3D printed concrete technology
As a novel construction method, 3D concrete printing has several merits for the construction industry in reducing project time, cost, and defects, while improving design flexibility and more environmentally friendly aspects of a project. Using this method, a predesigned building element can be built in 2D layers, laid on top of each other, the repetition of which results in the construction of a 3D object.
The innovative 3D printing technique has been successfully applied to build-up, layer by layer, construction-scale structures through the extrusion of various cementitious materials. Favourable buildability of fresh cement mixture and the hardened properties of the printed structures are essential requirements for 3D concrete printing. 3D printing technology has undergone rapid development in the past few years and it is now possible to print engineering structures.
A new additive manufacturing (AM) processing route is introduced for ultra-high-performance concrete. Experimental studies of four different mixtures of silica fume and nano-clay has significantly enhanced shape stability. One of the most commonly used artificial composites in the field of civil engineering are fiber-reinforced cementitious composites (FRCCs), which consist of the randomly distributed short fibers inside a cementitious matrix.
The composite of Portland cement paste and reinforcing short fibers (carbon, glass and basalt fibers, 3–6 mm) results in novel materials that exhibit high flexural (up to 30 MPa) and compressive strength (up to 80 MPa). A 3d-printed building utilises 60% less concrete, it is 3-5 times faster to build and the overall cost of the finished house is 30% cheaper. 3D printed house walls and parts make up 40-45% of total construction volume.
The process requires two people on site plus one for health & safety supervision. A printed building is seismically more stable because the walls have no lateral connections as they are made out of imbued singular structural material. Eurocode is accepting 3D concrete houses on one and two floors. In Wallenshausen, Germany company PERI is currently building 3-storey building already certified under the German code.
There is almost no use of steel rebars or armature except slabs (if necessary), no use of finishes internally or externally except liquid waterproofing paint in such buildings. Achieving UV values, using eco-friendly natural insulation materials like loose Rockwool, Perlit etc. by filling in the hollow body of the concrete/ mortar wall. There is no doubt that 3D concrete printing will continue to grow in recognition as the technology matures and becomes one of the key manufacturing technologies of the 21st century.
Building Structure is made of reinforced concrete and a column-free, reinforcement-free 3D printed concrete extrusion layering technology. Building base-built struc¬ture is considered as bottom-to-top construction, divided in two phases: 1st – rein¬forced concrete post-tension flat slab; 2nd – 3D Concrete Print. A pile foundation should be achieved for the building, subject to structural calculations based on the geo-technical Soil Survey Report provided. The slabs are supported with concrete column system. First floor slab acts as a primary foundation for a 3D Concrete Printer installation. Because of the printer’s maximum with of 12m, the 75m wide slab will be divided in 6 rows of printing.
Off-site printing prefabrication
For the 72m wide span the arched plywood temporary scaffolding/ mold is consid¬ered to be installed in the first place, to support 3D printed concrete walls. All 3D printed wall are made strictly vertical to match current world 3D printing capabili¬ties. The method would be based on an arch bricklaying technology, as incremental subdivision of the arch. The advantage of the off-site manufacturing of building elements is economy, timing and precision. Since the site preparation and erection of base-built reinforced concrete floors takes significant time, 3D printing can be completed during this time and brough to the site for quick assembly.
To sum up one may say that despite the buildings complicated geometry of wall shapes, using 3D printing current cutting-edge technology, it is the best way to achieve the proposed architectural design – faster, cheaper, controlled and sustain¬able. The structural system of the Museum project, is subject to careful structural calculations. With all preliminary assessment of the project, it is possible to do so. The technology and structure blends harmoniously into the architectural design while fulfilling all requirements of safety, economy and ecology.
Prefabrication & Recyclability
The prefabrication of all building parts or elements guarantees a high quality, especially concerning strength, surface qualities, colours and low geometrical tolerances. Prefabrication is also essential to achieve in factory. With regards to environmental concerns, prefabrication is the basis for easy-to-recycle buildings since each single part will be designed by us either as a monomaterial piece (one material per part only) or if several materials need to be assembled together in order to form one element, these material components will be easy-to-separate and subsequently easy-to-recycle.
Despite the fact that buildings typically stand for a relatively long time, the reduction of building waste is essential to reduce the production of waste in total. Prefa bricated elements which follow the outlines described above can be either reused (cradle-to-cradle) or they can be downcycled (a steel beam might become a car body or an aluminium facade panel might become a juice can). In order to allow for such perfect recycling, the identification of the building elements is essential.
Following techniques developed by the German car industry, the prefab-elements will either show a bar code or have an embedded Radio Frequency Identification tag. A RFID-tag is a chip typically 2x2mm or 2x4mm in size and it contains all information about a building part such as producer, material type, recycling regulations etc. RFID-tags do not contain batteries. It is in permanent sleep mode, only activated by a special reading unit which supplies the energy. Source and images Courtesy of Architects of Invention.