Early-Age Mechanical Properties of 3D-Printed Mortar with Spent Garnet

Abstract

This study determines the effect of spent garnet as a replacement for natural sand in 3D-printed mortar at early ages. Five mixes with different spent garnet amounts were prepared (0%, 25%, 50%, 75% and 100% by volume). The ratio of binder to aggregate remained unchanged. In all mixes the water/binder ratio was assumed as a constant value of 0.375. Tests were performed to confirm the printability of the mix (a path quality test using a gantry robot with an extruder). Determinations of key buildability properties of the mix (green strength and Young’s Modulus) during uniaxial compressive strength at 15 min, 30 min and 45 min after adding water were conducted. A hydraulic press and the GOM ARAMIS precision image analysis system were used to conduct the study. The results showed that an increase in spent garnet content caused a decrease in green strength and Young’s Modulus (up to 69.91% and 80.37%, respectively). It was found that to maintain proper buildability, the recommended maximum replacement rate of natural sand with garnet is 50%. This research contributes new knowledge in terms of using recycled waste in the 3D printing technology of cementitious materials.

Potential of Reusing 3D Printed Concrete (3DPC) Fine Recycled Aggregates as a Strategy towards Decreasing Cement Content in 3DPC

“…Firstly, it should be noted that the green strength obtained for materials modified with the fine recycled aggregate (fRA) ranges between 5.27 kPa and 11.09 kPa after 30 min and between 6.26 kPa and 14.73 kPa for specimens tested for 60 min. These values are in line with those presented in other studies [ 13 , 15 , 30 , 32 , 50 ]. Chosen research teams that focused on ordinary mixes without recycled aggregate incorporation obtained the following results after 30 min: Casagrande et al [ 32 ] reported values of between 4.30 kPa and 26.04 kPa, Wolfs et al [ 50 ] reported about 10.5 kPa, Panda et al [ 51 ] reported about 10.65 kPa, and Skibicki et al [ 30 ] reported about 9.02 kPa.…”

“…Other studies dedicated to the incorporation of recycled aggregates present inconclusive results. For example, Ding et al [ 15 ] indicate an increase in green strength after incorporating recycled sand, from 10.68 to 12.23 kPa, while Skibicki et al [ 13 ] prove that the addition of recycled aggregate leads to a decrease in green properties (from about 14 kPa to 3.8 kPa). Based on the presented examples, (i) in both studies, the recycled aggregate was used as a substitution for a natural aggregate, while, in the presented paper, the authors substituted the binder; and (ii) the obtained values in the presented papers [ 13 , 15 ] are comparable to the values obtained in this current study.…”

“…The tests were performed using a special precision press device with a precise LVDT and a force sensor (up to 500 N, HBM C9C 0.5 kN, Darmstadt, Germany) coupled to a HBM MGC Plus AB22A bridge (HBM, Darmstadt, Germany). The device and testing methodology were described comprehensively in [ 13 , 25 ]. The tests were conducted on the cylindrical specimens (D = 60 mm, H = 120 mm).…”

“…Moreover, the compressive, tensile splitting, and flexural strengths of the recycled sand 3D printed concrete were significantly anisotropic. As previously stated, while there may be some slight decay in performance, research has shown that 3D printed concrete made using recycled aggregates still performs satisfactorily [ 12 , 13 , 14 , 15 ]. Additionally, several proposed methods have been made for improving the properties of these aggregates, including carbonation modification, which has been proven effective at enhancing the recycled fine aggregates and aiding in carbon dioxide sequestration [ 11 ].…”

Building a Greener Future: Advancing Concrete Production Sustainability and the Thermal Properties of 3D-Printed Mortars

“…Despite reducing flowability and extrudability in the fresh state, AMFs improved the hydration reaction speed with increased shape stability and long-term strength [111]. The relation between printability and mechanical performance with size gradation and interlayer distribution was proved by incorporating recycled concrete, desert sand, and river sediment [112] and preserving buildability with up to 50% replacement of sand with spent garnet [113].…”