偏高岭土掺合料对高强混凝土抗压强度的影响

通过控制混凝土的偏高岭土掺量、龄期、水胶比和矿物掺合料组合等条件,进行偏高岭土单掺,偏高岭土与矿渣复掺及偏高岭土、矿渣与粉煤灰复掺等量取代水泥试验,研究偏高岭土对高强混凝土抗压强度的影响。结果表明:水胶比分别为0.18、0.21和0.24时,较于基准混凝土,3组试验制配的高强混凝土3、7和28d抗压强度都显著增强。偏高岭土、矿渣与粉煤灰三元复掺时,偏高岭土与矿渣的掺量控制在20%左右,能明显提高混凝土的早期强度,最佳水胶比均为0.18。通过单一降低水胶比不能显著提升偏高岭土混凝土的抗压强度。偏高岭土混凝土三元复掺的抗压强度一般大于其二元复掺的抗压强度,其二元复掺的抗压强度一般大于其单掺的抗压强度。     

偏高岭土混凝土力学性能研究

研究了0、5%、10%和15%四种掺量下单掺偏高岭土和偏高岭土与粉煤灰、矿渣粉按不同比例复掺后混凝土的抗压强度和抗折强度。结果表明,在单掺偏高岭土时,低掺量的偏高岭土有利于混凝土的早期强度,而高掺量的偏高岭土则有利于混凝土的后期强度。在复掺偏高岭土中,偏高岭土和粉煤灰、矿渣粉三种矿物掺合料复掺时具有最好的效果,能够显著增强混凝土的早期和后期强度。     

活性偏高岭土对混凝土性能影响的试验研究

本文采用偏高岭土、粉煤灰、矿渣为辅助性胶凝材料,取代部分水泥配制混凝土,对混凝土的力学性能和耐久性能进行了试验研究,结果表明,偏高岭土可有效提高混凝土抗压强度,改善混凝土的抗碳化性能和抗氯离子渗透性能。     

多掺矿物掺合料再生混凝土力学性能研究

通过测试再生混凝土坍落度、立方体抗压强度及劈裂抗拉强度,并对再生混凝土微观形貌、矿物组成进行分析,探究矿物掺合料种类及掺量对再生混凝土力学性能的影响。研究结果表明：将粉煤灰分别与矿渣、硅灰、偏高岭土组合使用能够明显改善再生混凝土和易性;单掺矿物掺合料中,偏高岭土能显著提升再生混凝土力学性能,相较于基准组,养护龄期90 d时,抗压强度和劈拉强度分别提升24.0%和11.0%;复掺矿物掺合料中,粉煤灰-偏高岭土对混凝土的劈拉强度提升效果突出,劈拉强度提升14.0%,抗压强度提升6.5%;三掺矿物掺合料中,粉煤灰-硅灰-偏高岭土对再生混凝土的劈拉强度提升较好,劈拉强度提升9.8%,抗压强度提升4.6%;粉煤灰-矿渣-硅灰-偏高岭土四掺再生混凝土力学性能表现良好,抗压强度最高提升18.4%,劈拉强度最高提升15.5%。     

矿物掺合料对碱矿渣粉燥灰胶凝材料改性研究

研究沸石粉和偏高岭土2种矿物掺合料对固态碱矿渣粉煤灰胶凝材料的改性效果.结果表明,偏高岭土对碱矿渣粉煤灰胶凝材料的抗压强度具有明显增强效果,但降低了抗折强度:沸石粉对抗压强度和抗折强度均有增强作用;作为碱矿渣粉煤灰胶凝材料的活性掺合料,沸石粉优于偏高岭土,具有进一步研究的价值:偏高岭土和沸石粉在碱矿渣粉煤灰胶凝材料中发挥的强度优势不及矿渣粉煤灰混合料明显.     

偏高岭土对混凝土抗压强度的影响研究

以偏高岭土、粉煤灰、矿粉为掺合料,主要对单掺、双掺、三掺条件下,偏高岭土对混凝土7d、28d抗压强度的影响展开了研究。结果表明,偏高岭土的火山灰活性要远高于粉煤灰和矿粉,在混凝土中掺入适量的偏高岭土可以大幅提高混凝土的抗压强度。     

高活性偏高岭土微粉的制备及复合效应的研究

本文研究了高活性偏高岭土(MK)微粉的制备及与多种矿物掺料复合效应。以10％MK替代水泥，28d抗压强度提高约10MPa；以8％MK取代水泥配制高性能混凝土，其作用效果与硅灰相当，与矿渣基复合掺料复合(8％MK与35％复合矿渣替代水泥)掺入混凝土中，使混凝土物理、力学性能优干硅灰相同掺量的复合效果；与粉煤灰复合，可以使水泥标准稠度用水量降低，抗折、抗压强度提高，干缩率减少。     

