Experimental Study on 3D Printing of Concrete with Overhangs

Abstract

The construction industry has been receiving in the recent past years the 3D printing technology as an emerging technology. Several researchers and companies have been reporting a number of case studies that show the possibilities of this technology regarding the dimensions, shape, building time, finishing and the material characteristics. It is commonly accepted that one of the big advantages of 3D printing is its possibility regarding the shape of the printed object since it can be easily changed each time a new piece is printed. This possibility raises some challenges regarding the printing limits, that are needed to the project design, such as to create overhangs. In this sense, a work was carried out to evaluate and optimize concrete printing mixtures and assess the 3D concrete printing of elements with overhangs. This paper presents the work carried out, showing the optimization of mixture composition for the binder/aggregate ratio, cement/fly ash ratio, and amount of superplasticizer and hardening accelerator, and evaluating their printing performance and mechanical properties. Printing of overhangs was possible for angles with the vertical direction till 17.5o.