Large-scale additive manufacturing processes for construction utilise computer-controlled placement of extruded cement-based mortar to create physical objects layer-by-layer. Demonstrated ...applications include component manufacture and placement of in-situ walls for buildings. These applications vary the constraints on design parameters and present different technical issues for the production process. In this paper, published and new work are utilised to explore the relationship between fresh and hardened paste, mortar, and concrete material properties and how they influence the geometry of the created object. Findings are classified by construction application to create a matrix of issues that identifies the spectrum of future research exploration in this emerging field.
Around 80% of domestic heat demand in Great Britain (GB) is supplied by natural gas, but continuing to heat dwellings in this way is unlikely to be compatible with national emission reduction ...targets. Electrical heating using heat pumps is expected to play a significant role in future space heating and hot water provision. The assessment of future heating technologies requires knowledge of the current demand for heat at short time intervals in order to evaluate peak demands and possible storage requirements. Existing half-hourly national heat demand estimates are built on data from small samples of dwellings. This paper provides estimates of GB domestic heat demand under mild, normal and cold weather conditions based on data from over 6000 dwellings collected between May 2009 and July 2010 that participated in the GB smart meter trial. The calculated peak domestic heat demand of 170 GW is around 40% lower than previously calculated suggesting that the difficulties surrounding the electrification of heat are far less profound than previously assumed. These results can be used in the development of future energy pathways and scenarios.
•GB half-hourly domestic heat demand was estimated from monitored data.•Peak heat demand is 170 GW, around 40% lower than previously thought.•Maximum ramp rate is 60 GW/h, around 50% lower than previously thought.•Electrification of domestic heating therefore less problematic than assumed.
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.
► Built a full-scale of extrusion-based additive manufacturing (AM) machine for Freeform Construction. ► Developed a high performance concrete for Concrete Printing process. ► Created a variety of prototype parts, including the world's first reinforced concrete AM component — WonderBench.
•Two models for estimating small power consumption and demand profiles are presented.•Predictions of energy consumption correlate well with metered data for both models.•Prediction ranges for power ...demand profiles are representatives of metered data.•Both models provide an improved method for predicting small power performance.
Small power is a substantial energy end-use in office buildings in its own right, but also significantly contributes to internal heat gains. Technological advancements have allowed for higher efficiency computers, yet current working practices are demanding more out of digital equipment. Designers often rely on benchmarks to inform predictions of small power consumption, power demand and internal gains. These are often out of date and fail to account for the variability in equipment speciation and usage patterns in different offices. This paper details two models for estimating small power consumption in office buildings, alongside typical power demand profiles. The first model relies solely on the random sampling of monitored data, and the second relies on a ‘bottom-up’ approach to establish likely power demand and operational energy use. Both models were tested through a blind validation demonstrating a good correlation between metered data and monthly predictions of energy consumption. Prediction ranges for power demand profiles were also observed to be representative of metered data with minor exceptions. When compared to current practices, which often rely solely on the use of benchmarks, both proposed methods provide an improved approach to predicting the operational performance of small power equipment in offices.
Digital Fabrication with Concrete (DFC) encompasses 3D Concrete Printing (3DCP) and many other methods of production. DFC is emerging from an era of invention and demonstration to one where the ...merits of one principle over another needs to be quantified systematically. DFC technologies vary in characteristics, complexity and maturity which hampers the synthesis of research and comparisons of performance. The interdependence of design geometry, material properties and process characteristics is well recognised. Materials research has made significant progress in recent years and there have been many applications with varying design geometries demonstrated. Far less has been done to guide the definition and description of the processes used. This work takes a step forward by presenting classification and process description guidance for DFC. The approach was developed by engaging a broad cross-section of the international community through the activities of the RILEM Technical Committee 276 between 2016 and 2020.
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.
This paper presents the hardened properties of a high-performance fibre-reinforced fine-aggregate concrete extruded through a 9mm diameter nozzle to build layer-by-layer structural components in a ...printing process. The printing process is a digitally controlled additive method capable of manufacturing architectural and structural components without formwork, unlike conventional concrete construction methods. The effects of the layering process on density, compressive strength, flexural strength, tensile bond strength and drying shrinkage are presented together with the implication for mix proportions. A control concrete (mould-cast specimens) had a density of approximately 2250kg/m3, high strength (107MPa in compression, 11MPa in flexure) and 3MPa in direct tension, together with a relatively low drying shrinkage of 175μm (cured in water) and 855μm (cured in a chamber at 20°C and 60% relative humidity) at 184days. In contrast well printed concrete had a density of 2350kg/m3, compressive strength of 75–102MPa, flexural strength of 6–17MPa depending on testing direction, and tensile bond strength between layers varying from 2.3 to 0.7MPa, reducing as the printing time gap between layers increased. The well printed concrete had significantly fewer voids greater than 0.2mm diameter (1.0%) when compared with the mould-cast control (3.8%), whilst samples of poorly printed material had more voids (4.8%) mainly formed in the interstices between filaments. The additive extrusion process was thus shown to retain the intrinsic high performance of the material.
The utilisation of automation technology and processes control found in the automotive and aerospace industries is not paralleled in modern day construction. The industry also struggles to improve ...health and safety issues and still uses traditional methods of procurement. These problems are compounded by the diminishing skills in the labour force. Methods of production must change if these issues are to be resolved. Rapid Manufacturing is a family of digitally controlled additive processes that have the potential to impact on construction processes. This paper outlines some of the major issues facing construction technology and gives examples of the use of large scale Digital Fabrication in the industry. The term ‘Freeform Construction’ is defined. Potential applications derived from an industrial workshop are presented and results from a series of preliminary studies indicate the viability of mega-scale Rapid Manufacturing for construction.
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Heating homes using gas boilers is incompatible with the UK’s target of net-zero greenhouse gas emissions by 2050. One solution is to shift to heat pumps (HPs) supplied from ...decarbonised power plant, but this could place an unmanageable burden on the electricity supply network.
National heat demand profiles depend on the heating patterns adopted by households which, in turn, depend on the type of heating system and its control. The largest data sets available, from around 6600 gas-heated homes and 600 homes with HPs, are used to create an empirical model of Great Britain’s (GB) half-hourly domestic heat demand. The model is used to estimate the annual half-hourly heat demand of the GB housing stock for both current and future weather conditions.
The demand profile when using HPs is compared to the current profile for gas heating. In a cold year, the calculated total annual heat demand of a typical mix of ground source and air-source HPs was 422TWh, 8% greater for than for gas-heated homes. However, the peak heat demand of 157GW was 8% lower than for gas heating, and the maximum heat ramp rate of 21GW/h, 67% lower. These results are due to the different ways that households use gas boilers and HPs. The accurate modelling of heating patterns is necessary to achieve reliable predictions of national heat demand. Policy initiatives, financial incentives or other interventions that influence the daily pattern of HP usage could also have a marked and positive influence on the GB heat demand profile.
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