Brittleness of the normal concrete has an adverse effect on its application in structures undertaking the bending load. In the current study, concrete was modified by in situ polymerization of acrylic acid (AA) and 1-acrylanmido-2-methylpropanesulfonic acid (AMPS) during cement hydration to strengthen their flexural strength and durability. By adding 7 wt% of AA-AMPS to the concrete, the flexural strength of concrete showed an increment of 61.2% in comparison to the reference one, which was attributed to the polymerization reaction of AA-AMPS monomers that took place at the early stage of the cement hydration, and the rapid formation of polymer network could also densify and compact the interfacial transition zone (ITZ) in the cement matrix. The water and chloride resistances were also enhanced with the increased amount of AA-AMPS. In conclusion, this strategy has great potential to develop high performance concrete with enhanced flexural properties and durability.