CEE Oct-Dec 2002

• 90% minus 80 mm • 95% minus I 00 mm • 99% mim~:> 120 mm. t\s the feed material mi xtu re can hav..: a moisture con tclll or up to 1-t% H_O. all the main p;trts of the impactor comi ng into comact \\'ith the matL:rial. such as inlet and impnct aprons are fitted \\ ith a henting system. Thermal oil is pumped throug h channels. the refore heating the parts, which results in the immedi ate evaporation of the feed-material surface wa ter o n contact and reduci ng the caking hazard to a mtnli11Uill. In orde r to g uarantee th e necessary co nsistent c ross– -;cctional be lt loading for the cross– belt anal) scr. a smnll intermediate hopper is provided underneath the impactor outlet, frl'lll '' hich a light\\'e ight dc:.ign ap1 u11 con\'cyor can continuou~ly c:-; tr:Kt a cnn ~tan t amount nf material. 1 he COil\ cyor is mounted on load ee l b. ~u that the m<ttcrial 1low can be measured at the same time. The apron feeder discharges its constant load on to the downstream belt conveyor for further transport to the mixing bed. Shou ld there be any deviations from the set vn lucs, the co rrect mixtu re ratio ca n he restored by ndjusti ng the cnll\cy ing rat e of the co rresponding ma tLTi a l apron conveyor that ked~ the impactor. This means that a mo re or less homogeneous mixture of a relatively cons istent quality is avai lab le even before it reac hes the mixing bed, and the result ant r roduct can be optimised still further utili sing the mixing bed hntching facilities. Courtesy: World Cement Sep. 2002, Pp !OJ - 102, EmJltiJy nn. 28, Fax: +..f-1(0) 1252-718992 ,,__·-mail : IIWil!a)ll'OrLdcement.c:om (IRL: ll'W\11. worldcement.com GRADATION OF PPC AND PSC Gradation of PPC and PSC is a !ong standin g issue und er consideration of BIS ( Bureau of Indi an Standa rd s) . The 1 J'h meet ing of the Cement and Concrete Sectional Comm i t tee. CED 2 in joint sess ion with the 12' 11 meeting of the CemenL Pozzolana and Cement Add iti ves sub– committee CED 2- 1 held on March 7. 2002 at Bangalore had detailed discussion among members on the subject. The minutes ofthe meeting finali sed subsequently and circu lated by BIS vide their leller CED 2/A-2 II of September 06, 2002 covers the high lights of the di scuss ions and the genera l consensus for inclusion of strength grades for PPC nnd PSC in relevant standard. Extracts Ji·om the minutes arc given below: 7 . 1.3 In c lusi on of 43 and 53 Strengths C lasses in PPC and PSC 7. 1.3 I In th e contex t of the co ntent s in the A gend a note on the subject, several members pointed out that j ust because CMA 's formal stand is that it does no t have any consensus on the grading of PPC and PSC a matter of thi s na ture so important f or the consumer in particular and the nati on in general can not be allo"ved to drag on any IIIure c111d some finality has to be brought to the issues involved. 7.1.3.2 The Cha irman , Dr Visvesva ra"ya agreed that sufficient time had been g iven to all interests the subject having been debated for almost a decade now. He said that, many o f the points made out almost a decade ago may not now be relevant or valid in view 37 of tremendous advances which had taken place in the collection and disposal or industrial wastes, in the sc ience and techno logy or utilization of ind ustr ial wastes, in the ma nu facturing technologies and processes in the cement industry and 111 the utilization of cements, blended mnterials. admi xtu res, etc. in concrete mak ing by the user and also in the app reciatio n or th e advances in co rp orating them in concre te and mortar m1xes used 111 the cons truct ions. Ini tiating the discussions, the Cha irman referring to h is o pen ing remark s reiterated th at all the members shou ld give their conside red views in the matter dispassionately, also looking into the need of the day in view or the status of thecement industry today in terms of the prec isi on acquired over the years in qua l ity contro l, th e confidence generated in the minds of the users with the drive on apr ropriateness of the use of various types of cement for different end applications, crystallization of the research ti nding;s and v iews about the advantages associated with the se lection and use of th e appropriate type of cemen t in Goncrete product ion for use in locations subject to adve r se cond iti ons, the chang i ng scenari o of r roduc tion and use of quality flyash i n th e cou ntry, the suppo rt avai Iab l e from th e Government of India. etc,