Is it normal to have haircrack in new concrete slab? We just poured concrete yesterday at 95 degree temperature, 4 hours after finished we sprinkle water on concrete rightaway and noticed haircrack. I'm concerned that will it reduce its strength. Thanks in advance for your response.

Concrete tends to crack when it cures, don't worry about a hairline crack.

How to Identify, Evaluate, & Repair Shrinkage Cracks in Poured Concrete Slabs (http://www.inspect-ny.com/structure/SlabCracks1.htm)

Thanks for your response and concrete website.

Yes concrete does crack but you crack was accelerated because you should have draped damp cloth on the pour earlier than 4 hours. As your concrete trid to cure some of the moisture evaporated in the 95 degree temp.