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Fundamental Study on the Method of Mixing Concrete Under Reduced Pressure

减压混凝土搅拌方法的基础研究

基本信息

批准号：
62460152
负责人：
YAMAMOTO Yasuhiko
金额：
$ 4.54万
依托单位：
University of Tsukuba
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1987
资助国家：
日本
起止时间：
1987 至 1989
项目状态：
已结题

项目摘要

Basic problems related to the new method of mixing concrete under a reduced pressure (MURP method) and properties of mortar and concrete produced by the method were studied, expecting that air-entrained concrete of high strength and high freeze-thaw durability may be produced if air bubbles in fresh concrete behave In accordance with the Boyle's law.The followings are main findings or conclusions.1. The rate of water loss from mixing materials under water vapor pressure is dependent mainly on the capacity of evacuating system. However, even when evacuated to such a low pressure, the total amount of water lost through the use of ordinary vacuum pumps during the required evacuating time and mixing time is negligible compared with the water content in actual mortar or concrete mixes, and the temperature of the mixes is not altered.2. When cement paste, mortar or concrete is mixed by MURP method keeping the dosage of AE agent constant, nearly the same amount of air as that by ordinary mixing method is entrained, and the entrained air behaves in a similar way as can be expected by Boyle's law. However, in the cases of mortar and concrete, the expected effects are impaired after their exposure to the atmospheric conditions, due to the intrusion of air into the mixtures from their surroundings during their discharging from mixer and/or agitation.This undesirable phenomenon becomes prominent as the content of aggregate is increased.As the result, the expected effects through the use of MURP method are reduced to nearly a half in the case of mortar, and to negligible extent in the case of concrete.3. Concrete produced by MURP method has characteristics of low losses of air and slump with time. Its air loss under vibration is also lower compared with ordinary concrete.

研究了减压搅拌混凝土新方法（MURP法）的基本问题及所制砂浆和混凝土的性能，期望在新拌混凝土中气泡符合波意耳定律的情况下，可制得高强度、高冻融耐久性的掺气混凝土。主要发现或结论如下：在水蒸气压力下，物料混合的失水速率主要取决于疏散系统的能力。然而，即使抽真空到如此低的压力，在所需的抽真空时间和搅拌时间内，通过使用普通真空泵损失的总水量与实际砂浆或混凝土混合料中的含水量相比可以忽略不计，并且混合料的温度不会改变。在AE剂掺量一定的情况下，用MURP法混合水泥浆、砂浆或混凝土时，所夹带的空气量与普通混合法所夹带的空气量几乎相同，且夹带空气的行为与波义耳定律相似。然而，在砂浆和混凝土的情况下，预期的效果在它们暴露于大气条件后受到损害，因为在它们从搅拌机和/或搅拌中排出时，空气从周围进入混合物。随着骨料含量的增加，这种不良现象变得更加突出。结果表明，在砂浆的情况下，使用MURP方法的预期效果降低了近一半，在混凝土的情况下可以忽略不计。MURP法生产的混凝土具有空气损失率低、随时间坍落度低的特点。与普通混凝土相比，它在振动下的空气损失也更小。