9. Utilization of Recycled Crushed Stones for Soil Structures

      Recycled crushed stones (crushed concrete blocks from construction sites with adjusted grain size) are expected to be used for soil structures.
      In order to apply recycled crushed stones to the soil structures of railways, the Railway Technical Research Institute (RTRI) has studied compaction characteristics, durability under repeated train loads and the effects of rainwater on material deterioration.
      The study showed that the water absorption, indicating the water absorption capacity of crushed stones, is a good indicator of compaction characteristics, strength characteristics and durability against repeated loads. As an example (Fig. 1), the percentage of grain crush occurrence increases with the water absorption, depending on the repeated load range.
      Based on the above results, an applicable range of recycled crushed stones to soil structures was fixed, taking into account trainload and water influence, and the relevant quality (the water absorption and the abrasion loss indicating the abrasion disposition) was proposed.
      Fig. 2 shows an example of the applicable range of embankment and quality requirements. Recycled crushed stones are applicable to any range except track beds where the influence of train load is particularly strong, and the top one-meter layer of embankments. For temporary construction, however, all areas fall into the applicable range.

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