What is the name of the material placed in the gaps between the concrete sections?

Cement

answer #2

The material is an asphalt impregnated fiber material designed to block and penetration of water and be somewhat flexible. During the lifetime of the roadway the maintenance efforts will often fill the gaps with a liquid tar based sealant to keep water out and prevent the creation of potholes. Water gets through and washes out the supporting structures which causes cracking. Water and ice are the enemies that cause potholes and other problems.