January 28, 1999

Takenaka Corporation

Japan's construction by-products problem is becoming increasingly serious, due to the short lives of buildings and the scarcity of disposal sites. A rapid increase in dismantling work is predicted for the future, and further reduction and recycling of construction by-products has become a dominant trend in the construction industry. In light of this trend, Takenaka together with Sekisui Chemical Co., Ltd. (Head Office: Osaka City, President: Susumu Nishizawa) has developed a method of obtaining three types of recycled products from waste PVC pipe rubbish.
The three types of recycling are as follows: (1) Recycling into general purpose PVC pipes (2) Recycling into short-term use PVC pipes, and (3) Recycling into coarse aggregate of a secondary concrete product.
PVC pipe is widely utilized in the construction industry mainly for water supply pipes and sewer pipes, due to its light weight, ease of processing, corrosion resistance, durability, and low cost.
In piping work, however, product of a fixed length (four meters) is carried in to building sites, so scrap is generated as rubbish, depending on the nature of the work. Incinerating this rubbish or PVC pipe rubbish from dismantled buildings has an undesirable impact on the environment, such as the generation of dioxins. In response to this problem, Takenaka is already tackling the development of mold materials from PVC resin waste materials, and on this occasion by engaging in new cooperation directly with a manufacturer, Takenaka has striven towards the development and implementation of a recycling method that will create high-quality products.

(1) Recycling into General Purpose PVC Pipe

In the manufacture of PVC pipe, the quantity of additives varies according to the purpose of use, which gives rise to many different types of pipe, which again differ slightly from manufacturer to manufacturer.
Restricting scrap to the same type of pipe from the same manufacturer enables a uniform product with no change in quality to be reproduced. In buildings such as collective housing where to a large extent the same product is used in large quantities, it is easy to collect scrap of the same type from the same manufacturer. Cooperation between the users, the general contractors, and the manufacturing side is of the utmost importance.
In terms of cost, taking into account the cost of recovery, it has been estimated to be approximately the same as existing products.

(2) Recycling into Short-Term Use PVC Pipe

If PVC pipe of different types and different manufacturers is mixed together, problems occur in terms of quality, so the product cannot be used for permanent buildings. These recycled products are for short-term use in temporary piping for construction work and so forth.
The cost of these recycled products is roughly equivalent to that of existing products, and conscious efforts must be made to promote the use of these products from the perspective of conserving the global environment.

(3) Recycling into Concrete Secondary Product Coarse Aggregate

Rubbish to which adhesive is attached, or which has already been used cannot be used as a recycling material for PVC pipe itself, so it is used as coarse aggregate of a concrete secondary product, such as concrete interblocking.
When manufacturing the concrete secondary product with crushed PVC chips, several percent of crushed PVC chips by weight is mixed in and stirred before being used.