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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%。 相似文献
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通过正交试验,研究了再生骨料取代量、硅粉掺量、粉煤灰掺量和聚丙烯纤维掺量对新拌再生骨料混凝土坍落度和抗压强度的影响。研究结果表明,再生骨料取代量、硅粉和聚丙烯纤维掺量越大,粉煤灰掺量越小,新拌再生骨料混凝土的坍落度越小;再生骨料混凝土的抗压强度随着再生骨料取代量的降低、硅粉和聚丙烯纤维掺量的增加而提高,粉煤灰对抗压强度的影响很小。 相似文献
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C50再生骨料混凝土的试验 总被引:2,自引:0,他引:2
试验采用正交设计的方法,利用再生骨料配制高强(C50)混凝土,同时研究水胶比、再生骨料取代量、硅粉和粉煤灰掺量对再生骨料混凝土和易性和抗压强度的影响。试验结果表明:坍落度随着水胶比的增大、再生骨料取代量和硅粉掺量的减小而增大;粉煤灰掺量对坍落度的影响较小;再生骨料混凝土的抗压强度随着水胶比和再生骨料取代量的降低、硅粉掺量的增加而提高,粉煤灰对抗压强度的影响较小。随着水化的发展,再生骨料对混凝土抗压强度的不利影响将逐渐减小。 相似文献
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高效减水剂与粉煤灰对再生混凝土的和易性影响研究 总被引:1,自引:0,他引:1
通过对3种不同的再生混凝土和易性影响研究,发现随着再生骨料取代率的不断增大,再生混凝土的流动性均降低,降低幅度的顺序为再生混凝土③>再生混凝土①>再生混凝土②;掺粉煤灰后再生混凝土拌合物的坍落度有所增加,但增加幅度并不大;正交试验显示,影响坍落度的4因素主次顺序为:再生骨料①取代率、高效减水剂、再生骨料②取代率、粉煤灰掺量,再生混凝土中加入高效减水剂和粉煤灰,可显著提高新拌再生混凝土的流动性,且粘聚性和保水性也较好。 相似文献
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为寻求一种新型绿色建筑墙体,以粉煤灰、矿渣两种工业废料为混凝土基底,再生砖作为粗骨料部分或完全取代天然骨料,制备不同砖骨料取代率下的地聚物再生砖混凝土砌块。通过混凝土砌块抗压强度试验、抗折强度试验,对不同砖骨料取代率(0%、25%、50%、75%、100%)下的地聚物再生砖混凝土砌块抗压强度、抗折强度及试验曲线进行分析,探究砖骨料取代率对地聚再生砖混凝土砌块性能的影响。试验结果表明,随着砖骨料取代率的增大,地聚物再生砖混凝土砌块的抗压强度、抗折强度逐渐下降,而相应的地聚物再生砖混凝土砌块抗压、抗折荷载-位移曲线上升段斜率也逐渐下降;地聚物再生砖混凝土砌块抗折强度与抗压强度比值可保持在1/9.4~1/7.0范围内,且最低抗压强度等级高于MU7.5,符合混凝土砌体规范要求。 相似文献
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钢纤维粉煤灰再生混凝土强度正交试验研究 总被引:4,自引:0,他引:4
利用正交试验方法对钢纤维粉煤灰再生混凝土(以下简称再生混凝土)的强度性能进行了试验,考察了粉煤灰取代率(质量分数)、钢纤维掺量(体积分数)和再生粗骨料取代率(质量分数)对再生混凝土28d立方体抗压强度、劈裂抗拉强度和抗折强度的影响,并对试验结果进行了系统分析.结果表明:粉煤灰取代率对再生混凝土抗压与抗折强度的影响规律一致,但对其劈裂抗拉强度的影响规律却不相同;再生混凝土抗压强度、劈裂抗拉强度和抗折强度均随钢纤维掺量的增加而增大,但钢纤维掺量对劈裂抗拉和抗折强度的影响显著,对抗压强度的影响较小;再生粗骨料取代率对抗压强度、劈裂抗拉强度和抗折强度的影响规律基本一致,强度总体上随再生粗骨料取代率的增大而增大.要使再生混凝土强度得到提高,需降低粉煤灰的取代率,增大钢纤维掺量和再生粗骨料取代率.当粉煤灰取代率在30%以内、钢纤维掺量在18%以内时,粉煤灰取代率对再生混凝土抗压强度的影响最大,其次是再生粗骨料取代率,最次是钢纤维掺量;钢纤维掺量对再生混凝土劈裂抗拉强度和抗折强度的影响最大,其次是粉煤灰取代率,最次是再生粗骨料取代率. 相似文献
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采用偏高岭土、粉煤灰和矿渣等量取代水泥,并将偏高岭土与粉煤灰、矿渣分别复掺配制混凝土,对混凝土的工作性、抗压强度和耐久性进行了研究.结果表明,偏高岭土用作混凝土掺合料且掺量合理时,其对混凝土坍落度和抗压强度的影响优于粉煤灰和矿渣,配制的混凝土抗腐蚀性和抗冻融性均有所提高. 相似文献
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Mechanical properties of fly ash‐based geopolymer concretes at high temperature At present, concretes based on alkali‐activated binders, so‐called geopolymer concretes, are investigated intensively in the building materials industry and by the research community as environmentally friendly alternative to Portland cement‐based concretes. These inorganic binders, which are based on industrial by‐products such as fly ash and ground granulated blast furnace slag, exhibit high resistance against corrosive acids and salts, if properly designed. The mechanical properties of fly ash‐based geopolymer concretes at high temperatures are subject of systematic investigations at the