Bituminous mixes and materials require the use of anti-stripping agents to maintain the adhesion between bitumen and aggregates, especially when submerged in water. These agents help to prevent stripping by enhancing the affinity between hydrophilic aggregates and bitumen, which is essential for the durability and effectiveness of the pavement. Without anti-stripping agents, water can cause the bitumen film to separate from the aggregates, leading to reduced pavement life and increased maintenance costs.
By using anti-stripping agents in bituminous mixes, it is possible to improve the overall quality of the pavement by preventing water damage and ensuring that the aggregates remain securely bonded to the bitumen. This is especially important in areas with high rainfall or where the pavement is frequently exposed to water, such as bridges and coastal roads. The use of anti-stripping agents can also reduce the need for frequent maintenance and repair work, resulting in cost savings over the life of the pavement.
Overall, the importance of anti-stripping agents in bituminous mixes and materials cannot be overstated. These agents play a critical role in maintaining the adhesion between bitumen and aggregates, even when submerged in water, and can significantly improve the durability and effectiveness of the pavement. By using anti-stripping agents, it is possible to ensure the long-term integrity and safety of the pavement, while reducing maintenance costs and minimizing disruptions to traffic.
Material Requirement
The paragraph describes the requirements for anti-stripping agents. According to the paragraph, these agents should be composed of fatty acid amines with a long hydrocarbon chain. Additionally, the agents must meet specific chemical and physical standards, which are detailed in a table that is not included in the given context.
| Sl No | Test | Method | Limit |
| 1 | Appearance | Visual | Liquid/Solid |
| 2 | Odor | Smelling | Agreeable |
| 3 | Specific gravity 27oC | IS: 1202-1978 | 0.860-1.03 |
| 4 | Pour point oC Maximum | IS: 1448 | 42 |
| 5 | Flashpoint (COC) Minimum | IS: 1448 | 150 |
| 6 | Water content percent Vol. Maximum | IS: 1448 | 1 |
| 8 | Total base value mg KOH/g minimum | ASTM D 664 | 200 |
| 9 | Nitrogen content percent Wt. minimum | Elemental Analyser | 7 |
| 10 | Stripping value with bitumen containing 1 percent Wt. anti-stripping compound at 40oC, 24 hours | IS: 6241 | No stripping |
| 11 | Underwater coating test | IS: 6241 | Complete Coating |
| 12 | Thermal stability at 163oC, 5 hours | IS: 6241 | Should not lose its efficacy |
| 13 | Boiling water test percent minimum coating | ASTM D 3625 | 95 |
| 14 | Retained Marshall Stability percent minimum | Marshall Stability Test | 75 |
Storage and Handling
Anti-striping agents are a type of chemical used in various industrial processes. It is crucial to store them correctly to prevent any potential hazards. These agents must be stored in closed containers made of steel or aluminum. Containers made of zinc, copper, polythene, PVC, and most types of rubber are not suitable for storing anti-striping agents.
It is important to note that most anti-stripping agents can cause skin irritation and eye irritation. Therefore, it is imperative to take necessary precautions while handling them, especially in the case of liquid anti-stripping agents. Protective gloves for hands and goggles for the eyes should be used to prevent any contact with skin or eyes.
In summary, to ensure safe handling of anti-striping agents, proper storage in appropriate containers made of steel or aluminum is required. Additionally, it is important to use protective gear like gloves and goggles while handling these agents to prevent any potential health hazards caused by skin or eye contact.
1. Use in Sprayed Work
a. Additive Dosage
The determination of the appropriate dosage of an anti-stripping agent for an aggregate depends on two factors: the nature of the aggregate and its size, also known as the stepping value. A table is provided with the recommended minimum dose of the anti-stripping agent for sprayed work, but it is important to note that the actual dosage needed for a specific site must be determined in the laboratory.