废弃砖粉复合掺合料对混凝土强度及耐久性的影响

本文研究了废弃砖制备的砖粉掺合料与矿渣粉、石灰石粉、粉煤灰复合掺入对混凝土耐久性的影响。结果表明:在混凝土抗压强度方面,矿渣粉和砖粉复掺时,混凝土7d和28d抗压强度与矿渣粉和粉煤灰复掺时相近,优于矿渣粉和石灰石粉复掺时混凝土的强度;同一水胶比时,矿渣粉、砖粉复合掺合料配制的混凝土抗氯离子渗透性能及抗碳化性能,与矿渣粉、砖粉复合掺合料混凝土相当,优于矿渣粉、石灰石粉复合掺合料混凝土的抗氯离子渗透性能。     

偏高岭土与矿渣复掺对混凝土性能改善的研究

通过偏高岭土与矿渣的不同复掺比例研究了偏高岭土与矿渣复掺对混凝土强度和耐久性能的影响.结果表明:往矿渣混凝土中掺入偏高岭土后,混凝土的强度和耐久性能均有所提高,矿渣和偏高岭土在胶凝材料中的掺量越大,混凝土的氯离子导电量越小.矿渣和水泥的优化比例为3:7左右,这样既保证了混凝土的强度,又使得混凝土具有优越的抗氯离子扩散性能.     

偏高岭土混凝土抗冻融性能试验研究

在固定水胶比下,对单掺偏高岭土、偏高岭土与矿粉双掺及偏高岭土、矿粉与粉煤灰复掺的高强混凝土进行力学和快速冻融循环试验,研究掺量对混凝土性能的影响。结果表明:在单掺偏高岭土时,随着掺量增加,混凝土的抗冻性及抗压强度逐渐增强;在偏高岭土与矿粉双掺且取代水泥量为定值时,偏高岭土与矿粉存在最优配合比使混凝土抗冻性及抗压强度最好;在偏高岭土、矿粉与粉煤灰复掺且取代水泥量为定值时,三者之间存在最优配合比使混凝土的抗冻性及抗压强度最好;当复合掺和料取代水泥的量相同时,三元复掺的混凝土抗冻性和抗压强度最好。     

不同材料增强处理再生骨料对混凝土抗压强度的影响

研究了水泥浆、偏高岭土地聚物、掺粉煤灰偏高岭土地聚物、水泥浆-偏高岭土地聚物增强处理再生骨料对混凝土抗压强度的影响。结果表明:四种增强材料处理的再生骨料对混凝土抗压强度的影响顺序大小为水泥浆-偏高岭土地聚物>偏高岭土地聚物>水泥浆>掺粉煤灰偏高岭土地聚物。     

矿物掺合料对混凝土抗压强度和氯离子渗透性能的影响

就单掺粉煤灰、单掺矿渣微粉,以及复掺粉煤灰与矿渣微粉对混凝土抗压强度和氯离子渗透性能的影响进行了试验研究。结果表明,粉煤灰和矿渣微粉明显降低了混凝土的早期抗压强度,但后期强度发展良好,而两者复掺更有利于后期强度的增长;粉煤灰和矿渣微粉都不同程度的降低了混凝土的氯离子扩散系数,随着龄期的延长,矿物掺合料提高混凝土抗氯离子渗透性能的能力越显著。     

矿物掺合料对植生混凝土抗压强度及pH值的影响研究

采用矿物掺合料等量取代水泥的方法配制植生混凝土,研究了粉煤灰、硅灰及偏高岭土对混凝土抗压强度和内部孔隙pH值发展的影响规律。研究结果表明:单掺粉煤灰、硅灰及偏高岭土植生混凝土,28 d抗压强度达8.0~10.0 MPa,孔隙率为30%以上,90 d孔溶液pH值降低至11.6~11.8。满足河流护岸、道路护坡等对植生混凝土要求。     

早期高温养护对预制混凝土构件长期抗压强度的影响

混凝土构件的早期养护条件是决定其长期抗压强度的重要因素,为研究早期养护温度对预制混凝土构件长期抗压强度的影响,制作了单掺粉煤灰(SPC)、双掺粉煤灰、矿渣(DPC)和三掺粉煤灰、矿渣、硅灰(TPC)以及对比普通水泥混凝土(OPC)试件,按照有、无预养分别进行了40℃、60℃和80℃的水养护,达到设计强度后取出放置在室内大气环境,再分别测试其28 d、100 d、200 d和300 d龄期的抗压强度。研究结果表明:无论普通混凝土还是矿物掺合料混凝土,早期养护温度越高,混凝土达到设计强度所需的养护时间越短,但长期的抗压强度越低。掺加矿物掺合料和20℃的预养有助于增强混凝土抵御高温养护导致的热应力问题,有利于预制混凝土构件长期强度的提高。     

Strength and corrosion properties of Portland cement mortar and concrete with mineral admixtures

This work aims to validate the design assumptions by the California Department of Transportation in order to better define the strategies used to design concrete structures with adequate corrosion mitigation and thus a “maintenance-free” service life. To this end, various laboratory tests were conducted to investigate the compressive strength of and chloride diffusivity in mortar and concrete samples with cement partially replaced by various minerals (class F and class N fly ash, ultra-fine fly ash, silica fume, metakaolin, and ground granulated blast-furnace slag), the porosity of mineral concretes, the freeze–thaw resistance of mineral mortars in the presence of deicers, and the effect of supplementary cementitious materials on the chloride binding and chemistry of the pore solution in mortar.     

