broken brick (burnt clay) coarse aggregates for use in lime concrete
1986 Edition

Per the standard, burnt clay brick coarse aggregates should adhere to specific grading limits outlined in the sieve analysis as per IS 2386 (Part 1) - 1963. The aggregate must conform to the particle size distribution detailed in the relevant table, ensuring proper proportions passing through IS sieves such as 20 mm, 10 mm, and 4.75 mm. This grading ensures the aggregate possesses a suitable texture for lime concrete use.

According to the standard, the water absorption of burnt clay brick coarse aggregates must not exceed 20%, determined by immersing the sample in water for 24 hours and calculating the weight gain. The formula used is: Water Absorption (%) = ((W2 - W1) / W1) × 100, where W1 is the dry weight and W2 the weight after immersion. Additionally, water soluble matter content should be limited to 1%, measured through extraction and evaporation techniques described in the standard.

Samples should be taken from well-fired bricks conforming to Class 50 or higher as per IS 1077, avoiding underburnt clay, soluble salts, and surface contaminants like soil or silt. Handling must be minimized to reduce fines, which should not exceed 5% passing the 4.75 mm sieve. The bricks are crushed carefully to produce coarse aggregate, sieved to remove excess fines, and representative samples collected for testing bulk density, aggregate impact value, water absorption, and soluble matter content.

The standard specifies the use of well-fired bricks with a class designation of 50 or above according to IS 1077-1986. Both well-burnt and overburnt bricks meeting this classification are acceptable. Bricks that are underburnt or contain contaminants such as soluble salts, soil, or silt coatings are unsuitable. These quality requirements ensure the durability and strength of aggregates produced for lime concrete.

Burnt clay brick coarse aggregate is recommended primarily for lime concrete where natural coarse aggregates are scarce or expensive. Typical uses include foundations and low-strength concrete works in conditions of mild exposure. It is not advised for high-strength or heavily loaded structural concrete due to the variable properties of brick aggregates. This provides a cost-effective alternative when quality burnt bricks are available.