Experimental study reveals continuous shearing regulates structural build-up and setting time in cement pastes, indicating a method for real-time control in 3D concrete printing.
Key Points
To evaluate the efficacy of continuous high-rate shearing as an active, real-time method to control the structural build-up and physical setting time of fresh cementitious pastes for 3D printing applications.
Tested two binder systems across water-to-binder ratios of 0.40 and 0.48: 100% Limestone Portland Cement (PLC) and a blend of 80% PLC with 20% Class C fly ash (FAC).
Measured structural build-up evolution via static yield stress at 10-minute intervals using a rheometer until reaching a rigid threshold under both static and dynamic (continuous shearing) conditions.
Continuous dynamic shearing significantly delayed structural build-up and altered physical setting time across all evaluated mixtures relative to static conditions.
Higher water-to-binder ratios increased paste responsiveness to dynamic agitation, leading to greater delays in structural hardening.
Incorporating 20% Class C fly ash improved the ability to actively manipulate structural build-up and setting rates through mechanical shearing without requiring mix design modifications.