量有害碱,能适应海工等强腐蚀性环境。     

碱—熟料—矿渣水泥混凝土的碱集料反应研究

采用砂浆测长法研究了碱－熟料－矿渣水泥砂浆的碱集料反应膨胀率;分析了碱组分种类及熟料掺量等因素对该类砂浆碱集料反应膨胀率的影响;综合砂浆测长结果及ＳＥＭ分析,探讨了碱－熟料矿渣水泥系统碱集料反应的特性。     

Properties of cementitious rendering mortar prepared with recycled fine aggregates

The results of an experimental study on investigating the properties of cementitious rendering mortars prepared with a recycled fine aggregate (RA) were presented. The RA was obtained from a recycling plant in which mixed demolition wastes were processed by mechanical crushing, sieving and sorting operations. Two series of rendering mortar mixes were prepared with a constant water/cement and a constant aggregate/cement ratios of 0.55 and 3 respectively. River sand and natural crushed rock fine were originally used in the two series separately, and they were consistently replaced by 25%, 50%, 75% and 100% by the recycled aggregate. The experimental results showed that mechanical properties, such as compressive strength, flexural strength and modulus of elasticity of the mortars prepared with the RA were lower than the mortars made with the natural aggregates. Nevertheless, the bond strength at the interface between the mortar and masonry bricks determined by the Triplet test was found to be higher for the mortars prepared with the RA.     

高性能填充轻集料混凝土试验研究

为了解决钢管混凝土结构高性能填充材料的制备问题,选用高强水泥、粉煤灰、硅灰、膨胀剂、页岩陶粒、页岩陶砂与天然砂组成的混合细集料、高效减水剂和增稠剂制备出具有轻质、微膨胀和自密实性能的高强混凝土,设计18个试验组对比分析了混合细集料中天然砂体积分数、胶凝材料用量和体积砂率对混凝土工作性能、物理力学性能和硬化变形性能的影响规律.研究结果表明:选用上述原材料,采用内掺法和松散体积法进行掺合料和混合细集料用量设计,调整混合细集料中天然砂和陶砂的体积比来改良颗粒级配,每m3混凝土掺入540~570 kg胶凝材料,体积砂率取值47%左右,可制备出适用于钢管轻集料混凝土结构的高性能填充轻集料混凝土.     

Preparation and properties of a new composite of epoxy emulsion (EEM) modified cement

High performance cement based composite materials was prepared by adding epoxy emulsion. The epoxy emulsion was synthesized with epoxy phosphoric acid ester and poly-glycol in laboratory. This epoxy emulsion has advantages over other emulsion, such as dehydrated slightly, and, well film formation abilities. The mechanical properties corruptness resistance and structure of epoxy emulsion modified cement mortars were studied. Experimental results show that the mechanical properties of modified cement mortars are slightly increased with increasing epoxy emulsion content, especially the flexure strength. The corruptness resistance of all modified mortars is better than the unmodified mortar. The polymer film forms the bridge phases between the matrix and the aggregate regions, and forms a three-dimension structure in the cement hydration system, which improves the mechanical properties of modified mortars.     

Calculation of alkali silica reaction (ASR) induced expansion before cracking of concrete

A calculation method for predicting the formation of alkali-silica gel and analyzing the relationship of ASR induced expansion and aggregate size was proposed. The complicated chemistry of alkali silica reaction was simplified to be controlled by the diffusion process of chemical ions into reactive aggregates. The transport of chemical ions was described by the Fick’s law. The ASR induced expansion was assumed to be directly related to the volume of produced alkali-silica gel. The finally expansion of a representative volume element (RVE) of concrete was then calculated according to the ratio of volume of alkali-silica gel and RVE. The input parameters of the model contains radius of reactive aggregate, volume fraction of reactive aggregate, initial concentration of chemical ions and porosity of cement paste. The applicability of the model was validated by an experiment of ASR-affected concrete specimens containing glass aggregate. It is shown that the amount of alkali-silica gel and ASR induced expansion can be well predicted. The expansion increasing with the decreasing aggregate size can be reproduced by the proposed model.     

