|
 |
Always use a concrete mix suitable for its intended application. Tables I
and II give details of mixes appropriate for the more usual types of work on the farm.
The following general rules apply to all concrete, whether site mixed or readymixed. |
|
| 1. |
Concrete must be sufficiently workable to allow full compaction after
placing. Air voids left in the concrete reduce its strength and durability. |
| 2. |
As workability starts to decrease shortly after mixing, only the quantity
of concrete that can be placed and compacted within one hour should be produced at any one
time. This is particularly important in hot dry weather. |
| 3. |
The addition of extra water to either increase workability unnecessarily
or to restore workability to concrete left unused for extended periods weakens the cement
‘glue’ and reduces the overall performance of the concrete. |
|
TABLE I |
| Volume Batching on the
Job |
| Application |
Portions by Volume
Cement: all in Aggregate |
Water |
Foundations
Bases
Dry internal floors |
1 : 6 |
22 - 25 litres
(5 - 5.5 gals.) per 50kg bag of cement depending on mix and moisture content of aggregate.
Aim always for the lowest water content which allows full compaction. |
Floors
Yards
Slurry tanks
General reinforced concrete |
1 : 5 |
Silage pits
Effluent tanks containing silage
Milking parlour floors
Areas subject to severe abrasion |
1 : 4 |
|
|
| Note re Aggregate - 60% coarse aggregrate and 40% sand by volume generally
gives acceptable results |
|
TABLE II |
| Readymixed Concrete |
| Application |
Mix Designation |
|
Foundations
Bases
Dry internal FloorsFloors
Yards
General reinforced concrete |
Medium workabiliy
30N20
Minimum Cement
Content 325kg/m3 |
|
Silage pits
effluent tanks containing silage
Milking parlour floors
Areas subject to severe abrasion |
Medium workabiliy
40N20
Minimum Cement
Content 350kg/m3 |
|
|
|
| Medium Workability = 75mm slump |
|
|
