LCALINE CONCRETES FREE OF FORTLAND CEMENT

Ana María Fernández-Jiménez, Angel Palomo, Cecilio López

Abstract


Nowadays Portland cement concrete is the most widely used building material. Its mechanical properties, the quality/price ratio, performance in general, have contributed to the success ofthis material along 20th century. However the process of fabrication of Portland cement involves some problems (energetically and environmentally speaking) qffecting the general opinionn ofmodern societies on thepotential risks ofsuch a process of fabrication: Very high temperatures need to be reached (J400"C- 1500°C); natural quarries are destroyed during the extraction of raw materials; CO2 and NOX are emitted to the atmosphere. Finally, traditional concrete also presents some durability problems, which are currently difficult to overeó me. This paper offers some resulls obtained in an ongoing investigation. The investigation is related with the elaboration ofalkaline concrete: concrete in which the Portland cement is completely replaced (100%) byfly ash and the mixing water by an alkaline dissolution. This new alkaline concrete may reach a compressive strength of50 -60 MPa at 20 hours after the mixing. Additionally, alkaline concrete has a very good dimensional stability (it hardly undergoes shrinkage). Also, the adherence between the matrix and the steel reinforcement is very good; and because ofthe very similar chemical and mineral composition ofalkaline cements with natural zeolites, it is expected that the new concrete will have very good durability properties. Finally the pnce ofthe new concrete is competitive with Portland cement concrete prices and the application ofthe new material in theprecast industry could be done with almost no problems. 

Keywords


Concrete, alkali activation, fly ash

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