Completely remove any weeds before you start any repair work. You will not be able to combat weeds that have taken root inside the joints or underneath the paving using new joint filler alone.
Use joint cleanser and a high-pressure washer for weed removal. Be careful not to damage the paving or surface underneath.
Spray at a narrow angle as low as possible from an appropriate distance, and clean the paving and its edges with water and maybe a little cleanser. Make sure that the paving edges and side faces are clean to ensure that the polymeric block paving fix adheres well. You might find laying new paving faster than repair.
After cleaning, follow the