粉煤灰与矿渣对再生骨料混凝土力学性能影响的研究

研究了粉煤灰单掺、粉煤灰与矿渣双掺对再生骨料混凝土(RAC)力学性能的影响,并初步探讨了其影响机理;建立了再生骨料混凝土立方体抗压强度与抗折强度、劈拉强度的相关关系式。试验结果表明：粉煤灰单掺降低了再生骨料混凝土的强度和弹性模量;粉煤灰与矿渣双掺对混凝土强度和弹性模量的影响随两者组合比例不同而有显著差异。     

Influence of supplementary cementitious materials on engineering properties of high strength concrete

The influence of supplementary cementitious materials (SCMs), namely silica fume, metakaolin, fly ash and ground granulated blast-furnace slag, on the engineering properties of high strength concrete (HSC) has been investigated in this study. Workability, compressive strength, elastic modulus, porosity and pore size distribution were assessed in order to quantify the effects of the different materials. The results show that the inclusion of the different SCMs has considerable influence on the workability of HSC. Silica fume and metakaolin significantly enhanced the strength of HSC. Fly ash reduced the early-age strength; however, it enhanced the long-term strength of the HSC. Likewise, ground granulated blast-furnace slag impaired the early-age strength, but marginally improved the long-term strength at low replacement levels. The general effect of the different SCMs on the elastic modulus of HSC is rather small compared to their effect on strength. There are good correlations between both static and dynamic moduli and compressive strength. The EC 2 and ACI 209 provide a good estimate of static modulus of elasticity from compressive strength, while the BS8110 gives a good estimate of static modulus of elasticity from dynamic modulus of HSC containing the different SCMs. Porosity and pore size were reduced with the addition of the different SCMs. The volume of mesopores in the ranges of <15 nm and 15 – 30 nm was notably increased for HSC containing SCMs, whereas the percentage of macropores was significantly reduced.     

双掺矿物掺合料轻骨料混凝土性能试验研究

试验研究了粉煤灰、矿渣粉复合掺合料对LC30页岩陶粒轻骨料混凝土坍落度、抗压强度、抗冻融性能、抗碳化性能和自由收缩性能的影响规律。结果表明:总掺量不变时随着粉煤灰相对掺量的增加,坍落度逐渐增加;矿物掺合料提高了混凝土后期抗压强度,总掺量为30%、粉煤灰矿渣粉掺入比例2∶3时28 d抗压强度高于基准试验组14.3%;总掺量一定时掺入比例为2∶3的试验组,混凝土抗冻性能、抗碳化性能和抗自由收缩性能最佳;掺入比例一定时,掺量为30%的试验组的力学性能和耐久性能更优。     

粉煤灰和磨细矿渣对北京地铁5号线清河斜拉桥大体积混凝土性能的影响

本文研究了粉煤灰和磨细矿渣对大体积承台混凝土抗压强度、水化热、收缩率的影响。试验结果表明：在水泥掺量一定时,随矿渣粉掺量的增加水化放热量、最大放热速率和干缩率均增大;水泥用量为200kg／m^3、粉煤灰为140kg／m^3、矿渣粉为50kg／m^3时,混凝土水化热较小、干缩率较小;SEM形貌图表明,粉煤灰和磨细矿渣的综合效应,使火山灰反应更加充分,Ca(OH)2含量降低,在水泥用量200kg／m^3时,混凝土28天结构致密。     

Strength and drying shrinkage properties of self-compacting concretes incorporating multi-system blended mineral admixtures

Drying shrinkage can be a major reason for the deterioration of concrete structures. The contraction of the material is normally hindered by either internal or external restraints so that tensile stresses are induced. These stresses may exceed the tensile strength and cause concrete to crack. The present study investigated compressive strength and particularly drying shrinkage properties of self-compacting concretes containing binary, ternary, and quaternary blends of Portland cement, fly ash (FA), ground granulated blast furnace slag (GGBFS), silica fume (SF), and metakaolin (MK). For this purpose, a total of 65 self-compacting concrete (SCC) mixtures were prepared at two different water to binder ratios. It was observed that drying shrinkage lessened with the use of FA, GGBFS, and MK while incorporation of SF increased the drying shrinkage.