social skills

So, i ran into this lady i know and she happened to be with her husband, who i have never met. As she was introducing me to her husband she was telling him about what i do for a living and we all started talking about environmental stuff. To continue the conversation, i asked the husband "what do you do?" He said, "i drive a cement truck for construction." and i was totally thrown off. I had no idea what to say. I had no follow-up question. nothing. blank. The job is pretty much self-explanatory, and it's not really interesting enough to spur a conversation. I felt so bad just sitting there not saying anything, but i had nothing to work with. luckily i had a drink, so i was just sipping that, concentrating on drinking. after about 5 seconds of silence between us, he just nodded his head and said "yep." I forget how we got the ball rolling again, but by then, i already felt so bad and awkward for my unintended condescension, it was all just a lost cause. I'm always one of those people who try to relive past moments to see what i could have (or should have) done differently but i am still at a loss. I still cannot think of a follow-up question or any comment to "i drive a cement truck," especially when that phrase follows a whole conversation about me being an engineer.