This presentation will introduce recent development of standards, guidelines, manuals, etc. published in Japan including the aspect of environmental safety to promote recycling of by-products in construction works. All of these are based on a common concept called "Basic Idea on Environmental Safety Quality and Inspection Method Common to Recycled Materials" proposed by METI (2012). Based on the basic concept, environmental safety quality was introduced to JIS and guidelines of slag and coal ash, etc. As a summary of them, "Recycling Guidelines for Port and Airport Maintenance" by MLIT has compiled the environmental safety quality stipulated in the recent standards, guidelines, manuals, etc. for each type of work, application, and kind of materials (amended 2018).
Before the basic concept, environmental safety of recycled materials had been evaluated conventionally according to the test method for soil in any case. As the test is applied on 2-mm sieved soil, concrete specimens had been crushed and sieved. Or, the test was conducted with the recycled material only, even though in actual recycling it is mixed with other materials and solidified. Thus, there had been concern that recycling of by-products could not proceed smoothly. The common basic concept was developed to solve such irrationality. However, since by-products are sometimes used to improve soil quality by mixing with soil, in such cases it is necessary to evaluate as soil.
Considering those points, a flow chart for typing of recycled material is proposed. First, application of the focusing recycled material is determined. Based on the application, if the recycled material is used as soil or will be reused as soil, tests for soil contamination countermeasure law should be applied. Otherwise, the material is classified according to possibility of direct ingestion path and arrival destination of leaching path such as sea water or groundwater. In case direct ingestion should be considered, an acid extraction test JIS K 0058-2 should be applied which simulates direct ingestion and extraction by stomach acid. Depending on the difference in leaching path, environmental safety criteria will be different. In case the leaching path is sea water the criteria for port application will be set, and the other cases the criteria for general application (severer than port application) will be set.
Under the common concept, recycled materials are evaluated based on their application condition. For example, slag aggregate for precast concrete is required to evaluate as road bed material. In this case concrete specimens with slag aggregate are cured and crushed to adjust the particle size to fit recycled roadbed material. Then, both leaching test using deionized water without further crushing (JIS K 0058-1 clause 5) and acid extraction test using 1M HCl using <2 mm sample (JIS K 0058-2) are conducted on the sample.
To reduce efforts in inspection, a two steps inspection system consisting of "Environmental Safety Type Inspection" (ESTI) and "Environmental Safety Delivery Inspection" (ESDI) is introduced. The “Application-simulating sample” is required to prepare in ESTI step only, for example, every 3 years of recycled material production. Here, all the hazardous items (Pb, As, Cd, Se, Cr(VI), Hg, F, B) should be measured. On the other hand, ESDI is required, for example, every 1 month or every lot. Raw by-product may be tested. Measured hazardous items can be reduced to Pb, As and Cd in case of copper slag.
Development of testing methods and standardization , Regulations and legislation
