Grass spreads easily to new areas, a good thing if you are reseeding a lawn but a pain if it is spreading into the cracks in sidewalks or between pavers in walkways. While herbicides kill the grass, they also kill any nearby plants they come in contact with and add harmful chemicals to the soil. Pulling the grass is only a stop gap measure, as it quickly grows back. Instead, use common household items to organically kill the grass between sidewalks and prevent it from growing back for the season.
Bring a kettle or pot of water to boiling on the stove top. Bring outside and pour over the grass in the cracks while the water is still boiling. This destroys the roots and the grass will die within two days. Be careful where you pour, since the boiling water will kill any roots it comes in contact with--even those of grass you want or landscape plants.
Remove the dead grass. Pull it up out of the sidewalk cracks, pulling as much of the roots up as you can in case they are still viable.
Sprinkle salt in the cracks , at the rate of approximately 1 teaspoon per foot. Water it in lightly so it doesn't wash away before being absorbed into the soil. Salt stops plant growth, so avoid getting it on nearby plants.
Salt every two months during the growing season. Salt sooner if grass begins growing back into the cracks.