what happens if you do not prime a concrete surface? Im confused why it would be ness? Why would the self leveler pull up if heavy floor is atop it?

Thank you for your inquiry regarding MAPEI Products! Primers act as "bond promoters" before applying a Self Leveler to a subfloor. MAPEI specifically follows the TCNA (Tile Council of North America) and the NWFA (National Wood Flooring Association) Installation Guidelines for their specific floor preparation requirements and are listed as follows: Existing Cement Mortar Beds and Cement Screeds 6.1 The use of an appropriate MAPEI primer is required. Consult Reference Guide RGC0609, “Primers for Self-Leveling Materials – Product Selection Guide,” for primer selection. Refer to current TDSs for details. 6.2 Do not install MAPEI self-leveling underlayments over any patching compounds or skimcoating products. 6.3 MAPEI self-leveling underlayments may be installed over cement screeds and cement mortar beds when they are sound and durable, securely bonded, stable, clean, dry and fully cured. 7. Gypsum-Based Concrete, Existing Gypsum-Based Poured Please review and call us here at Tech Support Mon-Fri from 8 am to 5:30 pm EST at 800-992-6273 for more assistance if necessary. Thank you! Product Advisor # 11