Hello Geoffrey,

I know it has been awhile since hearing from us. Have been very busy and a little discouraged with the testing of the bricks and the different soils. I am sending three different soil samples that I have been working with to arrive to the perfect sample …if that is possible.

### one more question

Hello Geoffrey, Every step seems to present their own set of hurdles to overcome. I think I´ve finally found a good mix with the soil and other elements locally. The 1:4 mix seems to work the best with 10% cement (1 soil, 4 sand, 10% cement) and 21 days to cure. I had at one time one of your work sheets to help calculate costs, but have misplaced it. What I need to know is how many full size bricks can be produced per 1 square meter of mixed product? Steve

### calculation

Dear Steve,

Your diligence and good thinking are admirable. I'm happy to hear you have a mix that you like and are confident with. The soil you have chosen apparently has a high clay content. So, you are using a high sand content mix with a very economical cement content. I believe you'd like to know how many blocks you can produce per a unit volume of sand, soil and unit weight of cement. In the appendix of one of my books there is a method for calculating the cost of a block. I have developed a new calculation method that I like better but the old one will also work. In any case, you need to start with your mix sheet which gives you amounts (weights and volumes) of materials in your mix. You also need to know the weight of your block; the charge weight is preferred (the weight of material that you put into the block press). The cured weight of a block might be slightly different.

The basic calculation method is: find the quantity of blocks that one mix can produce. Divide the amount of each individual material in the mix by that quantity of blocks. You'll have the amount of material per block. Then take your purchasing unit for each material and divide it by the amount of that material in one block. Your units must be consistent. For example, if one block weighs 8 kg and your total mix weight is 48.6 kg then you get 6.1 blocks per mix. If the mix contains 4.5 kg cement then the amount of cement in one block is 4.5kg / 6.1blocks. So, there is 0.738 kg cement/block If your cement comes in a 50 kg bag then take 50kg / bag divide by 0.738kg/block and you'll see that you can get 67.8 blocks per bag of cement. For the sand and soil you can calculate in the same manner only with units of volume (FYI, there are 1000 litres in a cubic meter).