Purchase a large wheelbarrow to mix concrete in. Using a standard household bucket, add 2 buckets of sand, 3 buckets of gravel, 2/3 bucket of Portland cement and 1/3 bucket of fly ash to the wheelbarrow. Adjust amounts proportionally to match the size of concrete batch you need.
Mix dry ingredients well using a shovel. Slowly add ½ bucket of water and mix continuously until reaching an even consistency. Increase water proportionally to any increase in the other materials.
Continue mixing for 2 to 3 more minutes to help begin the hydration process. Do not mix too long or the concrete will begin to harden and become difficult to work. Scoop the finished concrete mixture into the prepared mold(s) for your project. Smooth and let harden.