A new adhesive for solid connections
The line for Dubai’s new metro – the world’s longest driverless rapid transit system –comprises 11,400 precast concrete elements. The adhesive used for connecting the separate elements had to meet high requirements: It was expected to exhibit consistently good processing properties in at times extreme climatic conditions. And, the joints would have to withstand heavy vibrations intermittently caused by moving trains.
Thanks to the adhesive Concresive 1441, the separate concrete parts of the transit construction behave like one single element. Because of this, impacting forces – vibrations for example – are dissipated and absorbed in a much better way.
Customized solutions for summer and winter
The BASF team designed two versions of the epoxy resin based adhesive on site: One for usage during the cooler winter months, and a summer version that is easy to process, without any segregation, during the hotter parts of the year. Concresive connects the concrete elements durably and prevents water or sand from penetrating the joints. During the construction process, the BASF experts supported the engineers and workers with application tests and trainings.
Tunnel Breakthrough
The ground through which the tunnel boring machines (TBM) had to dig for the construction of the Dubai Metro network posed several challenges: On the one hand, the groundwater level was only one meter below the surface, and the water was extremely saline and thus highly aggressive. On the other hand, the substrate was very heterogeneous. During the tunnel boring, high risks were to be expected, mainly water ingress to those stations as well as giving way of the ground above the connecting area.
BASF provided two solutions: injections into the ground from the surface and injections with a liquid colloidal silica mortar into the substrate. To do so, Rheocem® 650 was first injected into the ground through a series of boreholes from the surface. Then, the TBM – which was equipped with pumps directly behind the cutting wheel – could advance. Through the pumps the liquid MEYCO® MP 320 colloidal silica mortar was pressed into the substrate.
In order to render the substrate sufficiently solid and to minimize the risk of it giving way in any direction even a little bit, little pressure was used, as was a precisely calculated quantity of the product with a closely adjusted gel time.