Abstract: An expansion joint sealing element, consisting of an arrow-shaped elastomer strip (1), defined by a triangular head (2) and a rear insertion section (3) with an angled end (4), while its lateral walls (5) are externally corrugated (6), an arrangement that is repeated on the external surface of the base (7) and on the lateral sections of the head (2), which, along with the insertion section (3), have various internal, longitudinal hollow sections defined by various interior walls (8), forming an insufflation chamber (9), so that one end of the strip (1) is closed off, while the other is fitted with a cover (10) and a valve (11), the latter being used to inject air so that the walls of the elastomer strip press against the adhesive applied to its lateral walls, where ridges considerably increase the area of adhesion and prevent the strip from moving while said adhesive cures.