The Laboratory has 24 reaction blocks with a capacity of 20 K (89 kN). They may be stacked together to form temporary reaction walls and buttresses of various shapes and capacities.
They are each 4 x 4 x 8 ft(1.2 x 1.2 x 2.4 m) in size and perforated in three directions with anchor holes that match the 2 ft by 2 ft (0.61 x 0.61 m) grid in the test floor.
Each has been cast to meet tight dimensional and flatness tolerances. Blocks are assembled together and anchored to the floor and/or the strong wall using hydrostone and Dywidag post-tensioning bars.
Steel forms are available to cast additional blocks should they be necessary.