CEE Oct-Dec 2002

Based on the resu lts and the discussions, the follow ing cone I us ions can be given about the e ffects or the usage of marble \Vastes in cement as additive. I. Ca rb on atoms 1n the neighborhood of marble partieles and etched surface of calcite crystals in the hydrated pastes prove that the CaC0 1 dissolves 1n the paste. Therefore, marble waste takes part in hydration reactions and it is not simply an inert filler in cement. In marble-added cement pastes, the reaction products tend to accumulate on calcite crystals producing a dense and less porous zone around. This fact proves the nuclei effe ct of calcite crystals rrom marble. 3. Cll crystals in cement pastes w·ith marble are dispersed to the matrix as small co lumnar crystals. Whereas, in portland cement pastes, CH c rysta ls appear as large and well developed crystals. 4. Setting time or marble-added pastes increases w it h increasing marble amount. But this increase in settin g ti me does not resu lt in problems regarding the standards even at 30 % marble replacement. .5. Normal consistency of cement pastes with marble dec reases with increasing marble additive amount. It is suggested that this is rhc result of calcite crysta ls having well-developed rhombic and non-porous structure with smooth surfaces, as detected by SEM. This structure decreases internal friction by decreasing the amou nt of interlo cking crystals in cement when some part or portland cement clinker is replaced by marble. Courte.\y : Cement and Concrete World. Jul. -Aug 2002. Pp 50-62, Fax: (90312) 2879272 E-mail: injorg)cma.orgtr Web: www lema org.tr TACKLING THE TYRE MOUNTAIN lnrernarional Roundup, World Cement Oct. 2002 Each year over 40 mi II ion lyres arc scrapped in the UK, caus ing a real disposal problem. New European legislation banning the disposa l of tyres in landfi ll I S coming into force over the next 4 years, making the problem worse. Lafarge cement already uses tyres as fuel at three other UK sites, Cau ldon in Stafrordshire, Dunbar in East Lothian and Westbu ry in Wi ltshire. The tyre chips replace some of the fuel , which is mainly coal. A series of repo1ts submitted by the company show that one of the main emissions, oxides of nitrogen. is cut by up to 30% when lyre chips are used. Other emissions remain within limits set in th e wo rks ' ope rati o nal permit by the Environment Agency. The 3-mi llion-plus tyres that could be used at Hope plant in Derbyshire an nu ally wou ld save over 25,000 t of coal, enough to provide energy tor more than 7000 homes for a yea r. but Lafarge says that the benefits of using tyres are set to go beyond just saving fuels. It expects the reduction in the main emission to give it the opportunity to impro ve th e q uality of the prod uct. The compa ny has asked the Agency for permi ss ion to use up to 2 tph of tyre chips on each kiln to heat raw materi a ls in gas temperatures of more than 800 o C before they enter the plants' two ki lns. 6 1 C 'ourte.\)1: rVorld Cement Oct. 2002, f 5. , Fw.:: +-1-1(0) 1252718992 E-mai 1: ma i Ira 1 For/dee men!. con1 TVeh: \1'11'11". worldcement WASTE AS FUEL ALTERNATIVE Asia Pacific Tech Monitor 1 8(-1): 10 - 1 i (2001) The need tor sustainable fuels has con tinued to ri se in the last decade. Hence, Castle Cement Limited in the UK has sta1ted to use a new eco-friendly kiln fuel. The fuel , ca lled Profuel, I S manufactured fron1 materials which cannot be recycled, such as paper packaging, low- ch lorine plastics and offcuts from the production of carpets and nappies. When burnt, a significant amount of energy is produced and the intense inferno– like temperatures produced within the kil n make certain that all the materials arc completely consumed. preventing the release of black smoke or smell. In addition, any ash rormed rrom the process is harmlessly locked away in the crystalline structure of the finished cement product. The usc orthis fuel has huge advantages over using coal alone. Not only will it reduce the amoun t of fossil fuels used, saving them fo r future generations. but a lso conclusive trials have shown a 40% i1i1provement in the overall envi ronmental performance compared with burning only coal. Profue l a lso ha s comp et itive advantages as it helps to keep the fuel costs down. Courte.1y: SESJ Newslef!er Special Issue, P 10, Tel: 91-11-6959759. Fax: 91-11 -6959669 E-mail: Sesi(a!.vsnl. net