Steel Fibre Reinforced Concrete/Polymer
UHPFRC is a highly dense, steel fibre-reinforced cementitious composite material having compressive strength in excess of 170 MPa; a tensile strength of over 8 MPa; and a flexural strength of more than 30 MPa. The high strength of UHPFRC is achieved by improving concreting techniques and materials (the addition of ultrafine pozzolans) and by having a very low water-cement ratio, high quality and higher dosages of superplasticizers, high cementitious material content, and optimum volume of high strength ductile steel fibres. The use of steel fibres is to prevent the growth and interconnectivity of microcracks by absorbing the tensile stresses. The microcracks join together forming macrocracks.
For further information, contact:Why UHPFRC?
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1. Low water-cement ratio: As a rule of thumb in concrete technology, the lower the water-cement ratio, the higher will be the strength. A low water-cement ratio helps in reducing pore spaces and further increasing the binding between hydration products and aggregates. In addition to the w/c ratio, other strengthgoverning parameters are properties of the constituents, mixing procedure, mixer type, curing regime, and curing type.
2. Ductility: The higher flexural and tensile strengths of UHPFRC are due to the addition of steel fibres. The steel fibres in the vicinity of the flexural and tensile cracks offer more efficient transfer of stresses. Thereby, reducing the crack propagation rate enhances the ductility of the material.
In case of Tunnels and Underground Structures, water seepage is the most common cause of deterioration of concrete and its structures. However, deficiencies could be the result of substandard design/construction, or the result of unforeseen or changing geologic conditions in the ground that supports the tunnel. Another common reason for repairs is that many tunnels might have outlived their designed life expectancy and therefore the construction materials themselves could start degrading. Due to
Causes of Tunnel Degradation
Deterioration in tunnels may be caused by any of the various factors listed below:
- Water Infiltration
- Cracked and separated joints
- Lack of tightness
- Design or construction mistakes
- Corrosion of embedded metals
- Thermal load Effects
- Steep fill slopes above tunnels
- Changing of geologic conditions
- Poor Workmanship
- Deterioration of mortar
- Degradation in concrete strength
- Longitudinal loads on tunnels
- Longitudinal spreading of foundations
- Longitudinal differential settlement
- Swelling soil and invert damage
- Spall of tunnel crown joints.
- Loss of support due to erosion
- Seismic load and shape distortion
- Chemical action on lining
- Damage to surface finishes
- Clogging drainage due to fines
- Cracks in track/road slab
- Inclined tension cracks at the base
- Differential movement at crown
- Ingress of dissolved gases
- Damage in repair system
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