Cold mix asphalt plants are emerging as innovative solutions in road construction, enabling the production of asphalt mixtures at ambient temperatures. Unlike traditional hot-mix asphalt (HMA) which requires heating aggregates and bitumen to around 150–170°C, cold mix asphalt (CMA) is produced without high-temperature heating. This technology is particularly valuable for incorporating reclaimed asphalt pavement (RAP) – recycled old asphalt – into new pavements, aligning with global sustainability and cost-efficiency goals. Asphalt is one of the world’s most recycled materials; in the United States, RAP is reused at a higher rate than any other material. By leveraging cold mixing processes (often termed “Cold RAP” when emphasizing recycled asphalt use), infrastructure projects can conserve resources, reduce energy consumption, and lower emissions. Industry trends worldwide show a growing demand for such eco-friendly asphalt production methods, and companies like Polygonmachine are at the forefront of delivering these advanced cold mix asphalt plants for a global market.

What is Cold Mix Asphalt (Cold RAP)?

Cold mix asphalt (CMA) refers to asphalt concrete that is mixed and applied at ambient or lower temperatures, rather than being heated to high temperatures as in hot mix asphalt. In practice, cold mix is typically produced by blending asphalt binder (bitumen) with water and an emulsifying agent to create an asphalt emulsion, which is then mixed with aggregates and RAP at normal air temperature. Because the binder is dispersed in water, the mixture remains workable without heating; it gradually sets and gains strength as the water evaporates and the emulsion “breaks,” bonding the aggregates. This contrasts with HMA, where the bitumen must be liquefied by heat to coat the aggregates during mixing.

The term “Cold RAP” highlights the use of Reclaimed Asphalt Pavement in cold mix processes. RAP consists of milled or excavated asphalt from old roads, which can be crushed and reused as aggregate in new asphalt. Cold mix plants designed for RAP utilization (often called cold recycling plants) can produce new asphalt concrete by combining a high percentage of recycled asphalt chunks with a bitumen emulsion and minimal fresh aggregates. This approach allows contractors to reclaim and reuse existing pavement material on-site or at a central plant, drastically reducing waste and the need for virgin materials. Importantly, cold RAP recycling achieves these results without the need for high-temperature heating, making it far more energy-efficient and environmentally friendly than conventional hot asphalt production. In fact, recycling asphalt at lower temperatures avoids the combustion of additional fuel and the production of associated greenhouse gases.

Technology and Equipment of Cold Mix Plants

A cold mix asphalt plant shares some similarities with a conventional asphalt plant but has key differences in its components due to the low-temperature process. Aggregate handling and RAP feeding: Instead of superheated dryers, cold mix plants use ambient-temperature feeders. RAP and aggregates (if added) are typically fed from bins through controlled conveyors into the mixing unit. Often a pugmill mixer (a twin-shaft continuous mixer) is the core of the plant, vigorously blending the materials. This mechanical mixing ensures the emulsified binder coats the RAP/aggregate thoroughly. Pugmill-based cold mixers are usually portable and can be rapidly set up near a job site or RAP stockpile. The portability reduces hauling costs and allows on-demand production – a significant advantage for remote projects or quick repairs.

Binder dosing system:

Cold mix plants are equipped with systems to store and dose bitumen emulsion (or sometimes foamed bitumen or cutbacks). Precise pumps and spray bars inject the liquid binder at a controlled rate into the mixing chamber to achieve the desired asphalt content. Some plants also include additive systems – for example, the ability to add cement, lime, or chemical additives to improve mix stability and cure time. Modern cold mix equipment can accommodate a variety of additives and even supplementary recycled materials. For instance, certain designs allow inclusion of recycled asphalt shingles (RAS), fly ash, or crushed concrete alongside RAP to create a “green mix” with up to 100% recycled content.

No heating drum:

Because the process does not require superheating of aggregates, traditional drum dryers or asphalt kettles are absent (or greatly minimized) in cold RAP plants. In some advanced configurations, a mild pre-heater or infrared heater may be used to gently dry RAP aggregates or evaporate excess moisture without reaching HMA-level temperatures. This “gentle heating” (well below HMA temperatures) avoids burning the aged bitumen in RAP and prevents thermal stress to the material. The elimination of a burner and drying drum means significantly lower energy usage and also simplifies the plant’s emissions controls – often no dedicated asphalt fumes incinerator or extensive air pollution control is needed. A cold mix plant typically operates without visible emissions and may not require complex air permits, as exemplified by modern mobile units that produce up to ~200–220 tons per hour with negligible emissions.

Control system:

Despite the simpler process, cold mix plants utilize advanced control systems (PLC/SCADA based) to ensure proper blending ratios and consistency. The moisture content of RAP, the flow of emulsion, and mixing time all need to be regulated for optimal results. The plant operator can adjust settings to achieve the target mix design. Many systems also allow mix data logging and recipe management, which is helpful for quality assurance when producing cold asphalt for important works.

