摘要
水工建筑物往往以其体积庞大,所处工作环境恶劣和运营变化而对混凝土的强度变形耐久等性能的要求更加严格。越来越多的工程实践表明,大体积水工混凝凝土的开裂问题,已成为影响其耐久性的主要因素之一。尤其是在寒冷地区。国内外研究表明:虽然混凝土的开裂往往难以避免,但是若采用切实有效的综合防裂措施,则是可以控制其有害程度的。本文以大体积蒲石河水电站闸墩混凝土研究为背景,从国内外文献上了解到国际上对于寒冷地区大体积混凝土的技术指标,确定解决寒冷地区大体积混凝土抗裂问题技术路线,并进行深入探讨,分析确定了本次试验所采用的混凝土矿物掺合料与外加剂的性能,明确多种外加剂在混凝土长期工作中的效应。确定了寒冷地区大体积混凝土的初步配合比,对各种混凝土进行主要性能测试。得出能应用于蒲石河水电站闸墩混凝土实际施工的最佳配合比,并给出该配合比相关试验性能数据。对大体积混凝土的抗裂机理微观分析进行阐述。
本次研究成果的混凝土配合比,其抗渗等级、抗冻等级均能满足设计要求。特别是抗极限拉伸性能要优于普通混凝土(图5-1、图5-2)。其中最为突出的试验研究结果,是粉煤灰+膨胀剂的掺合料组合混凝土的综合性能(主要侧重于抗裂)要优于其它掺合料组合的混凝土。混凝土水化热峰值变化比较大,初期出现的水化热峰值较高,且水化热出现峰值比较慢,消退也慢,这个可能是由膨胀剂引起的。试验用配合比明显比普通混凝土水化热低(表5-12)。本文的主要研究成果为针对寒冷地区大体积混凝土的抗裂性问题,较以往的研究不同,本次研究是从混凝土自身混凝土抗裂方面来分析并解决问题的。尤其是为混凝土在施工期间采取何种防裂措施以及混凝土掺合膨胀剂UEA采取的防裂措施提供了有效参考,为蒲石河水电站闸墩和混凝土自身抗裂提供理论基础,并提出一个实际可行的施工理论配合比。
The large volume of hydraulic structures , the bad working environment , the changes of operation , all of these make us strict to the performance of concrete as the strength , the deformation , the endurance and so on . More and more engineering practice show that the crack issue of the concrete of large volume hydraulic structure become the major factor which effect the endurance , especially in cold areas . Domestic and international research show that the cracks of the structure are inevitable , but the degree of the harmful could be control if we used feasibly and effectice measures of the comprehensive prevent fissure . This paper based on the study of the large volume pier concrete of the PuShi-river hydropower station , we know the international technical index about large volume concrete in cold areas from the literatures in home and abroad . To solve question of refuse crack of large volume concrete in cold areas and determinate the technology routes and further discussion , analysis and determined the performance of the concrete mineral admixture and the admixture in this time , understand the effect of many kinds of the concrete admixture on long-term working . Determined the primary combining ratios of the large volume concrete in cold areas , performance function test on the different kinds of concrete from JiLin . Obtained the best combining ratios of the practical constructions what can be used in the pier of the PuShi-river hydropower station , and given the experiment performance datas of the combining ratios . The paper expounds the anti-crack mechanism of large volume concrete and made a microanalysis .
The result of this paper is the impermeability grade and frost resistant grade of concrete mix ratios , all of them meet the design requirements . Especially , the anti-limit tensile is better than the normal concrete . As Fig.5-1 and Fig.5-2 . The most outstanding result of the test is that the comprehensive performance of the concrete which admixture combination by fly ash and expansion agent is better than the other concrete (emphasize anti-crack). The hydration heat peak of concrete changes relatively large , the hydration heat peak appeared at the early time is higher , but the peak of hydration heat occurred slowly and regression slowly too , this maybe caused by expansive agent . The hydration heat of this test with the mixture ratios is lower than normal concrete significantly . As the table 5-12 . The different from the research before is that the main results of this paper is the antifreeze resistance of the large volume concrete in cold area . The main study of this paper is analysis and solve the questions by the concrete itself , especially provide a effective reference for the measures of the concrete prevent fissure during the construction and the measures of concrete with the expansive agent UEA prevent fissure . Provide a powerful and reliable theory combining ratios of the constructions for the pier of the PuShi-river hydropower station and cracking resistance of concrete .
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