Earlier this year, Colas Ireland launched a “Go Green with Colas” initiative to raise awareness with our many customers and stakeholders of how Colas can help them meet their carbon reducing targets.
Since its establishment over 70 years ago, the Colas Group has led the way in the development of environmentally friendly pavement materials. In fact, the name Colas comes from the words COLd ASphalt. Cold-mix asphalt, as it is called, is similar to the more commonly used “hot-mix” asphalt but is produced by using a bitumen emulsion instead of the conventional hot bitumen.
As bitumen emulsions can be used with aggregates at ambient temperatures, as opposed to the high temperatures required to manufacture hot-mix asphalt, there are considerable energy and, hence, carbon savings to be achieved by their use.
Figure 1: Cold-mix asphalt trial in Colas yard in Mallow, 1984
Colas first introduced the cold-mix asphalt technology into Ireland in the 1980’s. In 1990, a cold-mix asphalt called “Grave-émulsion” was used in the base course of a 40 km section of the N8 from Dublin to Cork. At that time, the N8 was the heaviest trafficked road in the country. But the grave-émulsion cold-mix material well and truly survived the test of time. In fact, when it had reached the end of its design life in 2006, there were no signs of distress or failure, with no cracking, an average rut depth of only 3 mm (versus the failure criteria of > 10 mm) and an IRI smoothness indicator of 1.7, which is well below the smoothness criteria for a new road!
Since then, Colas Ireland has led the development and promotion of other emulsion-based materials and techniques such as surface dressing, cold-asphalt micro-surfacing and in situ pavement recycling.
Figure 2: Surface dressing with bitumen emulsion technology is the most environmentally friendly road re-surfacing technique – in addition to being the most cost effective
In situ cold recycling is one of the most environmentally sustainable and low carbon maintenance techniques that is available to the Local Authority Engineer. In addition to being a cold technique, use is also made of the aggregate material already in the pavement.
Consequently, there is less use of this valuable resource and there is less or no transporting of aggregates from a quarry or asphalt plant to the jobsite. In addition, the bituminous binder already present in the pavement can also be recycled.
Much of these developments have been made possible thanks to Colas Ireland owning and operating its own speciality chemicals company in Oranmore, Co. Galway. Chemoran’s range of emulsifiers and bitumen additives enables Colas subsidiaries worldwide to design their emulsions and asphalt mixtures to best meet their customers’ needs.
Chemoran’s bitumen additive called CWM™ has been used for the production of over 7 million tonnes of warm-mix asphalt worldwide and its adhesion agents extend the service-life of hot-mix asphalt by improving the bond between the binder and the aggregate and, hence, its durability.
In terms of making a change to reduce the industry’s carbon footprint, switching to warm-mix asphalt, instead of hot-mix asphalt, is probably the easiest transition. By simply adding an additive, such as CWM™ into the bitumen, mixing temperatures at the hot-mix plant can be reduced by at least 30 °C. Temperature reductions of up to 40 °C have been achieved, even with the very dense EME mixtures used in France.
Needless to say, the further the reduction in mixing temperatures, the greater the savings in energy use at the asphalt mixing plant and, as a consequence, the greater the reduction in greenhouse gas emissions. It has been widely reported in the literature that energy savings of the order 15 to 20 % can be achieved when the mixing temperatures are reduced by 30 to 40 °C. In Ireland’s case, as we manufacture approximately 3 million tonnes of hot-mix asphalt per year, this would equate to a reduction in carbon emissions of the order 15,000 tonnes of CO2 eq. per annum.
In terms of performance, during the past ten years it has been well established that warm-mix asphalts behave in the same way as conventional hot-mix asphalts. Since 2008, over 7 million tonnes of warm-mix asphalt have been made using the CWM additive alone. Many more millions of tonnes have been produced using other additives. Warm-mix asphalt has been used in every bituminous layer of the pavement from base to surface course, including mixes that contain high percentages of RAP, and under all traffic levels.
