Processing of Set on Demand Solutions for Digital Fabrication in Architecture

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

“…The single hydration peaks of the U_A samples appear at similar times even with slightly less accelerator while the silicate and aluminate reaction peaks of the S_A_SP mixes are occurring later with smaller maximum when more superplasticizer is added upon acceleration. The penetration resistance recorded with slow penetration tests in Figure 5 (right) increases with material age and more so with higher aluminium sulfate dosages for all accelerated U_A and S_A_SP samples similarly as previously reported in [7,9]. The S_A_SP mix variants show an immediate rapid increase of penetration resistance with a lower starting point for higher superplasticizer addition while the strength build-up of the U_A compositions is initially delayed.…”

“…The calorimetry results are represented in Figure 5 (left). Qualitatively, a high reaction rate can be observed after activation for both U_A_4 and S_A_4 mixes (the retarded base mixes with the same composition are reported in [9]). The single hydration peaks of the U_A samples appear at similar times even with slightly less accelerator while the silicate and aluminate reaction peaks of the S_A_SP mixes are occurring later with smaller maximum when more superplasticizer is added upon acceleration.…”

“…In this paper, two different retarded base mix formulations were tested for ACDC: an UHPC (noted 'mix U') with a mix design based on [10] and a self-compacting mortar (noted 'mix S') adjusted from previous SDC formulations [9,11]. 'U' comprises 0.1-0.4mm silica sand, a CEM I 52,5N Portland cement, silica fume, two types of limestone fillers while 'S' contains 0-4mm siliceous sand aggregates, a CEM I 52.5R Portland cement and silica fume.…”

“…'Mix S' is accelerated with a combination of an activator (aluminium sulfate solution with 30.0% concentration by mass) and a flow enhancer (superplasticizer). The amounts are based on [9] and are represented in Table 1. The dosing happens at the robotic setup (Figure 2) by one (U_A) or two peristaltic pumps (S_A_SP).…”

“…Although ACDC requires a formwork, with the gradual deposition and initially fluid and then fast hardening material it provides the possibility 2 to build it from thin, flexible or bendable materials that would burst or largely deform with traditional casting techniques (Figure 1). Two potential set on demand mortars potentially suitable for the needs of ACDC were previously developed in lab tests and published in [9], however, those formulations had to be tested with the continuous material processing of the robotic setup discussed in Section 3.1. These initial experiments follow an experimental approach to quantify material properties, especially yield stress, and relate them to formwork deformations on a straight geometry to define the most suitable mix and fabrication parameters for the production of the large folded structure in the second experimental phase.…”