Rapidmix plant speeds up soil stabilization project

Mobile continuous-mixing plant selected by US contractors

Sub-contractors, AECOM, commissioned a Rapidmix 400C mobile continuous-mixing plant, manufactured by Rapid International Ltd, to perform soil stabilization work on ground from a county-owned park in Arlington, Virginia.

The machine, sold to AECOM by Rapid Int USA, proved to be far superior to AECOM’s original plant and increased production and facilitated the smooth running of the project.

The overall project objective was the construction of a county-owned park in Arlington, VA. The park includes: three flood-lit soccer fields, a multi-storey car park, esplanade with walkways and scenic views. 

AECOM performed the following tasks:

• environmental pre-characterization of lead-contaminated soils to determine levels of contamination
• excavation of soil in any of four categories based on levels of contamination
• relocation of soils to engineered placement zones on site
• stabilizing highly contaminated soils using 8.5% Portland Cement blend by weight using the Rapimix400 and relocating to prescribed placement zones on site
• performing confirmation sampling on stabilized soils as necessary to ensure compliance with target stabilization of 0.75mg/l for TCLP Lead EPA method SW6010C.

The project successfully completed in November 2010.

The Rapidmix 400 is sold via a dealer network in the US that is overseen by Rapid Intl USA. The plant is totally mobile and completely self-contained with its own power source. It is fitted with a self-erecting system, which uses hydraulics, which means that the plant can change from travel mode into a fully operational within a few hours.

All work on this project could be carried out using the Rapidmix 400. The untreated material was run through the aggregate bins, which in turn feds into the pugmill mixing unit. Neutralizing additives were added from the on-board silo and mixed through the twin-shaft continuous pugmill mixer that incorporates specifically designed paddles. The mix was then transferred onto an outgoing conveyor and discharged through the gob hopper.

On major projects such as this one with AECOM, traceability is important and the proportioning of different materials can all be carried out through the control panel.  A printer is fitted for tickets or reports to be generated. Variable-speed drives allow the feed rates of material to be adjusted according to the recipe.