Mix Design

Developing the lighter than water mix can be one of the most challenging tasks. The iterative proccess should be started immediatelly - even before the strength requirements derived from the structural analysis are known.

Resources

The spreadsheets above may help to reduce the number of mixes that need to be tested by estimating the final unit weight. However, I recommend that you check the spreadsheet before using it. In some versions the ammount of water and superplasticizer are input manually. As the rules change, the percentage of fly ash and sand to include will also change. Proportions can be changed by editing column 'c.' Values are input as a percentage of the cementitous materials (cement and flyash).

Methods

Fiber Reinforce or Engineer Cementious Composites
The 2002 Canoe, the Duke, was reinforced eclusively with polymer fibers. This produced an extremely durable lightweight canoe. Engineered Cementitous Composites (ECC) is a specially developed mix proportioning and placement method for fiber reinforced concrete patented by Professor Li's ACE-MRL group. In general, a very loose mix will be required to achieve adequate dispersion of the polymer fibers.

Ferrocement
Actually a method of construction, it is commercially used to built boats. The 2003, the Great Javan Rhino, uses this method. Alternating layers of Concrete and reinforcing mesh are placed to form a laminated cross-section. The concrete can have a thick consistency that is easier for forming. Professor Naaman recently wrote a book on the subject.

Composite
uncharted territory for the MCC, this method requires fewer layers of reinforcming mesh but includes fibers for secondary reinforcing. In 2003, Michigan Tech used this method.