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Piping is a problem that commonly occurs downstream of hydraulic structures under the influence of upward seepage. Piping is considered as the main mechanism of hydraulic structures failures. In this work an experimental program was set for determining the seepage velocity and piping resistance for unreinforced and randomly reinforced silty sand samples. Two types of fiber were used for preparing the reinforced samples. The experimental tests were carried out for different fiber contents (0.5, 0.75, 1.0 and 1.25%) and fiber lengths (5, 25 and 35 mm) under different hydraulic heads. Discharge velocity and seepage velocity of water flow through unreinforced and reinforced samples were calculated and compared with unreinforced sample. The results show that the inclusion of fibers reduced the seepage velocity, increased the piping resistance and increased the critical hydraulic gradient hence, considerably delaying the occurrence of piping. Furthermore, the amounts of increase in the piping resistance and hydraulic gradient are functions of percent and length of fibers. 相似文献
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利用化工废石膏制备新型道路建筑材料的研究 总被引:8,自引:1,他引:7
研究了激发剂对化工废石膏-粉煤灰新型道路建筑材料的强度和自由线膨胀率等性能的影响,以及减水剂的作用和新型道路建筑材料的抗硫酸盐侵蚀性能等。本研究选用3种不同类别粉煤灰与化工废石膏进行复合试验的结果表明,当原状粉煤灰与高钙粉煤灰混合后再与化工废石膏复合研制的材料,比两种灰单独掺加的效果更好,本研究研制的新型道路建筑材料具有较高的力学性能和优异的抗硫酸盐侵蚀性能。 相似文献
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Vallarasu Manoharan SOUNTHARARAJAN Dr. Anandan SIVAKUMAR 《Frontiers of Structural and Civil Engineering》2013,7(4):429
The present study focuses on the improvement of pozzolanic reaction of fly ash particles with the cement hydration products. Low and high volume fly ash concrete mixtures were studied systematically with the addition of accelerating admixtures and accelerated curing of the concrete specimens in a steam chamber for 18 h at 75°C. Also, the reinforcing effects of glued steel fibers addition on the compressive and flexural performance of fly ash concrete were investigated. The test results indicated that the addition of accelerator improved the rate of hardening and the inclusion of steel fibers provided higher flexural performance. Also, it can be noted that the high volume fly ash (50%) addition in concrete showed a reduction in strength; however, the addition of accelerator has compensated the deceleration in strength gain. The proper selection of concrete ingredients, addition of accelerator and initial steam curing for 18 h showed better improvement on the engineering properties in fly ash concrete. A maximum increase (41.7%) in compressive strength of fly ash concrete around 52.90 MPa was noticed for 25% fly ash substitution and 1.5% steel fibers addition. Dynamic elastic modulus was also calculated in loaded concrete specimen using ultrasonic pulse velocity test and showed a good agreement with the experimental value. 相似文献
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《Construction and Building Materials》2007,21(7):1486-1491
The results of an experimental investigation to study the effects of replacement of cement (by weight) with three percentages of fly ash and effects of addition of steel and polypropylene fibers are presented. Current day knowledge of concrete technology focuses attention primarily on the use of different materials in the production of concrete, industrial wastes in particular. The use of fly ash in concrete today is an important subject and is growing in importance day by day. Using fly ash in concrete may both provide economical advantages and better properties in the production of concrete. Besides, concretes produced with three different replacement ratios of fly ash and three different types of steel and polypropylene fibers were compared to those without fibers used in concrete with FA. According to the results of the study, addition of fibers provide better performance for the concrete, while fly ash in the mixture may adjust the workability and strength losses caused by fibers, and improve strength gain. 相似文献
