AP Lift foams have an inverse relationship between expansion and strength. The more they expand, the less compressive strength they have. The less they expand, the more compressive strength they have.
AP Lift 420 has the highest expansion which means it is the most economical product in terms of filling a void. It also has the lowest compressive strength.
AP Lift 475 expands less than half the amount of AP Lift 420, but the compressive strength is 370% stronger.
Understand that these expansion rates and compressive strengths are based on free rise foam. Free rise means that the material is allowed to expand with no resistance (example: foam that was mixed and expanded in an open cup). In most cases you are injecting these products into soil or into a void that is closed off on most sides. The foam meets resistance as it expands. The resistance reduces the amount of expansion and therefore increases the compressive strength. How much expansion is reduced varies from job to job and is influenced by soil conditions, void size and shape, quantity of material injected, etc.
Although each product can be used in multiple applications, here is a quick guide to product selection:
AP Fill 420 – Filling large voids, Deep Lift process
AP Lift 430 – Residential slab lift applications
AP Lift 440 – Highway concrete slab lift applications
AP Lift 475 – Heavy duty slab lift applications
Note: All of these products are designed to work in wet environments.