Crockpot Sloppy Joes

3 pounds ground beef
1 c. onion, finely-diced
1/4 c. finely-diced celery
1/2 green bell pepper, diced
2 cloves garlic, minced
2 Tblsp. Worcestershire sauce
1 c. ketchup
1 (6-oz) can tomato paste
1-1/4 c. water
2 tsp. beef bouillon granules
1 tsp. paprika
1/4 tsp. black pepper
3 Tblsp. cider vinegar
3 Tblsp. brown sugar
1 tsp. dry mustard

In a skillet, cook meat until no longer pink. Drain fat then return to skillet. Add celery, bell pepper, onion and garlic. Saute until vegetables are softened. Pour meat mixture into crockpot. Next add all remaining ingredients to the meat & vegetable mixture to the crockpot. Stir until well combined. Cover & cook on Low for 6 to 8 hours or High for 3 to 4 hours. Serve over toasted hamburger buns or bread slices.