高性能贝利特硫铝酸盐水泥混凝土性能研究

为了推进新型低碳低能耗的高性能贝利特硫铝酸盐水泥在工程中的应用,对比研究了高性能贝利特硫铝酸盐水泥和硅酸盐水泥制备的不同强度等级的混凝土的各项性能。结果表明:较之硅酸盐水泥混凝土,高性能贝利特硫铝酸盐水泥混凝土的工作性能优良,C30和C50混凝土各龄期的抗压强度分别平均提高4MPa和9MPa,高性能贝利特硫铝酸盐水泥混凝土的抗水和氯离子渗透性、抗硫酸盐侵蚀性、抗冻性、干燥收缩性能均好于硅酸盐水泥混凝土,抗碳化性能相对较弱,抗钢筋锈蚀能力两种水泥混凝土差别不大。     

水灰比对硫铝酸盐水泥基高性能混凝土性能的影响

文章研究了水灰比对硫铝酸盐水泥基高性能混凝土性能的影响,主要针对水灰比对混凝土抗压强度、抗碳化性的影响,并利用SEM对其进行微观机理分析.研究结果表明:随着水灰比的增加,硫铝酸盐水泥基高性能混凝土抗压强度和抗碳化性逐渐下降;随着养护龄期增长,硫铝酸盐水泥基高性能混凝土抗压强度和抗碳化性逐渐增加.SEM微观分析表明:随着...     

超高性能混凝土在中国的研究和应用

超高性能混凝土作为一种新型水泥基材料,具有强度高,耐久性优异的优点.本文综述了超高性能混凝土在中国的研究和应用.使用常规辅助性胶凝材料取代水泥和硅灰,在普通工艺下,也可制备出满足性能要求的超高性能混凝土.硅灰和纳米二氧化硅可加速超高性能混凝土胶凝材料的水化速度,但矿粉延缓了超高性能混凝土胶凝材料的水化速度.超高性能混凝土具有均匀致密的微观结构.超高性能混凝土的抗拉、抗弯、抗剪、粘结强度、峰值应变等均远大于普通混凝土,掺入钢纤维可显著增大超高性能混凝土的韧性.超高性能混凝土的抗冻性和抗锈蚀性能均优于普通混凝土.自从中国2005年第一次将超高性能混凝土应用于工程中,超高性能混凝土已经广泛应用于电缆槽盖板、高速铁路、地铁、桥梁、挂檐板和人行道盖板中.     

C50渡槽高性能混凝土耐久性研究

基于渡槽混凝土病害严重、耐老化性能差等问题,采用萘系和聚羧酸盐两种高效减水剂,根据不同水胶比、粉煤灰掺量、粉煤灰矿粉复掺配制出C50渡槽高性能混凝土,并测试混凝土的抗氯离子扩散系数、抗冻性和抗碳化性能等耐久性指标,分析水胶比、粉煤灰掺量、粉煤灰矿粉复掺对其耐久性的影响。结果显示:随着粉煤灰掺量增加,混凝土的抗氯离子渗透性能有所提高,但抗冻性能和抗碳化性能均呈下降趋势;粉煤灰矿粉复掺提高了混凝土的抗氯离子渗透性能和抗碳化性能,抗冻性略有降低。     

碳化环境下混凝土的耐久性能研究

本文采用了快冻法、自然浸泡法以及干湿循环方法来研究了碳化行为对混凝土材料的抗冻性、抗氯离子扩散性以及抗硫酸盐侵蚀性的影响作用.试验结果表明碳化后的混凝土试件抗冻性有所提高,但是抗氯离子扩散性变差.同时发现,碳化混凝土试件在经历硫酸盐干湿循环后抗折强度损失大于未碳化试件,降低混凝土的抗硫酸盐侵蚀性能.     

