CTF混凝土增效剂在高强混凝土中的试验研究

试验采用粉煤灰、矿粉、硅灰三种常用矿物掺合料和高性能外加剂,通过水胶比、矿粉掺量、粉煤灰掺量、砂率四个配合比参数进行配合比正交设计,制备了具有大流动性、坍损小的高强混凝土,研究了不同配合比以及CTF混凝土增效剂对强度等级大于C60的掺合料混凝土的工作性能和强度的影响。试验结果表明:CTF的掺入有利于改善高强混凝土的和易性,提高其强度,且可以保证在强度不降低的情况下节省基准水泥用量,具有可观的经济效益。     

粉煤灰硅灰复掺对混凝土抗冻耐久性的影响研究

在硅灰掺量一定的情况下,研究粉煤灰硅灰复掺对混凝土抗冻耐久性能的影响。试验结果表明:保持硅灰掺量为10%,随着粉煤灰掺量从0%增加到20%,混凝土经冻融循环试验后强度损失率先减小,后增加。当硅灰掺量为10%,粉煤灰掺量为10%时,混凝土强度损失率最小,为2.6%,此时,混凝土28d抗压强度为44.9MPa,120d抗压强度为55.0MPa,综合考虑抗压强度与抗冻性能,建议粉煤灰硅灰二者掺量皆为10%。     

双掺硅灰、粉煤灰轻骨料混凝土试验研究

基于松散体积法配制同时加入硅灰和粉煤灰两种矿物掺合料的轻骨料混凝土,采用正交试验设计,通过改变净水灰比、粉煤灰掺量、砂率、硅灰掺量四个影响因素,浇筑不同配合比的轻骨料混凝土试块,测定其干表观密度、28 d抗压强度和比强度,分析各影响因素对轻骨料混凝土性能的影响.研究结果表明:硅灰能显著提高轻骨料混凝土抗压强度,且硅灰掺量在3％～6％之间较为合理.并配制出了结构用强度等级为LC30～LC45的双掺硅灰、粉煤灰轻骨料混凝土,为双掺硅灰、粉煤灰轻骨料混凝土的应用提供依据.     

建筑垃圾多孔混凝土的力学改性研究

试验研究采用卵石骨料配比作为基础配合比(水胶比0.28,建筑垃圾取代率15%,目标孔隙率12%),用碎石替代卵石,并用粉煤灰、矿粉、硅灰部分取代水泥以及添加胶粉的方法来改善多孔混凝土的力学性能。结果表明:碎石骨料替代卵石骨料提高了混凝土强度,单掺矿物掺合料、胶粉不仅改善了多孔混凝土拌合物的性能,还大大提高了其强度,尤其硅灰改善效果更为显著。基准多孔混凝土28d抗压强度27.8MPa,硅灰最佳掺量8%时,多孔混凝土28d抗压强度为37.8MPa,抗折强度为3.5MPa,孔隙率为11.8%,透水系数0.65mm/s,抗冻等级D35。     

矿物添加剂对混凝土力学性能的影响

对掺加矿渣、粉煤灰、硅灰等矿物掺合料混凝土力学性能进行了研究。结果表明,单掺矿渣与硅灰能提高混凝土的保水性、黏聚性,但对于拌合物流动性的提高要比单掺粉煤灰的差。随着掺量的增加,单掺粉煤灰或矿渣的混凝土强度降低,单掺粉煤灰早期强度下降较大。双掺粉煤灰、矿渣混凝土,混凝土强度随着矿渣掺量的增加而降低;矿渣、粉煤灰掺量分别为30.5%、20.5%时,混凝土91 d的抗压强度要比基准混凝土的抗压强度高。在掺合料总量不小于61%时,AB组混凝土28、91 d的抗折强度和基准混凝土强度比较接近。其91 d强度甚至超过了基准混凝土。双掺粉煤灰、硅灰混凝土,当粉煤灰掺量不变时,单掺硅灰对提高混凝土强度比较显著。对于粉煤灰、矿渣、硅灰三掺的混凝土,与同等掺量的双掺组AB和AC相比,该组混凝土具有较高的抗压强度。     

