Whenever an article says something is stronger then concrete they always leave off the important part of the comparison, such as: "stronger then concrete by weight". In this case the plastic bricks are stronger then the compressive strength of concrete, the plastic is the binder not the bulk of the brick. These bricks are deforming but not breaking, giving a false reading of strength. Notice that they only use them as pavers. Try making a structure from hot glue and sand. Measuring a flexible material by compressive force is a false metric, they need to measure plastics by the tensile strength, ultimate elongation, yield point and modulus of elasticity.