Page 457 - New Trends in Eco efficient and Recycled Concrete

Application of alkali-activated industrial waste 407

Ashes from agricultural wastes are crucial raw materials for the design of new
AAMs, either as co-precursors in binary systems or as rich in silicon and alkaline
elements components to prepare activator. These ashes are usually available in
developing countries, so they could become a great opportunity to avoid or limit
the dependence on large Portland cement corporations.
The use of AASs in the manufacture of RAC, including them as substitution of
cement, have been studied in an effort to mitigate their detrimental effect with an
appropriate mix design.
The alkali-activation of RCA with a proportioned alkali-activator can favour the
possibility of producing AASc or AASm, showing suitable properties to be
acceptable on an industrial scale.
As a general conclusion, the use of waste for the formation of geopolymers is
considered to be very positive, because of the reduction of CO 2 emissions produced
in the manufacture of cements and increasing the rates of using waste and by-
products in construction and building materials. The different sources for a given
waste make specific studies on reactivity necessary to be carried out when used as
raw materials for AAMs; this is similar to the protocol followed when supplemen-
tary cementing materials are used for the design of OPC-blended cements.
The available amount and distribution of waste must be taken into account when
waste is selected for preparing a new binder. Possible manufacturers and users of
geopolymers should be involved in future investigations in order to push geopoly-
mer industries to favour the use of waste in the formation of geopolymers and by
demonstrating the environmental benefits of using these cementitious materials,
reducing the production of OPC in the medium- and long-term.

Acknowledgments

The authors wish to express their gratitude and consideration to the researchers Francisca
Puertas and Marı ´a del Mar Alonso for their expert contributions to this chapter.

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