Experimental Tests on Lightweight Cement Mortar and Concrete with Recycled Plastic Wastes

The management of plastic waste has become a fundamental issue in recent decades and several studies have focused on finding proper solutions to recycle and reuse these secondary raw materials in different sectors. Using plastic waste in the building sector allows for long-term application and reduces the number of times the recycling process is needed. This research focuses on experimenting with two building products, namely lightweight screed and concrete, with the addition of plastic waste in the form of irregular granules. The screed was produced by adding plastic granules of different sizes, while the concrete was produced by replacing different percentages of the coarse and fine aggregates with plastic granules and pulverized plastic. The screed has been tested under compressive and three-point bending tests, while the concrete has only been tested under compressive tests. The results have shown that the addition of plastic waste in both products led to the desired weight reduction. On one hand, plastic waste have provided a decrease in both tensile (−16%) and compressive (−25%) strengths of the screed with an increase of ultimate tensile strain (+60%). On the other hand, the only acceptable concrete mixture resulted to be the one with 25% of aggregates substitution, which exhibited a decrease in compressive strength (−40%) and an increase of ultimate strain (+38%), whereas samples with higher percentages of plastic aggregates have been not considered to be suitable as building materials.