scholarly journals Effects of Autogenous and Stimulated Self-Healing on Durability and Mechanical Performance of UHPFRC: Validation of Tailored Test Method through Multi-Performance Healing-Induced Recovery Indices

2021 ◽  
Vol 13 (20) ◽  
pp. 11386
Author(s):  
Estefanía Cuenca ◽  
Francesco Lo Monte ◽  
Marina Moro ◽  
Andrea Schiona ◽  
Liberato Ferrara
Keyword(s):  
High Performance ◽  
Mechanical Performance ◽  
Concrete Structures ◽  
Chloride Penetration ◽  
Fiber Reinforced Concrete ◽  
Test Method ◽  
Experimental Methodology ◽  
Chloride Diffusion ◽  
Self Healing ◽  
Crack Sealing

Chloride diffusion and penetration, and consequently chloride-induced corrosion of reinforcement, are among the most common mechanisms of deterioration of concrete structures, and, as such, the most widely and deeply investigated as well. The benefits of using Ultra-High Performance (Fiber-Reinforced) Concrete—UHP(FR)C to extend the service life of concrete structures in “chloride attack” scenarios have been addressed, mainly focusing on higher “intrinsic” durability of the aforementioned category of materials due to their compact microstructure. Scant, if nil, information exists on the chloride diffusion and penetration resistance of UHPC in the cracked state, which would be of the utmost importance, also considering the peculiar (tensile) behavior of the material and its high inborn autogenous healing capacity. On the other hand, studies aimed at quantifying the delay in chloride penetration promoted by self-healing, both autogenous and autonomous, of cracked (ordinary) concrete have started being promoted, further highlighting the need to investigate the multidirectional features of the phenomenon, in the direction both parallel and orthogonal to cracks. In this paper, a tailored experimental methodology is presented and validated to measure, with reference to its multidirectional features, the chloride penetration in cracked UHPC and the effects on it of self-healing, both autogenous and stimulated via crystalline admixtures. The methodology is based on micro-core drilling in different positions and at different depths of UHPC disks cracked in splitting and submitted to different exposure/healing times in a 33g/L NaCl aqueous solution. Its validation is completed through comparison with visual image analysis of crack sealing on the same specimens as well as with the assessment of crack sealing and of mechanical and permeability healing-induced recovery performed, as previously validated by the authors, on companion specimens.

scholarly journals Mechanical Recovery of Cracked Fiber-Reinforced Mortar Incorporating Crystalline Admixture, Expansive Agent, and Geomaterial

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Abdul Salam Buller ◽  
Fahad ul Rehman Abro ◽  
Kwang-Myong Lee ◽  
Seung Yup Jang
Keyword(s):  
Water Flow ◽  
Mechanical Performance ◽  
Water Flow Rate ◽  
Self Healing ◽  
Test Results ◽  
Fiber Reinforced ◽  
Dissipation Energy ◽  
Expansive Agent ◽  
Strength Recovery ◽  
Crack Sealing

This research is sought to characterize the stimulated autogenous healing of fiber-reinforced mortars that incorporate healing agents such as crystalline admixtures, expansive agents, and geomaterials. The effects of the healing materials on mechanical performance and water permeability were evaluated experimentally. Furthermore, microscopic and microstructural observations were conducted to investigate the characteristics and physical appearance of healing products within healed cracks. Test results are presented herein regarding index of strength recovery (ISR), index of damage recovery (IDR) and index of dissipation energy gain (IDEG) in relation to crack healing, and reduction of water flow rate. The self-healing capability of the mortars was greater in terms of resisting water flow rather than recovering mechanical performance likely because water flow depends on surface crack sealing, whereas mechanical performance depends on bonding capacity as well as full-depth healing of cracks; thus, mechanical performance may further be improved after longer healing duration.

Chloride Ion Diffusion Coefficient of HPFRCC after Loading

2014 ◽  
Vol 898 ◽  
pp. 391-394
Author(s):  
Kyung Joon Shin
Keyword(s):  
Tensile Strength ◽  
High Performance ◽  
Chloride Ion ◽  
Fiber Reinforced Concrete ◽  
Chloride Diffusion ◽  
Fiber Reinforced ◽  
Ion Diffusion ◽  
High Performance Fiber ◽  
Inherent Problem ◽  
Chloride Ion Diffusion

Various methods have been used to reinforce cementitious material such as mortar and concrete that have weak tensile strength. Fiber Reinforced Concrete is one of the reinforcing methods that mixes a matrix with fibers that have strong tensile strength. Recently, High Performance Fiber Reinforced Cementitious Composites (HPFRCC) have been developed. HPFRCC provides a possible solution to this inherent problem of cracking by smearing one or several dominant cracks into many distributed microcracks. The present study explores the ductility characteristics of HPFRCC by measuring chloride diffusion coefficients after load is applied.

scholarly journals Performance of Cracked Ultra-High-Performance Fiber-Reinforced Concrete Exposed to Dry-Wet Cycles of Chlorides

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Longlong Niu ◽  
Shiping Zhang
Keyword(s):  
Reinforced Concrete ◽  
Flexural Strength ◽  
High Performance ◽  
Chloride Ion ◽  
Fiber Reinforced Concrete ◽  
Steel Fibers ◽  
Self Healing ◽  
Fiber Reinforced ◽  
High Performance Fiber ◽  
Corrosion Of Steel

