Kumar IronUpdated
In this guide
Which size for which job
| Aggregate | Typical use | Note |
|---|---|---|
| 10 mm | Thin members, fine work, floor toppings, small pours with tight bars | Needs more cement paste, so costs more cement per cubic metre of concrete |
| 20 mm | Roof slabs, beams, columns, lintels, most RCC work | The standard choice for house construction |
| 40 mm | PCC under foundations and floors, mass concrete, footings with wide bar spacing | Not for slabs or columns with closely spaced bars |
A simple rule: the largest aggregate piece should be well under the gap between bars and the cover. That is why 20 mm gitti is used for slabs and columns, and 40 mm only where there is little steel.
Brass, cubic metre and tonne
In North India gitti is sold by the brass, and sometimes by the tonne or truck. One brass is 100 cubic feet, which is about 2.83 cubic metres.
Weight depends on the stone and moisture. Loose crushed aggregate usually has a bulk density of roughly 1.4 to 1.7 tonnes per cubic metre, so one brass weighs somewhere around 4 to 4.8 tonnes. It varies with the stone, the size mix and whether it is wet, so treat this as an estimate and confirm with the weighbridge slip on delivery.
| Quantity | Equals |
|---|---|
| 1 brass | 100 cu ft, about 2.83 m³ |
| 1 m³ | about 35.3 cu ft, or 0.35 brass |
| 1 brass in weight | roughly 4 to 4.8 tonnes, varies with stone and moisture |
How much gitti for a slab
For a nominal M20 mix (1:1.5:3), the dry volume of material is about 1.54 times the wet concrete volume, and gitti is 3 parts out of 5.5. That works out to roughly 0.8 to 0.9 cubic metre of gitti for every cubic metre of concrete.
Example: a 1,000 sq ft roof slab at 5 inches (125 mm) thickness is about 11.6 m³ of concrete. That needs about 9.5 to 10.5 m³ of gitti, close to 3.5 brass. Add 5 percent for wastage. Mix ratios on site differ, so use this only to plan the order.
Use the cement calculator and the guide on cement bags for slab and house to size the other materials.
Quality checks at the delivery point
- Dust and fines: a heap that leaves a thick layer of dust on your palm needs washing or rejecting. Too much dust weakens the bond with cement.
- Flaky and elongated pieces: pick a handful and look. Many thin, flat or needle-shaped pieces make concrete harsh and weaker.
- Clean and angular: crushed stone with sharp faces bonds better than rounded pebbles.
- No clay, mud, roots or soft stone mixed in.
- Size consistency: a 20 mm lot should not be mostly dust and 10 mm chips.
- Dry the truck load fairly: wet aggregate is heavier by weight but not more by volume.
Storage on site
Keep gitti on a clean, hard surface or a layer of bricks so it does not pick up soil. Keep different sizes apart and cover heaps when heavy rain is expected so the water content stays steady between batches.
Ordering
Tell us the slab area, thickness and where it goes, and we will help estimate the number of brass. Rates move with the crusher and transport, so call or WhatsApp the store for the current figure.
Frequently asked questions
- How many cubic feet in one brass?
- One brass is 100 cubic feet, about 2.83 cubic metres.
- Which gitti is best for a roof slab?
- 20 mm crushed aggregate is the usual choice for roof slabs, beams and columns.
- Can I use 40 mm gitti in a slab?
- Generally no. It does not pass easily between closely spaced bars. Use it for PCC and mass concrete.
- How many tonnes are in one brass of gitti?
- Roughly 4 to 4.8 tonnes, but it varies with the stone and moisture. Check the weighbridge slip.