Concrete mixes are made from a ratio of 3 items: cement, water and aggregate which is sand and rock. Sometimes, other additives may be added to the mixture for special purposes, such as accelerating the drying process. No proper configuration of the concrete mix, just proportions. Note that the blends may vary depending on the purpose of concrete.
Portland cement and water
Portland cement, when mixed with water, forms a paste which joins all aggregate materials. Water added to the cement reacts chemically with it to begin the drying process. The amount of water affects the thickness and the ability to work of the paste that was formed. The less water is in the mix, stronger and less permeable is the cement produced. Here, the ratio of water and cement is the most important factor that affects the quality of concrete.
Aggregates
The sand is used as a fine aggregate and gravel, or crushed stone, part of the course. The stronger concrete used the hardest mixed with the largest aggregate coarse sand and good. For finer finishes or delicate concrete, use smaller sand stones. For structures such support, large stones strengthen the finished concrete. Moreover, smaller aggregates are required for one that will be pumped.
Proportions of water to cement
The proportions of water is generally around 50%, in severe conditions of sulfate, the Uniform Building Code 1997 recommends a maximum of 45% water in the proportion of cement. For conditions where this material will be exposed to severe conditions of freezing and thawing, the maximum rate is 50%. The permeability or the tendency to absorb water increase exponentially if a mixture of concrete has a higher proportion than 50% water; note that durability and strength will also decrease. A proportion of 45% can withstand about 4500 pounds per square inch (2,401 kilograms per square cm), whereas a proportion of 50% only withstand about 4000 psi (1,814 kilograms per square cm).
Formulas
A suitable proportion of water to cement is obtained by dividing the amount of water with equal volume of cement. One cubic yard (0.76 cubic meters) of water weighs about 235 pounds (106.5 kilograms), with 470 pounds (213 kilograms) of concrete will have a share of 50%. When you calculate the gallons (liters) of water, multiply the number of gallons by 8.33 to obtain the number of pounds (liters) of water. A formula to add water to cement 2-2-1 could use a cubic yard (0.76 cubic meters) of water, a cubic yard (0.76 cubic meters) of concrete and half cubic yard (0.38 cubic meters) aggregate. Speak well with your concrete supplier to inform you about the best mixing ratio must be used for the job you’re going to do. He can make several suggestions, but up to you to make the final decision for the type of work you are going to perform.