共查询到18条相似文献,搜索用时 171 毫秒
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针对变态混凝土注浆施工中出现浆液堵管、扩散不均等问题,研究了不同硅微粉掺量对浆液的流动性、流变性、稳定性、强度和时变特性的影响。采用熵权理想点法综合考虑浆液工作性及经济性确定最优配合比。试验结果表明,掺加硅微粉可改善浆液泌水率,提高抗压强度。水胶比0.4时,掺硅微粉使浆液屈服应力与流动度减小、塑性粘度增大;水胶比0.5~0.7时,流变参数随硅微粉掺量增加而增大,浆液流变性与水膜厚度呈线性相关。随水胶比增大,硅微粉对浆液性能的影响逐渐减弱。浆液屈服应力随时间呈线性增长趋势,塑性粘度呈指数增长。基于熵权理想点法,可得到固定水胶比下的最优配合比方案。 相似文献
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针对透水模板布(CPFL)在排除模板内新浇混凝土多余水气时易产生机械淤堵进而导致渗透反滤衰减的问题,采用自研渗透淤堵装置模拟现实工况,分析了新拌混凝土流变参数(塑性粘度η和屈服应力τ0)、侧压力对CPFL淤堵特性的影响规律和淤堵主要成因,并给出CPFL孔隙变化率表征其淤堵程度。试验结果表明,几何参数是CPFL淤堵的主要成因;其淤堵程度与混凝土η及τ0呈负相关关系,而与等效侧压力则呈正相关关系。 相似文献
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以用于渠道衬砌的混凝土为例,利用二次通用旋转组合设计优化渠道衬砌用混凝土配合比参数,选取粉煤灰、矿渣、粗骨料体积率、水灰比4个因素,以渠道衬砌用混凝土硫酸盐冻融300次后的相对动弹性模量为指标,建立回归模型,通过对试验结果的方差分析及对所建立模型的优化得到混凝土的最优配合比。结果表明,混凝土抗硫酸盐冻融最优参数为粉煤灰掺量110kg/m^3,矿渣掺量70kg/m^3,粗骨料体积率为0.335,水灰比0.4,在该最优条件下混凝土相对动弹性模量为90%,二次通用旋转组合设计优化所得混凝土配合比具有良好的抗冻耐久性。 相似文献
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对碾压混凝土的溶蚀和渗透耐久性进行了化学、宏观、微观等方面的阐述,揭示了碾压混凝土的溶蚀机理,简述了碾压混凝土临界水力梯度及渗透、溶蚀耐久性的关系。为直接使用碾压混凝土作为大坝防渗体、减少防渗层厚度、进一步降低内部碾压混凝土的水泥用量和大量掺用粉煤灰提供了理论依据 相似文献
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基于氯离子扩散模型和骨料级配理论,采用PYTHON语言和COMSOL软件构建再生混凝土随机多边形骨料细观计算模型,并结合已有试验结果验证模型有效性,开展新老砂浆扩散系数、老砂浆厚度及再生骨料取代率等不同工况下再生混凝土抗氯离子侵蚀计算分析,研究氯离子在再生混凝土内部的扩散规律及各细观组分等关键因素对再生混凝土抗氯离子侵蚀的影响规律。结果表明,模拟结果与试验结果吻合较好,该方法能较好地模拟氯离子在再生混凝土内部的扩散过程;再生混凝土氯离子扩散浓度与深度的关系曲线呈现不连续性特征;随着新老砂浆扩散系数的增加,混凝土内氯离子浓度逐渐增大;再生混凝土抗氯离子侵蚀能力随老砂浆厚度、再生骨料取代率的增加而降低。 相似文献
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变态混凝土加浆环节因加浆液稳定性不良易出现泌水、沉淀,导致加浆堵管和均匀性效果差等问题。为提高变态混凝土加浆液稳定性,尝试采用掺加硅微粉制备浆液,探讨了该类浆液泌水稳定性及流动性特点。结果表明,由于硅微粉颗粒粒径小、提升了浆液Zeta电位,有效缓解了颗粒团聚、大尺寸絮凝多的问题,因而泌水稳定性提高;浆液流动性随着硅微粉掺量增加先提高后降低,原因在于水膜厚度改变是制约流动性关键指标,即硅微粉添加使混合粉体填充密度不断提高,但比表面积亦不断增大导致水膜厚度先增后减;应用改性浆液的变态混凝土其拌合物均匀性显著改善,抗压强度与弹性模量提高,抗渗能力增强。 相似文献
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模袋混凝土抗裂性能影响因素分析与评价 总被引:1,自引:0,他引:1
为分析模袋混凝土抗裂性能的影响因素,采用极限拉伸试验,以极限拉伸值和轴向抗拉强度作为混凝土抗裂能力的评价指标,研究等强度条件下粉煤灰掺量、含气量及粗骨料体积分数对其抗裂性能的影响规律。通过对比试验,探讨模袋布对混凝土抗裂性能的影响。结果表明,等强度条件下,粉煤灰掺量增加,混凝土的轴向抗拉强度和极限拉伸值提高;混凝土的轴向抗拉强度和极限拉伸值与含气量之间呈"中间高,两边低"的变化规律;混凝土的轴向抗拉强度和极限拉伸值与粗骨料体积分数呈单调递减趋势。模袋混凝土试件破坏时,其轴向抗拉强度和极限拉伸的峰值大约为素混凝土的1.1、1.3倍;模袋混凝土的极限变形能力提高,模袋布显著改善了混凝土的综合抗裂性能。研究成果可为模袋混凝土抗裂性能的理论完善提供试验数据和理论依据。 相似文献
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Satish Kumar Gurprit Singh S.K. Mohapatra 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2016,38(20):2955-2962
