scholarly journals Physical-mechanical properties and durability of ultra-high performance concrete (UHPC)

2021 ◽  
Vol 64 (2) ◽  
pp. 109-117
Author(s):  
Stefan Mitrović ◽  
Dragana Popović ◽  
Miroslav Tepavčević ◽  
Dimitrije Zakić
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Mean Value ◽  
Average Density ◽  
Chloride Ions ◽  
Ultra High Performance Concrete ◽  
History Of Development ◽  
History Of ◽  
Hardened State ◽  
Further Development

This paper presents the results of the authors' laboratory testing of physical, mechanical and durability properties of Ultra-high Performance Concrete (UHPC). The short history of development and application of UHPC concrete is presented in the first part of this paper while the second part deals with the experimental investigation, presenting the results of material characterization obtained from physical-mechanical and durability tests. Based on the results shown in the paper, the mean value of compressive strength obtained at 28 days is 114 MPa, with the average density of 2270 kg/m3 in hardened state. The results showed that tested UHPC belongs to the highest class of water impermeability V-III, as well as the highest class MS0 (without visible damage) in a simulated freeze-thaw environment and de-icing salt attack test. Also, the highest class XM3 for abrasion resistance was achieved. Additional tests showed that the tested concrete fulfils the requirements for the highest exposure classes XC4 and XD4, in terms of resistance to carbonation and the penetration of chloride ions. Conclusions and recommendations for further development and possible application of UHPC are presented at the end of paper.

scholarly journals Achieving Ultra-High Performance Concrete by Using Packaging Models in Combination with Nanoadditions

2021 ◽  
Author(s):  
Jesús Díaz ◽  
Jaime C. Gálvez ◽  
Marcos G. Alberti ◽  
Alejandro Enfedaque
Keyword(s):  
High Performance ◽  
Cement Hydration ◽  
High Performance Concrete ◽  
Discrete Models ◽  
Hydration Process ◽  
Ultra High Performance Concrete ◽  
Ratio And Proportion ◽  
Hardened State ◽  
Large Groups ◽  
Nanometric Size

This paper describes the packaging models that are fundamental for the design of ultra-high-performance concrete (UHPC), and their evolution. They are divided into two large groups: continuous and discrete models. The latter are those that provide the best answer in obtaining an adequate simulation of the packing of the particles up to nanometric size. This includes the interaction among the particles by means of loosening and wall coefficients, allowing a simulation of the virtual and real compactness of such particles. In addition, a relationship between virtual and real compactness is obtained, through the compaction index, which may simulate the energy of compaction that the particles undergo in their placement in the mold. The use of last-generation additives allows such models to be implemented with water-cement (w/c) ratios close to 0.18. However, the premise of maximum packing as a basic pillar for the production of UHPC should not be the only one. The cement hydration process affected by nanoadditions and the ensuing effectiveness in the properties in both fresh and hardened state according to the respective percentages in the mixture should also be studied. An adequate ratio and proportion of these additions may lead to an obtaining of better results even with lower levels of compactness.

Water Transport Properties and Depth of Chloride Penetration in Ultra High Performance Concrete

2016 ◽  
Vol 711 ◽  
pp. 137-142 ◽  
Author(s):  
Daniel Dobias ◽  
Radka Pernicova ◽  
Tomas Mandlik
Keyword(s):  
Water Transport ◽  
High Performance ◽  
Moisture Absorption ◽  
High Performance Concrete ◽  
Chloride Transport ◽  
Chloride Ions ◽  
Chloride Penetration ◽  
Chloride Diffusion ◽  
Ultra High Performance Concrete ◽  
Depth Of Penetration

Properties of water transport and depth of chloride penetration into the Ultra High Performance Concrete (hereafter as UHPC) with mild steel fibres are presented in this paper. The main aim of this experimental part of work is to obtain sufficiently accurate input data for the evaluation of long-term durability of architectural concrete which are connected with water transport and its accompanying effects such as biological degradation or chloride transport. The article also presents the one dimensional chloride diffusion into UHPC which can be potentially dangerous particularly for durability of reinforced concrete structures. For the simulation of aggressive environments the concrete samples were exposed to chloride solution for one year. Measured data were examined in relation to the depth of penetration of chloride ions into the UHPC structure. Comparative measurements with normal strength concrete (hereafter as NSC) are done as well. An about five-time lower value of moisture absorption of UHPC compared to the NSC was observed and further the curve of chloride penetration into the structure is significantly steeper for UHPC samples.

Development on the Corrosion of Steel Fiber and Prevention in the Ultra-High Performance Concrete (UHPC)

2021 ◽  
Vol 1036 ◽  
pp. 358-370
Author(s):  
Zhen Wen Guo ◽  
Xin Zhi Duan ◽  
Qiang Wang ◽  
Si Jia Wang ◽  
Xiao Lu Guo
Keyword(s):  
High Performance ◽  
Steel Fiber ◽  
High Performance Concrete ◽  
Chloride Ions ◽  
Control Methods ◽  
Ultra High Performance Concrete ◽  
Hybrid Fibers ◽  
Steel Bar ◽  
Corrosion Of Steel

Chloride ions, water, and oxygen could cause the corrosion of steel fiber in the aggressive environment. The corrosion of steel fiber in UHPC is a long-term process and the rate is very slow. As one of the important components of ultra-high performance concrete (UHPC), the corrosion of steel fiber is the result of multiple factors. The characteristics of steel fiber corrosion in UHPC, the factors influencing the corrosion of steel fiber in UHPC (including nanomaterials, curing condition and crack width), and effects of steel fiber corrosion on the UHPC performance (including mechanical properties, matrix rehydration and corrosion of steel bar), are emphatically elaborated. And the control methods of steel fiber corrosion in UHPC are briefly introduced, i.e. hybrid fibers and stainless steel fibers.