矿物掺合料对胶砂力学性能试验研究

以不同龄期的胶砂试件为研究对象,在基准胶砂配合比的基础上,设计了单掺硅灰、复掺硅灰和粉煤灰共18种配合比,其硅灰掺量分别为3%、6%、9%,粉煤灰掺量分别为10%、15%、20%、25%、30%,通过抗压、抗折两类强度指标研究其力学性能规律,结果表明:单掺硅灰时,胶砂抗压和抗折强度均随着硅灰掺量的增加而增加,9%硅灰掺量时抗压值较未掺时增加10.12%-20.37%;复掺情况下,硅灰掺量为3%时,粉煤灰掺量在10%-20%时具有更好的力学性能,硅灰掺量为6%时,粉煤灰掺量越多,力学性能越差,硅灰掺量为9%时,在粉煤灰掺量为20%时力学性能最佳,且20%-30%具有较好的性能;粉煤灰掺量一定时,低粉煤灰掺量(10%-20%)时,以硅灰掺量为6%时较好,而对于高粉煤灰掺量的(25%-30%)胶砂,则以9%为最佳掺量。     

矿物掺合料改性再生混凝土性能试验研究

为了研究单掺矿物掺合料(粉煤灰、硅灰)对再生混凝土性能的影响,以再生骨料替换率(25%、50%、75%)、粉煤灰掺量(10%、15%、20%)、硅灰掺量(6%、8%、10%)为变量设计了再生混凝土配合比,并取普通混凝土作为对照组,分析了不同掺量下的粉煤灰和硅灰对再生混凝土工作性能和抗压强度的影响规律。研究结果表明,单掺粉煤灰或硅灰都能在一定程度上改善混凝土拌合物的和易性,但当再生骨料替换率为75%时,坍落度不再受矿物掺合料掺量的影响。基于矿物掺合料具有良好的火山灰效应和填充效应,单掺粉煤灰或硅灰均可提高再生混凝土的抗压强度,但当粉煤灰掺量大于20%时,水化产物数量减少反而降低了其抗压强度。     

粉煤灰对轻骨料混凝土性能的影响

为了探究粉煤灰的掺入对轻骨料混凝土的影响,采用外掺0%、15%、20%、30%、50%的粉煤灰代替等量的水泥制作浮石混凝土,研究不同掺量粉煤灰的浮石轻骨料混凝土在28~90d养护龄期间强度变化情况,并对养护28d的试块进行了快速冻融循环试验,通过试块的抗压强度、动弹模量及破坏特征,研究粉煤灰的掺入对轻骨料混凝土抗压强度及抗冻性能的影响。结果表明:粉煤灰的掺入对轻骨料混凝土60d的抗压强度影响较大,能大幅度提高轻骨料混凝土强度,20%的粉煤灰掺入为最优粉煤灰掺量;粉煤灰的掺入还能提高轻骨料混凝土的抗冻性,当掺量不超过30%时,均表现出比基准组好的抗冻性,而过多的掺入则使抗冻性降低。     

活性矿物掺料品种与掺量对混凝土强度的影响

根据不同掺量的硅灰、粉煤灰配制高强混凝土,结合28d的立方体试块抗压强度,分析了活性矿物掺料品种以及掺量对高强混凝土强度的影响,并对高强混凝土的配合比设计进行了一般阐述,以进一步推广高强混凝土的应用。     

利用铁尾矿粉制备保温砌块的研究

以水泥、铁尾矿粉、粉煤灰、硅灰为主要原料,双氧水为发泡剂,聚丙烯纤维为增强材料,辅以硬脂酸钙为助剂,制备泡沫混凝土砌块。通过分析粉煤灰、铁尾矿粉、硅灰、聚丙烯纤维、硬质酸钙掺量对泡沫混凝土砌块性能的影响研究,结果表明:配合比为铁尾矿粉掺量12%、粉煤灰掺量15%、硅灰掺量2.4%、纤维掺量0.2%、硬脂酸钙掺量0.8%,水胶比0.48,可制备出密度等级为600Kg/m3的泡沫混凝土砌块。     

硅粉、粉煤灰作掺合料的C80高性能混凝土研究

研究了硅粉、粉煤灰掺量对混凝土强度与流动性的影响和硅粉、粉煤灰混凝土28d强度规律及混凝土的后期强度增长规律。采用P.O.42.5级普通硅酸盐水泥、中砂、5~25mm碎石及适量NF2-6缓凝高效减水剂,水胶比0.28,硅粉掺量5%,粉煤灰掺量5%~15%或硅粉掺量10%~15%,粉煤灰掺量5%~20%及水胶比0.31,硅粉掺量15%,粉煤灰掺量5%~10%时,可配制出C80高性能混凝土并且给出混凝土配合比参考公式。     

