Actually, "Betonada" is defined in the dictionary as a "large, mobile block of concrete, usually cube- or box-shaped, used as a type of barrier/obstacle for a variety of purposes; A concrete wall or a temporary concrete structure, used for shielding/protection".

The suggested translation in Rav-Milim is "concrete barricade" or "concrete block".. I actually like "barricade" more as it's less ambivalent. But I also thought of "barrier" which actually represents the exact meaning in your sentence - a block could be interpreted as a building block (and indeed if you search google you'll find small concrete blocks all around). I've looked "Concrete barrier" and this term actually has a dedicated Wikipedia page with terms such as "F-shaped barrier" and "Alaska barrier" which are exactly what Israeli speaking audiences think of when they hear "Betonada" (you can also look at Google image search pictures and see what I'm talking about).