粉煤灰高性能砼试验分析

粉煤灰混凝土在早期往往会出现强度低于设计标准值、抗冻性能差、易碳化、耐久性偏低等缺陷,笔者通过研究发现,加入适量的元明粉、石灰粉以及激发剂后,粉煤灰混凝土其强度损失明显降低,极大提高了混凝土的抗冻性、抗碳化等性能,提高了粉煤灰混凝土的质量,这对以后粉煤灰高性能砼的实际应用具有一定参考价值。     

掺粉煤灰混凝土的碳化及抗冻性能试验研究

研究了不同水胶比、不同粉煤灰掺量混凝土的碳化及抗冻性能。试验结果表明,随着水胶比和粉煤灰掺量的增加,混凝土碳化深度增加,混凝土碳化深度按方程D=K·tb回归,相关系数大于0.95;碳化深度与粉煤灰掺量及水胶比二元线性回归较好,混凝土抗压强度越高,抗碳化性能越好。水胶比是影响混凝土抗冻性能的主要因素,粉煤灰对混凝土抗冻性能具有不良影响。     

锰渣对混凝土力学性能和耐久性的影响

采用基本的力学方法研究了不同掺量的锰渣对混凝土抗压强度和抗折强度的影响.并通过加速碳化试验和抗冻性试验探究了锰渣混凝土的抗碳化性能和抗冻性.采用压汞法技术探究了锰渣混凝土内部的孔结构.结果表明:当锰渣掺量大于10％时,随着锰渣掺量的增加,混凝土的抗压强度和抗折强度降低;掺加30％锰渣混凝土的抗碳化性能和抗冻性最差,碳化56 d时其碳化深度已达10.0 mm,冻融循环240次,其相对动弹性模量降低到0.71;碳化之后孔隙率降低,孔径细化,冻融循环导致孔隙率增大,孔径粗化.     

硫铝酸盐水泥基混凝土抗碳化性能的研究

主要研究了水灰比、标准养护龄期、掺合料掺量对硫铝酸盐水泥基混凝土抗碳化能力的影响,并与普通硅酸盐水泥基混凝土抗碳化能力进行了对比,采用SEM和XRD分析进行微观性能测试.研究结果表明:硫铝酸盐水泥基混凝土抗碳化能力随着水灰比的减小而增加;随着标准养护龄期的延长而增大;掺合料的加入可以提高其抗碳化能力,其最佳掺量为20%.相同条件下,硫铝酸盐水泥基混凝土抗碳化能力高于普通硅酸盐水泥基混凝土抗碳化能力.     

再生混凝土的强度及耐久性能研究

基于基本的力学方法和耐久性方法研究了再生混凝土的抗压强度、抗碳化性能和抗冻性能.并采用压汞法对再生混凝土的孔结构进行研究.结果表明:再生混凝土的抗压强度比普通混凝土的抗压强度略有降低,孔隙率相比普通混凝土的孔隙率增加了49.5%;其抗碳化能力小于普通混凝土的抗碳化能力;再生混凝土的抗冻性远远小于普通混凝土的抗冻性,180次循环之后其质量损失率接近普通混凝土质量损失率的3倍.     

Recovery of bitumen from oilsands: gelation of ultra-fine clay in the primary separation vessel

The bulk of bitumen recovery from oilsands takes place via a flotation/settling process in the primary separation vessel (PSV). Under certain conditions, some oilsands slurries become non-segregating, i.e. both fines and coarse solids remain in suspension and little or no bitumen froth is generated. An ultra-fine (<0.3 μm) component of the oilsands fines fraction (<44 μm) is identified as having the potential to be the major contributor to the thickening (gelation), or sludging, phenomenon observed in some ores.In this work we determined the amounts of ultra-fines in oilsands from different depositional environments. Although a generally linear correlation exists between ultra-fines and fines or clay contents, some samples were found to have a disproportionately high ultra-fines contribution relative to other oilsands. Waste units, in particular, were found to be extremely rich in the ultra-fines and clay-sized fractions.We used a ²H NMR method to measure both the rate and degree of gelation of ultra-fines suspensions separated from oilsands. Sludging conditions are reached when the ultra-fines concentration is between about 1.5 and 2.0 w/w%. Measurement of ultra-fines gelation times showed them to be of the same order as slurry residence time in the PSV. Laboratory jar tests have demonstrated that poor segregation of oilsands components can be correlated with the gelation conditions determined by NMR measurements.     

