Accelerated electric curing of steel fibre reinforced concrete - associated data

All the data from laboratory testing undertaken for the publication "Accelerated electric curing of steel-fibre reinforced concrete". This includes:- mechanical testing with raw data and graphs- curing data including electrical and temperature both raw and graphical</div

Reinforced Autoclaved Aerated Concrete (RAAC) crack program

This executable program identifies cracks in RAAC survey images.Reinforced Autoclaved Aerated Concrete (RAAC) panels have been extensively used in the UK since the 1960s as structural roofs, floors and walls. The lack of a longitudinal, objective, consistent defect data capture process has led to inaccurate, invalid and incomplete RAAC data, which limits the ability to survey RAAC within buildings and monitor performance. Therefore, an accurate, complete and valid digital data capture process is needed to facilitate better RAAC performance and defect monitoring. This project focused on the development of an Artificial Intelligence (AI)-driven RAAC crack defect capture tool for improving the quality of RAAC survey data. RAAC crack defect image data was collected, curated and trained. A deep learning approach was employed to train RAAC surveyed defects (cracks) images from two hospitals. This approach mitigated unavoidable occlusions/obstructions and unintended ‘foreign’ objects and textures. An automatic RAAC crack identification tool has been developed to be integrated into RAAC survey processes via an executable code. The executable code categorises RAAC survey images into ‘crack’ or ‘non-crack’ and can provide longitudinal graphical evidence of changes in the RAAC over time.</p

External sulphate attack of sprayed mortars with sulphate-resisting cement: Influence of accelerator and age of exposition

© 2020 Elsevier Ltd This work evaluates the influence of the accelerator type, the cement type and age of exposure on the degradation mechanism and the durability of sprayed mortars subjected to external sulphate attack (ESA). Cores and prisms were extracted from panels sprayed with 8 mortar compositions (with 2 sulphate-resisting cement types and 4 setting accelerators) and then exposed to a sulphate solution at the ages of 7 or 28 days for 400 days. The evolution of the ESA was assessed through XRD, SEM, compressive strength, dimensional variation and ultrasonic pulse velocity. Results show that alkaline accelerators increase drastically the vulnerability of the matrix to the ESA. The degradation is enhanced by the higher solubility of aluminate phases and the increased formation of expansive phases. Results reveal that the use of sulphate-resisting cement might not suffice to mitigate severe material degradation

Flexural behaviour of AR-glass textile reinforced 3D printed concrete beams

3D concrete printing (3DCP) enables automation of construction manufacturing through digital design and workflow, adding value through high degrees of form freedom. The process constraints during the printing, however, hamper the application of reinforcement and hence limit the ductile behaviour that is achievable in 3D printed concrete structures. Although a number of reinforcement strategies have been developed and these strategies can to some extent address these limitations, the reinforcement challenges of 3D printed concrete structures are not satisfactorily addressed yet. This paper proposes another reinforcement strategy of incorporating alkali-resistant (AR)-glass textile between the printed concrete layers. To validate the strategy, small-scale printed concrete beam specimens reinforced with one to three layers of textiles were tested under three-point bending. The results were compared to those obtained from equivalent ‘cast’ specimens. Comparable flexural behaviours were observed between the cast and printed textile reinforced concrete (TRC) specimens. Moreover, the flexural behaviours of printed specimens exhibited lower scatter than the flexural behaviours of cast specimens, which was probably due to the precise digitally controlled printing process. Future research should focus on the application of textile reinforcement in more complex 3D printed concrete structures

Assessment of plasterboards containing chemically modified gypsum waste

The standard recycling process for construction, refurbishment and demolition plasterboard waste involves several mechanical steps that include manual segregation, grinding, sieving, and ferrous and non-ferrous magnetic separation. However, one of the main challenges to obtain suitable recycled gypsum from refurbishment and demolition (post-consumer) plasterboard waste comes from the difficulty of achieving consistently high purity levels via current mechanical recycling technologies. In addition, post-consumer plasterboard waste contains water-soluble impurities that affect paper-gypsum bonding during plasterboard production. As a result, most post-consumer plasterboard waste is not recycled and ends up in landfills, decomposing and releasing toxic hydrogen sulphide, or used in low-grade applications such as agriculture or additive in cement production. A modified mechanical process and a novel acid leaching purification process were developed and combined to obtain a recycled gypsum product from post-consumer plasterboard waste with consistent purity values above 96 wt%, fulfilling all quality requirements from plasterboard manufacturers. After acid leaching, the purified gypsum was recovered via two methodologies: i) filtration and gypsum cake washing, and ii) acid neutralisation and filtration. Then, plasterboards with dimensions 200 mm × 200 mm × 12.5 mm were prepared at laboratory scale containing either 35 wt% of purified gypsum (washed or neutralised) or 10 wt% of business-as-usual recycled gypsum. These plasterboards were characterised to determine their thermal, physical and mechanical properties. The results showed no significant differences in the thermal, physical and mechanical properties of the plasterboards containing 35 wt% purified gypsum and the plasterboard with 10 wt% recycled gypsum. These findings validate the introduction of high shares of purified gypsum (35 wt%) during standard plasterboard manufacturing. </p

Impact of circular silica aerogel on plasterboard recycling

Silica aerogels have high specific surface area, high porosity, low density, and high thermal insulation values. These properties enhance the thermal performance of plasterboards but can have deleterious effects on the mechanical properties. At the end of life, plasterboards containing silica aerogel could be recycled via physical and acid leaching purification processes. The main aim of this work was to determine the impact of circular silica aerogel on plasterboard recyclability. Circular silica aerogel was produced through hydrothermal conversion of silica-based building waste. The circular silica aerogel was easily recovered during the acid leaching purification stage of the recycling process. Future work will evaluate the impact of silica aerogel on the thermal conductivity and mechanical strength of plasterboard containing circular silica aerogel.</p

Hyperspectral imaging sorting of refurbishment plasterboard waste

Post-consumer plasterboard waste sorting is carried out manually by operators, which is time-consuming and costly. In this work, a laboratory-scale hyperspectral imaging (HSI) system was evaluated for automatic refurbishment plasterboard waste sorting. The HSI system was trained to differentiate between plasterboard (gypsum core between two lining papers) and contaminants (e.g., wood, plastics, mortar or ceramics). Segregated plasterboard samples were crushed and sieved to obtain gypsum particles of less than 250 microns, which were characterized through X-ray fluorescence to determine their chemical purity levels. Refurbishment plasterboard waste particles 98 wt%. These findings underpin the potential implementation of an industrial-scale HSI system for plasterboard waste sorting.</p