I would like to pour a 24'x 20'x 4" slab using only a 5 cu.ft. portable mixer. This will mean pouring only a small section at a time. Will it be possible to "rock" the seams invisible later or should I go the extra expense of having the entire slab poured at once to eliminate these seams? This will be a wood working shop/garage so rolling a shopsmith around with seams in the floor is out of the question. Thanks in advance, Vince Blackerby