According to a recent shareholder letter from…
Shimizu Corporation has created a “LACTM” fiber-reinforced mortar that uses a concrete 3D printer to construct buried column formwork. Problems have been addressed, such as the optimal hardening time and the integration of laminated surfaces held by traditional concrete for 3D printers.
19:36 GMT, Saturday, November 28, 2020
It is also distinguished by its strong durability and strength. It would contribute to labour savings and labor savings in reinforced concrete construction by building the buried formwork on site using a 3D printer.
And when it is piled until it hardens, Rakutum can retain its form without collapsing. An experiment was performed by Shimizu Corporation and verified that even if Rakutum is extruded at a rate of 2 to 4 cm in diameter, 0.7 cm in thickness, and 10 cm per second, it is possible to form a shape with a height of 2.1 m in about 2 hours. The power was strong enough to cast concrete twenty hours after the end of printing.
With ordinary mortar, the outline can not be preserved when attempting to create a thin structure such as a formwork with a 3D printer, and it collapses if it is stacked up to a height of around 10 cm. There was a problem because it would not lead to more productive jobs if the mortar was lined up while waiting for it to harden so that it would not crumble.
Furthermore, on the laminated surface, air bubbles and voids are likely to form and water and air can enter and cause degradation. The laminated surfaces can be added because Rakutum can be stacked without waiting for it to harden. The incorporation of the laminated surfaces using a tool to test the durability of concrete was verified by Shimizu Corporation.
Nearly no water was absorbed from the cut surface of Raktum, which met the consistency level of general concrete, by calculating the water absorption rate of the concrete surface layer. It was verified from this that the laminated surfaces were incorporated.