No abstract

Additive manufacturing in construction is beginning to move from an architect"s modelling tool to delivering full-scale architectural components and elements of buildings such as walls and facades. This paper discusses large-scale additive manufacturing processes that have been applied in the construction and architecture arena and focuses on "Concrete Printing", an automated extrusion based process. The wet properties of the material are critical to the success of manufacture and a number of new criteria have been developed to classify these process specific parameters. These criteria are introduced and key challenges that face construction scale additive manufacturing are presented.

This paper presents the experimental results concerning the mix design and fresh properties of a high-performance fibre-reinforced fine-aggregate concrete for printing concrete. This concrete has been designed to be extruded through a nozzle to build layer-by-layer structural components. The printing process is a novel digitally-controlled additive manufacturing method which can build architectural and structural components without formwork, unlike conventional concrete construction methods. The most critical fresh properties are shown to be extrudability and buildability, which have mutual relationships with workability and open time. These properties are significantly influenced by the mix proportions and the presence of superplasticiser, retarder, accelerator and polypropylene fibres. An optimum mix is identified and validated by the full-scale manufacture of a bench component.

10 11 12This paper presents the hardened properties of a high-performance fibre-reinforced 13 fine-aggregate concrete extruded through a 9 mm diameter nozzle to build layer-by-14 layer structural components in a printing process. The printing process is a digitally 15 controlled additive method capable of manufacturing architectural and structural 16 components without formwork, unlike conventional concrete construction methods.

Despite an increasing demand for housing and wider concerns over the need to improve performance, the industry seems to be reluctant to adopt offsite technologies. Many studies have attempted to scrutinize the barriers and seek ways forward, but the perspectives of housebuilders remain unclear. This research aims to investigate UK housebuilders' views on the use of offsite Modern Methods of Construction (offsite-MMC). This was carried out through a combination of personal interviews and a questionnaire survey of the top 100 housebuilders by unit completion. Results suggest that the traditional drivers of time, cost, quality and productivity are still driving the industry in deciding whether to use offsite technologies. Nearly two thirds of the firms believed that there needs to be an increase in the take-up of such technologies. However, current barriers relate to a perceived higher capital cost, complex interfacing, long lead-in time and delayed planning process. Strategies recommended centred on changing peoples' perceptions, improving procurement, providing better cost data, tackling planning and regulations, encouraging political levers and providing practical guidance. The suggestions present a model for encouraging the take-up of offsite-MMC in the future.