You are changing the mix design. Then you just have to do concrete test to make sure it meets your spec. Doesnt matter what aggregate you are using as long as you meet the 28 days strength that you want.
ahunt is correct. Compressive strength will be no problem, but shrinkage and cracking will be. Therefore the largest practical MSA mix should be used.
Factors affecting the selection of MSA are outlined in ACI 318 Section 3.3.2..other factors include the concrete coverage for reinforcing steel (used no more than 3/4 cover) and method of placement. The minimum diamter of the pump wll depend inter-alia, on the MSA and grading of the mix.
Smaller aggregate mixes require more water to achieve the same level of workability as mixes with larger MSA.
Check out the link posted by dik in the ACI forum.
under step 3, you'll notice that the water required for 3/8-inch (9.5 mm) mix is about 20% more than that required for a 1-inch (25 mm)mix.
Beyond the water required for hydration, there is quite a bit more required for lubrication of the 3/8-inch mix...which will result in more drying shrinkage, when compared to the 1-inch mix.
For building structures, 3/8-inch mixes should only be used where the reinforcement is congested...example: columns. 1-1/2 inch mixes will work for footings, if tailgated. 1-inch or 3/4 inch mixes can be used for everything else...pump or tailgate.
