Relative to Rogers comment ( well done Roger ), you will want to do an "on call" for the last load to adjust the amount.
Also, notice he scaled down the yard to 26.5 ( there abouts ), that is why we used to use 75 instead of 80.
Mud work is hard. Smokingcobra, if you are going to do this one yourself, get 2 grunts and two or three finishers. Pay the grunts $100. ( might be more in your area ) for the job. Pay the finishers $200 each ( cash ) for the job ( here again, might be more in your area ). 4 hours of work to do the pour.
Just a bit more info.
Steve, spalling look real bad.
