Robotic 3D Printing of Mineral Foam for a Lightweight Composite Concrete Slab

Abstract

This paper presents the design and fabrication of a lightweight composite concrete slab prototype using 3D printing (3DP) of mineral foams. Conventionally, concrete slabs are standardized monolithic elements that are responsible for a large share of used materials and dead weight in concrete framed buildings. Optimized slab designs require less material at the expense of increasing the formwork complexity, required labour, and costs. To address these challenges, foam 3D printing (F3DP) can be used in construction as demonstrated in previous studies for lightweight facade elements. The work in this paper expands this research and uses F3DP to fabricate the freeform stay-in-place formwork components for a material-efficient lightweight ribbed concrete slab with a footprint of 2 x 1.3 m. For this advancement in scale, the robotic fabrication and material processing setup is refined and computational design strategies for the generation of advanced toolpaths developed. The presented composite of hardened mineral foam and fibre-reinforced ultra-high-performance concrete shows how custom geometries can be efficiently fabricated for geometrically complex formwork. The prototype demonstrates that optimized slabs could save up to 72% of total concrete volume and 70% weight. The discussion of results and challenges in this study provides a valuable outlook on the viability of this novel fabrication technique to foster a sustainable and resourceful future construction culture.

A Scientometric Review on Mapping Research Knowledge for 3D Printing Concrete

“…As a result, there are rising concerns regarding natural resource depletion. Thus, 3D printing concrete reduces the cement requirement, resulting in sustainable construction with reduced CO 2 emissions [ 80 , 81 , 82 ]. The application of 3D printing concrete may also have resolved difficulties in waste management, specifically in the formwork [ 3 , 10 ].…”

Digital Fabrication of Ribbed Concrete Shells Using Automated Robotic Concrete Spraying

“…Much work has been done in evaluating the potential of thin-shell concrete structures as a materially efficient alternative to flat concrete slab flooring [8][9][10][11]. Combined with low carbon concrete mixes, thinshell concrete forms have the potential to offer an 80% lower carbon footprint compared to traditional flooring systems [12].…”

“…However, the construction of these thin-shell concrete floors is still for the most part a manually intensive endeavour, with the concrete often cast manually onto curved timber surfaces. The inclusion of ribs -which has the potential of significantly improving structural performance -is also performed manually through the placement of material blocks made by cutting [8,10] or 3D printing [11] formers to create voids in the concrete. The extra material used for these rib formers inevitably leads to an increase in the overall embodied carbon of the structure.…”

Structural design and testing of material optimized ribbed RC slabs with 3D printed formwork

“…[9][10][11] Using automated formwork production for customized two-way RC ribbed slabs (see Figure 1a,b) could significantly reduce material consumption on a structural level 12 , as slabs require approximately 80% of the concrete volume in typical multistorey buildings 13,14 or approximately 55% in smaller buildings. 15 Despite the importance of this structural typology, only a few studies have addressed digital fabrication of slabs [16][17][18][19][20][21][22][23][24] (see Figure 2 and Table 1). These studies describe various slab prototypes using various concepts for formwork, reinforcement and concrete.…”

“…Several studies [25][26][27] have addressed the challenge of introducing conventional reinforcement into digital fabrication processes. Accordingly, the studies described in Table 1 primarily focus on approaches that do not use conventional reinforcing bars, either by using FRC or UHPFRC 18,[20][21][22] or by relying on post-tensioning, [18][19][20] both causing higher cost and CO 2 emissions than conventional reinforcing bars. Furthermore, the use of concrete types that require more cement (UHPFRC, 18,[20][21][22] 3Dprinted concrete 16,24 ) contradicts the aim to produce sustainable structures.…”