Marshall Method ျဖင့္ ႏိုင္လြန္ကတၱရာ ( Hot Mix Asphalt) ဒီဇိုင္းျပဳလုပ္ျခင္း

အေ၀းေျပးလမ္းစီမံကိန္းတစ္ခုမွာ အသုံးျပဳခဲ့တဲ့  ႏိုင္လြန္ကတၱရာ Mix Design ျပဳလုပ္ပုံအဆင့္ဆင့္ကို ဘာသာျပန္ရန္ အခ်ိန္မရပါေသးပါသျဖင့္ စာနည္းနည္း ဓါတ္ပုံမ်ားမ်ားျဖင့္ မွ်ေ၀ေပးလိုက္ပါသည္။ စိတ္ပါ၀င္စားသူမ်ားအတြက္ ဗဟုသုတရႏိုင္လိမ့္မည္ဟု ထင္ပါသည္။

The correct design and physical testing of bituminous mixture for the road is important for sound, durable pavement to be constructed economically, and to ensure minimum maintenance during the design life of the pavement.

The following illustration is the procedure of Design and testing of bituminous mixture.

1. Heating constituents and apparatus
Bring all mix constituents and compaction mold assembles to the required temperature. e.g for 60/70 penetration grade bitumen a temperature of 130°C to 170°C.



2. Mix
Mix the heated constituents for each batch separately ensuring that the specimen is at the correct temperature for compaction.
The bowl temperature should be maintained by adjusting the Heater. Time from charging the bowl to compacting the mix procedure is 2 minutes.
Mix and subsequently compact the specimens in progressively increasing or decreasing order of bitumen content.



3. Compact
Charge the heated mold assembly with mixture; apply 75 blows of the hammer at a rate of 60 blows/minute. Reverse the mold, apply 75 blows to the lower face of the specimen. On completion, immerse the mold and specimen in cold water for at least 10 minutes.



4. Extrude and Store
Extrude the specimen from the mold and store at ambient temperature until ready to test.



5. Check Density
Weight in air and water; calculate the relative density and compacted aggregate density.



6. Temperature Curing
Prior to testing immerse specimens in water at 60°C for 45 to 75 minutes. Bring the Breaking Head to the same temperature immediately prior to testing.



7. Stability and Flow Test
Test each of the specimen in turn commencing with richer bitumen contents. Test for stability and flow at a nominal rate of strain of 50 mm/minute. Complete each test within 40 seconds of removing the specimen from the water bath to recording the reading.



8. Evaluate and Report
Stability, mix density, aggregate density and flow value are all used to determine the optimum bitumen content for the mix design. These are usually presented in graphical form. (Detailed Mix Design not included in this topic)




Ref : (1) Manual for Asphalt Pavement 1989 by Japan Road Association
        (2) Field Records

San Nwe, 02-Sep-2015