Development of an appropriate grout for the consolidation of the column foundations in Our Lady’s Basilica at Tongeren (B).

Archaeological excavations inside Our Lady’s Basilica at Tongeren (Belgium), one of the most beautiful religious monuments in Belgium, are made possible through an adequate consolidation of the columns masonry foundations. The project includes a large archaeological excavation of the central nave up to a depth of more than three meter. To prevent instability of the columns, the foundation masonry is injected with a hydraulic grout. For the preservation of the archaeological remains, possibly available in the soil, the penetration of the grout into the layered soil must be prevented. Specific properties of the grout are thus required. The fluidity of the grout must be sufficient during injection, but has to decrease rapidly after a pre-determined period. Combined with an effective injection procedure, only the foundation masonry will be filled. The archaeological artefacts will thus be preserved. The grout has to be stable and bleeding must be under control. The compressive and bending strength must be sufficient and secured in time. The injectability of the grout in the foundations must be assured. The development of an appropriate grout for the injection of the columns foundation masonry will be described in this paper. The selections of the grout composition, as well as the design of an effective injection procedure are based on laboratory and on site tests. It is demonstrated that a grout containing a mixture of slaked lime and hydraulic cement performed excellently within the preset boundary conditions.status: publishe