I live in Charlotte, NC and have a 4 year old home on crawlspace with a curtain wall / pillar type of foundation. I had some major foundation issues that were repaired (via helical coils) and the last step of the repair was to fix the cracks in the brick/mortar in the curtain wall. The brick mason came out and repaired the cracks early last month 12/7/10. He rebuilt a small section of the curtain wall (3' x 3'), but most of the work was repairing mortar cracks. The mortar cracks he ground out to about 1/2" deep and then tuck-pointed them. The temperatures during the day were hovering in the mid 30's and it was below freezing at night. I asked him about the cold temperatures and he didn't think it would be a problem for this type of repair. He used a small heater when working on the small section of rebuilt wall, but not when working on the mortar cracks. So it's been over a month since the repair was completed and I am concerned with the mortar. The mortar seems hard in that I can take a knife and push into it without causing any damage. However, if I take my finger and rub over the mortar, sand comes off (not chunks, just grains). If I rub the old mortar, no sand comes off. Is this normal? I showed the brick mason and he didn't think it was a problem since the mortar was hard and not broken. He did offered to come back in March to re-evaluate (when the weather is warmer) and fix whatever needed it.