Garden Guides | How to Mortar Limestone Blocks
With every block you lay, position it straight and level using the string to guide you. Step 5. Mix limestone mortar in a wheelbarrow. Use 6 parts brickies (bricklaying) sand to 1 part lime and 1 part cement. For example, combine 3 lbs. brickies sand with 1/2 lb. each of lime and cement. Stir the mortar mix with a trowel.