||Fine and coarse concrete aggregates fill 60 to 75 percent of the concrete volume. Fine aggregates are less than 5 mm and consist of natural sand and crushed gravel. Coarse aggregates are larger than 5 mm but are usually between 20 and 40 mm in size. They consist of gravel or crushed aggregate such as recycled concrete, slag, quarry rock, boulders, cobbles and large gravel. Aggregates must be clean, hard, strong, durable, abrasion resistant, and free from absorbed chemicals and clays that could affect concrete hydration and bonding. Aggregates should be acid and alkali resistant. Aggregates containing shale, soft and porous rocky material and chert should not be used because they weather and cause surface defects on the concrete. Porous aggregates can absorb water, freeze and cause disintegration of the concrete.|
Materials In Concrete.
2.Concrete Aggregates - Concrete Slump.
3.Concrete Placement - Vibration - Hydration.
4.Types of Portland Cement - Concrete Moisture & Cracking.
5.Watertight Concrete - Supplementary Cementing Materials.
6.Supplementary Cementing Materials.
7.Chemicals That Damage Concrete.
8.Concrete Aggregate Properties.
9.Angular & Smooth Aggregate Properties.
12.Air Entraining Admixtures.
13.Air Entraining Admixtures Continued.
14.Conditions Affecting Concrete Air Volume.
15.Superplasticizers & Other Admixtures.
16.Ordering & Mixing Concrete.
17.Concrete Mixing - Subgrade Preparation.
18.Subbase Preparation - Concrete Placement.
22.Hot Weather Concreting.
23.Cold Weather Concreting.
24.Concrete Slump Test.