First insights into a 3D-printed composite of Portland cement paste and reinforcing short fibers (carbon, glass and basalt fibers, 3–6 mm) are presented, resulting in novel materials that exhibit high flexural (up to 30 MPa) and compressive strength (up to 80 MPa). Alignment of the fibers, caused by the 3D-printing process is observed, opening up the possibility to use the print path direction as a means to control fiber orientation within the printed structures. Apart from completely dense cementitious bodies, hierarchically structured bodies, displaying precisely adjusted macroporosity, are presented, the latter exhibiting a unique combination of strength and materials efficiency.

Properties of 3D-printed fiber-reinforced Portland cement paste

This study develops a rheology control method to improve steel fiber distribution and flexural performance of ultra-high-performance concrete (UHPC) by adjusting the rheological properties of the suspending mortar of UHPC before steel fibers are added. Correlations among the plastic viscosity of the suspending mortar, the resulting steel fiber distribution, and flexural properties of UHPC are established. This was done by changing the dosage of viscosity modified admixture (VMA) for investigated UHPC mixtures. The optimal plastic viscosity of the suspending mortar that allows for the optimized fiber distribution and flexural performance of UHPC is determined. The plastic viscosity is correlated with the mini V-funnel flow time, which provides a simple alternative to evaluate the plastic viscosity. For a UHPC mixture with 2% micro steel fibers, by volume, the optimal mini V-funnel flow time of suspending motar was determined to be 46 ± 2 s, which corresponded to the optimal plastic viscosity (53 ± 3 Pa s) that ensures the greatest fiber dispersion uniformity and flexural performance of UHPC. However, increasing the VMA dosage retarded the hydration kinetics and reduced the degree of hydration, compressive strength, and the bond properties of the fiber-matrix interface of UHPC.

Improving flexural performance of ultra-high-performance concrete by rheology control of suspending mortar

Heavy metal oxide glasses as gamma rays shielding material

Experimental and numerical study of the flexural behaviour of ultra-high performance fibre reinforced concrete beams

Influence of fibre orientation on the tensile behaviour of ultra-high performance fibre reinforced cementitious composites

http://repositorium.sdum.uminho.pt/bitstream/1822/26273/1/IJ%28ISI%29_69.pdf

Relation between fibre distribution and post-cracking behaviour in steel fibre reinforced self-compacting concrete panels

In this work, mode I fracture parameters of steel fibre reinforced self-compacting concrete (SFRSCC) were derived from the numerical simulation of indirect splitting tensile tests. The combined experimental and numerical research allowed a comparison between the stress–crack width (σ–w) relationship acquired straightforwardly from direct tensile tests, and the σ–w response derived from inverse analysis of the splitting tensile tests results. For this purpose a comprehensive nonlinear 3D finite element (FE) modeling strategy was developed. A comparison between the experimental results obtained from splitting tensile tests and the corresponding FE simulations confirmed the good accuracy of the proposed strategy to derive the σ–w law for these composites. It is concluded that the post-cracking tensile laws obtained from inverse analysis provided a close relationship with the ones obtained from the experimental uniaxial tensile tests.

/pdf/tensile-stress-crack-width-law-for-steel-fibre-reinforced-3p6gorxu2r.pdf

Tensile stress–crack width law for steel fibre reinforced self-compacting concrete obtained from indirect (splitting) tensile tests

A meso-mechanical model to simulate the tensile behaviour of ultra-high performance fibre-reinforced cementitious composites

Adding fibres to concrete provides several advantages, especially in terms of controlling the crack opening width and propagation after the cracking onset. However, distribution and orientation of the fibres toward the active crack plane are significantly important in order to maximize its benefits. Therefore, in this study, the effect of the fibre distribution and orientation on the post-cracking tensile behaviour of the steel fibre reinforced self-compacting concrete (SFRSCC) specimens is investigated. For this purpose, several cores were extracted from distinct locations of a panel and were subjected to indirect (splitting) and direct tensile tests. The local stress-crack opening relationship (?-w) was obtained by modelling the splitting tensile test under the finite element framework and by performing an Inverse Analysis (IA) procedure. Afterwards the ?-w law obtained from IA is then compared with the one ascertained directly from the uniaxial tensile tests. Finally, the fibre distribution/orientation parameters were determined adopting an image analysis technique.

/pdf/the-influence-of-fibre-orientation-on-the-post-cracking-39a9snjexn.pdf

Amin Abrishambaf

Papers

Relation between fibre distribution and post-cracking behaviour in steel fibre reinforced self-compacting concrete panels

Influence of fibre orientation on the tensile behaviour of ultra-high performance fibre reinforced cementitious composites

Tensile stress–crack width law for steel fibre reinforced self-compacting concrete obtained from indirect (splitting) tensile tests

A meso-mechanical model to simulate the tensile behaviour of ultra-high performance fibre-reinforced cementitious composites

The influence of fibre orientation on the post-cracking tensile behaviour of steel fibre reinforced self-compacting concrete