Diffusion of Chloride Ions in Ultra High Performance Concrete

2015 ◽  
Vol 1106 ◽  
pp. 21-24 ◽  
Author(s):  
Daniel Dobiáš ◽  
Radka Pernicová
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Concrete Surface ◽  
Chloride Ions ◽  
Transport Sector ◽  
Reinforcement Corrosion ◽  
Ultra High Performance Concrete ◽  
Depth Of Penetration ◽  
Chloride Ions Diffusion ◽  
Normal Strength

The article is dealing with study of chloride ions diffusion in ultra-high performance concrete UHPC, which might be potentially dangerous. Life of concrete structures, in particular in transport sector is jeopardized by risk of steel reinforcement corrosion with regards to exposure of the concrete surface to direct impact of de-icing salts. Measured data were examined in relation to the depth of penetration of chloride ions into the concrete structure. Experiment results proved that UHPC concretes are more resistant to penetration of chlorides than normal strength concretes.

scholarly journals Effect of Graphene Oxide on Mechanical Properties and Durability of Ultra-High-Performance Concrete Prepared from Recycled Sand

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1718 ◽  
Author(s):  
Hongyan Chu ◽  
Yu Zhang ◽  
Fengjuan Wang ◽  
Taotao Feng ◽  
Liguo Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Graphene Oxide ◽  
High Performance ◽  
High Performance Concrete ◽  
Construction Material ◽  
Chloride Ions ◽  
Raw Material ◽  
Ultra High Performance Concrete ◽  
River Sand ◽  
The Impact

Ultra-high-performance concrete (UHPC) has been used as an advanced construction material in civil engineering because of its excellent mechanical properties and durability. However, with the depletion of the raw material (river sand) used for preparing UHPC, it is imperative to find a replacement material. Recycled sand is an alternative raw material for preparing UHPC, but it degrades the performance. In this study, we investigated the use of graphene oxide (GO) as an additive for enhancing the properties of UHPC prepared from recycled sand. The primary objective was to investigate the effects of GO on the mechanical properties and durability of the UHPC at different concentrations. Additionally, the impact of the GO additive on the microstructure of the UHPC prepared from recycled sand was analysed at different mixing concentrations. The addition of GO resulted in the following: (1) The porosity of the UHPC prepared from recycled sand was reduced by 4.45–11.35%; (2) the compressive strength, flexural strength, splitting tensile strength, and elastic modulus of the UHPC prepared from recycled sand were enhanced by 8.24–16.83%, 11.26–26.62%, 15.63–29.54%, and 5.84–12.25%, respectively; (3) the resistance of the UHPC to penetration of chloride ions increased, and the freeze–thaw resistance improved; (4) the optimum mixing concentration of GO in the UHPC was determined to be 0.05 wt.%, according to a comprehensive analysis of its effects on the microstructure, mechanical properties, and durability of the UHPC. The findings of this study provide important guidance for the utilisation of recycled sand resources.

Flexural design of precast, prestressed ultra-high-performance concrete members

PCI Journal ◽  
2020 ◽  
Vol 65 (6) ◽  
pp. 35-61
Author(s):  
Chungwook Sim ◽  
Maher Tadros ◽  
David Gee ◽  
Micheal Asaad
Keyword(s):  
Prestressed Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
Limit State ◽  
Design Guidelines ◽  
Design Tool ◽  
Supplementary Cementitious Materials ◽  
Ultra High Performance Concrete ◽  
Concrete Members ◽  
Cylinder Strength

Ultra-high-performance concrete (UHPC) is a special concrete mixture with outstanding mechanical and durability characteristics. It is a mixture of portland cement, supplementary cementitious materials, sand, and high-strength, high-aspect-ratio microfibers. In this paper, the authors propose flexural design guidelines for precast, prestressed concrete members made with concrete mixtures developed by precasters to meet minimum specific characteristics qualifying it to be called PCI-UHPC. Minimum specified cylinder strength is 10 ksi (69 MPa) at prestress release and 18 ksi (124 MPa) at the time the member is placed in service, typically 28 days. Minimum flexural cracking and tensile strengths of 1.5 and 2 ksi (10 and 14 MPa), respectively, according to ASTM C1609 testing specifications are required. In addition, strain-hardening and ductility requirements are specified. Tensile properties are shown to be more important for structural optimization than cylinder strength. Both building and bridge products are considered because the paper is focused on capacity rather than demand. Both service limit state and strength limit state are covered. When the contribution of fibers to capacity should be included and when they may be ignored is shown. It is further shown that the traditional equivalent rectangular stress block in compression can still be used to produce satisfactory results in prestressed concrete members. A spreadsheet workbook is offered online as a design tool. It is valid for multilayers of concrete of different strengths, rows of reinforcing bars of different grades, and prestressing strands. It produces moment-curvature diagrams and flexural capacity at ultimate strain. A fully worked-out example of a 250 ft (76.2 m) span decked I-beam of optimized shape is given.

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