If the drip rate is quicker than one drop per minute, most of the CaCO will be carried to the ground, still in solution. The leachate solution then has a chance to absorb CO from the atmosphere (or degas CO depending on reaction) and deposit the CaCO on the ground as a stalagmite.
In most locations within manmade concrete structures, calthemite stalagmites only grow to a maximum of a few centimetres high, and look like low rounded lumps. This is because of the limited supply of CaCO from the leachate seepage path through the concrete and the amount which reaches the ground. Their location may also inhibit their growth due to abrasion from vehicle tires and pedestrian traffic.