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# Laterite Road Building - Definition Question

## Laterite Road Building - Definition Question

(OP)
Looking for some help on definition terminology.

In a document on laterite roads the following data is presented

Base properties
PI = 15, P425 = 48; PM = 720
CBRs @ 98% BS Heavy = 24%
Cum. Traffic to end 2003 = 0.28 MESA

My question -
1) P425 represent a fraction but on what scale. is this percent passing 425 um sieves
2) What does PM stand for - I'm guessing screen size but would expect to see 710 um
3) BS Heavy - I understand what CBR is and associated percentage.
3) What does MESA stand for - I think Million Equivalent Single Axials

### RE: Laterite Road Building - Definition Question

1. P425 = Percentage material passing the 0.425 mm Sieve
2. PM = Plastic Modulus
3. BSH = British Standard Heavy Compaction

Tests involving moisture-density relationships, CBR and unconfined compression were carried out using the British Standard Heavy (BSH) energy level. If the British Standard Light (Proctor) compaction mould is utilised, the compactive effort for the BSH consist of the energy derived from a 4.5kg rammer falling through 45cm onto five layers, each receiving 27 blows. When the CBR mould is used, the BSH compactive effort is also derived from a 4.5kg receiving 62 blows in five layers (Osinubi 1998). Compaction was only carried out at BSH energy level to simulate the maximum expected strength gain that can be achieved on site.

4. MESA = Million equivalent standard axles

### RE: Laterite Road Building - Definition Question

(OP)
Great - thanks

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