Bond-slip behavior between stainless steel rebars and concrete

Maintenance of reinforced concrete structures is a prevailing topic, especially with regard to lifeline structures and bridges, many of which are now designed with a service life beyond 100 years. Reinforcement made of ordinary (carbon) steel may corrode in aggressive environments. Stainless steel, being much more resistant to corrosion, is a valid solution to facilitate the protection of the works, increasing the service life and reducing the need for repair and maintenance. Despite the potential for stainless steel to reduce maintenance costs, studies investigating the influence of stainless steel on the behavior of reinforced concrete structures are limited. This study investigated the bond behavior of stainless steel rebars by means of experimental tests on reinforced concrete specimens with different concrete cover thicknesses, concrete strengths, and bar diameters. In each case, identical specimens with carbon steel reinforcement were tested for comparison. The failure modes of the specimens were examined, and a bond stress-slip relationship for stainless steel bars was established. This research shows that the bond behavior of stainless steel rebars is comparable to that of carbon steel bars

Experimental investigation on confinement of columns with TRC: a comparison between basalt and carbon textile fabrics

The use of Textile Reinforced Concrete (TRC) is a promising solution in the confinement of RC columns. Based on an experimental campaign on 15 short cylindrical RC columns, this work aims to get a better understanding about the performance of basalt textile in the confinement of short RC columns by comparing basalt and carbon TRC. Furthermore, the impact of mixing short steel fibers in the TRC concrete matrix (F/TRC) is investigated. The test results show that columns confined with basalt textile and carbon textile are, in terms of strength and, to some extent, post-elastic behaviour, comparable. Basalt textile seems to be a valid alternative to carbon, without significant loss of performance, and it provides less environmental impact. Columns reinforced with F/TRC show that adding 2.5 Vol.-% of short steel fibers has a beneficial effect in the confinement

Fast relaxation in a fragile liquid under pressure

The incoherent dynamic structure factor of ortho-terphenyl has been measured by neutron time-of-flight and backscattering technique in the pressure range from 0.1 MPa to 240 MPa for temperatures between 301 K and 335 K. Tagged-particle correlations in the compressed liquid decay in two steps. The alpha-relaxation lineshape is independent of pressure, and the relaxation time proportional to viscosity. A kink in the amplitude f_Q(P) reveals the onset of beta relaxation. The beta-relaxation regime can be described by the mode-coupling scaling function; amplitudes and time scales allow a consistent determination of the critical pressure P_c(T). alpha and beta relaxation depend in the same way on the thermodynamic state; close to the mode-coupling cross-over, this dependence can be parametrised by an effective coupling Gamma ~ n*T**{-1/4}.Comment: 4 Pages of RevTeX, 4 figures (submitted to Physical Review Letters

Experimental Investigation of Basalt/Fibre Textile Reinforced Concrete Under Uniaxial Tensile Force

Among the various solutions to retrofit existing structures, local strengthening of structural elements with Textile Reinforced Concrete (TRC) is a relatively recent technology which is considered as a possible alternative to the well-known Fibre Reinforced Polymers (FRP). As a matter of fact, due to the drawbacks of FRP, such as the difficulty to be applied on wet surfaces, the hazardousness for the workers who apply the material, and the poor behaviour at high temperature, TRC is recently gaining more popularity. The current concern about environmental issues is leading to a higher interest about the impact of materials production and their disposal at the end of life. With reference thereto, basalt textile fabrics is a material that is gaining attention due to its mechanical performances and low environmental impact. Admixing short fibres in the cementitious matrix of the TRC leads to a new material called Fibre/Textile Reinforced Concrete (F/TRC), which performs significantly bet-ter on strengthening solutions. The aim of this work is to investigate the different behaviour of a layer of Basalt-TRC (B-TRC) and Basalt-F/TRC (B-F/TRC) under tension via uniaxial tensile test. The experimental test campaign comprehends 3 B-TRC and 3 B-F/TRC specimens. The presence of short steel fibres in the cementitious matrix remarkably improves the performances of TRC in terms of maximum tensile force reached during the test and crack distribution. The significant improvement of performances of B-F/TRC com-pared to the B-TRC is expressed by the average maximum force, which increased of about 84%

CONFINEMENT OF COLUMNS WITH TEXTILE REINFORCED CONCRETE: AN EXPERIMENTAL COMPARISON BETWEEN BASALT AND CARBON TEXTILE REINFORCED CONCRETE

Confinement of existing RC columns by means of Textile Reinforced Concrete (TRC) is a technology developed in recent times. When using TRC as a mean of confinement, basalt textile fabrics are of particular interest due to their mechanical properties combined with low environmental impact. Furthermore, research performed by the Authors shows that the concrete matrix admixed with short dispersed fibres significantly improves the performance of TRC strengthening solutions in general. The addition of short dispersed steel fibres in the concrete matrix leads to a new material called Fibre/Textile Reinforced Concrete (F/TRC). Through an experimental campaign, an investigation about the influence on the confinement of the following two variables was conducted: the material of the textile fabric (basalt and carbon), and the presence of short dispersed steel fibres admixed to the concrete matrix. A total of 15 short cylindrical RC columns were tested under uniaxial compression. The results show that the performances of basalt and carbon textiles used for confinement are comparable, both in terms of strength and, to some extent, of post-elastic behaviour, highlighting the possibility of using basalt as an alternative to carbon without significant performance losses and combined with reduced environmental impact. Furthermore, F/TRC solutions outperformed traditional TRC, showing the beneficial effect of the short dispersed steel fibres to the performance of the strengthened specimens

CONFINEMENT OF COLUMNS WITH TEXTILE REINFORCED CONCRETE: AN EXPERIMENTAL COMPARISON BETWEEN BASALT AND CARBON TEXTILE REINFORCED CONCRETE

Confinement of existing RC columns by means of Textile Reinforced Concrete (TRC) is a technology developed in recent times. When using TRC as a mean of confinement, basalt textile fabrics are of particular interest due to their mechanical properties combined with low environmental impact. Furthermore, research performed by the Authors shows that the concrete matrix admixed with short dispersed fibres significantly improves the performance of TRC strengthening solutions in general. The addition of short dispersed steel fibres in the concrete matrix leads to a new material called Fibre/Textile Reinforced Concrete (F/TRC). Through an experimental campaign, an investigation about the influence on the confinement of the following two variables was conducted: the material of the textile fabric (basalt and carbon), and the presence of short dispersed steel fibres admixed to the concrete matrix. A total of 15 short cylindrical RC columns were tested under uniaxial compression. The results show that the performances of basalt and carbon textiles used for confinement are comparable, both in terms of strength and, to some extent, of post-elastic behaviour, highlighting the possibility of using basalt as an alternative to carbon without significant performance losses and combined with reduced environmental impact. Furthermore, F/TRC solutions outperformed traditional TRC, showing the beneficial effect of the short dispersed steel fibres to the performance of the strengthened specimens