This means that the recommended dosage provided in the table may not be suitable for every site condition. Therefore, it is necessary to conduct laboratory tests to determine the appropriate amount of anti-stripping agent needed based on the aggregate’s nature and size in relation to the specific site conditions. This ensures that the correct dosage is used, which can prevent the occurrence of stripping, a phenomenon where the bond between the asphalt and the aggregate is weakened, leading to premature pavement failure.
| Aggregate stripping value | Dose of the anti-stripping agent in percent by weight of bitumen | Dose of the anti-stripping agent in percent by weight of bitumen | Dose of the anti-stripping agent in percent by weight of bitumen | Dose of the anti-stripping agent in percent by weight of bitumen |
| Surface dressing with precoated aggregate | Penetration Macadam/Built-up spray grout | Surface Dressing with uncoated aggregate | Liquid seal coat | |
| 0-25 | 0.5 | 0.6 | 0.7 | 0.8 |
| 25-50 | 0.6 | 0.7 | 0.8 | 1.0 |
| 50-100 | 0.8 | 1.0 | 1.0 | 1.0 |
b. Mixing Procedure During Construction
The proper method for incorporating an anti-stripping agent into bituminous material involves thorough mixing of the agent with either liquid bitumen or the bitumen itself. The agent can be obtained in either liquid, solid, or concentrated form.
When straight run bitumen is used, the correct dosage of the anti-stripping agent should be mixed in a hot bitumen tank boiler. Both constituents must be agitated until the anti-stripping agent is completely blended with the bitumen.
It may be necessary to increase the dose of the anti-stripping agent if the binder is expected to remain in the bitumen boiler for an extended period. By doing so, the effectiveness of the agent will be maintained, thereby reducing the likelihood of stripping.
Use In Premix Work
a. Additive Dosage
To determine the appropriate dosage of an anti-stripping agent for a given aggregate, several factors must be considered, including the nature and size of the aggregate. These factors are important because they can impact the effectiveness of the anti-stripping agent.
For sprayed work, a minimum recommended dosage of the anti-stripping agent has been established and is presented in a table. It is important to follow these recommendations to ensure that the aggregate is properly treated and that the risk of stripping is minimized.
Overall, the dosage of an anti-stripping agent must be carefully determined and applied in accordance with established guidelines to ensure that it is effective in preventing stripping and maintaining the quality of the pavement.
| Aggregate stripping value | Dose of the anti-stripping agent in percent by weight of bitumen | Dose of the anti-stripping agent in percent by weight of bitumen | Dose of the anti-stripping agent in percent by weight of bitumen |
| Void content 3-5 % | Voids content 5-10 % | Voids above 10 % | |
| 0-25 | 0.3 | 0.4 | 0.5 |
| 25-50 | 0.4 | 0.5 | 0.6 |
| 50-100 | 0.6 | 0.8 | 1.0 |
b. Mixing Procedure During Construction
To ensure a homogeneous mix, it is necessary to pour the required amount of anti-stripping agent into the hot bitumen tank and stir or circulate it for 15 to 30 minutes. It is crucial to use a stable anti-stripping agent or increase the dose if the expected degradation occurs. Another option is to pump the appropriate amount of the agent into the bitumen line using a pump. The agent is then mixed with bitumen and sprayed on the aggregate in the mix, eliminating the need for a separate mixing period for the agent and bitumen.
During rolled asphalt and bitumen mastic surfacing activities, precoated chippings are pushed into the hot surface to make it skid-resistant. To achieve this, the chippings should be pre-coated with bitumen treated with an anti-stripping compound.
FAQs
What is the use of anti-stripping agents in the bituminous mix?
Bituminous mixes and materials often require the use of anti-stripping agents to promote adhesion between the bitumen and aggregates. These agents are particularly useful in situations where the aggregates are hydrophilic in nature and may become submerged in water.
Without the use of anti-stripping agents, the adhesion between the bitumen and aggregates may be compromised. This can lead to the separation of the two materials and a breakdown in the overall integrity of the bituminous mix or material.
To prevent this from happening, anti-stripping agents are added to the mix. These agents work by modifying the surface of the aggregate, making it more compatible with the bitumen. This, in turn, helps to improve the overall adhesion between the two materials, even when submerged in water.
By using anti-stripping agents, the lifespan of the bituminous mix or material can be extended. This is particularly important in situations where the mix or material will be exposed to water or other sources of moisture. By ensuring strong adhesion between the bitumen and aggregates, the mix or material can remain structurally sound for longer periods of time, reducing the need for costly repairs or replacements.
What is the storage and handling procedure of an anti-stripping agent?
Anti-striping agents are required to be stored in containers made of steel or aluminum that are tightly sealed. It is not recommended to use containers made of zinc, copper, polythene PVC, or rubber for storing these agents.
It is important to note that many anti-stripping agents can cause irritation to the skin and eyes upon contact. Therefore, it is necessary to take proper precautions while handling them. In particular, when dealing with liquid anti-stripping agents, it is crucial to wear protective gloves for the hands and goggles for the eyes.