Conditions and Specifications. Concrete is required for a pavement that will be exposed to moisture in a severe freeze-thaw environment. A specified compressive strength, fc, of 35 MPa is required at...

Conditions and Specifications. Concrete is required for a pavement that will be exposed to moisture in a severe freeze-thaw environment. A specified compressive strength, fc, of 35 MPa is required at 28 days. Air entrain- ment is required. Slump should be between 25 mm and 75 mm. A nominal maximum size aggregate of 25 mm is required. No statistical data on previous mixes are avail- able. The materials available are as follows: Cement: Type GU (ASTM C 1157) with a rela- tive density of 3.0. Coarse aggregate: Well-graded, 25-mm nominal max- imum-size rounded gravel (ASTM C 33 or AASHTO M 80) with an ovendry relative density of 2.68, absorption of 0.5% (moisture content at SSD condi- tion) and ovendry rodded bulk den- sity (unit weight) of 1600 kg/m2. The laboratory sample for trial batching has a moisture content of 2%. Fine aggregate: Natural sand (ASTM C 33 or AASHTO M6) with an ovendry relative density of 2.64 and absorption of 0.7%. The lab- oratory sample moisture content is 6%. The fineness modulus is 2.80. Air-entraining admixture: Water reducer: Wood-resin type (ASTM C 260 or AASHTO M 154) ASTM C 494 (AASHTO M 194). This particular admixture is known to re- duce water demand by 10% when used at a dosage rate of 3 g (or 3 mL) per kg of cement. Assume that the chemical admixtures have a density close to that of water, meaning that 1 mL of admixture has a mass of 1 g?