Workability of concrete is the characteristic of freshly mixed concrete which defines the ease and homogeneity with which it can be mixed, transported, placed, compacted, and finished as described by ACI Standard 116R-90 (ACI 1990b).
As per ASTM “that property determining the effort needed to manipulate a freshly mixed quantity of concrete with minimum loss of homogeneity is called workability of concrete”.
Types of Workability of Concrete
The workability of concrete can be classified into 3 types as follows.
- Highly Workable Concrete
- Medium Workable
- Unworkable Concrete
Table of Contents
1. Highly Workable Concrete
Highly Workable Concrete is very easy to mix, pour, consolidate due to the high water content in mixed concrete. Transportation and placing of concrete can be a bit difficult due to the high amount of water present in the concrete mixture. Normally it is used where compaction or vibration is not possible. This type of concrete is highly flowable and self-consolidating. Due to the lack of manual compaction, concrete can segregate.
2. Medium Workable Concrete
Medium Workable Concrete is used in most of the construction work. Water-Cement ratio varies from 0.40 to 0.50 ( as per ASTM ). Medium workable concrete allows manual compaction. Due to the low water-cement ratio, the chances of segregation are low.
3. Unworkable Concrete
Unworkable concrete or harsh concrete contains a low amount of water. The water-cement ratio for unworkable concrete is less than 0.40. Hand mixing for this type of concrete is very difficult. This type of concrete has high segregation due to improper mixing.
Factor affecting concrete workability
- Water-cement ratio
- Evaporation
- Methods of compaction
- Duration of compaction
- Mixing of admixture
- Transporation from long distance
- Placement methods