Reuse of Returned Concrete by Hydration Control: Characterization of a New Concept

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Title: Reuse of Returned Concrete by Hydration Control: Characterization of a New Concept

Author(s): F. D. Kinney

Publication: Special Publication

Volume: 119

Issue:

Appears on pages(s): 19-40

Keywords: activators; chemical compounds; circulation; concretes; hydration; performance; ready-mixed concrete; retempering; stabilizers (agents); Materials Research

Date: 9/1/1989

Abstract:
Discusses a chemical approach to dealing with returned concrete that has the potential of reducing the amount of waste in concrete production to a level unmatched by other methods. This approach allows use of concrete up to 72 hr after batching and the reduction of wash-out slurry and reclaimer debris. This two-part chemical system is comprised of a stabilizer that strongly retards the hydration of all clinker minerals and a hydration initiator or activator added to stabilized concrete prior to its placement. Data presented on commercial portland cement and individual clinker minerals treated with this system show the effects of the stabilizer and initiator on the different clinker phases and were drawn from calorimetry, x-ray diffraction, and SEM studies. Control of nucleation and nuclei growth are proposed as the mechanism by which the chemical system works. Data from field-batched mixes demonstrate that the plastic and hardened properties of concrete made using this chemical system are no different than those of conventionally batched concrete.