Patches usually appear darker than the surrounding concrete. Therefore, some white cement should be mixed in the patching mortar or concrete where appearance is important. Samples should be applied in an inconspicuous location, perhaps a stem wall foundation several days in advance to determine the most suitable proportions of white and gray cements. Steel troweling should be avoided since this makes the match appear dark in color.
The mortar should be mixed as stiff as practicable, using 1 part portland cement to 2.5 parts sand, just enough water to form a ball when the mortar is squeezed gently in the hand and 2 other ingredients I will keep secret. After the cavity has been cleaned of oil and loose material and kept damp for several hours, the mortar should be tamped into place in 1/2 thick layers. Vigorous tamping and adequate curing will ensure good bond and minimum shrinkage of the patch. jb.
