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通过海砂混凝土不同条件下力学性能和耐久性的测试,对海砂高强混凝土中的钢筋锈蚀能力进行了研究。结果表明,海砂中氯离子含量在0.123%、在混凝土中使用量低于320kg/m3的条件下,对强度高于50MPa的混凝土立方体抗压强度、碳化性能、抗氯离子扩散性能影响不大;海砂混凝土的钢筋锈蚀失重率随着海砂掺量的增加和水胶比的增大而增加;阻锈剂的掺入和保护层厚度的增加,可使海砂混凝土的抗钢筋锈蚀能力有所改善,钢筋锈蚀程度有所下降。 相似文献
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机制砂中通常含有粒径小于0.075 mm的石粉,这也是机制砂区别与天然河砂的显著特征之一。通过试验探究石粉含量对机制砂高性能混凝土工作性能、体积收缩变形、抗压强度、弹性模量、抗渗性能、抗碳化性能及抗冻性能影响。试验结果表明,随着石粉掺量的增加,混凝土流动性能降低,工作性能变差。随着石粉掺量的增加,混凝土收缩变形先增大后降低,应考虑石粉掺入对混凝土收缩变形出现的不利影响。石粉的掺入可以提高混凝土抗压强度,但同时也会导致混凝土弹性模量出现下降。掺加适量的石粉有利于提高混凝土抗渗性能、抗碳化性能,石粉的掺入对混凝土抗冻性能影响较小,可忽略石粉含量变化对混凝土抗冻性能产生的不利影响。 相似文献
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利用海水、原状海砂及再生粗骨料,制备了设计预期强度为C20~C50的海水海砂再生混凝土。通过240个标准立方体(150 mm×150 mm×150 mm)和96个棱柱体(150 mm×150 mm×300 mm)试件,完成了工作性能、立方体抗压强度、轴心抗压强度、劈裂抗拉强度以及弹性模量试验,研究了海水海砂再生混凝土的基本力学性能;最后基于试验数据,得到了海水海砂再生混凝土立方体抗压强度与轴心抗压强度关系公式以及弹性模量与轴心抗压强度关系公式。结果表明:海水海砂再生混凝土工作性能良好,C40和C50强度等级的坍落度比一般再生混凝土分别提高5%和33%;立方体抗压强度、轴心抗压强度和劈裂抗拉强度随着龄期变长而增加,且长期强度趋于稳定;与普通混凝土相比,海水海砂再生混凝土7 d立方体抗压强度提高13%~52%,28 d抗压强度降低约5%,90 d抗压强度降低约15%,180 d抗压强度降低18%~29%;海水海砂再生混凝土28 d弹性模量比普通混凝土略有降低,降低幅度在14%以内;再生粗骨料对混凝土力学性能、工作性能的影响大于海水海砂。 相似文献
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本文通过混凝土快速碳化试验,研究混凝土强度等级、胶凝材料掺量、矿物掺合料种类及混凝土工作状态对中低强度混凝土碳化深度的影响。研究结果表明:混凝土的抗碳化问题主要集中在中低强度混凝土,工作性正常的高强混凝土抗碳化问题较小。在相同的水胶比下,随着胶凝材料的增加,混凝土的碳化深度减小,但是减小幅度越来越少。在相同配比下,坍落度对混凝土抗碳化性能影响较小,而离析会大大降低混凝土的抗碳化性能。 相似文献
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使用海水、海砂代替传统的河水河砂制备混凝土,制备出一种早强低自收缩、高流动度低黏度的海水海砂高性能混凝土。相比河水河砂混凝土,海水海砂的使用可以使水化更充分,加速水化使混凝土具备较高的早期强度;海水海砂混凝土自收缩量降低了15%,收缩结束时间提前,减少了混凝土裂缝的产生;海水海砂混凝土黏度值为7 590 MPa·s,流动度为182 mm,降低了混凝土的黏度增加了流动度,使混凝土更易于泵送,降低了施工难度。28 d抗压抗折强度比使用河水河砂制备的混凝土分别降低了8.6%和25.4%;热水养护可以提高海水海砂混凝土的力学性能,其抗压、抗折强度分别提高了22.8%和23.1%。海水海砂混凝土孔隙液pH与河水河砂混凝土基本相同;使用热水养护会降低混凝土的孔隙液pH,最小值12.0111.50(钢筋钝化膜破坏的临界值)。研究了海水海砂制备高性能混凝土的力学与早期工作性能,为海水海砂混凝土的推广应用奠定了理论基础。 相似文献
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针对河砂资源日益枯竭的问题,结合地方海砂的实际状况,分析了海砂资源化的必要性与可行性;通过对国外海砂资源利用情况及氯盐限量、海砂淡化技术,以及海砂混凝土耐久性研究的综述,探讨了保持和提升海砂混凝土耐久性的方法,提出在硬化混凝土表面涂覆迁移型阻锈剂,可望实现海砂的合理利用和海砂混凝土耐久性的保持与提升;最后对我国海砂资源化过程中需要解决的问题提出了建议. 相似文献
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《建设机械技术与管理》2008,21(12)
Thorntonbank的项目包括安装总计60台风力发电机组,为用户提供总容量为300MW的电力。项目的第一期工程在今年夏季进行,一共安装6台涡轮发电机组。每台发电机都要安装到长颈瓶形状的混凝土基座上,距海床面120m高。 相似文献
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M. A. Lashteh Neshaei F. Ghanbarpour 《Frontiers of Structural and Civil Engineering》2017,11(4):369-379
Study of beach morphology has been one of the most important issues in coastal engineering research projects. Because of the existence of two important coastal areas located in the north and south parts of the Iran, in the present study an analysis of the coastal zone behaviour is made. Bed level elevations are measured and compared with the theoretical equilibrium profile. It is shown that the behaviour of the coastal zone in the region is consistent with the Dean (1991) equilibrium profile. In the next stage, following extensive investigations, the bed level changes due to arise in sea level at different locations in the surf zone are estimated. The mechanism of beach re-treatment due to a rise in sea level is considered based on the simplified model of Dean (1991) in which the mass balance of the sediments is taken into account. Comparison of the equilibrium profiles for different cases of sea level rise, clearly shows that because of the sediment transport induced by the fluctuation of the water level, the beach profile in the surf zone changes accordingly resulting in an erosion in the inner region of the surf zone and an accumulation of sediments towards the offshore. 相似文献
