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Penta-Ocean Construction Co., Ltd.
Takuzo Shimizu, President, CEO and Representative Director

Penta-Ocean Developed “Cured Road”, a construction method for curing invert concrete for a long period

Tokyo, Japan – May 22, 2018 – Penta-Ocean Construction Co., Ltd. (hereinafter “Penta-Ocean”) is pleased to announce that we have developed “Cured Road”, Kokai number, patent application laid-open disclosure number: 2018-25082, in cooperation with OKASANLIVIC. CO., LTD., Sekisui Plastics Co., LTD., and HAYAKAWA RUBBER CO., LTD., whose presidents are Katsutoshi Ogata, Masato Kashiwabara, and Masanori Hawakawa respectively. “Cured Road” is used for applying wet curing and insulated curing into the invert concrete of mountain tunnels for a long period in an effective and economical manner. Penta-Ocean has validated and found its practicability and effectiveness of curing, by implementing demonstration experiments at the construction sites.

For mountain tunnel construction work, it is typical to construct an invert at the rear of the working face, while the face operation is in progress, and that means it is necessary to secure a passage for carrying out excavation muck from the working face, and carrying in the machinery and equipment at the invert construction sites. Consequently, the following two methods have been provided so far: The first is a method to undertake the construction, dividing an invert into two, right and left, in order to secure the passage; The other is a method to construct the overall width at one time with a mobile pier. In both methods, however, once the invert obtains the strength to tolerate the wheel load of vehicle traffic in the tunnel, the invert concrete is reclaimed with the excavation muck without curing in an appropriate manner.
Inverts in the tunnel are one of the most crucial structural elements to secure the stability of the tunnel structure for a long period. It is essential to secure the long-term durability of the tunnel, by applying wet curing and insulated curing for a certain period of time and promoting a hydration reaction, in order to foster the strength revelation and densify the surface layer structure of the concrete, just like other concrete structures.
"URUON mat" is a curing mat, with high heat insulation property and water holding property against concrete planes and inclined grounds.
As a construction process of "Cured Road", lay the "URUON mat" on the entire concrete surface, then install an EPS block that is superior in durability and lightweight on the curing mat as a temporary roadbed. Thereby, "Cured Road" enables application of wet curing and insulated curing into the invert concrete for a long period, while the face operation is in progress, without dividing the invert into two right and left halves. Consequently, it helps develop the strength of the invert concrete, and densify the surface layer structure of the concrete.
The schematic views and use cases of "Cured Road" are shown in diagram 1, and picture 1 respectively.

The construction process of the present method, "Cured Road" is as follows:

  • 1.Once casting the invert concrete, manually lay the curing mat on the entire concrete surface
  • 2.Install the EPS block so it is manually cut according to the size and shape of the invert at a factory in advance, on the curing mat
  • 3.Lay an iron plate on the upper surface of the EPS block, in order to protect the EPS block, and disperse the wheel load
  • 4.Following the completion of the curing process, remove the iron plate, EPS block, and curing mat, and utilize them in the subsequent line.

The findings of the demonstration experiments at the construction sites are shown in diagram 2. It has been validated and found that strength increases by 24% in the invert, compared with the air curing method that is used in the standard construction process, and gas permeability, an index of density, decreases to 1/27.

Penta-Ocean has taken the initiative to promote "Cured Road", in order to improve the quality of construction work in mountain tunnels in an effective manner.

A wireless LAN boat”, (a tentative name)

Note 1: EPS block is available not only in the vehicle traffic zone, but also in an arbitrary range of spaces.
Note 2: EPS block can be divided into any number.

Diagram 1. Cross section of schematic views of "Cured Road"

  • Display of multiple design lines
  • Display of three-dimensional design lines

Picture 1. Usage examples of "Cured Road"

  • Display of multiple design linesa) Comparison of Compressive Strength for material age of 91 days
  • Display of three-dimensional design linesb) Gas Permeability for material age of 91 days

Diagram 2. Effect of wet curing and insulated curing applied to invert concrete for 28 days