Cement stabilised soil on the IC16

The opening of the A16 the 30^th of September 2009 as part of the Grande Lisboa Concession led to a  reduction of traffic on the IC19 and A5 thanks to the closing of a new ring road outside the Lisbon metropolitan area connecting the A9 - CREL to the A5, benefiting an estimated 640,000 inhabitants in the municipalities of Sintra and Cascais alone. 

The project was awarded to the consortium formed by MonteAdriano Group, Rosas Construtores, S.A. and Empresa de Construções Amândio Carvalho, S.A., commanded by MonteAdriano Group. 

MonteAdriano Holding was founded in January 2005 following the merger of Monte & Monte and Sociedade de Empreitadas Adriano becoming one of the most active civil construction holding in Portugal. MonteAdriano branched into other sectors as well as abroad with the opening of subsidiaries in Romania, Angola, and Cabo Verde.

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While works was taking place on the A16, MonteAdriano holding I&d team (Montinovação) developed an alternative paving solution which was presented to Lusolisboa, Auto estradas de Lisboa S.A.. The solution was a 23cm-thick cement-stabilised soil layer followed by a 12cm-layer of ”all-in” instead of  the 40cm “all-in” layer  prescribed in the original design,  a faster, less expensive construction solution, as it allowed  the incorporation of the natural soil of the foundation layer  into a structural layer. This method also makes possible to reduce the excavation volume and limit the use of higher quality borrowed soil, consequently decreasing the earthmoving volume transported to landfill, and getting the corresponding environmental and economic benefits.

Cement-stabilised soil is a homogeneous mixture of pre-established amounts of soil, cement, and water. In this work, the process began with the reclamation and crushing of soil in facilities close to the site, followed by its deposition in layers. The cement was spread over the layer and mixed thoroughly so as to mix the soil and cement together. Then, the amount of water corresponding to the optimum moisture content of the soil was sprinkled over the whole material. At the same time hydration of the cement took place. Once heavily compacted, the mixture hardens and develops the strength and durability necessary to form road foundations. 

The benefit of this cement-stabilised soil solution to the A16 highway was confirmed by a technical study which also defined the cement content required to meet the requirements stipulated. Based on that, the cement content was set as being between 3.0% when mixed with calcareous soils and 3.5% for a mixture with marly soils, using Cimpor's CEM II/A-L 42.5R cement.

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