I am working on using HDPE and LDPE in construction bricks. The most attractive property it has is that it is waterproof. I am using beach sand in different proportions in it. Changing the way of mixing the two, many a time to get the best result. Problems faced are how to increase melting point by adding which fire retardant and proper mixing of all of these in required proportions. I Would like suggestions and possible shortcomings if anyone will get it by thinking about it. My aim is to use them in cold countries and where there is a problem of water leakage.
*product is still in development phase and improving daily. Pics attached.
There’s no simple answer to that question as it has too many variables.
It will depend on the quality of the plastic, the sand, the machines etc. used and can largely vary per location, as even temperature, humidity and climate in general could influence the strenght of the bricks (both traditional as plastic).
In some aspects traditional bricks will perform better, in others (especially in light weight building) the plastic bricks will have the advantage.
Find the production method best suited to your environment and do tests and experiments.