a. The calculated mix proportions shall be checked by means of trial batches, quantities of material worked out in accordance by step by step procedure shall comprise Trial Mix no. 1.

b. The quantity of materials for each trial shall be sufficient for at least three 150mm size cube concrete specimens and concrete required to carry out workability test according to IS 1199-1959.

c. Workability of the Trial Mix No. 1 shall be measured. The mix shall be carefully observed for freedom from segregation and bleeding and its finishing properties.

d. If the measured workability of Trial Mix No.1 is different form the stipulated value, the water content shall be adjusted suitably.

e. With this adjusted water content, the mix proportions shall be recalculated keeping the free water cement ratio at the preselected value which will comprise Trial Mix NO. 2.

f. In addition, two more Trial Mixes No.3 and 4 shall be made with the water content same as Trial Mix No. 2 and varying the free water cement ratio by +/- 10 percent of the preselected value.

g. Mix trials give sufficient information to form relationship between strength and water cement ratio.

h. Using the relationship so obtained between the compressive strength and water cement ratio, and change needed in the water cement ratio to get the required target compressive strength may be easily obtained.