This　paper　proposes　an　ambient-cured　ultra-high　performance　concrete　(ACUHPC)　by　optimising　its　mixing　procedure　based　on　general　materials.　Seven　reinforced　concrete　(RC)　beams　were　designed　and　subjected　to　different　levels　of　damage　and　strengthened　using　the　proposed　ACUHPC.　Flexural　experiments　were　performed,　and　corresponding　finite　element　(FE)　models　were　developed　to　investigate　the　flexural　performance　of　the　strengthened　beams.　The　influence　of　the　level　of　damage　and　thickness　of　the　ACUHPC　strengthening　layer　on　the　response　of　the　beams　was　evaluated.　The　scope　of　application　of　the　proposed　ACUHPC　strengthening　method,　suggestions　for　its　implementation,　and　methods　for　estimating　the　flexural　capacity　and　mid-span　deflection　of　the　strengthened　beams　are　presented　herein.　The　results　indicated　that　using　the　ACUHPC　can　significantly　increase　the　flexural　capacity　and　effectively　decrease　the　deflections　and　maximum　crack　width　of　the　strengthened　beams.　Furthermore,　the　flexural　capacity　of　the　most　severely　damaged　beam　was　enhanced　by　36.3%　after　strengthening.