不同养护条件对大掺量粉煤灰混凝土抗碳化性能试验研究

通过加速碳化试验,系统研究了不同养护条件和粉煤灰掺量的大掺量粉煤灰混凝土碳化规律.并利用扫描电镜和压汞法研究了大掺量粉煤灰混凝土碳化前后的微观形貌和孔结构变化.结果表明:经标准养护后的粉煤灰混凝土的抗碳化能力大于经自然养护后的粉煤灰混凝土的抗碳化能力;随着粉煤灰掺量的增加,混凝土抗碳化能力减小;标准养护下粉煤灰混凝土孔隙率相比于其在自然养护下的孔隙率降低了19.6％;碳化后浆体密实度增加,孔径细化,孔隙率降低31.4％.     

活性粉末混凝土抗压强度试验研究

通过立方体抗压强度试验研究了活性粉末混凝土的受压破坏过程,并通过单因素对比试验研究了水胶比、石英粉、粉煤灰、纤维掺量和养护条件对活性粉末混凝土抗压强度的不同影响,并对低水胶下获得超高强度的原理进行深入分析;配制出了7d龄期常温养护条件下达105MPa和高温蒸汽养护条件下达193MPa的活性粉末混凝土.     

The influence of initial water curing on the strength development of ordinary portland and pozzolanic cement concretes

The effect of initial water-curing period on the strength properties of concretes was investigated. Three types of cement, one ordinary Portland cement (OPC) and two natural pozzolanic cements (blended and trass cements), were used in the concrete mixtures. Six different curing regimes were applied to the specimens, the first of which was continuous water storing, and the second continuous air storing. In the remaining four regimes, the specimens were stored under varying initial water-curing periods of 3, 7, 14, and 28 days, respectively. The compressive strength tests were carried out on the cubic specimens at the ages of 7, 14, 28, 90, and 180 days. The variation of compressive strength with time was evaluated by using a semilogarithmic function and the strength-gaining rates were calculated by using this equation for different curing conditions. It was found that poor curing conditions are more adversely effective on the strength of concretes made by pozzolanic cements than that of OPC, and it is necessary to apply water curing to the former concretes at least for the initial 7 days to expose the pozzolanic activity. However, when the pozzolanic cement concretes have sufficient initial curing, they can reach the strength of OPC concretes in reasonable periods of time.     

二氧化碳矿化养护加气混凝土试验研究

二氧化碳矿化养护混凝土技术使得混凝土早期在较短时间内快速成型和提升力学性能,极大缩短养护周期,提高生产效率,是颇具大规模工业化应用前景的二氧化碳利用方式。对基于工业固废的加气混凝土的二氧化碳养护技术进行了初步探索,着重研究了原料掺比、养护压力以及养护制度在CO₂矿化反应中的影响。二氧化碳养护加气混凝土配方主要由试件的抗压强度和固碳性能共同决定。通过SEM和XRD分析等方法表征了在不同养护工况下反应产物的变化特点,同时使用压汞法测定了CO₂养护前后的孔隙分布。结果表明,对自然养护4 d后的加气混凝土进行2 h CO₂养护,试件固碳率随着养护压力升高而升高,低压养护和梯级养护有利于降低加气混凝土试件的力学强度损失,梯级养护中CO₂浓度/分压力越高,加气混凝土试件表观固碳率越高;在相同的CO₂养护条件下,SEM观察到矿化反应产物有不同形貌,如球状和纺锤形等,XRD分析则进一步证明了碳酸钙有3种不同晶型;CO₂养护后,孔径0.01~0.10μm微孔降低明显,表观固碳率越高,对加气混凝土试件的填充效果越显著。     

桥梁伸缩缝超高性能混凝土关键性能的研究与应用

基于不同纤维混杂效应设计原理,利用PVA纤维或聚丙烯纤维与钢纤维二元混杂优化,制备了一种常温养护桥梁伸缩缝超高性能混凝土(UHPC),并探讨了其在实际工程中的应用.研究结果表明,采用这种方法所制备的混杂纤维增强UHPC不仅具有较高的强度且抗裂性好.当用掺量为20 kg/m的聚丙烯纤维与钢纤维混杂时,UHPC常温养护2 d时的抗折强度和抗压强度可分别达到13.6 MPa和40.9 MPa,28 d时可分别达到51.3 MPa和138.5 MPa,且无明显的收缩开裂现象.工程实践表明,利用该混杂纤维增强UHPC对桥梁伸缩缝混凝土的病害进行整治时,不仅可以达到技术性能使用要求,而且可实现快速恢复交通,具有广阔的推广应用前景.     

