Irish mixer turns JFK’s old asphalt runways into new concrete ones

In the past, substantial quantities of natural aggregates and crushed stone sources, have been discarded or rejected because of restrictive specifications, or other reasons. Much of this material could be used in concrete structural elements, if proper attention were given to developing mix designs to meet the structural requirements, and environmental conditions, to which it will be exposed.
This is where econocrete comes into its own. It is a lean concrete made with low-cost, locally available aggregates, that do not meet conventional specifications.
Stringent recipe
At JFK, the Conti Group is running a Rapid Mix 400, to make econocrete to a recipe designed for specific strength and durability levels. It is the largest runway rehabilitation contract for JFK in 20 years and has been developed to accommodate the new A380, the world’s largest passenger airliner.
It is through the use of econocrete that Conti has managed to economically accommodate this beast of an aircraft, and to reduce the total cost of the project.
Increasingly used in the US, interest in its use has developed in the last few years, due to the high cost and dwindling supplies of high-quality virgin aggregates, in some areas of the US.
The Federal Highway Administration, together with local governmental agencies, is now supporting the movement of the econocrete concept from laboratories to the field. Mixes are based on laboratory tests, and refined in accordance with their intended use.
Widespread applications
Possible applications are as varied as the many structural elements of modern highway paving systems, as it is a durable concrete, with a well distributed air void system. Water reducing admixtures are often included in the mix to improve workability at the low slump ranges that result in higher strengths.
The mobile and self contained Rapid Mix 400, has been a key tool at JFK. Made by Rapid International Ltd of Northern Ireland, it is capable of mixing up to 400tph, depending on the precise application.
It uses a hydraulic system to change the plant from its travel mode into a fully operational plant in minutes, which is perfectly suited to a project such as the JFK airport one. A 50t self-erecting silo, fitted with a twin shaft continuous mixer, enables it to be also used in applications such as soil stabilisation, and dam construction.
The Conti Group is producing econocrete at JFK, by milling asphalt recovered from the demolition of old runways, screening it, and then mixing it with cement and water in the Rapid Mix. Due to the fact that econocrete uses 70 to 80% of the material from the old runway, it provides huge economic benefits to the airport, as well as being environmentally friendly.
The project is ongoing, and has expanded to several other airports around the US. More information: Joanne Kettle, Rapid International Ltd, 96 Mullavilly Rd, Tandragee BT62 2LX, Co. Armagh, N. Ireland, +44 28 38 840 671, +44 28 38 840 880, info@rapidinternational.com, www.rapidinternational.com