Hot Mix Asphalt vs Cold Mix Asphalt? What are Their Differences?
Gajjar Equipments Private Limited:
Hot Mix Asphalt and Cold Mix Asphalt are two prevalent types of asphalt used in road construction, each with distinct differences in composition, production processes, and applications. Continue reading this article to discover their definitions and key differences.
What is Cold Mix Asphalt?
Cold Mix Asphalt (CMA) is a type of asphalt that can be applied at ambient temperatures, making it perfect for temporary repairs or in locations where hot mix asphalt is unavailable. It is composed of aggregates and liquid bitumen, such as cutback and emulsion bitumen.
What is Hot Mix Asphalt?
Hot Mix Asphalt (HMA) is a blend of pure bitumen, asphalt binder, and aggregate, all heated to high temperatures for road construction purposes. It is widely employed in paving projects because of its durability and its ability to withstand heavy traffic loads and severe weather conditions.
Cold Mix Asphalt vs Hot Mix Asphalt, What’s the Difference?
The difference between hot mix and cold mix asphalt lies in two main areas: Type of Bitumen Binder
Production Process
Hot mix asphalt uses bitumen binders that are paving grades. It involves different grades of penetration grade and viscosity grade bitumen, which are produced in a factory setting.
Penetration grade bitumen, also known as paving grade bitumen, is tailored for road construction under various environmental conditions. These grades, ranging from 30 to 120, are classified based on their hardness and consistency.
The primary purpose of grading bitumen by penetration is to determine its suitability for different construction methods and climatic conditions.
Viscosity grade bitumen, which includes VG10, VG20, VG30, and VG40, is the most widely used bitumen in India, replacing penetration grade bitumen as per Indian Standard (IS:73). This type of bitumen is preferred due to its reliability and advantageous properties.
In contrast, cold mix asphalt uses liquid bitumen such as bitumen emulsion and cutback bitumen. It can be produced directly at the project site or in mobile cold asphalt mixing plants.
The difference between hot mix asphalt and cold mix asphalt is described in the table below:
| Cold Mix Asphalt vs Hot Mix Asphalt | ||
| Hot Mix Asphalt (HMA) | Cold Mix Asphalt (CMA) | |
| Type of Bitumen | Penetration Grade Viscosity Grade | Bitumen Emulsion Cut Back Bitumen |
| Production Process | It is produced from the combination of broken and crushed aggregates with pure bitumen in the factory. The aggregates should be heated before mixing. | It is produced from the combination of broken and crushed aggregates with liquid bitumen. The aggregates should not be heated before mixing. |
| Implementation | It should be poured on the surface immediately after preparation and not long after its production. | It can be carried over long distances and has no time limit. |
Cold Mix Asphalt vs Hot Mix Asphalt, Advantages and Disadvantages:
Both CMA and HMA offer distinct advantages and are selected based on the project’s requirements, environmental conditions, and budget.
Cold Mix Asphalt is ideal for small-scale or emergency repairs and low-traffic roads, while Hot Mix Asphalt is preferred for major roads and highways with heavy traffic. Below is a summary table outlining the advantages and disadvantages of both cold mix and hot mix asphalt.
| Advantages and Disadvantages of CMA and HMA | ||
| Hot Mix Asphalt (HMA) | Cold Mix Asphalt (CMA) | |
| Advantages | Higher Durability and StrengthCreating Smooth SurfaceLonger lifespan compared to CMASuitable for a wide range of applications | Ease of UseCost-Effective (due to lower production costs and no heating required)Allowing to storage for on-demand useEnvironmental Benefits and Produces fewer emissions during production |
| Disadvantages | More expensive than CMARequires temperature control during production, transportation and applicationEnvironmental Impact: Higher energy consumption and emissions during production | Lower Durability and StrengthShort LifespanLimitations for use on high-traffic roadsCreating less flexible and rougher surface |
Production Process of Hot Mix Asphalt:
To produce hot mix asphalt, granulated and crushed aggregates are combined with hot bitumen at factory temperatures ranging from 120 to 180°C. Additionally, fillers are added to occupy any voids in the asphalt mixture.
Once prepared, this hot mix asphalt is spread onto the desired surface. The bitumen used in hot asphalt is pure, derived from the direct distillation of petroleum, and must be homogeneous and free of water. Various grades of penetration or viscosity bitumen should be utilized in hot mix asphalt to ensure optimal performance.
Production Process of Cold Mix Asphalt:
Cold asphalt is prepared by mixing aggregates with emulsion bitumen or cutback bitumen at ambient temperature and is spread at the same ambient temperature on the surface.
If bitumen emulsion is used, aggregates can be wet and mixed with bitumen. But if cutback bitumen is used, the aggregates must be dried at ambient temperature or they should be heated before mixing.
In some types of cold asphalt, if necessary, the bitumen may be heated before mixing, but other materials are mixed with bitumen without heating.
In most cases, two types of cut back bitumen including MC 3000 and SC 3000 are used in cold asphalt.
