Evaluation of suitability for 3D printing of high performance concretes

Abstract

Abstract. The article presents overview of additive manufacturing for concrete structures. Study focuses on specific tests used to determine suitability of high performance mixes for 3D printing. The tests include determination of compressive strength and evaluation of printing speed, extrudability and overall surface quality. Tests were performed on a HighPerformance Concrete mix with fine natural aggregate up to 2 mm. Mineral additives such as silica fume and fly ash, and superplasticizer were added to obtain proper consistency. The tests were performed using specially designed site consisting of Cartesian robot and pumping module. The design of printed paths were tailored for specific tests. The evaluation of pump performance was made by measuring pumped mix volume in time. The determination of correct pumping speed was made based on the visual quality of the printed layers. Study determines also the ability to print multilayered structures and printability window of proposed mix.

Automation in the Construction of a 3D-Printed Concrete Wall with the Use of a Lintel Gripper

“…The step motor (4) rotates the body (5), the position of which is determined by a limit switch (6). The gripper body (7) accommodates DC motors (8), which operate the gripper jaws (9). Presence sensor (10) are attached to the gripper jaws.…”

“…The concrete mix used in the experiments was designed on the basis of article [9], with a 0.23 water-cement ratio and a density of 2168 kg/m 3 (CoV = 0.24%, n = 3). The binder was composed of: (1) CEM I 52.5R Portland cement −70%; (2) fly ash −20%; (3) silica fume −10% of the total binder amount.…”

“…A 28-day strength of 113.7 MPa (CoV = 1.13%, n = 4), was obtained for the mix. Previous qualitative tests have shown that the open time of the mix ranges from 10 to 70 min [9]. During the mix preparation and printing operations, the ambient temperature was 20 • C ± 2 • C, while the relative air humidity was 60% ± 5%.…”

“…The printing head moves in 3D space over a programmed path, building up the designed structure layer by layer [2]. Various types of 3D printers are in use, including Cartesian robots [7][8][9], robotic manipulators [10][11][12] and Delta robots [13,14]. Several objects have already been produced with this technology, both for the purposes of demonstration as well as for practical uses [15][16][17][18][19].…”

Linking fresh paste microstructure, rheology and extrusion characteristics of cementitious binders for 3D printing

“…In extrusion‐based printing, the yield stress is a function of both the compacting pressure that the paste is subjected to in the extruder, and the structural reorganizations occurring due to time‐dependent chemical reactions (cement hydration). The window of time available to successfully print the mixtures is also dependent on these parameters . The rheological properties are also influenced by the extruder properties—shape, wall roughness etc., and extrusion rate, which also merit consideration …”