Builders, architects and masons know that if the cement they use is not of the required standards, their buildings will suffer from seepage in the first monsoon after construction

Tata Chemicals manufactures cement at Mithapur using wastes from its soda ash plant. The area around Mithapur has rich deposits of lime, which is required for manufacturing soda ash. After soda ash is manufactured, the lime and calcium left behind in the effluent slurry as waste products are recycled as raw material to manufacture cement. TCL manufactures ordinary Portland cement grade 43, ordinary Portland cement grade 53 and Pozzolana Portland cement under the brand name Shudh Cement at its 1,500 tpd capacity state-of-the-art cement plant at Mithapur.

After its re-launch in Gujarat state in December 2001, Shudh Cement has already acquired a five per cent share of the cement market in the state despite tough competition from its better-established competitors. It has been recognised in the market as a superior product, ideally suited for quality constructions. Incidentally, Shudh Cement far exceeds the quality norms and specifications prescribed by the Bureau of Indian Standards.

Ordinary Portland cement

Tata Chemicals' OPC is manufactured in two grades — grade 43 and grade 53 — the numbers indicating the compressive strength obtained after 28 days, when tested according to the stipulated procedure.

In comparison, grade 53 and grade 43 types of cement have nearly identical chemical compositions, and the main distinction is in the degree of fineness. The grade 53 cement is ground to a greater degree of fineness compared to grade 43 cement. Grade 53 cement has a fineness index of 329 compared to 293 for grade 43 cement. The finer grade 53 cement has a faster setting time of 120 minutes compared to 155 minutes for the coarser grade 43.

Apart from OPC, there are several other types of cement, most of them meant for special purposes, like TCL's Pozzolana Portland cement. Though Pozzolana does not have any cementing properties by itself, it combines chemically with Portland cement and water to form a strong cementing material. Pozzolana materials include power station fly ash, burnt clay, ash from certain burnt plant materials and silicious earth. The company's Mithapur plant produces a substantial quantity of effluent slurry which is rich in lime and calcium compounds - raw material for manufacturing cement. Besides, the company's power station produces waste fly ash, which again is a raw material in the manufacture of Pozzolana cement.

In India, Pozzolanas are mixed with Portland cement and sold as sblended cement, which in many respects is similar to Portland cement. TCL's ordinary portland cement grades 43, grade 53 and Pozzolana Portland cement are trusted by builders, architects and masons alike for their setting properties and strength.