I found this in a quick research on internet

Article Effects of Plastic Waste Materials on Geotechnical Propertie...

Hope it helps

As per the research yes plastic has its effects on the engineering properties of cement such as mechanical and durability properties. Change in concrete properties after adding plastic mainly depends on the type of plastic that is added and also the pre-treatment of plastic. This requires careful consideration of its effects on the engineering properties of the resulting concrete also Fire Resistance factor is more important to consider.

Attached few references. Hope this helps.

Study on Mechanical Properties of Concrete Using Plastic Waste as an Aggregate - IOPscience

Sustainability | Free Full-Text | Engineering Properties of Concrete with Waste Recycled Plastic: A Review (mdpi.com)

Performance of plastic waste for soil improvement (Performance of plastic waste for soil improvement | SpringerLink)

Soil Stabilization Using Waste Plastic Materials (Article Soil Stabilization Using Waste Plastic Materials

[Utilization of Waste plastic in Geotechnical Engineering Brian Chamba

I can think of many ways of using plastic waste to stabilize soil particles and improve cement-grade properties. Plastic wastes can include polythene, compound plastics, wrappers, and so on. One can stitch plastic pieces tightly with unconsolidated soil and apply various nominal stresses and shear forces. 1000-1500 Kpa can be tried at first with plastic-strips boundary at 5mm thickness and 1000 mm span. With notice taken to clay with 0.001 mm particle sizes, require the greatest compression to get rid of void pressures and hydrostatic pressures. Gravel has a large particle size of around 0.2-0.5 mm and requires less compaction. It can take a very long time to consolidate clay. One can increase plastic strips' density by wrapping soil particles with a thickness that can be increased for holding stresses. The holding stresses can be increased to 2000-3000 Kpa, with greater interbinds to hold silt or clay particles. The thickness of the plastic strips has to be increased to prevent rupturing and particle leaks. Solid plastic can be crushed and grid with asphalt, silt, and clay to make cement.

Depending on the percentage composition of the mix, compaction tests can prove the strength and yield of the different cement mixes.