Investigations in the Partially Balanced Incomplete Block (PBIB) designs having three or more associate classes have been limited to the works of Vartak [14], Raghavarao [7], Roy [9], Singh and Shukla [12] and Tharthare [13]. In this article we study the combinatorial properties, construction and non-existence of the cubic designs exhibiting a three associate class association scheme. The method of construction, discussed in this article, gives a new way of arranging a $p^3$ factorial experiment in blocks of sizes different from $p$ and $p^2$.