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This paper reviews the ambitions and importance of design proposals for inhabiting the sea from the 1960s and 1970s. Critics in subsequent decades dismissed projects for the sea as irrelevant utopias and technological fantasies. While the unique marine environment and the new city were sometimes taken up as opportunities for social and formal experiment, there are many technically resolved projects considered by architects and developers alike as viable alternatives to terrestrial cities. This paper argues that architects adopted technologies from the exploration, fishing, military and mining industries towards solving what were widely perceived as threats to human existence. Neither in ambition nor detail were these projects futuristic fantasies. They were, rather, prototypes, a model this paper uses to examine a wide variety of projects, raising questions about the validity of their testing and the reasons for their failure to flourish. Using current proposals for new cities in the sea, shifts in attitude towards community and technology are traced. 相似文献
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《Planning》2022,(4)
为研究不同藻类、刺参Apostichopus japonicus与马粪海胆Hemicentrotus pulcherrimus混养比例对刺参与马粪海胆生长、体成分和消化酶活性的影响,在水温9.5~16.5℃下,将体质量为(0.38±0.15) g的马粪海胆与体质量为(1.24±0.17) g的刺参混养于幼参育苗车间白色塑料箱(30 cm×40 cm×50 cm)中,各组刺参的初始放养质量为20 g,再按照胆参质量比3∶1、2∶1、1∶1、1∶2、1∶3投放马粪海胆,各组分别投喂新鲜黏膜藻Leathesia difformis(H组,H1~H5)或孔石莼Ulva pertusa(L组,L1~L5)各20 g,对照组(D组)仅投喂配合饲料20 g。结果表明:藻类种类和胆参混养比例对刺参增重率(WGR)及特定生长率(SGR)有显著性影响(P<0.05),黏膜藻组在胆参比为3∶1时,刺参特定生长率最高(0.94%/d);孔石莼组在胆参比为2∶1时,刺参SGR最高(1.36%/d);不同藻类和胆参混养比例对海胆生长有显著性影响(P<0.05),海胆的SGR均随胆参混养比例的减小而递增,在同一混养比例下,L组海胆SGR显著高于H组(P<0.05);刺参肠道的胰蛋白酶(TRY)、淀粉酶(AMS)活性随胆参混养比例的降低呈递减趋势,其中,L1和L2组两组间无显著性差异(P>0.05),但均显著高于其他各组(P<0.05);相同混养比例下,L组胰蛋白酶和淀粉酶活性高于H组(P<0.05);而脂肪酶(LPS)活性仅受胆参混养比例的影响,且随胆参混养比例的降低而递减;胆参混养比例对H组、L组刺参体壁水分、粗脂肪含量均无显著性影响(P>0.05),粗蛋白质含量随胆参混养比例的减小呈先增加后降低趋势,其中L3组最高(39.10%),且显著高于其他各试验组(P<0.05)。研究表明,以孔石莼为饵料时,胆参适宜混养比例为2∶1,而以黏膜藻为饵料时,则为3∶1,研究结果可为构建综合养殖模式及防控刺参池塘大型藻类暴发性增殖提供数据支持。 相似文献
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Nordic sub sea tunnel projects 总被引:1,自引:0,他引:1
Olav Torgeir Blindheim Eivind Grv Bjrn Nilsen 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》2005,20(6):570-580
The paper reviews the experience from Nordic sub sea tunnel benchmark projects, with main emphasis on sub sea road tunnels excavated in bedrock. More than 25 such tunnels have been built in the Nordic countries, representing a total length of more than 100 km, and with the majority of the projects located in Norway. The completed projects include tunnels with length up to 7.9 km and depth below the sea level down to 264 m. All these tunnels have been excavated by drill and blast. Important issues concerning investigation, planning, design and construction are described, and important lessons learned from these projects are discussed. Finally, plans for potential future sub sea tunnel projects are presented, representing tunnel lengths of up to 24 km and depths below sea level down to 400 m. 相似文献