Thermal power plants produce coal ash, and can supply it to civil engineers who can put it to effective use as road base material. The Kansai Electric Power Co., Inc. paved its private road using cement-stabilized fly ash as a road base material. The demonstration test verified its quality and the facility of the work.

2. Method of Demonstration and Testing

The material test of supplied coal ash detected no harmful matter. The mixture was then tested as to its strength capabilities as follows:

(1) Material test
(Physicochemical analysis, harmful matter elution analysis)

     - The test results verified that the material complied with the criteria 
       specified in the "Prime Minister's Decree for Standardizing Industrial 
       Wastes That Contain Metals" issued from the Prime Minister's Office in 
       1980.

(2) Mixture test

    - After a seven-day curing period, the road base shall have the unconfined
      compression strength qu of 30 kgf/cm2; the subbase, 10 kgf/cm2. Thus,
      13% cement served as additive content in the road base; 6% cement, in the 
      subbase.

(3) Structure design

    - The surface paving thickness was determined so that the test road section 
      (with cement-stabilized fly ash) had a surface paving thickness equal to 
      the converted equivalent of the control road section (with crusher-run and 
      other gravel). (See Fig. 1.)

Fig. 1  Overview Plan and Cross-section of Experimental Construction
        (Private Road at Nanko Power Station)

3. Demonstration Test Results

(1) Quality

    - The strength of the road surface meets the requirements specified in the 
      Plant-recycled Paving Technique Guidelines drawn up by the Japan Road
      Association.

    - According to the maintenance control indices (MCI) provided by the Ministry 
      of Construction, the long-term endurance duration proved to be excellent 
      because the five-year follow-up examination revealed little or no 
      irregularity across the road or irregularity along the road, deflection, 
      or percentage of cracks.
     (See Fig. 2.)

Fig. 2  Transitions in Maintenance Control Indices Provided by the Ministry 
        of Construction (Private Road at Nanko Power Station)

(2) Facility of work, and other problems

    -It was difficult to stir the mixture for uniformity, to readjust the water 
     content,and to compact loose material.  And it was necessary to halt 
     construction work for curing time.  Solving such problems involves 
     standardizing material treatment, construction technique, maintenance, and 
     other procedures.