Overall, the technology in a cold mix asphalt plant is geared towards maximizing reuse of materials and minimizing energy input. By mechanically mixing RAP with binder at low heat, these plants reflect a clever integration of pavement recycling and mixing technology. Polygonmachine’s own cold recycling equipment is designed exactly for this purpose: to process milled asphalt into new mix by breaking it down and mixing it with binders and fresh aggregates as needed, yielding high-quality recycled asphalt for road construction.

 

Key Advantages of Cold Mix Asphalt

Cold mix asphalt and cold RAP plants offer several compelling advantages for both project owners and the environment:

Versatility and All-Weather Use:

Because it doesn’t require high heat, cold mix asphalt can be produced and applied in a wider range of conditions. It is ideal for small batch production, remote locations, or cool climates where transporting hot mix long distances is impractical. CMA is frequently used for pothole patching, rural road surfacing, and emergency repairs, since it can be laid quickly without special heating equipment or waiting for summer temperatures. This flexibility in deployment minimizes delays and keeps projects on schedule.

Environmental Sustainability:

Cold mix technology is inherently greener. By avoiding the need to heat large quantities of aggregate and asphalt to 160°C, energy consumption is drastically reduced – studies show up to ~80% less energy per ton is used compared to producing virgin hot mix. Consequently, carbon emissions and fumes are much lower, improving air quality for workers and surrounding communities. Moreover, cold mix formulations can incorporate a high percentage of recycled materials (RAP, RAS, etc.), directly supporting circular economy principles. Using reclaimed asphalt means less new oil is needed for bitumen and fewer aggregates are quarried, conserving natural resources. The cold process thus yields asphalt mixtures that are among the most eco-friendly in the industry.

Durability and Performance:

Modern cold mix asphalt has improved significantly in performance. With proper mix design (e.g. using graded aggregates, quality emulsion, and sometimes additives), CMA can achieve strong resistance to cracking, rutting and moisture damage comparable to conventional hot mix. Its ability to flex with temperature changes often makes it less prone to thermal cracking. While cold mixes traditionally cured more slowly and were used mainly for low-traffic roads, advancements such as polymer-modified emulsions and rejuvenators have extended their durability even under heavy loads. In fact, when rejuvenating agents are added to offset the aged binder stiffness in RAP, research indicates that 100% recycled asphalt mixes can meet normal performance standards of asphalt concrete.

Wide Range of Applications:

The use of cold mix asphalt is not limited to temporary fixes. It finds application in parking lots, driveways, bike paths, and base or sub-base layers of major roads. Cold recycled asphalt base layers (often placed with a paver and then overlaid with a hot-mix wearing course) have become popular in many highway rehabilitation projects around the world. The ability to produce mix on-site using existing road material (via mobile cold recyclers) also makes it attractive for rehabilitating long rural roads and highways economically. From urban utility cut repairs to large-scale pavement recycling, cold mix has proven itself adaptable to various project scales.

Cost-Effectiveness:

Lower production temperatures translate to direct cost savings in fuel. A cold mix plant does not need massive burners or large quantities of fuel to dry aggregates, significantly cutting operating costs. The equipment is often simpler and easier to maintain (no combustion chamber, fewer emission controls), reducing maintenance expenses. Importantly, the ability to reuse RAP means material cost savings – agencies and contractors spend less on new asphalt binder and aggregates. Cold mixes can also be stockpiled for months (when using certain additives), providing a ready supply of patching material and avoiding the waste associated with leftover hot mix that cools off. All these factors contribute to a lower lifecycle cost for using cold mix asphalt, while still delivering a durable pavement.

In summary, cold mix asphalt technology offers a combination of versatility, sustainability, and economy. These benefits are driving its adoption globally, especially as infrastructure agencies seek greener construction methods and value-engineering alternatives.

Polygonmachine, as a leading manufacturer of asphalt and concrete plants, has been actively contributing to these global advancements in cold mix asphalt technology. The company’s ethos is grounded in innovation, quality manufacturing, and tailored solutions for construction needs. With over 15 years of industry experience and international certifications (including TSE and ISO 9001), Polygonmachine has established itself as a trusted name in providing high-performance equipment for roads and infrastructure. Their product range covers not only conventional hot-mix asphalt plants and concrete batching plants but also specialized machinery for asphalt recycling and cold mix production.

One of Polygonmachine’s notable offerings is its Asphalt Recycling Equipment (Cold RAP) line, which is designed specifically for cold recycling processes. These plants allow contractors to efficiently reclaim milled asphalt and process it into reusable mix for new pavement layers. By integrating features like RAP crushers, cold feeders, pugmill mixers, and emulsion dosing systems, Polygonmachine’s cold RAP plants can produce asphalt mix that meets standard specifications for road construction, all while operating at lower temperatures. The company emphasizes that this approach conserves resources and cuts costs for clients by re-utilizing available materials instead of relying entirely on new raw materials. Moreover, the cold recycling plants from Polygonmachine are built with environmental compliance in mind – minimal emissions and efficient dust control – aligning with the strictest regulations worldwide.