ACDC: The Admixture Controlled Digital Casting and Its Application to Thin Folded Concrete Structures

Abstract

Digital concrete technologies aim to minimize or eliminate the need for formwork, produce less waste, and build material efficient designs at increased productivity. This paper discusses how Admixture Controlled Digital Casting (ACDC) could address these aims by producing thin folded structures. For the process, a set on demand concrete composition was used to achieve minimal deformations when robotically filling weakly supported formworks. The formworks were constructed from bendable materials such as foil, geotextile or paper tensed between a frame on top and bottom and could be reconfigured for different geometries. The prototypes were assembled and post-tensioned to achieve a one-to-one scale fully functional architectural roof element. With the demonstrator presented, ACDC challenges the way we think about casting and formworks in the construction industry at the age of the 4 th industrial revolution.

In-Crease: Less Concrete More Paper

“…The experiments presented here consist of three primary operations: 1) the design of the folding patterns, 2) the fabrication of the formwork, and 3) the casting, for which two different digital casting techniques were used. One is the Admixture Controlled Digital Casting (ACDC) described in [13], which uses a self-compacting fast setting mortar. The aggregate content (sand 0-4 mm) for this mix was 52% by volume of concrete.…”

“…Superplasticizer ACE30 and a 30% sucrose solution as retarder were also used (0.84% and 0.37% by weight of cement respectively). For the mortar used in ACDC, the hardening is accelerated with an aluminium sulphate solution, while the fluidity for assuring self-consolidation of the material during the casting is controlled with the addition of flow enhancer [13]. This mix allows for demoulding after 1.5 hours, when the material has reached a strength of 15MPa.…”

“…Prior tests on the subject of thin formwork deformation were studied by Szabo et al [13], where a series of tests using thin suspended foils showed the correlation between formwork deformation and hydration and casting speed. To minimise the deformation a calibration between hydration and casting speed were found and further used in the following studies.…”

“…DCS allows for control of the hydration of a self-compacting concrete on the fly of production, thus reducing formwork pressure to a state that eliminates the need for heavy-duty formworks for concrete while also allowing for the inclusion of standard reinforcement systems that comply with norms. Over the past decade, the different DCS processes have used different formworks starting with dynamic slipforming known as Smart Dynamic Casting (SDC) [11], Eggshell, using ultra-thin fused deposition modelling (FDM) formworks [12], and lightweight formworks made from foil, textile or paper for Admixture Controlled Digital Casting (ACDC) [13]. Overall, these formworks show that a well-focused combination of traditionally disconnected fields can open new and simple ways to realize material-lean structural concrete elements.…”

“…Eggshell has amongst others, also made it into a real-world construction scenario where again a reinforced concrete column was produced for an exterior office landscape (Figure 1d). Further concepts of using thin formworks were investigated by Szabo [13], where weakly supported formworks made of suspended foil (Figure 1c), textiles, rammed boards or paper were filled with a digital casting process called ACDC to fabricate post-tensioned thin folded members [13,39]. The results demonstrate one of the most economically feasible ways to produce formwork for non-standard shapes for thin folded and reinforced plate structures.…”