This might be my favorite question in a long time. I have been to a lot of concrete pours and had to think for a bit about what is smells like! Like Tumbleweed_Tx said, it certainly smells like diesel exhaust, each pump has a big diesel engine running and there are typically 4-10 trucks lined up at each pump. there could be up to 50-60 concrete trucks around the site at any given time. The actual concrete doesn't smell like much, think about wet beach sand or how a road smells right after it starts raining. The concrete curing process is exothermic and does generate heat, but most of that is lost during the evaporation process or held deep within the mat. There wont be any noticeable temperature changes with the pour.