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在混凝土搅拌过程中,胶凝材料、砂石、外加剂等材料均可被准确计量,偏差很小,对混凝土质量的影响较小,但砂石含水率受货源供应、存储方式以及季节气候的影响,在生产过程中,对混凝土单方用水量影响较大。目前由于实验室混凝土配合比设计所用的砂石骨料都是干燥的,而生产使用的砂石骨料都具有一定的含水率,当然要按砂石实际含水率对配合比进行修正。与此同时,工程应用当中涉及到的砂石含水率问题逐步从越来越多的方面开始引起行业的关注。混凝土用水量是涉及混凝土工作性能和强度及耐久性的重要参数,易受到砂石含水量波动的较大影响,以C30每1m3混凝土胶凝材料用量400kg,用水量180kg,砂石用量1800kg计,砂石含水量增减1%(18kg),水胶比会增减10%左右。测量砂石含水率的目的是为了调整混凝土的加水量,以确保配制出的混凝土在工作性能及强度等方面的质量稳定。目前,实验室测量砂石含水率的方法主要是用烘箱烘干砂石,将烘干前后的质量差(即含水量)与干砂石的质量做比值,即为含水率;而在实际施工中多凭借经验,通过控制拌合物的坍落度和和易性来随时调整实际的用水量而间接的调整砂石的含水率;对于国内实验室测量含水率的做法,是以绝干状态进行混凝土配合比计算的,而实际上,当砂石含水率低于其面干的饱和含水率时,会从拌和水中再吸收水,这样混凝土配合比中的用水量实际上就减少了,因此会有这样的疑问:比起砂石绝干含水率,测量砂石面干饱和含水率是否更科学?而在日本,购买的砂石都要求含水饱和以上,进场后存储于封闭的仓中,使用前检测骨料饱和面干状态下的表观密度,用以按体积法来计算混凝土配合比。砂石的含水率大小易随着周围环境和各种条件的变化而不断变化,由于原材料变化而引起的单位用水量增减不能被及时发现,就会对混凝土质量造成影响,在实际配制混凝土的作业过程中,砂石的含水量很难适时测定和存在测量准确度问题的现状,砂石含水率的测定是否有更简捷、更方便的测量方法?下面针对砂石含水率的诸多问题请到几位专家来对此一一作答。
During the process of concrete mixing, the materials such as cementitious material, sandstone and admixture can all be accurately measured with little deviation and little impact on the quality of concrete. However, the moisture content of sandstone is affected by the supply, storage and seasonal climate Influence, in the production process, a greater impact on the concrete unilateral water consumption. At present, the gravel aggregate used in the laboratory concrete mix design is dry, and the gravel aggregate used in the production has a certain moisture content. Of course, the grading ratio should be corrected according to the actual moisture content of the gravel. At the same time, the problem of gravel water content involved in engineering application gradually began to attract more and more attention from the industry. Concrete water consumption is an important parameter related to the performance and strength and durability of concrete, susceptible to fluctuations in the water content of gravel greater impact to C30 per 1m3 concrete cementitious material dosage 400kg, water consumption 180kg, sandstone dosage 1800kg, Gravel water content increase or decrease 1% (18kg), water glue ratio will increase or decrease about 10%. The purpose of measuring the moisture content of gravel is to adjust the amount of water added to the concrete to ensure the quality of the formulated concrete is stable in terms of workability and strength. At present, the laboratory measure the moisture content of gravel mainly drying oven with sand and gravel, the poor quality before and after drying (ie, water content) and the quality of dry sand ratio, that is the moisture content; and in the actual construction The more by virtue of experience, by controlling the slump and workability of the mixture to adjust the actual water consumption at any time and indirectly adjust the moisture content of gravel; for the domestic laboratory measurement of water content is based on dry state In fact, when the moisture content of gravel is lower than the dry moisture content of the gravel, water will be reabsorbed from the mixing water, so the water consumption in the concrete mix will actually be reduced. Therefore, There is such a question as to whether it is more scientific to measure the dry saturated moisture content of gravel than dry gravel moisture content. In Japan, gravel purchased is required to be saturated with water and stored in a closed bin after entering the site , Before use to detect the apparent density of aggregate saturated surface dry state, in order to calculate the volume ratio of concrete mix. Gravel moisture content easily with the surrounding environment and a variety of conditions change constantly changing due to changes in raw materials caused by the unit water consumption can not be found in time, it will affect the quality of concrete in the actual preparation of concrete During the operation, it is difficult to measure the moisture content of gravel in time and there is a problem of measurement accuracy. Is there any simpler and more convenient measurement method to determine the moisture content of gravel? Several experts to answer this one by one.