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Chip Seal Design Methods

Chip Seal Design Methods. Vishwanath Pothukutchi. Introduction. Early practitioners used empirical methods to design sealing a pavement. It was considered an art. The Design involves calculating : Quantity of aggregate Quantity of bituminous binder. Introduction.

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Chip Seal Design Methods

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  1. Chip Seal Design Methods Vishwanath Pothukutchi

  2. Introduction • Early practitioners used empirical methods to design sealing a pavement. • It was considered an art. • The Design involves calculating : • Quantity of aggregate • Quantity of bituminous binder.

  3. Introduction • The various methods proposed were as follows: • Hanson’s Method (1934/35) • McLeod’s Method (1969) • Kearby’s Method (1953) • Modified Kearby’s Method(1981) • Road Note 39 (U.K.) • Austroads sprayed Seal Design Method. • TRH3(South Africa Method)

  4. Hanson’s Method • Designed primarily for cutback asphalt and was based on the Average Least Dimension(ALD) of the aggregate. • ALD was measured manually using calipers. • It was theorized that the voids after laying the aggregate in the binder were 50%.

  5. Hanson’s Method • When the layer is rolled it is reduced to 30%. • When the cover aggregate would be compacted by traffic it reduces to 20%. • Hanson specified that the % voids to be filled by binder to be 60% to 75%.

  6. McLeod’s Method • Aggregate application rate depends on gradation, shape and specific gravity. • Binder application rate depends on aggregate gradation, absorption, shape, traffic volume, residual asphalt content of binder. • Has been primarily developed for use with emulsion binders.

  7. McLeod’s Method Basic Principles : • The aggregate spread should be designed such that the resulting seal coat is one stone thick. • The binder spread rate should be designed such that the 70 % of the voids in aggregate are filled.

  8. McLeod’s MethodEquations for Aggregate spread rate Equations for Aggregate spread rate are as follows:

  9. McLeod’s Method • C is the Aggregate application rate V is the % of voids in loose aggregate H is the average least dimension G is the bulk specific gravity E is the traffic whip off factor.

  10. McLeod’s Method • The binder spread rate was given by the equation Here B is the binder spread rate. H is the Average least dimension T is the Traffic Volume Factor S is the Surface factor and A is the absorption factor and R is the % of asphalt residue.

  11. Kearby’s Method • In Kearby’s method the aggregate spread rate was dependent on average thickness, percentage aggregate embedment, bulk specific gravity, and quantity of aggregate required to cover one square yard of road way. • Kearby’s work resulted

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