METHODOLOGY FOR TACK COAT

 

Methodology for Tack Coat

 Tack coats should be applied uniformly across the entire pavement

1. Scope

This work shall consist of the application of a single coat of low viscosity liquid bituminous material to an existing bituminous road surface preparatory to the super imposition of a bituminous mix. Also application of tack coat to an absorbent granular surface is to prepare the surface for laying DBM layer over it.

2. Material & Manpower

The tack coat shall be rapid setting Bitumen Emulsion complying with IS.8887 and CSS – 1 Grade conforming to ASTM D2397/AASHTO M140, and shall be refinery produced. Reference to other controlling documents where appropriate as per technical specification.

3. Temporary Works

Temporary diversion will be constructed for vehicular traffic wherever necessary

4. Equipment

The distributor shall be self propelled bituminous pressure sprayer equipped for spraying the material uniformly at specified rates and temperature.    

5. Preparation of surface:

Where the surface is prime granular, all the loose material shall be removed. The surface on which the tack coat is to be applied shall be clean and free from dust, any extraneous material.

6. Application of Bituminous Primer

The rate shall cover the provision of tack coat at 0.20 to 0.25 Kg per Square Metre. The bituminous tack coat will be sprayed uniformly over the dry surface using  self  propelled sprayer equipped with self heating arrangement ,suitable pump ,adequate capacity   compressor  and  spraying bar with nozzles having constant pressure system capable of supplying tack coat at specified  rates and Temperatures  so as to provide a uniform unbroken spread of the tack coat.

7. Quality Control Work

For control of the quality of materials supplied and the works carried out, the relevant provision of Section 900 shall apply.

The contractor will submit an Inspection request to the Engineer at each relevant stage of works. 

Element	Visual Inspection	Quality Control Testing	Survey
Checking of prime top surface	*	*	*
Tack coat mix		*
Finished work	*	*

8. Safety

Caution boards will be placed at appropriate points cautioning/warning the approaching traffic and manpower with necessary cautioning equipments regulating the traffic and ensuring the necessary safety avoiding all hazards, which shall ensure the necessary safety precaution/mitigation measures                                                             

 9.   WORK METHODOLOGY

a)   Tack coat will be applied on the top of the prime coat / existing bituminous layer as per specifications.

b)      The materials used for tack coat are being tested in accordance with the technical specification .The tolerance limits were also checked in accordance with the technical specification.

c)  The surface to be tack coat will be swept clean, free from dust and will be dry.           

d)  Control checks will be carried out for the following and the frequency is as under.

i)        Quality of the binder ---Two samples per lot

ii)      Rate of spread of binder ----Two tests per day

iii)    These above said tests and frequencies are as per table 900-4 of MORT&H. The rate of spread of tack coat will be 2 to 2.5kg per 10 square meters as per Table 500-2 of MORT&H. In addition to these the sprayer nozzles will be cleaned at regular intervals.

CHECK LIST FOR PRIME COAT / TACK COAT 

Location          :                                                                       Date                :

Layer               :                                                                     Inspection No.           :

 

S.No.	Description	YES	NO	NA
1	Previous layer approved
2	Surface cleaned properly before spraying prime coat / Tack coat
3	Lab. equipments available for spray test
4	The surface to be primed shall be free from moisture
5	Weather is foggy, rainy, dusty or windy
6	Rate of spraying is as per calibrated
7	Quantity of spraying as per spec.
8	Surface temperature is more than 100C
9	Proper barricading is arranged for traffic management