The 1987 IRC 96 standard establishes provisional guidelines for applying two-layer surface dressing using cationic bitumen emulsion. It details the required materials, application procedures, and quality assurance protocols to enhance pavement longevity and performance, tailored especially for Indian road environments.
Overview
The 1987 IRC 96 standard establishes provisional guidelines for applying two-layer surface dressing using cationic bitumen emulsion. It details the required materials, application procedures, and quality assurance protocols to enhance pavement longevity and performance, tailored especially for Indian road environments.
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Contents
Structure
IRC 96 specifies provisional standards for road surface treatment via two-layer dressing using cationic bitumen emulsion, aiming to improve skid resistance and waterproofing. Key elements include material specifications for aggregates and bitumen emulsions, with focus on durability under Indian climatic and traffic conditions. Aggregate quality limits such as abrasion, impact, and water absorption are detailed alongside application formulas and parameters.
Defines physical and mechanical requirements for aggregates including Los Angeles abrasion, impact value, flakiness index, stripping value, water absorption, and soundness. Specifies aggregate grading for second coat (nominal 6.7 mm size) and typical material quantities per 10 square meters for both coats. Includes essential notes on temperature constraints during application and storage, base preparation standards, and binder handling.
Outlines precise quantities of cationic bitumen emulsion and aggregates per 10 square meters for the first and second coats. Reiterates aggregate quality limits and sizing for the second coat, emphasizing the importance of temperature thresholds and base preparation for successful application.
Details the construction methodology including aggregate requirements, material application rates, and base preparation. Specifies operational instructions related to weather limitations, binder preparation (rolling emulsion drums before use), uniform spraying methods, and aggregate spreading. Also covers rolling procedures to embed aggregates without crushing and sequence of operations for two-coat dressing.
Emulsions must be stored above 0°C and surface dressing applied only when ambient temperature exceeds 10°C. Base can be damp but free from standing water. These conditions are critical to ensure proper adhesion and durability of the surface dressing.
Describes shaping and grading the existing pavement base to a uniform level and camber, filling and compacting depressions and potholes, and thorough cleaning to remove dust and loose materials. For granular bases, washing is recommended. Specifies aggregate sizing and quantities as per the two-coat dressing requirements.
Specifies the use of cationic bitumen emulsion of rapid setting (RS) grade conforming to IS: 8887-1978 with minimum 60% bitumen content. Emulsions should be mixed by rolling unopened drums 5-6 times over 10 meters before use. Application must be done at temperatures above 10°C for optimal setting.
First coat involves spraying binder uniformly using mechanical sprayers or cans with 6 mm holes spaced at 30 mm intervals, followed by spreading coarse aggregate (nominal 13.2 mm size). Material quantities and weather conditions for application are specified to ensure proper bonding and surface integrity.
Second coat application uses finer aggregate (6.7 mm nominal size) and higher quantities of cationic bitumen emulsion compared to the first coat. Spraying and spreading techniques mirror the first coat with emphasis on temperature and base condition constraints.
Rolling should be performed with 6 to 8 tonne smooth-wheeled tandem rollers starting from edges towards the center, overlapping at least one-third of previous passes. Rolling aims to embed aggregates uniformly without crushing and includes adjusting aggregate distribution as required.
Traffic should preferably be allowed 24 hours after rolling the second coat, with a minimum of 4 hours if necessary. Initial traffic speeds should be restricted to 10 km/h to prevent displacement of aggregate. Surface maintenance involving addition of aggregates and binder may be required during early traffic.
Lists comprehensive tests for aggregates including abrasion, impact, flakiness, stripping, water absorption, and soundness. These ensure aggregates meet durability and strength requirements essential for long-lasting surface dressing.
Recommends conducting trial mixes to verify compatibility between aggregates and bitumen emulsion. Performance evaluation includes adhesion and stripping resistance tests as well as measuring surface texture and skid resistance after application.
Emphasizes proper storage conditions for bitumen emulsions, correct preparation of base and binder, and safe application practices including the use of mechanical sprayers. Highlights aggregate sizing and physical requirements to maintain safety and ensure quality in surface dressing.
Frequently Asked
IRC 96 specifies the use of cationic bitumen emulsion of Rapid Setting (RS) grade complying with IS: 8887-1978. It must contain at least 60% bitumen by weight and set by water breaking away to leave a black bitumen film. Advantages include lower fuel consumption, reduced pollution during heating, compatibility with all aggregates, resistance to wet conditions, and lower equipment costs, making it ideal for efficient two-coat surface dressing.
For the first coat, aggregates of nominal 13.2 mm size are used, spread right after spraying the cationic bitumen emulsion, ensuring removal of oversize particles for uniform coverage. The second coat requires finer aggregates with a nominal size of 6.7 mm, passing through a 9.5 mm sieve but retained on a 2.36 mm sieve. Application of the second coat should occur at least one hour after rolling the first coat, with quantity and rolling specifications to ensure proper embedment and adherence.
The standard recommends applying between 1.2 to 1.4 kg of bitumen emulsion per square meter with 0.01 to 0.012 cubic meters of aggregate for the first coat. For the second coat, use 1.6 to 1.8 kg of bitumen emulsion and 0.006 to 0.008 cubic meters of aggregate per square meter. Aggregates for the second coat should be 6.7 mm nominal size. Uniform spraying and rolling with a 6 to 8 tonne smooth roller are essential for durability.
Bitumen emulsions must be stored at temperatures above 0°C to prevent damage. Surface dressing application should only proceed when atmospheric temperature is above 10°C. The pavement base may be damp but must be free from any standing water to ensure proper adhesion and prevent premature failures.
Traffic should ideally be permitted 24 hours after rolling the second coat to allow the emulsion to cure fully and ensure aggregate bonding. If necessary, traffic may be allowed after 4 hours but at reduced speeds not exceeding 10 km/h. Traffic must never be allowed on the first coat alone to avoid loosening of aggregates.
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