In the recently published ‘Fiber-reinforced lightweight foamed concrete panels suitable for 3D printing applications,’ the authors present us with experimental results regarding a set of fiber-reinforced innovative lightweight panels (FRIL-panels) with a thickness of 12mm, created with a ‘peculiar’ foamed concrete featuring both high viscosity and cohesion.
While environmentally friendly solutions are sought after in many industries today, that is especially so within the 3D printing realm; however, it is difficult to have it all, and often it is hard to bring together both suitable mechanical properties and performance. Foamed concrete may be one of the answers as air bubbles act as a replacement for conventional cement, producing a more lightweight material—and reducing waste, ultimately. Microstructural air-voids are also extremely beneficial in comparison to concrete. The ‘cementitious matrix’ also includes good thermal insulation, acoustic absorption, and fire resistance.
Lightweight foamed concrete (LWFC) can be used to create foundation slabs, act as filler, and can also bolster soil. The authors point out that it is handy for precast too as LWFC can be used to create blocks and panels that can be ceilings, walls, and infills. The authors have created an extrudable LWFC (E-LWFC) that allows for better optimization and does not require formworks—improving expediency in production.
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Preparation of samples of FRIL-panels: a) realization of guides and placement of the bottom bi-directional grid reinforcement; b) pouring of fresh E-LWFC paste; c) polishing of the upper surface and placement of the top bidirectional grid reinforcement; d) final samples before removal of guides
E-LWFC can also be processed in 3D printing, ‘directly in situ.’ Due to the high viscosity, it is affordable, easy and fast to prepare, and use of the panels has the potential to save users substantial amounts of time. In this study, the researchers created and then evaluated five FRIL panels further, analyzing rupture, deflection, and collapse modes.
“The foamed concrete material is produced by mixing water, cement and VEA and gradually introducing a proper amount of foam (foam-to-cement ratio equal to 0.3) and mixing the resulting paste at a speed of 3000 rpm with a vertical mixer, so as to achieve a value of fresh density of the cementitious mix equal to 1050 kg/m3 , which corresponds to a dry density (evaluated after oven-dry the samples) roughly equal to 800 ± 50 kg/m3,” stated the researchers.
Samples were pre-cured for 12 hours in an open-air environment, as the researchers were careful not to allow expansion of air bubbles in the matrix which could cause external cracking. The pre-curing also created increased hydration, with the samples placed in the curing tank afterward. The researchers chose this type of curing because it speeds up production and means the material can be introduced into the construction market more easily. Production time was limited to two days.
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Typical collapse mode of FRIL-panels under three-point-bending test.
“The resulting force-displacement curves extracted from the three-pointbending tests have revealed that the lightweight foamed concrete panels abide by the requirements of the UNI EN 12467 in terms of MOR value and falls into class 1 (MOR > 4 MPa),” concluded the researchers. “This experimental work paves the way for new perspectives in the realization of economic blocks and panels with high thermal efficiency and acoustic absorption, reasonably good mechanical strength and rapid production process. Further research will be aimed at extending the present work by investigating other densities and curing conditions.”
3D printing with concrete and other materials is becoming increasingly more popular as enormous—and thriving—industries like construction are continually looking toward newer technology bringing forth studies regarding geopolymers, reinforced spatial structures, and even self-healing capsules.
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Preparation of samples of FRIL-panels: a) realization of guides and placement of the bottom bi-directional grid reinforcement; b) pouring of fresh E-LWFC paste; c) polishing of the upper surface and placement of the top bidirectional grid reinforcement; d) final samples before removal of guides