Block paving is designed to be interlocked using kiln-dried sand. This product collects seedlings & could sprout a blade of grass or moss/algae because of our damp climate. What I would recommend is scrape out residue from joints & power wash lightly the surface. Wait for area to dry & re-sand with kiln dried sand. Apply 2/3 coats of xylene sealer (Supplied by Askeaton paving). The sealer will act as a barrier to the elements & protect + enhance your paving finish. This sealer should be done again the following year 1 * Coat & this will protect your driveway for 3/5 years.