高钙粉煤灰作为添加剂制备赤泥偏高岭土胶凝材料

采用XRD、IR、SEM、和EDS等分析手段,研究了高钙粉煤灰作为添加剂制备的赤泥偏高岭土胶凝材料的力学性能和水化产物.结果表明:合适掺量的高钙粉煤灰(<14%)有助于试样力学性能的提高;高钙粉煤灰作为添加剂所制备的赤泥偏高岭土胶凝材料,其水化产物主要有水化硅酸铝钙、沸石相、羟基硅酸铝、钙长石、蓝晶石、水化硅酸钙和叙永石. 随着试样养护龄期的增长胶凝材料结构更密实,形成PSS型结构.     

骨料品种对混凝土体积变形特性的影响研究

采用相同的胶凝材料及混凝土配合比参数,试验分析骨料品种对混凝土线膨胀系数和自生体积变形的影响,并探究其本质原因,期望有利于工程研究。结果表明:骨料含量相当时,骨料线膨胀系数越大,含有该骨料混凝土的线膨胀系数也越大;不同岩性的骨料对混凝土自生体积变形影响显著,起因于骨料长龄期吸水特性的不同,并可从定性和定量的角度验证此结论。     

碱激发矿渣陶粒混凝土空心砌块砌体抗剪试验

为研究碱激发矿渣陶粒混凝土空心砌块砌体的受剪性能,对108个用Mb25~Mb130碱激发矿渣净浆和用Mb25~Mb80碱激发矿渣陶砂砂浆砌筑的碱激发矿渣陶粒混凝土空心砌块砌体进行抗剪试验.试验结果表明:碱激发矿渣净浆作砌筑浆体的砌体抗剪强度低于碱激发矿渣陶砂砂浆作砌筑浆体的砌体.碱激发矿渣陶砂砂浆作砌筑浆体的砌体抗剪强度低于用水泥砂浆和混合砂浆作砌筑浆体的砌体.砌体的抗剪强度随砌筑浆体抗压强度的提高而增大,Na2O含量、砂灰比对砌体抗剪强度的影响不容忽视.基于试验结果,分别建立了用碱激发矿渣净浆和碱激发矿渣陶砂砂浆作砌筑浆体时的碱激发矿渣陶粒混凝土空心砌块砌体抗剪强度计算公式.     

粉煤灰陶砂次轻混凝土的制备与性能

用碎石、粉煤灰陶砂和河砂作为混合集料配制不同细集料组成的次轻混凝土试样,研究它们的力学性能和热学性能。与普通混凝土相比,掺入少量粉煤灰陶砂（陶砂体积分数为25%）的次轻混凝土抗压强度得到提高,表现出较为理想的轻质高强特性。上述现象归功于混合细集料中大小颗粒搭配较好,陶砂的微泵内养护效应以及陶砂表面具有潜在活性物质参加火山灰反应,强化了陶砂与水泥石的界面强度,使掺入体积分数为25%陶砂的次轻混凝土在各龄期具有最高的强度。与普通混凝土相比,当次轻混凝土中陶砂体积分数为25%时,其导热系数可降低42%,即掺入适量陶砂可明显提高混凝土的保温隔热性能。     

Application of image analysis based on SEM and chemical mapping on PC mortars under sulfate attack

The degradation mechanisms of cementitious materials exposed to sulfate solutions have been controversial, despite considerable research. In this paper, two methodologies of image analysis based on scanning electron microscope and chemical mapping are used to analyse Portland cement mortars exposed to sodium sulfate solution. The effects of sulfate concentration in solution and water to cement ratio of mortar, which are considered as the most sensitive factors to sulfate attack, are investigated respectively by comparing the macro expansion with microstructure analysis. It is found that the sulfate concentration in pore solution, expressed as sulfate content in C-S-H, plays a critical role on the supersaturation with respect to ettringite and so on the expansion force generated.     

抛填骨料工艺超高强混凝土的制备研究

采用抛填骨料工艺制备强度超过100MPa的超高强混凝土。研究表明,采用分层均布的布料方式,可在不影响施工工作性的条件下制得粗骨料体积分数高达54%、骨料相互嵌锁的超高强混凝土,其力学性能、抗氯离子渗透能力均优于常规方法制得的超高强混凝土,更佳的颗粒级配分布(PSD)有利于其密实度的增加。采用贝雷参数检验法评估集料级配,表明级配更为合理。抛填骨料工艺超高强混凝土中胶凝材料的用量大幅度降低,对降低混凝土环境影响具有重要意义。