The strength and deformation characteristics of rock masses are required for almost any form of analysis used for the design of slopes, foundations and underground excavations. However, weak rock engineering in tropical climate frequently encountered problem ofground swelling and shrinkage. Swelling and shrinkage of rock are relevant in civil engineering such as ground heaving and closure of tunnel opening and slope failures, where these are the most alarming phenomenon in geotechniques. Previous records have proven that it is complex to differentiate between swelling and shrinkage conditions since both conditions are often present at the same time. The deformations and loss ofstrength usually can only be recognized months or even years later Argillaceous sedimentary formation along Route 6, Balik Pulau District, Penang especially along the stretch from KM 3.9 to KM 7.0 has been extensively exposed as cut slopes. It was observed that the design and construction of the cut slopes did not comply with any slope engineering rules. It is suspected that the lack of understanding of the heterogenous formation and their physical and engineering properties had caused severe geotechnical hazards not to mention the cost incurred. A proper and systematic characterization and classification of these rock materials could provide an answer to better explain what has and will be the future cause of failure of the geological structures in wet tropical climate. A study was conducted to re-characterize the properties and behaviors of these weakly cemented rocks which were found to be very sensitive to moisture changes. A real time laboratory study determines the typical free swell and shrinkage behavior of the materials that potentially induced slope failures.