After laying the concrete base footings, the next task was to cast the concrete piers enclosing the steel bars.
My original intention for moulds was to use standard cardboard tubes which are fitted with plastic linings for easy removal, but the cost proved prohibitive for a project of this size. Instead, I improvised using 8 inch plastic flowerpots, which were remarkably successful – even though removal of the flowerpots when the concrete was set involved destroying them.
I used a strong (‘C35P’) concrete mix of 1 part cement to approx. 3 parts ballast. An 18 inch length of steel rebar was inserted through a hole in the bottom of the flowerpot both as reinforcement for the pier and to provide a fixed location for the glacial boulder and floor beam. There was some difficulty getting the piers broadly the same height and the rods in the correct position and vertical, but at least the hole in the flowerpot kept the rod in position while the concrete was setting.
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