Tuesday, 9 May 2017

Moisture Content of RCCP

Moisture Content of RCCP

Moisture content of roller compacted concrete is a vital component that ultimately decides if the material will be a successful application or not.  An easy mental image to remember for properly proportioned RCC is a handful of damp gravel.  The two variables that moisture content can directly affect to is:

·         Adequate compaction
·         Long-term performance
Some things to consider regarding moisture content along the construction process are:
·         Verify the moisture content of the aggregates prior to mixing
·         Monitor the moisture content of RCC on the job site before paving begins
·         On the below moisture content curve, one ideally would like to be above the optimum moisture point to compensate for the loss of moisture during transportation and sitting time on the job site.  This is another reason why proper planning and preparation are so crucial to the construction process of roller compacted concrete.
There are several results that can be attained from either an RCC mix that is either too wet or too dry.  A mix with excessive moisture can lead to:
·         Poor compaction
·         Continous deformations during compaction
·         Adhesion to roller drum, causing more deformed surface textures
The results that can be possible due to a drier mix are:
·         Poor compaction
·         Segregation of the mixture, leading to a weaker, inconsistent pavement
·         Surface raveling, tears, and overall rough, open surface texture
Construction Practices
The process of applying RCCP from production to construction to compaction, is one that requires a timely schedule and minimal interruptions.  This cannot be said enough, following the basics can attribute to a successful application of RCCP.  To go along with the above stated, there are a few aspects of paving RCCP that one should keep in mind.

·         Production rates should match that of paving rates
·         Joint(fresh/cold) dimensions should be planned prior to construction
·         RCCP should be compacted no longer than 60 minutes after hydration of cement
The compaction times should be noted that these times can vary with variables such as ambient temperatures, wind speed, and retarding/accelerating admixtures.  The typical construction process of RCCP includes a typical ready mix concrete batch plant or RCC mixer(for more info see bottom), dump truck for transportation, and the standard “paving train” used for asphalt pavement.  Roller compacted concrete can be processed and compacted through a standard asphalt paver or high-density paver.  It should be noted that RCC should not and can not be applied through a conventional concrete paver or similar slip-form pavers.
Construction Process Photos of RCCP

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