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对碾压钢纤维粉煤灰混凝土的性能进行了试验研究,侧重分析了钢纤维掺量和粉煤灰掺法及掺量对碾压钢纤维粉煤灰混凝土工作性能的影响.试验结果表明,随钢纤维掺量和粉煤灰掺量的增加,碾压钢纤维粉煤灰混凝土的工作度较基体混凝土大、密实性优于基体混凝土,大多数钢纤维在与振动及压重方向垂直的平面上呈二维乱向分布,其路用性能较常态钢纤维混... 相似文献
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基于正交试验制备生土基复合墙体材料及其热湿综合性能分析 总被引:1,自引:0,他引:1
基于正交试验设计,以石灰和粉煤灰为改性剂制备了生土基复合墙体材料.通过多元非线性回归,分析研究了改性剂掺量和含水率对生土基复合墙体材料热湿综合性能的影响,并得到生土基复合墙体材料的优化配方.结果表明:改性剂掺量和含水率对生土基复合墙体材料热湿综合性能的影响显著,敏感程度依次为含水率>粉煤灰掺量>石灰掺量>空白因素;生土基复合墙体材料的优化配方为石灰掺量6.24%+粉煤灰掺量8.93%+含水率13.57%,此时其导热系数为0.721W/(m·K),平衡含湿量为7.645%,且抗压强度和耐水性均满足相应要求.通过墙体材料组成结构分析和微观形貌分析可知,粉煤灰在碱性环境中的水化作用使得优化生土基复合墙体材料内部呈现出更加致密的结构体系. 相似文献
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分别进行了掺入钢纤维、粉煤灰及两种混杂对混凝土抗压性能、抗拉性能增强效果的试验研究.讨论了钢纤维掺量、粉煤灰掺量对混凝土抗压、抗拉性能的影响.试验结果表明:在保证其强度、耐久性、节约材料、降低造价的同时,确定了钢纤维粉煤灰混凝土中合理的钢纤维和粉煤灰掺量;同时表明,钢纤维的掺入对混凝土的强度和变形有明显的改善效果. 相似文献
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蒸压粉煤灰砖属于可以替代烧结普通砖的新型墙体材料,提高蒸压粉煤灰砖砌体的抗剪性能是改善此类砌体结构抗震、抗裂能力的关键。带肋蒸压粉煤灰砖通过改善砖的外形,在砖的表面开槽形成肋状,可提高砖砌体的抗剪能力。本文对带肋蒸压粉煤灰砖砌体、普通蒸压粉煤灰砖砌体和烧结普通砖砌体的抗剪性能进行了比较研究,并结合相关规范条文探讨了带肋蒸压粉煤灰砖的有关抗震、抗裂措施,为蒸压粉煤灰砖在地处地震高发区同时具备气候干燥,年温差、日温差大的新疆地区推广应用提供理论依据。 相似文献
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《Construction and Building Materials》2007,21(2):356-361
In this paper, the resistance to chloride penetration of concrete containing fly ash of various finenesses was examined. Three different fly ash finenesses viz., original fly ash, 45% fine portion and 10% fine portion fly ashes were used for the study. Chloride resistance of concretes was evaluated using the measurement of the Coulomb charge as per ASTM C1202 and by determination of chloride ingress after different periods of exposure to 3% NaCl solution in full immersion and partial immersion modes. From the tests, it is found that the resistance to chloride penetration of concrete depends on the fineness of fly ash. The rapid chloride permeability test (ASTM C1202) clearly indicates that the Coulomb charge of concrete at the age of 28 days is significantly reduced with the incorporation of fly ash. The decrease is promoted with an increase in fly ash fineness. The immersion of cut cylinders in the 3% NaCl solution for 3 and 6 months confirm that the resistance of the chloride penetration of concrete increases with an incorporation with fly ash and with an increase in the fly ash fineness. 相似文献
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粉煤灰作为轻质材料填筑公路路堤已有很多研究成果和工程实践,但其存在着遇水强度不稳定的弱点,限制了其在道路工程中大规模的应用,因此,提高粉煤灰的抗剪强度,增强它的整体性、稳定性,是一个值得研究的课题。本研究在粉煤灰中加入固化剂JNS-1,对其进行固化。根据室内试验结果,分析了固化剂JNS-1固化粉煤灰的无侧限抗压强度的变化规律及不同掺入比和龄期的应力—应变关系,给出了强度预测公式和应力—应变关系式,可供实际工程参考。 相似文献
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This paper reports on a comprehensive study on the properties of concrete containing fly ash and steel fibers. Properties studied include unit weight and workability of fresh concrete, and compressive strength, flexural tensile strength, splitting tensile strength, elasticity modulus, sorptivity coefficient, drying shrinkage and freeze–thaw resistance of hardened concrete. Fly ash content used was 0%, 15% and 30% in mass basis, and fiber volume fraction was 0%, 0.25%, 0.5%, 1.0% and 1.5% in volume basis. The laboratory results showed that steel fiber addition, either into Portland cement concrete or fly ash concrete, improve the tensile strength properties, drying shrinkage and freeze–thaw resistance. However, it reduced workability and increase sorptivity coefficient. Although fly ash replacement reduce strength properties, it improves workability, reduces drying shrinkage and increases freeze–thaw resistance of steel fiber reinforced concrete. The performed experiments show that the behaviour of fly ash concrete is similar to that of Portland cement concrete when fly ash is added. 相似文献
