Chip Seal Design Methods

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# Chip Seal Design Methods - PowerPoint PPT Presentation

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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### Chip Seal Design Methods

Vishwanath Pothukutchi

Introduction
• Early practitioners used empirical methods to design sealing a pavement.
• It was considered an art.
• Quantity of aggregate
• Quantity of bituminous binder.
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)
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%.
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%.
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.
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.
McLeod’s MethodEquations for Aggregate spread rate

Equations for Aggregate spread rate are as follows:

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.

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.

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