The project aims to replace the coarse aggregates and fine aggregates (sand) with two categories of plastic wastes - Polypropylene (PP) and High Density Polyethylene (HDPE) at varying percentages in order to determine the crushing strength and properties of mortar blocks. These types of mortar blocks could be used in constructing lightweight non-structural elements in both domestic and commercial usages such as block walls, step foundations, trench fillings, kerbs and drainage works. The materials used are Portland composite cement, fly ashes, plastic wastes and water. These are hand-mixed together with different water/cement ratios and casted in rectangular timber moulds. The plastic wastes fill up the air voids in the mortar blocks. As a result, the crushing strength of mortar blocks would be lower as compared to that of concrete blocks. The different water/cement ratios affect the dampness of the mix and the resulting crushing strength of the samples. More testing needs to be carried out to determine the right mix proportion and the corresponding optimum crushing strength of such mortar blocks.