https://researchbank.swinburne.edu.au/file/7a73c7db-01bd-4899-a967-7b4720cafb78/1/2019-marchment-method_of_enhancing.pdf

Method of enhancing interlayer bond strength in construction scale 3D printing with mortar by effective bond area amplification

Advances in recycling can exceed traditional practice in that a non-renewable resource can at least become a partially renewable resource. This research attempts to support the cradle-to-cradle concept by testing the effect of reused recycled concrete aggregates (RRCA) on the fresh, physical, mechanical, and microstructure properties of self-compacting high-strength concrete (SCHSC). Two generations of recycled aggregate concrete (RAC) are produced; the first and second are created by recycled concrete aggregate (RCA) and by RRCA, respectively. For each generation, two replacement amounts are used (25% and 50% by mass). Results show that using RRCA does not affect the fresh properties of SCHSC, and up to 50% RRCA replacement amount by mass can be adopted for enhancing the mechanical and microstructure properties of reused recycled aggregate concrete (RRAC). Computed tomography indicates that the porosity of RRCA is less than that of RCA.

Properties of self-compacting high-strength concrete containing multiple use of recycled aggregate

Aggregate-bed 3D concrete printing with cement paste binder

Lack-of-fusion (LOF) in digital concrete fabrication is one of the paramount technical issues that must be elucidated before mass industry implementation of this emerging technology. This review paper initially accentuates the ramifications of poor interlayer bonding, which include impaired mechanical and thermo-mechanical performance in the hardened concrete state, durability issues pertaining to corrosion of reinforcing steel and the complexities associated with numerical modeling of 3D printed structures. Focus is then placed on the mechanisms that induce LOF, which constitute an intricate combination of mechanical interaction, chemical bonding and intermolecular forces between filaments. Comprehension of these mechanisms is required to develop appropriate solutions to this problem. The paper presents current interlayer bond strength (IBS) characterization tests and their associated (dis)advantages. Lastly, solutions employed in literature to reduce LOF are presented to give readers a holistic perspective of the current state-of-the-art surrounding LOF in 3D concrete printing.

A compendious review on lack-of-fusion in digital concrete fabrication

Influence of the pore morphology of high strength concrete on its fatigue life

Pore characteristics (>0.1 mm) of non-air entrained concrete destroyed by freeze-thaw cycles based on CT scanning and 3D printing

Evaluation of Damage in Concrete Suffered Freeze-Thaw Cycles by CT Technique

The mechanism of concrete deterioration in sodium sulfate solution is investigated. The macroperformance was characterized via its apparent properties, mass loss, and compressive strength. Changes in ions in the solution at different sulfate attack periods were tested by inductively coupled plasma (ICP). The damage evolution law, as well as analysis of the concrete’s meso- and microstructure, was revealed by scanning electron microscope (SEM) and computed tomography (CT) scanning equipment. The results show that the characteristics of concrete differed at each sulfate attack period; the drying-wetting cycles generally accelerated the deterioration process of concrete. In the early sulfate attack period, the pore structure of the concrete was filled with sulfate attack products (e.g., ettringite and gypsum), and its mass and strength increased. The pore size and porosity decreased while the CT number increased. As deterioration progressed, the swelling/expansion force of products and the salt crystallization pressure of sulfate crystals acted on the inner wall of the concrete to accumulate damage and accelerate deterioration. The mass and strength of concrete sharply decreased. The number and volume of pores increased, and the pore grew more quickly resulting in initiation and expansion of microcracks while the CT number decreased.

Experiment Analysis of Concrete’s Mechanical Property Deterioration Suffered Sulfate Attack and Drying-Wetting Cycles

Concrete damage characteristics were investigated by X-ray computed tomography (CT) under uniaxial compression, with medical X-ray CT and a loading device used to carry out real-time uniaxial compression scanning tests, obtaining two-dimensional CT images of crack generation, propagation, coalescence, and failure. Damage deterioration of internal structures under different loading conditions was analyzed by means of a digital image-processing technique, which allowed the recognition and extraction of meso cracks. Furthermore, the crack lengths were extracted and measured from CT images. Methods of divisional regions were applied to carry out the quantitative analysis of CT numbers in specific representative regions. The fractal dimensions (FDs) of crack propagation in CT images were estimated using the box-counting dimension, and the relationship between the strain, crack propagation, and FD examined. Complicated and disordered internal cracks were clearly observed with increased load. The results indicated that such CT tests were a promising means for identifying the evolution and propagation of internal cracks and for studying the mesoscopic damage fracture mechanism under uniaxial compression.

Wei Tian

Papers

Pore characteristics (>0.1 mm) of non-air entrained concrete destroyed by freeze-thaw cycles based on CT scanning and 3D printing

Evaluation of Damage in Concrete Suffered Freeze-Thaw Cycles by CT Technique

Experiment Analysis of Concrete’s Mechanical Property Deterioration Suffered Sulfate Attack and Drying-Wetting Cycles

Evaluation of Meso-damage Processes in Concrete by X-Ray CT Scanning Techniques Under Real-Time Uniaxial Compression Testing

Analysis on meso-damage processes in concrete by X-ray computed tomographic scanning techniques based on divisional zones