Cement, Energy and Environment July-Sep 2002

s upp ly parity that th e cement industry is awaiting for will have to wait for at least :mother 3-4 years,'' said an analyst. While there is not much cost involved in sourcing fl y ash, except the freight, the total cost ofsourcing slag, including freight, work out to around Rs 425 per tonne. Clinker, on other hand, is a more expensive raw material at price of around Rs 600 per tonne. The increase in consumption of blended cements has been driven la rge ly by PPC with its share increasing from 26 per cent to 32 per cent in the last fiscal. The share or PSC has however remain ed almost fl at at around 12.5 per cent. "Even as the realisation on blended cement is lower by Rs 5-7 per bag, cement manufacturers tend to gain as their cost of production is lower by Rs 12-15 per bag,'' said an analyst. Accord ing to an indu stry official: "whi le it makes sense to sell more of blend ed cements, it is difficult to keep in creas ing the output. After all , tlyash and slag are available only in select centres and manufacturers can prod uce more onl y if thei r fac iliti es are located next to nca r the source of th e additive." Courtesy: The Economics Times 13 Jlfay, 02, [' I0 VIE\VS ON SILICA FUME CONCRETE TECHl\OLOGY I~ I~DIAJ\ CONTEXT N. !'. Rajwnane, Scientist, SERC Madras Silica Fume (SF), also known as ' microsilica' or condensed silica fume, is a by -product from sil icon metal or ferrosilicon alloy industries [ASTM C 1240 1]. Si lica Fume is ve ry fi ne no n- crysta lli ne sili ca produced in electric arc furnaces as a by-product duri ng the production of elemental silicon or fe rro-alloys containing silicon. Its high siliceous composition and very fine patticle size were utilised beneficiall y to improve the properti es of fresh and hardened cement concretes. Many stmctures of importmice and public utility have been constrLtcted all over th e worl d with conc re tes conta in ing SF, ex plo iting th e superi or durability and strength charac teri stics of s ili ca fum e concretes (SFCs) [CEB-FIP, 1994]. However, the actual degree of improvement in propertie's of cement conc retes (CCs) depe nd upon numerous factors such as: type and characteristics of cements and sili ca fume, prope rtie s and proportions of other ingredients of co nc rete, conc re te mi xi ng technique, besides compaction and curing procedures adopted. In spite of usage of SF in many important structures in In dia and numerous conventi onal and special structures abroad (including bridges), bui lt succe ss fully ove r the las t few decades, the recent pub li cat ion (October 2000 ) of Indian Roads Congress, IRC:2 1-2000, does not mention exp licitly SF ( and also other mineral admixtures). There is. an urgent need to revise this Code in view of the we ll establi shed superior durabi Iity characteristics of concretes containing silica fume and other mined admixtures (MAs) so that durabl e concretes can be encouraged in road bridge structures. Thi s is particul arly in view of th e large-sca le infrastructure developmenta l works being planned in India. It is significant to note that IS: 456-2000 publi shed sl ightl y earlier (Ju ne 2000) by Bureau of .Indian Standards gives many references to blended cement concretes and also a separate clause on MAs (such as SF, fl y ash etc.). Cement concrete produces calcium hydroxide (CH) to an extent as much as 20-25 per cent by weight of cement used to make concrete [Nev ill e, 1996]. The pozzola nic reaction occurring between CH and the reacti ve sili ca content of SF. results in format ion C-S-H gel , which contributes to improvement in properties of, hydrated cement matrix [Hewlet t, 1998]. However, the actual advantages achieved in any particul ar concrete depends upo n var ious fa cto rs such as– prope rti es o f ing redients of concrete, water-binder ratio, type and dosage of superplasticiser used, wo rk ability leve l of concrete , me thods ado pted for mixing, compacti on and curi ng, besides properties ofSF itself[Oewar, 1999; Larrard., 1999]. Courtesy: A faterbuilder. Apr.-May 02, P 87 Fax: 8529259 Email: dicomnet@vsnl.com Web: www. masterbuilderindia.com THE BUGBEAR OF CAPACITY CREATION The Business Line, Monday, 24 June 02 In a commod ity indu stry where volumes and effi c ienc ies ought to play a maj or ro le in influencing protltabi lity levels, it is clear that the cement industry has become dependent on price changes for profit growth. Th is does not mea n th at vo lume growth and efficiencies are not important. But what this points to is the fact that at the industry leve l, efficiency improvements are capped and the hi gh proportion of inputs with ad ministered pric ing leave little room for manoeuvrabil ity on the cost front. The average price levels for cement in key markets have remained in a very narrow range despite peri od ic surges and dips. The dips and fl at prices prevail more often as the surges come only whe re producers put together arrangements to ramp prices up.