L&T is one of the best construction companies all over the world. Now if you have submitted your answer sheet with in time then you have nothing to worry about it. You will get the mail in sometime. There are sometimes problems in servers and other issues for which delays can occur. Now if you don't get the confirmation within 3 official days then I would recommend you to contact the coordinator of the examination.

I hope this answer helps. All the very best for your future endeavors!