Bundesanstalt für Materialforschung und ‐prüfung (BAM) to create a basis for the structural design of fire exposed concrete members based on alkali‐activated binders. The concrete specimens, produced with quartz aggregates or lightweight aggregates and heated to a maximum temperature of 750 °C, exhibited a decrease of compressive strength up to temperatures of ca. 300 °C, attributed to formation of microcracks caused by dehydration. At higher temperatures the compressive strength of the investigated geopolymer concretes recovered partly, due to sintering processes starting from ca. 500 °C. Because of this beneficial property when compared to conventional concretes, geopolymer concretes can potentially be applied in infrastructure facilities where fire resistance is critical. From the results of the thermomechanical tests stress‐strain relationships are derived that can be used for the structural design of members made from geopolymer concretes. 相似文献
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Cold-bonded fly ash aggregate concrete with fly ash as part of binder or fine aggregate facilitates high volume utilization of fly ash in concrete with minimum energy consumption. This paper investigates the influence of fly ash on strength and sorption behaviour of cold-bonded fly ash aggregate concrete due to partial replacement of cement and also as replacement material for sand. While cement replacement must be restricted based on the compressive strength requirement at desired age, replacement of sand with fly ash appears to be advantageous from early days onwards with higher enhancement in strength and higher utilization of fly ash in mixes of lower cement content. Microstructure of concrete was examined under BSEI mode. Replacement of sand with fly ash is effective in reducing water absorption and sorptivity attributable to the densification of both matrix and matrix–aggregate interfacial bond. Cold-bonded fly ash aggregate concrete with a cement content of 250 kg/m3, results in compressive strength of about 45 MPa, with a total inclusion of around 0.6 m3 of fly ash in unit volume of concrete. 相似文献
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以C30混凝土为基准,将2种粉煤灰分别按照5种设计掺量等质量替代水泥,研究粉煤灰对混凝土抗压强度的影响。试验结果表明,掺入的粉煤灰品质及质量不同,对混凝土强度的影响程度不同;粉煤灰混凝土的前期强度增长较弱而后期较强;粉煤灰等质量最佳替代水泥量为30%。 相似文献
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变温条件下粉煤灰对混凝土抗压强度的影响 总被引:1,自引:0,他引:1
以混凝土绝热温升为温度参考依据,模拟混凝土早龄期的变温过程,研究了在变温条件下掺加粉煤灰对混凝土抗压强度的影响.强度等级为C30级时.粉煤灰混凝土3 d后的抗压强度高于纯水泥混凝土;强度等级为C80级时,粉煤灰混凝土4 d后的抗压强度高于纯水泥混凝土.通过工程实例研究了不同养护条件对大掺量粉煤灰混凝土强度发展的影响,发现温度匹配养护下7 d的抗压强度远高于在标准养护和同条件养护下的抗压强度. 相似文献
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Xianming Shi Zhengxian Yang Yajun Liu Doug Cross 《Construction and Building Materials》2011,25(8):3245-3256
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. 相似文献