Characteristics of lightweight concrete containing mineral admixtures

This research investigates the properties of fresh and hardened concretes containing locally available natural lightweight aggregates, and mineral admixtures. Test results indicated that replacing cement in the structural lightweight concrete developed, with 5–15% silica fume on weight basis, caused up to 57% and 14% increase in compressive strength and modulus of elasticity, respectively, compared to mixes without silica fume. But, adding up to 10% fly ash, as partial cement replacement by weight, to the same mixes, caused about 18% decrease in compressive strength, with no change in modulus of elasticity, compared to mixes without fly ash. Adding 10% or more of silica fume, and 5% or more fly ash to lightweight concrete mixes perform better, in terms of strength and stiffness, compared to individual mixes prepared using same contents of either silica fume or fly ash.     

Compressive strength and stability of sustainable self-consolidating concrete containing fly ash,silica fume,and GGBS

This paper presents the findings of an experimental program seeking to understand the effect of mineral admixtures on fresh and hardened properties of sustainable self-consolidating concrete (SCC) mixes where up to 80% of Portland cement was replaced with fly ash, silica fume, or ground granulated blast furnace slag. Compressive strength of SCC mixes was measured after 3, 7, and 28 days of moist curing. It was concluded in this study that increasing the dosage of fly ash increases concrete flow but also decreases segregation resistance. In addition, for the water-to-cement ratio of 0.36 used in this study, it was observed that the compressive strength decreases compared to control mix after 28 days of curing when cement was partially replaced by 10%, 30%, and 40%of fly ash. However, a fly ash replacement ratio of 20% increased the compressive strength by a small margin compared to the control mix. Replacing cement with silica fume at 5%, 10%, 15%, and 20% was found to increase compressive strength of SCC mixes compared to the control mix. However, the highest 28 day compressive strength of 95.3 MPa occurred with SCC mixes in which 15% of the cement was replaced with silica fume.     

基于不同掺和料的透水混凝土性能试验研究

透水混凝土是一种利于促进水循环,改善城市生态环境的环保型建筑材料,本文通过分析目标孔隙率、粉煤灰的量、硅粉的量和纳米SiO₂的量等因素对透水混凝土正交试验影响。结果表明:透水混凝土抗压强度的最优配合比为目标孔隙率取16%、硅灰掺量取8%、粉煤灰掺量取10%、纳米SiO₂掺量取0.5%;透水混凝土孔隙率的最优配合比为目标孔隙率取24%、粉煤灰掺量取10%、硅灰掺量取2%、纳米SiO₂掺量取1%;透水混凝土透水系数的最佳配合比为目标孔隙率取24%、硅灰掺量取8%、粉煤灰掺量取20%、纳米SiO₂掺量取1%。     

Mechanical and durability properties of high performance concretes containing supplementary cementitious materials

An experimental investigation was carried out to evaluate the mechanical and durability properties of high performance concretes containing supplementary cementitious materials in both binary and ternary systems. The mechanical properties were assessed from the compressive strength, whilst the durability characteristics were investigated in terms of chloride diffusion, electrical resistivity, air permeability and water absorption. The test variables included the type and the amount of supplementary cementitious materials (silica fume, fly ash and ground granulated blast-furnace slag). Portland cement was replaced with fly ash up to 40%, silica fume up to 15% and GGBS up to a level of 70%.The results confirmed that silica fume performs better than other supplementary cementitious materials for the strength development and bulk resistivity. The ternary mixes containing ground granulated blast-furnace slag/fly ash and silica fume performed the best amongst all the mixes to resist the chloride diffusion. The mix containing fly ash showed favourable permeation results. All the ternary combinations can be considered to have resulted in high performance concretes with excellent durability properties.     

掺稻壳灰/硅灰混凝土的性能研究

研究了稻壳灰、硅灰、稻壳灰+粉煤灰、硅灰+粉煤灰对混凝土抗压强度、抗折强度、抗硫酸侵蚀能力和抗碳化能力的影响.结果表明:掺加5％～10％稻壳灰或硅灰有助于提升混凝土的抗压强度和抗折强度,且稻壳灰、硅灰掺量越高抗压强度越高,掺硅灰混凝土相对于掺稻壳灰混凝土的抗压和抗折强度更高,掺稻壳灰+粉煤灰、硅灰+粉煤灰试件的抗压和抗...     