For more information about Warm-Mix Asphalt see our Warm-Mix section here
Perhaps as importantly, another significant benefit to reduced mixing temperatures is a reduction in VOCs emitted at the laying site, i.e. less smoke and fumes. It has been established that, as a general rule, for every 12°C degree drop in mixing temperatures, VOC emissions are reduced by half at the job site. At a trial site in Dublin in 2012, the reduction in VOCs was measured and found to be 80% lower than that of the conventional hot-mix, when the mixing temperatures were reduced by 35°C.
Figure 4: Laying CWM-modified warm-mix in France (at 40 °C lower) – no smoke behind the screed!
Another benefit of reduced mixing and laying temperatures is that the pavement will cool to ambient temperatures more quickly and, therefore, can be reopened to traffic sooner. Consequently, there is a less of an inconvenience on the road user.
In terms of the costs to implement such a change, the cost of the warm-mix additive will be offset by the savings in fuel use. In addition, if the cost of carbon credits is increased to the ¤80 per tonne mark (as is now promised by this government), the net increased cost to the asphalt producer and, consequently to the client, i.e. the Irish taxpayer, will be zero!
The road construction/maintenance industry and the asphalt industry, in particular, has within its grasp the ability to play a significant role in achieving Ireland’s carbon reduction targets by promoting and/or even insisting on the use of both warm-mix and cold-mix asphalt. The benefits are obvious and can be implemented immediately.
See below to for more about Colas Go Green processes;
WARM-MIX ASPHALT
A warm-mix asphalt is simply a hot-mix asphalt manufactured at a lower mixing temperature. As a result, less energy is needed.
Use of a bitumen additive called CWM, enables the mixing temperatures to be reduced by up to 35°C. CWM works by reducing the surface tension at the bitumen-aggregate interface.
In Ireland, carbon emissions could be reduced by over 10,000 tonnes per annum, if warm-mix asphalt was used in place of hot-mix asphalt.
No smoke at jobsite.
Energy use at the hot-mix plant is reduced by 20%;
Carbon emission are also reduced by 20%;
Smoke and VOCs at the jobsite are reduced by 80%!!
Performs like hot-mix, in every other way;
Over 7 million tonnes have been paved worldwide, since 2008.
Hot-mix asphalt is so-called because the aggregates used are heated up to 170-1900C. However, thanks to the bitumen emulsion technology used, the aggregates are not heated for the production of cold-mix asphalt.
As a result, the manufacture of cold-mix asphalt requires a lower fuel use (i.e. lower energy) with a consequent reduction in carbon emissions.
Carbon emissions are reduced by up to 18 %, when compared to the conventional hot-mix options.
Laying Cold-Mix asphalt base course on the N21 Ring of Kerry 2014
Cold-mix asphalt such as Grave-émulsion and Stabilized Wet-Mix have been paved by the Colas Group in Ireland since the 1980’s;
Suitable for the base and binder course for all road categories;
Bitumen emulsion technology results in a more flexible mix with a longer fatigue life.
In addition to being a cold technique, in-situ recycling with bitumen emulsion makes use of the pavement materials that are already on site.
This combination results in this recycling process being one of the most environmentally sustainable and low carbon road maintenance techniques. There is less use of valuable aggregate resources and there is less transporting of pavement materials from a quarry / asphalt plant to the jobsite.
Carbon emissions are reduced by up to 80 %, when compared to a conventional 6 cm thick mill out and replace hot-mix overlay.
Cold In-situ recycling site
Is used worldwide, under all traffic levels;
Mostly used to form a new base course;
The bituminous binder already present in the pavement can also be recycled;
The process is fully described in the “IAT Best Practice Advice for Cold In Situ Recycling of Low Traffic Volume Roads”.
Cold-mix-asphalt is produced by coating aggregates with a bitumen emulsion. As the name implies, it is an entirely cold process, because the aggregate does not need to be heated.
ValorColTM cold-mix has an even lower carbon footprint, as 80 to 100% of the aggregate consists of RAP.
