Cement, Energy and Environment July-Sep 2002

handled without segregation. It is a lso refe rred as se lf-l eveling concrete, super workable concrete, sel f-consolidating concrete, highly– flowabl e concrete, non-vibrating concrete, etc. Use offly ash and blast furnace slag reduc es the dosages of superplasticizer in self-compacting concrete needed to obtain similar slump/fl ow compared to concrete made with portland cement only. The we ll known beneficia l advantages of using fly ash in concrete such as improved rheological properties and reduced c racking of concrete due to the reduced heat of hydration of concrete can also be incorporated in sec by utili sa tion of thi s material as a fi ll er. sec often incorporates several mineral and chemical admixtures, in particular a superplasticizer and a viscosity– modifying admixture (YMA). The su perpl asticizer is used to insure high fluidity and reduce the water– to-cementitious materials ratio. The YMA is incorporated to enhance the yield value and viscosity ofthe fluid mixture, hence reducing bleeding of the concrete. The homogeneity and uniform ity of the self-compacting concrete is not affected by the skill of workers and shape and bar arrangement of structures because of high flu idity and resisting power of segregation of materials. Courtesy: ICI Journal Jui-Sep. 2002, P-9, Fax: 9/-.1-/-4-1551-18 £mail: ici3@vsnl.in Web: wlvw./pcsadvt,comlici 'COST CAN BE REDUCED BY CONCRETE ROADS' India Express Mumbai, 03. 06. 2002 Minister of State for Commerce and Industry Raman Singh has said the amount of Rs. 2500 crore which is invested every year for ru ral road development can be saved by usage of concrete roads since maintenance cost, fuel costs wi II come down . drastic a ll y. Stress ing on rural road development, Singh said: "developments in states start with roads and good roads contribute immensely to the economy of a state. The Cement Manufacturers' Association and Maharashtra State Road Development Corporation held a seminar in Mumbai to share views about India's first access controlled expressway - Mumbai– Pune'. Inaugurating the seminar Raman Singh congratulated every one invo lved in successfu ll y completing the Mumba i -Pune Expressway in a record time of 33 months. Courtesy: Cement News Digest 0!-07 June 2002, P 4, Fax: 022-20./{}582 E-mail:cmabb@ bom3vsnl. net. in Web: www. cmaindia. org EFFECTS OF RICE HUSK ASH ON THE STRENGTH AND DURABILITY OF CONCRETE N. R. D. Murthy, P.Rathish Kumar, Seshu D.R.- REC Warangal, M. V. Seshagiri Rao-J NTU Co llege of Engg., Hy derabad Concrete is a tradition a l materi a l used in .construction industry for the past one century and it has become ind ispensable despite its inhe rent deficienc ies. The concrete for future has to satisfy the cond itions of strength and durability, to meet the requirements of huge construction works with least maintenance costs. Efforts are mad e a ll-round th e g lobe for developing concrete. of enhanced li fe . The durab il ity . ca n be determined based upon its resistance to penetration by external agen ts, res istance to interna l deterioration due to the chemical composition of its ingredients and structual requ irements. The product ion of concrete involves se lection of suitable ingredients, their careful proportions and quality control. Une of the salient features of concrete with good performance is its strength apart from other things. However it is generall y agreed that hi gh performance concrete need not always be of high strength alone. Mehta P. K. et al hav e di sc ussed in detai I the principles of production of Hi gh Performance Concrete. The strength requirements are not the only necess ity, but it could be more resistant to unacceptable rate of deteri oration. As a lready mentioned, the main ingred ients of performance concrete are cement, agg regate s, wate r, mineral admixtures wh ich include micro fillers, chemical admixtures such as supe rpl at ic izers , re tarders a ir entraining agents etc. A number of investigations have been reported using mineral admixtures such as silica fume, flyash etc which act as microfillers and thereby the microstructure of the hardened cement material becomes denser and stronger which improves its strength durability characteristics . Mehta P. K. and Y M. Malhotra have reported investigations using Rice Husk Ash (RHA) as minera l admixture in place of si lica fume, and reported it as an exce llent replacement of s ilica fum e. However little work is reported in India about the usage of Rice Husk as an admi x ture for Indian conditions. The concrete mixes of normal strengths with and wi thout RHA replacements have been reported . 40% ofRHA as partial replacement for cement the strength of concrete of I: 2:4 mix has improved i.e. for mixes designated A I to A4, beyond which there is reduction in strength. However, in case of mixes from A6 to A9 and A 10 to A 12, the improvement in strength wi th addition of RHA was observed up to 30% ash content, beyond which there was decrease. It can also be noted fro m the table th a t th e m