Influence of limestone filler on technological parameters of mixtures for 3D concrete printing

Abstract

This paper focuses on the use of fine-ground limestone filler (LP) from Rakke Limestone production (R0) as SCM in 3D Concrete Printing (3DCP) mixtures to partially replace OPC. Important technical aspects of the mixture, such as flowability, extrudability and buildability, are explored and investigated. To properly deploy 3DCP, two conflicting material qualities must be balanced. On one hand, the mix must be pumpable enough to be delivered by hose from the mixer to the nozzle, and on the other, after extrusion, the mix must retain its shape without any supporting formwork while bearing the load from succeeding filaments. In cooperation with MIRA Ehitusmaterjalid OÜ experimental mixtures with various OPC replacements were produced, which were printed on a gantry printer at Tallinn University of Applied Sciences. A comparison was made using industrial mixtures from Weber Saint-Gobain - Beamix 145-2 and ESL. LP has been found to enhance mix printability despite higher water requirement. This can be attributed to additional finely dispersed flocculation centres provided by LP additive. With the same, LP reduces buildability of the mixtures caused by slower yield stress growth and retarded stiffening.