IS 4860 Class I Requirements
| Characteristic | IS 4860 Class I | What it tells you |
|---|---|---|
| Water absorption | 2% maximum | How dense the brick is. Low absorption means acid cannot soak into the body. |
| Compressive strength | 700 kg/cm² minimum | Load the brick carries before crushing, important for floors and heavy vessels. |
| Flexural strength | 100 kg/cm² minimum | Resistance to bending and impact, important for floors under traffic. |
| Resistance to acid (loss in weight) | 1.5% maximum | How much of the brick is dissolved after exposure to acid in the standard test. |
| Warpage | 2.5 mm maximum | Flatness. A flat brick gives uniform, thin joints, and the joints are where linings fail. |
| Resistance to wear | 2 mm maximum | Abrasion resistance for floors with trolleys, forklifts and dragged containers. |
Our standard acid proof bricks are 230 x 114 x 38 mm and 230 x 114 x 75 mm. Bricks of 40 mm and thicker are made to order. Each lot is checked for thermal durability and for resistance to acids and to physical and mechanical shock before despatch.
Class I and Class II
IS 4860 has two classes. Class I is the stricter grade, with lower permitted water absorption and higher minimum strength. Class II allows a more porous, weaker brick. For tanks, vessels, pits and process floors that see continuous chemical exposure, Class I is the grade normally specified, and it is the grade we manufacture.
Properties of Acid Proof Bricks
- Dense, vitrified body fired from selected clays with minimal iron, so acid has no path into the brick
- Resistant to acids and alkalis, with the mortar setting the limits of the finished lining
- High compressive and flexural strength for floors, vessel walls and impact
- Thermal durability, and service up to 900 C when laid in potassium silicate mortar
- Abrasion resistance for floors under heavy traffic
Acid proof bricks are not suitable for hydrofluoric acid and fluoride salts, which attack silica. Carbon bricks are used for that service.
The Mortar Specification Matters as Much as the Brick
A brick lining is only as good as its joints. Chemical resistant mortars are covered by IS 4832, and we manufacture the full range alongside the bricks:
| Mortar | Compressive strength | Max temperature |
|---|---|---|
| Furane resin | 350 kg/cm² | 170 C |
| Phenolic resin | 350 kg/cm² | 170 C |
| Cashew CNSL resin | 280 kg/cm² | 190 C |
| Potassium silicate (K-silicate) | 150 kg/cm² | 900 C |
| Epoxy resin | 500 kg/cm² | 90 C |
| Polyester resin | 500 kg/cm² | 90 C |
| Sulphur (hot melt) | 250 kg/cm² | 90 C |
Full mortar data, including bond strength, mixing ratio and shelf life, is on our acid proof mortar and cement page.
How to Write the Brick Specification in a Tender
A clear specification avoids substitution with weaker bricks. A typical clause reads:
Replace the thickness and mortar with what your process needs. If you send us the chemicals, concentrations and operating temperature, we will recommend both. If your specification calls for a chemical analysis or other tests, send it with the enquiry and we will confirm compliance.