The sounds that you are hearing are caused fromwhat is called{expansion and contraction}. All materials will do this from the changing of temp. You will really hear this at night after sun has gone down and early morning. Uselly up to noon. A railroad track,may have 1 to2 in. Opening at night but by noon be closed,a loud noise. Concrete will expand up to 3 or more inches. There is no danger and there is nothing any human can do about thisbut live with it.:"