Effect of steam curing on class C high-volume fly ash concrete mixtures

The effect of steam curing on concrete incorporating ASTM Class C fly ash (FA), which is widely available in Turkey, was investigated. Cement was replaced with up to 70% fly ash, and concrete mixtures with 360 kg/m³ cementitious content and a constant water/binder ratio of 0.4 were made. Compressive strength of concrete, volume stability of mortar bar specimens, and setting times of pastes were investigated. Test results indicate that, under standard curing conditions, only 1-day strength of fly ash concrete was low. At later ages, the strength values of even 50% and 60% fly ash concretes were satisfactory. Steam curing accelerated the 1-day strength but the long-term strength was greatly reduced. Setting time of fly ash-cement pastes and volume stability of mortars with 50% or less fly ash content were found to be satisfactory for standard specimens. In addition, for steam curing, this properties were acceptable for all replacement ratios.     

掺级配良好再生PVC骨料混凝土的力学和吸能性能

将级配良好的再生聚氯乙烯(PVC)颗粒以不同掺量等体积替代天然细骨料后加入混凝土中制成试件,进行力学性能试验和冲击试验,得到立方体压缩强度、劈裂抗拉强度、卸载弹性模量、能量吸收率和微观结构图,用来探究不同掺量的再生PVC骨料混凝土的力学和吸能性能。结果表明,当PVC骨料掺量为0%,5%,10%,15%,20%,30%时,其混凝土压缩强度分别为49.34,52.44,45.79,46.41,45.6,43.46 MPa,劈裂抗拉强度为2.73,3.58,3.2,2.92,2.69,2.44 MPa,混凝土的压缩强度和抗拉强度均随掺量增加呈先增加后缓慢降低趋势,并且用级配良好的再生PVC颗粒替代天然细骨料加入混凝土的力学性能比单一粒径塑料颗粒优良;随PVC骨料掺量增加,混凝土脆性得到改善且延性增强;混凝土的能量吸收能力随再生PVC细骨料掺量增加呈直线增加趋势。     

Influence of initial curing on sulphate resistance of blended cement concrete

The paper presents results of an investigation on the effect of initial curing conditions on the sulphate resistance of concrete made with ordinary portland cement and using pfa, silica fume and ground granulated blast furnace slag for partial replacement of cement. In addition, porosity and pore structure analysis of representative pastes was carried out to examine the relationship between these properties and sulphate resistance of concrete. The depth of carbonation in specimens of pastes was also determined.

Three different initial curing conditions immediately after casting of specimens were adopted, namely: WET/AIR CURED at 45°C, 25% RH; AIR CURED at 45°C, 25% RH; AIR CURED at 20°C, 55% RH. The results show that pore volume and pore structure of the paste bear no direct relationship with the sulphate resistance of concrete. The presence of a carbonated layer on the surface is generally accompanied by superior sulphate resistance—there are, however, important exceptions. Low humidity curing at high temperature (45°C) results in higher depths of carbonation but lower sulphate resistance than similar curing at 20°C.

The sulphate resistance of concrete increases with the replacement of cement with 22% pfa, 9% silica fume and 80% ggb slag. The sulphate resistance also increases due to drying out of concrete during early curing at low relative humidity and due to carbonation. The possible common factor which leads to this improved sulphate resistance is the reduced Ca(OH)₂ content which leads to smaller volume of the expansive reaction products with sulphate ions. The effect of initial curing at high temperature (45°C) is significantly harmful to the sulphate resistance of plain concrete but much less so to the blended cement concretes.     

曼尼希改性二乙烯三胺环氧建筑胶固化剂的制备

选用苯酚（P）、甲醛（F）对二乙烯三胺（DETA）进行曼尼希反应改性,研究了产物黏度、胺值与原料配比的关系。将改性的固化剂与环氧树脂E51进行配胶浇注,研究了胶体的力学性能与潮湿环境下的粘接性能。结果表明,P、DETA与F物质的量比[n（P）：n（DETA）：n（F）]=1．5：1．5：1．5的产物综合性能最佳。该固化剂黏度适宜（6542mPa·s）,与E51配胶浇注后,拉伸强度为40MPa,压缩强度达80MPa,潮湿环境下的钢一钢剪切强度为9．2MPa,与混凝土的粘接拉伸强度达47MPa,为混凝土内聚破坏。