混凝土聚集体的性质是什么?

Engineering Properties of Aggregates

聚集体用于混凝土,以提供混凝土成本的经济性。聚集物只充当填充物。这些不会与水泥和水反应。

但是聚集体的性质或特征,影响了混凝土混合物的性质。这些如下。

  1. Composition
  2. Size & Shape
  3. Surface Texture
  4. Specific Gravity
  5. Bulk Density
  6. 空隙
  7. 孔隙度和吸收
  8. Bulking of Sand
  9. 骨料的细度模量
  10. Surface Index of Aggregate
  11. 有害物质
  12. 填充物的填充物
  13. 影响值of Aggregate
  14. Abrasion Value of Aggregate

1.Composition

Aggregates consisting of materials that can react with alkalies in cement and cause excessive expansion, cracking and deterioration of concrete mix should never be used. Therefore it is required to test aggregates to know whether there is presence of any such constituents in aggregate or not.

2.Size & Shape

骨料颗粒的尺寸和形状大大影响了混凝土混合中所需的水泥量,因此最终的混凝土经济。为了制备经济混凝土混合物,应使用最大的粗骨料可行的结构。IS-456建议提出建议决定在P.C.C&R.C.C混合中使用的粗骨料的最大大小。

Maximum size of aggregate should be less than

  • One-fourth of the minimum dimension of the concrete member.
  • 钢筋混凝土构件的最小尺寸的五分之一。
  • The minimum clear spacing between reinforced bars or 5 mm less than the minimum cover between the reinforced bars and form, whichever is smaller for heavily reinforced concrete members such as the ribs of the main bars.

Remember that the size & shape of aggregate particles influence the properties of freshly mixed concrete more as compared to those of hardened concrete.

Also read: How to Classify Aggregates Based on Size

Also read: How to Classify Aggregates Based on Shape

3.Surface Texture

骨料颗粒和水泥浆之间的硬粘合强度的发展取决于聚集颗粒的表面纹理,表面粗糙度和表面孔隙率。

如果表面粗糙但多孔,最大的粘合强度也会发生。在多孔表面聚集体中,由于孔中的水泥浆料的设置,粘合强度增加。

4.Specific Gravity

干燥聚集体的重量比在100至110的温度下保持24小时0C,通过饱和干燥表面骨料移位的等同水的重量称为聚集体的比重。

比重主要是两种类型。

  • Apparent specific gravity
  • Bulk specific gravity

比重是决定骨料适用性的平均值。低比重通常表示多孔,弱和吸收材料,而高比重表明质量好的材料。新利客户主要聚集体的比重落在2.6至2.9的范围内。

在设计混凝土混合时也使用比重值。

Also read: Specific Gravity & Water Absorption Test of Aggregates

5.Bulk Density

It is defined as the weight of the aggregate required to fill a container of unit volume. It is generally expressed in kg/litre.

聚集体的堆积密度取决于以下3个因素。

  • 压实程度
  • Grading of aggregates
  • 骨料颗粒的形状

6.空隙

骨料颗粒之间的空空间被称为空隙。空隙的体积等于聚集体质量的总体积与单独颗粒占据的体积之间的差异。

Also read: Bulk Density & Void Test of Aggregate

7.孔隙度和吸收

分钟孔形成in rocks during solidification of the molten magma, due to air bubbles, are known as pores. Rocks containing pores are called porous rocks.

吸水可以定义为非常干聚集体的重量与具有表面干燥条件的饱和聚集体的重量之间的差异。

Depending upon the amount of moisture content in aggregates, it can exist in any of the 4 conditions.

  • 非常干骨料(没有水分)
  • 干骨料(含有一些毛孔中的一些水分)
  • Saturated surface dry aggregate (pores completely filled with moisture but no moisture on surface)
  • Moist or wet aggregates (pores are filled with moisture and also having moisture on surface)

8.Bulking of Sand

它可以定义为在相同量的干燥或完全饱和的沙子的体积上的湿润条件下的砂质(即细聚集体)的大量体积增加。干燥时,由于沙子体积的湿砂体积的比例称为膨胀因子。

Fine sands bulk more than coarse sand

When water is added to dry and loose sand, a thin film of water is formed around the sand particles. Interlocking of air in between the sand particles and the film of water tends to push the particles apart due to surface tension and thus increase the volume. But in case of fully saturated sand the water films are broken and the volume becomes equal to that of dry sand.

Also read: Bulking of Sand – What, Why & How

9。细度模量

Fineness modulus is an empirical factor obtained by adding the cumulative percentages of aggregate retained on each of the standard sieves ranging from 80 mm to 150 micron and dividing this sum by 100.

细度模量通常用于了解骨料的粗糙或细腻的概念。更细度模量值表明聚集体是粗糙的,细度模量的小值表明聚合是更精细的。

还阅读:聚合物的聚合物模量 - 什么,为什么和如何

10。集合的比表面

The surface area per unit weight of the material is termed as specific surface. This is an indirect measure of the aggregate grading. Specific surface increases with the reduction in the size of aggregate particle. The specific surface area of the fine aggregate is very much more than that of coarse aggregate.

Also read: How to Calculate Total Surface Index of Aggregate

11.有害物质新利客户

Aggregates should not contain any harmful material in such a quantity so as to affect the strength and durability of the concrete. Such harmful materials are called deleterious materials. Deleterious materials may cause one of the following effects

  • 干扰水泥的水合
  • 防止发展适当的债券
  • To reduce strength and durability
  • To modify setting times

通常在聚集体中发现的有害新利客户物质可以分组为下面

  • 有机杂质
  • 粘土,淤泥和灰尘
  • 盐污染

还阅读:聚集体中的轻质碎片的测定

12.Crushing Value

聚集体破碎值给出了逐渐施加压缩载荷的聚集体对压碎的相对测量。聚集强度值是在经受压缩负荷时了解聚集体的行为的有用因素。

还阅读:聚集体的压碎值测试

13.影响值

聚集抗冲击值给出了突然震动或撞击的骨料电阻的相对衡量标准。聚集体的冲击值有时用作其破碎价值的替代品。

还阅读:聚集体的影响值测试

14.聚集体的磨损值

磨损值给出了在汽缸中旋转时磨损的聚集体的电阻的相对措施,以及一些研磨剂。

Also read: Abrasion Value Test of Aggregates

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