With increasing environmental awareness, utilization of fly ash has become an attractive alternate to disposal. The objective of the present study was to investigate the physical, chemical, mineral, and rheological characteristics of fly ash for their potential utilization in stowing operation. The study was conducted with fly ash collected from the ash disposal system of Guru Govind Singh thermal power plant, Ropar, Punjab, India. From the characterization of the fly ash sample, it was found that the ash sample is enriched predominantly in silica; alumina and iron oxides fall under the category of F-type fly ash. The major mineral crystalline phase identified in the ash sample is quartz and mullite. Because of the properties of fly ash, it can be used as a stowing material in coal mines. The data obtained for critical velocity will help design a slurry pipeline system for the hydraulic stowing of fly ash slurry at any concentration and pipe size. 相似文献
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在保证混凝土水胶比、砂率、外加剂掺量不变的条件下,混凝土坍落度控制在160~180mm范围内,研究了人工砂中石粉含量对两种水胶比(0.45、0.37)的二级配泵送水工混凝土性能的影响。结果表明,随着人工砂中石粉含量从12%增至28%,混凝土用水量呈先增后减趋势;对于水胶比较大的A组混凝土,增加石粉含量显著降低了拌合物1.5、2.0h的坍落度经时损失率,而对水胶比较小的B组的坍落度经时损失率影响略小;拌合物的含气量随石粉含量增加而降低,而相同含气量时,引气剂的掺量必然随石粉含量的增加而增大;凝结时间随石粉含量的增加整体呈下降趋势;当石粉含量上限值增至20%时,混凝土的抗压强度高于原级配混凝土,抗冻性能满足设计要求。综合考虑,二级配泵送水工混凝土所用人工砂的石粉含量可控制在15%~20%之间。 相似文献
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A. G. Iscan M. V. Kok 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2013,35(10):939-949
Abstract Fluid loss during drilling operations has a very significant effect on both reservoir formation damage and monetary terms. There are many additives to control this unwanted phenomenon. Nevertheless, most of these substances are artificial chemicals. Thus, they are not only expensive, but also hazardous to the environment. In this article, a more natural method was applied to overcome the higher filtration problems by employing carboxyl methyl cellulose (CMC) and polymers (XT), DSHV, and MAC PR. Drilling fluids were prepared due to American Petroleum Institute (API) standards. The fluid weights were adjusted as 9 ppg. API filtration tests were applied to fluid samples including the chemicals. Tests were also conducted with non-treated bentonites + barite fluids without chemicals for comparative purposes. All of the rheological parameters including plastic and apparent viscosity and yield points were determined. Comparative graphs of shear stress vs. shear rates were plotted. The optimum CMC and polymer amounts were selected by graphical analysis of the results of rheological tests made by using shear meter and filtration tests. An optimization of the fluid loss control due to addition of the chemicals was made. The behavior of water-based fluids with CMC and polymers was examined. The accurate and sensitive industrial application of this study would reduce drilling fluid loss expenditures effectively. 相似文献