Transit-mix concrete may be used for the construction of the base course in two-course concrete work. Transit-mix topping will not be allowed for the top course in two-course work. Transit-mix concrete shall conform to all applicable specifications of "Concrete for Sidewalks, Curbs and Gutters," particularly in regard to materials, placing, finishing, curing, protection and intent. A properly designed mix that will develop such concrete, using not more than 51/2 gallons of water per ninety-four-pound sack of cement, including the free moisture in the aggregate, and with a slump of two inches, plus or minus one inch, will be approved.