Construction Method
Section showing wall construction and defects
Masonry (brick and concrete block) is commonly used for the construction of walls for buildings and retaining walls. Concrete blocks, especially those with hollow cores, offer various possibilities in masonry construction. Filling some or all of the cores with concrete, with or without reinforcing steel, offers much greater resistance to bending. Such a construction system is called reinforced masonry or hollow block reinforced wall and it is widely used for the construction of large external wall panels, retaining walls, swimming pools, bund walls, etc.
In hollow block reinforced walls construction, the blocks must be laid and bonded so that the cores align vertically. By placing reinforcement in the cores and then infilling with concrete, the masonry becomes a composite of block, concrete and reinforcement which has strength similar to that of reinforced concrete. The concrete used for the infill should have a high workability; a super-plasticiser is often used.
The problem
Major performance and durability problems can arise if the reinforced cores are not fully filled with concrete, or if specified reinforcement is omitted. The question is, how can you tell?
The survey
Due to the ability of Ground Penetrating Radar to detect changes in the subsurface, including voids and steel, it is an ideal survey technique to identify voided cores and missing reinforcement. The site survey is non-intrusive, non-disruptive and quick.
The Results
Data analysis is undertaken off-site to identify voided or unfilled cores and missing rebar. Results are presented on simple to understand CAD drawings.
GPR radargram showing reinforcing steel and filled and voided cells
Blockwork wall survey results plotted in CAD