Carbon emissions are reduced by up to 70 %, when compared to a conventional hot-mix binder course overlay.
A ValorColTM Pavement in France
RAP can be supplied from returns to the hot-mix plant or from road millings;
ValorColTM is mixed using a mobile mixing plant that can be brought to the RAP stockpile;
The use of valuable raw-materials is significantly reduced;
Can be used in the base, binder or surface course of low traffic volume roads.
ColmatTM micro-surfacing is a cold-applied thin bituminous overlay that can help road engineers to reduce their carbon footprint.
Micro-surfacing is the ideal solution for re-sealing and re-profiling pavements that are otherwise in a good structural condition. As the aggregates are bound using a bitumen emulsion, it is an entirely cold process with no energy required to heat the aggregates used.
Carbon emission are reduced by at least 70 %, when compared to a conventional hot-mix overlay.
Versatile application process
Is used worldwide, under all traffic levels;
The jobsite can be re-opened to traffic within 1 hour;
Extends the pavement life by 6 to 10 years;
Provides an excellent preparation for the surface dressing of rural roads that have a poor surface profile
In addition to being the most economical, surface dressing is also the most low-carbon option for surfacing Ireland’s roads.
The use of bitumen emulsion technology ensures that the aggregates do not need to be heated. Instead, the bitumen emulsion seals the road surface from water ingress, thereby improving the durability of the pavement. A layer of chippings is then bonded to the road surface by the bitumen emulsion.
Carbon emissions are reduced by 70 %, when compared to a conventional hot-mix overlay.
The emulsion seals the pavement and glues the chippings to it
Over 90% of Ireland’s road network is surface dressed;
Provides the highest level of surface texture and skid resistance;
Mostly used on non-National roads;
The process is fully described in the “IAT
Guidelines for Surface Dressing in Ireland”.
The Colas PenTack Active SealingTM treatment system is a pavement preservation technique that is used to extend the service life of asphalt pavements by up to 6 years.
The treatment system replaces some or all of the binder mastic (bitumen + fine aggregate) that has been eroded from the existng asphalt surface over time. The loss of this mastic from the asphalt leads to chip-loss and / or ravelling of the mix and eventual failure.
Carbon emission are reduced by up to 95%, when compared to the conventional option of mill and replace with hot-mix.
A section of the M1 motorway, 5 days after the PenTack treatment
Based on Colas’s emulsion technology;
The emulsion penetrates into and seals the existing surface pavement and halts the ageing process;
Suitable for all road categories, from car parks to motorways and runways;
A much quicker operation than “mill and replace”, meaning less traffic disruption.
In recent years, durable solar roadways are becoming more of a reality. Years of collaborative research between INES, France's National Institute for Solar Energy, and Colas, has led to a new incredibly thin solar panel roadway surface called Wattway.
Wattway does not require the replacement of roads, rather the tile-like panels lay directly on the current road's surface. Wattway is manufactured with a new type of solar panel that is amazingly thin. Each panel is made up of a film of polycrystalline silicon coated in a resin substrate keeping the photovoltaic cells safe. These energy-producing photovoltaic panels are glued to the pavement surface. An electrical cabinet is installed with a battery to store the power produced by the panels. The equipment connected to Wattway becomes energy autonomous (charging station for bicycles or electric scooters, closed circuit security cameras, connected benches & bus shelters, dynamic signs, etc.). Installation work is minimal, allowing for very quick commissioning. This solution is particularly suitable for remote areas where connecting to the existing electrical grid is an issue.
In France, Wattway has been successfully installed to produce electricity for;
Lighting of pedestrian bridges at night
Powering secure bicycle shelters for charging of electric bikes
Charging stations for electric cars
Since the Wattway project was unveiled to the press in October 2015 for COP 21, some forty trial sites have been built in France and abroad. The point is to facilitate the roll out of new services for users and to enhance safety in off-grid areas, a solution that was awarded a Solar Impulse Foundation label in early 2019.
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