Developed precast PC floor slab with waterproof performance

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NEXCO EAST (Chiyoda-ku, Tokyo) is working with Obayashi Corporation (Minato-ku, Tokyo) to reduce the time required for slab replacement work and improve the durability of slabs in the Expressway renewal project. We have developed a waterproof precast PC slab using reinforced concrete (UFC: Ultra High Strength Fiber Reinforced Concrete).

1 History of development

In order to provide safe and secure Expressway services, it is necessary to minimize the impact of construction regulations. The same is true for the slab replacement work in the Expressway renewal project, and it is important to reduce the number of work regulations during the construction period.

Therefore, we thought that it would be possible to shorten the number of construction days at the site by giving waterproofing properties to the precast concrete manufactured in the factory in advance, and in April 2018, we proceeded with development by joint research with Obayashi Corporation.

In addition, it has been known that reinforced concrete slabs accelerate the deterioration of concrete and reinforcing steel due to the effects of water resulting from cracks on asphalt pavement and damage to bridge surface drainage devices. It is important. By taking advantage of UFC's excellent water-blocking performance, it is possible to realize a highly durable floor slab without water penetrating inside the floor slab.

(1) Conventional method

(2) New construction method

2 Technology overview

UFC, which has excellent water barrier performance, is adhered to the upper surface of the floor slab at a thickness (2 to 5 cm) that does not cause cracking due to the load action during the production and operation of precast concrete, preventing the penetration of rainwater into the interior of the floor slab You.

The joint between UFC and precast PC floor slabs uses slim cleat R developed by Obayashi Corporation to ensure waterproof performance.

Using the full-scale floor slab cut-out model, a wheel load running test that considered the effects of repeated vehicles was performed, and the following performance was confirmed.

• Fatigue durability equal to or higher than conventional precast PC slabs
• The integrity of the concrete in the normal part of the precast slab and the UFC must be ensured
• Waterproof is maintained

3 Future plans

Through various structural examinations, performance confirmation experiments and wheel load running tests, it was confirmed that the precast PC slab had sufficient integrity, waterproof performance, strength and fatigue durability.

In the future, we will consider applying it to a real bridge in the Expressway renewal project.