Mechanical properties of layered geopolymer structures applicable in concrete 3D-printing

This paper focuses on inspecting the structural buildability of layered objects. Simulating extrusion method process was used to investigate three geopolymer mixes, three-time gaps, and two layering patterns through 18 layered samples. This paper also evaluates effects of the layering process on hardened properties of build-up materials through 9 standard specimens. The used materials were Gladstone fly ash, sand, 8 M sodium hydroxide solution, and D-grade sodium silicate. The weight ratio of sodium silicate to sodium hydroxide was 1, and activators to fly ash was 0.26. Mix 1, mix 2, and mix 3 contained 0%, 1% steel fibers, and 0.5% polypropylene fibers respectively. The structural buildability of layered samples and the influence of the layering process were assessed in terms of flexural strength through .3-point bending tests. Flexural strength results indicated that the layering process has negative impact on the mechanical strength of build-up materials. Also, mix 2 resulted in the highest flexural strength values in standard specimens and layered samples. However, the most bond separation issues between additive layers were achieved with layered samples produced with mix 2. Most layered samples produced with minimum time gaps recorded the highest flexural strength results. (C) 2018 Elsevier Ltd. All rights reserved.