Development of Self-compacting Concrete with Good Shape Stability for Slipform Construction

Abstract

The aim of this research project was to modify a conventional self-compacting concrete (SCC) for use in a slip-form paver. For this purpose, two alternatives were investigated: (1) thixotroping agents (concept A) that were added to the original concrete mix and (2) viscosity-increasing additives (concept B) that were intermixed shortly before the concrete was finally placed to reduce the concrete’s flowability. The investigations were performed preliminarily on pastes and mortars and only subsequently on concretes. For the modification of pastes and mortars, thixotroping additives mainly based on modified starches and modified polymers were used. For modification of the viscosity, superabsorbent polymers and naphthalene sulfonates in combination with polycarboxylate ether (PCE) were considered. The conducted investigations indicated that it is quite difficult to create slip-form SCC using thixotroping additives because the thixotropic effect is reversible and results in a low “green strength” when the concrete is mixed for a second time (e.g., during the delivery and placement process). When superabsorbent polymers and naphthalene sulfonate were added during the concrete placement, the stiffening effect was irreversible.