This paper presents an experimental study on the performance of cracked ultra-high-performance fiber-reinforced concrete (UHPC) exposed to dry-wet cycles of 3.5% NaCl solution under the temperature of 60°C. The results show that the wider the crack, the higher the corrosion degree of steel fibers embedded in UHPC, and the deeper the chloride ion diffusion on both sides of the crack. With the increase of dry-wet cycles, the flexural strength of precracked UHPC first decreases and then increases, and the lowest flexural strength was observed in 60 dry-wet cycles. Although self-healing is hard to cease the corrosion of steel fibers, it can relieve the corrosion of steel fibers and improve the flexural strength exposed to 100 dry-wet cycles.

scholarly journals Improving the Mechanical Performance of Shell Precast Concrete Blocks for Coastal Protection Structures of Hydraulic Works

2021 ◽  
Vol 11 (1) ◽  
pp. 6787-6791
Author(s):  
N. Viet Duc
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
High Performance ◽  
Mechanical Performance ◽  
Precast Concrete ◽  
Reference Beam ◽  
Concrete Cover ◽  
Fiber Reinforced Concrete ◽  
Bending Test ◽  
Coastal Protection

Although the use of concrete and reinforced concrete for construction has been widespread, more studies are needed on marine structures exposed directly to corrosive environments to prolong their service life. This paper proposes a new type of shell precast concrete block for coastal structures, studying a beam consisting of 15mm High-Performance Glass Fiber-Reinforced Concrete (HPGFRC) at the bottom and 45mm Traditional Concrete (TC) for the rest of the structure. Steel bar reinforcements were placed at the bottom with a concrete cover of 25mm to avoid abrupt failure. The strength classes of HPGFRC and TC were 60MPa and 30MPa respectively. A reference beam consisting of TC only was also prepared for comparison. The four-point flexural bending test results showed that the first cracking strength of the proposed beam was 20% higher, as HPGFRC performed better on tension than TC. Additionally, HPGFRC's maximum strength was 25% greater than TC's. Furthermore, HPGFRC possessed more durable characteristics such as waterproof grade, abrasion resistance, and shrinkage than TC, promising to protect the reinforcement from the aggressive marine environment and corrosion, prolonging the service life of the structure.

scholarly journals Analysis of Chloride Penetration Into High Performance Concrete

2020 ◽  
Vol 3 (3) ◽  
pp. 295-305
Author(s):  
Silvija Mrakovčić ◽  
Natalija Bede ◽  
Ivan Ušić
Keyword(s):  
Reinforced Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
Concrete Structures ◽  
Chloride Penetration ◽  
Reinforced Concrete Structures ◽  
Wetting And Drying ◽  
Chloride Corrosion ◽  
Structure Degradation ◽  
Astm C1202

Corrosion of reinforcement is one of basic destruction mechanisms of reinforced concrete structures. In that sense, the most affected structures are those by the sea, especially their parts subjected to cycles of wetting and drying. Chlorides penetrate to concrete mostly by diffusion, faster if the concrete is more permeable, destructing reinforcement passive protection and causing its corrosion, reduction of reinforcement cross section and bearing capacity of the structure. Retardation of chloride corrosion that causes structure degradation in marine environment can be achieved by the usage of quality concrete with enhanced strength and permeability parameters in regards to ordinary concrete. Mixes of ordinary and high performance concrete with different ratio of silica fume have been made. Compressive strength and resistivity to chloride penetration have been tested on the specimens 28 days after mixing. The resistivity to chloride penetration has been determined by fast chloride penetration test according to ASTM C1202 standard, using appliance that measures electrical conductivity of concrete specimens. Based on test results, the suitability of building reinforced concrete structures by the sea using high performance concrete has been analysed.

scholarly journals Failure Analysis of Ultra High-Performance Fiber-Reinforced Concrete Structures Enhanced with Nanomaterials by Using a Diffuse Cohesive Interface Approach

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1792
Author(s):  
Umberto De Maio ◽  
Nicholas Fantuzzi ◽  
Fabrizio Greco ◽  
Lorenzo Leonetti ◽  
Andrea Pranno
Keyword(s):  
Reinforced Concrete ◽  
High Performance ◽  
Concrete Structures ◽  
Structural Response ◽  
Short Fiber ◽  
Fiber Reinforced Concrete ◽  
Fiber Reinforced ◽  
Graphite Nanoplatelets ◽  
Cohesive Interface ◽  
High Performance Fiber

Recent progresses in nanotechnology have clearly shown that the incorporation of nanomaterials within concrete elements leads to a sensible increase in strength and toughness, especially if used in combination with randomly distributed short fiber reinforcements, as for ultra high-performance fiber-reinforced concrete (UHPFRC). Current damage models often are not able to accurately predict the development of diffuse micro/macro-crack patterns which are typical for such concrete structures. In this work, a diffuse cohesive interface approach is proposed to predict the structural response of UHPFRC structures enhanced with embedded nanomaterials. According to this approach, all the internal mesh boundaries are regarded as potential crack segments, modeled as cohesive interfaces equipped with a mixed-mode traction-separation law suitably calibrated to account for the toughening effect of nano-reinforcements. The proposed fracture model has been firstly validated by comparing the failure simulation results of UHPFRC specimens containing different fractions of graphite nanoplatelets with the available experimental data. Subsequently, such a model, combined with an embedded truss model to simulate the concrete/steel rebars interaction, has been used for predicting the load-carrying capacity of steel bar-reinforced UHPFRC elements enhanced with nanoplatelets. The numerical outcomes have shown the reliability of the proposed model, also highlighting the role of the nano-reinforcement in the crack width control.

Sign in / Sign up

Export Citation Format

Share Document