 |
 |
 |
 |
|
|
|
|
|
|
Admixtures
are ingredients, other than Portland cement, that are added to the concrete mixture just before or
during mixing. The types of admixtures used are air entraining,
water reducing, retarding, accelerating and superplasticizer
admixtures. Air entraining admixtures entrain or suspend, and spread
small air bubbles throughout the concrete. Entrained air makes the
concrete more resistant to damage caused by freezing and thawing, and surface
scaling caused by deicers. It also increases concrete workability, and
reduces bleeding and segregation. Water reducing strength increasing
admixtures reduce the water needed to produce concrete at a
required slump, reduce the ratio of water to cement, reduce the total amount
of water and cement needed, and increase the slump. When the water to cement ratio is reduced, concrete strength
increases. Water reducing
admixtures can cause an increase in drying shrinkage, and, if the water
to cement ratio is maintained while water is lost, a decrease in
concrete compressive strength. |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |