Variability in the Unconfined Compressive Strength of EICP-Treated "Standard" Sand

Three different batches of "standard"Ottawa 20-30 sand were biocemented using enzyme-induced carbonate precipitation (EICP). The specimens from each batch were treated using the same biocementation procedure. The unconfined compressive strength (UCS) of the treated specimens varied from 0.22 to 1.6 MPa depending on the batch of sand used to prepare the specimens. These results show that sand of the same predominant mineral composition (e.g., >98% silica), of the same grain size distribution, and from the same geological formation but from different quarries within the formation do not necessarily respond in the same manner to biocementation. Hence, standard sands for mechanical geotechnical testing should not be considered a priori to be a standard sand for biogeotechnical testing.