蒸养混凝土抗氯离子渗透性能研究

蒸汽养护能促进混凝土早期强度的增长,但影响混凝土长期力学性能和抵抗氯离子等侵蚀性介质渗透的能力。本文研究了粉煤灰、硅灰矿物掺合料对蒸养混凝土抗压强度与抗氯离子渗透性能的影响。试验结果表明：蒸养普通混凝土抗氯离子渗透性能低于相应标养混凝土,掺入粉煤灰、硅灰等矿物掺合料后,可以显著改善蒸养混凝土的抗氯离子渗透性能。     

不同掺合料对高性能混凝土工作性能影响的试验研究

通过在C50高性能混凝土中以等量取代水泥用量的方法单掺粉煤灰、硅粉,双掺粉煤灰硅粉及同时掺粉煤灰、硅粉和聚丙烯纤维,研究了不同掺合料及不同掺量对HPC拌合物工作性的影响。结果表明:在高性能混凝土中加入粉煤灰,能使混凝土具有更好的工作性能,使拌合物黏聚性和可塑性提高;在6%硅粉掺量内,硅粉的加入提高了高性能混凝土的工作性能,但随着掺量进一步增大后,硅粉高性能混凝土的流动性将降低,稠度增大,整体工作性能降低,需要提高高性能减水剂的用量;双掺粉煤灰和硅粉后,粉煤灰高性能混凝土的工作性能随着硅粉掺量的增加而呈降低趋势;聚丙烯纤维对高性能混凝土的工作性能影响不明显,但聚丙烯纤维的掺入,提高了混凝土黏聚性,能抑制拌合物的离析和泌水。     

矿物掺合料对铁铝酸盐水泥力学性能影响研究

针对铁铝酸盐水泥早期水化热高的问题,提出采用掺加矿物掺合料的方法改善铁铝酸盐水泥性能。研究了单独掺加不同掺量粉煤灰、矿粉、石灰石粉、粉煤灰微珠、硅灰的铁铝酸盐水泥用水量、力学性能,以及复合掺加粉煤灰-矿粉、粉煤灰微珠-矿粉、粉煤灰微珠-硅灰及石灰石灰石粉-矿粉的铁铝酸盐水泥用水量、力学性能。结果表明,粉煤灰等掺合料均会降低铁铝酸盐水泥强度,但是对用水量的影响不同,粉煤灰及硅灰会显著增加铁铝酸盐水泥用水量,石灰石粉及粉煤灰微珠会降低用水量。当掺合料单独掺加或复合掺加等量取代30%水泥时,复合胶凝体系的抗压强度降至45.0MPa左右,掺合料的掺量宜控制在30%以内。     

Effect of electric arc furnace dust on the properties of OPC and blended cement concretes

This paper presents results of a study conducted to evaluate the mechanical properties and durability characteristics of ordinary Portland cement (OPC) and blended cement (silica fume and fly ash) concrete specimens prepared with electric arc furnace dust (EAFD). Concrete specimens were prepared with and without EAFD. In the silica fume cement concrete, silica fume constituted 8% of the total cementitious material while fly ash cement concrete contained 30% fly ash. EAFD was added as 2% replacement of cement in the OPC concrete and 2% replacement of the total cementitious content in the blended cement concretes. Mechanical properties, such as compressive strength, drying shrinkage, initial and final setting time, and slump retention were determined. The durability characteristics were evaluated by measuring water absorption, chloride permeability, and reinforcement corrosion. The initial and final setting time and slump retention increased due to the incorporation of EAFD in both OPC and blended cement concretes. The drying shrinkage of EAFD cement concrete specimens was more than that of concrete specimens without EAFD. The incorporation of EAFD was beneficial to OPC concrete in terms of strength gain while such a gain was not noted in the blended cement concretes. However, the strength differential between the blended cement concretes with EAFD and the corresponding concretes without EAFD was not that significant. The water absorption and chloride permeability, however, decreased due to the incorporation of EAFD in both the OPC and blended cement concretes. The corrosion resistance of OPC and blended cement concrete specimens increased due to the addition of EAFD.