There are cracks here and there in the garage concrete floor towards the door. A week or two ago, we started noticing something white grown out of the cracks. They did not grow rapidly for these past 2 weeks until last night.

Look how much it has grown in this pic. The stuff is at least 1/2 in tall or more

The stuff attacked even along the edge of the door, where there is no crack.

We are in GA, but it was so warm these past 2-3 weeks (78 degree on Christmas day. Then, it gradually decrease the temperature. Last night, the night temperature drastically reached down to 45, the coolest for the past 3 weeks). We had a lot of rain 3 weeks ago for the entire week, and then rained again, and rained for almost another week. It finally stopped yesterday.

What is it, and what can we do? Thanks