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为研究聚乙烯醇(PVA)纤维的分散程度对水泥砂浆和水泥稳定碎石性能的影响,用粉煤灰对PVA纤维束进行分散处理,同时采用灰度共生矩阵图像处理法对PVA纤维的图像纹理进行熵分析,建立单因素方差分析数学模型,用以检验粉煤灰对PVA纤维分散程度的显著性影响,得出PVA纤维的分散程度与图像熵之间的关系;然后采用质量均分称重法对灰度共生矩阵图像处理法进行验证分析;再通过室内试验研究水泥基复合材料的力学性能与PVA纤维分散程度之间的关系.结果 表明:PVA纤维的分散程度随着添加的粉煤灰与PVA纤维质量比(简称质量比)的增加而增大,当质量比大于50:1时,PVA纤维束能在水泥基复合材料中均匀分散;图像熵随质量比的增加而增加,纤维均值的变异系数随质量比的增加而减小;水泥砂浆的抗折强度、破裂能和水泥稳定碎石的劈裂强度随图像熵的增加而增大.由此可知,提升PVA纤维在水泥砂浆和水泥稳定碎石中的分散程度,可提升水泥砂浆和水泥稳定碎石的力学性能. 相似文献
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试验以骨料聚苯颗粒、水泥、粉煤灰、激发剂和纤维为原料,采用模压法制备新型水泥基复合保温板。通过粉煤灰取代水泥最佳掺量的确定,研究粉煤灰掺量对复合保温板强度的影响;通过激发剂最佳掺量的确定,研究激发剂对复合保温板力学性能的影响;通过纤维最佳掺量的确定,研究纤维对复合保温板性能的影响。并通过扫描电镜观察试样内部微观形貌,研究各组分相关作用机理。 相似文献
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粉煤灰加固处理吹填泥浆的试验研究 总被引:2,自引:0,他引:2
人工吹填造陆技术,为解决我国东南沿海地区经济建设所需陆域不足的问题提出了新思路,但对软土地基进行快速、经济的加固处理也成为急需解决的技术问题。采用粉煤灰作为添加剂,对福建吹填泥浆进行了加固处理,并对加固后吹填土体工程地质性质和微观结构特征进行了研究。研究中发现加固后土体的工程地质性质得到改善,且土体的工程地质性质的改善是与微观结构特征的变化密切相关的。因此,从宏观的工程地质性质到微观结构特征变化都说明粉煤灰作为添加剂加固处理吹填泥浆是可行的,并给出了确定粉煤灰掺入比的建议,从而为吹填土软土地基的加固处理提供了一种更经济的加固手段。 相似文献
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《Construction and Building Materials》2007,21(1):150-156
This paper presents a study on the fresh and mechanical properties of a fiber reinforced self-compacting concrete incorporating high-volume fly ash that does not meet the fineness requirements of ASTM C 618. A polycarboxylic-based superplasticizer was used in combination with a viscosity modifying admixture. In mixtures containing fly ash, 50% of cement by weight was replaced with fly ash. Two different types of steel fibers were used in combination, keeping the total fiber content constant at 60 kg/m3. Slump flow time and diameter, V-funnel, and air content were performed to assess the fresh properties of the concrete. Compressive strength, splitting tensile strength, and ultrasonic pulse velocity of the concrete were determined for the hardened properties. The results indicated that high-volume coarse fly ash can be used to produce fiber reinforced self-compacting concrete, even though there is some reduction in the concrete strength because of the use of high-volume coarse fly ash. 相似文献
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Performance Capacity of Concrete containing Fly Ash The conception to take into account the addition of fly ash to structural concrete presented in the German Standard DIN 1045‐2 should guarantee a high resistance of concrete structures against corrosive attack. In this context, criteria such as compressive and flexural strength of concrete, modulus of elasticity, bond strength, shrinkage and creep as well as the pore structure are focused in this paper. The obtained results on concretes containing a maximum of fly ash according to DIN 1045‐2 compared with concretes produced only with ordinary Portland cement show similar strength values at the age of 28 days while the strength development is somewhat lower for the fly ash concretes. However, at the age of one year the strength of fly ash concretes in particular also the flexural strength is considerably higher. Shrinkage and creep of the fly ash concrete is lower resulting in an overall reduced risk of shrinkage and thermal cracking. 相似文献
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The paper describes the interface behaviour of bottom ash, obtained from two thermal power plants, and geogrid for possible utilization as a reinforced fill material in reinforced soil structures. Pullout tests were conducted on polyester geogrid embedded in compacted bottom ash samples as per ASTM D6706-01. Locally available natural sand was used as a reference material. The pullout resistance offered by geogrid embedded in bottom ash was almost identical to that in sand. In order to study the influence of placement condition of the material on pullout resistance, test were conducted on uncompacted fill materials. Pullout resistance offered by geogrids embedded in uncompacted specimen reduced by 30–60% than that at the compacted condition. 相似文献