《拌砼和易性》PPT课件

第四章 新拌砼的性质
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Fresh concrete is a mixture of water, cement, aggregate and admixture (if any). After mixing, operations such as transporting, placing, compacting and finishing of fresh concrete can all considerably affect the properties of hardened concrete.
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一 砼和易性的定义：指砼拌和物
易于施工操作（拌和、运输、浇灌、捣 实）并能保证质量均匀、成型密实的性 能。它包括流动性(mobility )、粘聚性 (cohesiveness)和保水性(water retentivity)三 方面的含义。
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和易性包括三个方面：
1、流动性 指砼拌和物在自重或施工机械振
ability of concrete to maintain its uniformity is governed by its stability（稳定性）, which depends on its consistency and its cohesiveness （粘聚性）.
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. For practical purposes workability generally implies the ease with which a concrete mix can be handled from the mixer to its finally compacted shape. The three main characteristics of the property are consistency, mobility and compactability. Consistency is a measure of wetness or fluidity. Mobility defines the ease with which a mix can flow into and completely fill the formwork or mould. Compactability is the ease with which a given mix can be fully compacted, all the trapped air being removed.
generally associated with harsh mixes (low mortar
shear slump and collapse slump, as illustrated in figure
13.2. A true slump is observed with cohesive and rich
mixes for which the slump is generally sensitive to
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第一节——和易性
• 一、砼的和易性定义 • 二、和易性的测定 • 三、影响和易性的因素 • 四、调整和易性的措施
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The characteristics of fresh concrete(新拌混凝土) which affect full compaction are its consistency（稠 度）, mobility（流动性） and compactability（易密 性）. In concrete practice these are often collectively known as workability（工作性，和易性）. The
variations in workability. A collapse slump is usually
associated with very wet mixes and is generally
indicative of poor quality concrete and most frequently
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混凝土分层离析
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外分层
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内分层
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新拌混凝土ቤተ መጻሕፍቲ ባይዱ水示意图
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二、和易性的测定方法
• 砼拌和物坍落度试验 • 维勃稠度试验 • 扩展度试验
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坍落度
二、砼拌和物坍落度的测定
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The three types of slump usually observed are true slump,
捣的作用下，能够流动并均匀密实地填满模板的 性能。
2、粘聚性 保持整体均匀，不发生分层离析
现象。
3、保水性 保持水分不使之泌出。
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Three tests widely used for measuring workability are the slump, compacting factor and V-B consistometer tests. Slump test was developed by Chapman in the United States in 1913. A 300mm high concrete cone, prepared under standard conditions (BS 1881 : part 2) is allowed to subside and the slump of reduction in height of the cone is taken to be a measure of workability.
results from segregation of its constituent materials.
Shear slump occurs more often in leaner mixes than in
rich ones and indicates a lack of cohesion which is