Studying concrete porosity and absorption is very important for determining thecompatibility and durability of concrete repair materials. The objectives of this researchwere: to know the absorption, porosity and compatibility of various repair materials, toknow the extent of protection given by various repair materials on concrete based on themeasurement of absorption and porosity. Percent of absorption and porosity weremeasured according to ASTM C642-06. Scanning Electron Microscope analysis wasconducted to study the porous and bond behaviour of concrete with repair materials.Absorption and porosity rate were determined based on ASTM C 1585-04.The result showed that UPR-Mortar 50 % repair material had the lowest absorption andporosity measurements indicating that it provided sufficient protection. This repair materialis compatible based on porosity and absorption, but incompatible based on bond strengthbecause it had weakest bond with concrete when exposed to temperature. The highestmeasurement values for absorption and porosity were found for concrete with normalmortar repair material indicating that it did not provide sufficient protection. This repairmaterial was compatible based on bond, but incompatible based on porosity andabsorption.Based on Scanning electron microscope analysis, normal mortar repair with normalconcrete had more pores but with strongest bond whereas UPR-mortar 50% repair materialhad weak bond after exposed to high temperature but lowest pores. The peculiar feature ofthis research is that better bond compatibility between repair materials and concrete doesnot guarantee good protection from absorption and porosity. Materials with weak bondstrength can surprisingly have protection from concrete absorption and porosity.Keywords: Absorption, Compatibility, Concrete, MS, Porosity, Protection, Repairmaterials, SEM