Development of a fiber reinforced composite with alkali activated ground granulated blast furnace slag

High performance binders are indispensable materials in the production of mortar, concrete and fibre reinforced composites with superior high mechanical and durability properties. High performance fibre reinforced composites (such as RPC and SIFCON) require high strength binders to achieve desirable properties. Cement content of these composites may be as high as 800 - 1000 kg/m3. Such a high cement content may cause several technical, economical and environmental problems.Materials that have amorphous structure such as fly ash and slag can be modified to a strong binder by using some activators. The product of modification reaction of type F fly ashes is an inorganic polymer called geopolymer. While the main reaction product of glassy blast furnace slag is a hydrated calcium silicate, similar to the C-S-H structure of a cementitious binder.Alkali-activated binders are characterized by their high mechanical performance, low energy cost and low pollutant gases emission (CO2, SO2, NOx, etc.) as well as their less environmental deterioration (almost exclusively usage of secondary raw materials instead of surface-excavated natural resources). Related to the properties and characteristics of alkali - activated binders and concretes, some advantages with respect to the traditional Portland cements and concretes such as earlier and higher strengths, lower heat of hydration and better resistance to aggressive chemicals are worth mentioning.The object of this research was to develop a high performance binder by modifying ground granulated blast furnace slag by NaOH and water glass solutions. Optimum activator concentration has been investigated with respect to Ms ratio (SiO2/Na2O) and Na2O content under various curing conditions (normal water curing, low pressure steam curing and autoclave curing). Silica fume, fly ash, metakaolin, plaster of Paris and some chemical admixtures (air entraining, shrinkage reducing admixture and anti-foam agent) were also tried in the mixtures besides slag in order to improve the properties of composite. As a result, an alkali activated steel fiber incorporated composite ARPC, having a compressive strength over 200 MPa was developed. Rheological, mechanical, micro structural (SEM, XRD, thermal analysis, mercury porozimeter etc.) and durability properties of ARPC were determined and compared with the conventional RPC (KRPC). Test results indicate that both of the RPC mixtures have desirable durability properties. Additionally, ARPC generally exhibits better durability properties than KRPC.