When working with concrete, you want to ensure that the mix is prepared properly in order for it to cure. Yet determining the amount of sand -- a primary component of concrete -- needed can be difficult to estimate if you have never worked with concrete before. Following these basic guidelines will put you on your way to preparing concrete for your next home improvement project.
While people commonly consider sidewalks to be composed of cement, they are actually made of concrete. Concrete is a combination of aggregates and paste. The aggregates are usually sand, gravel or pulverized stone, and the paste is made of water and cement. Once the components of concrete are mixed, the cement and water solidify and bind the aggregates to form a rock-solid material. The hardening process persists over time, gradually getting harder every year as the concrete mixture continues to fortify.
General Mix Proportions Guidelines
The Portland Cement Authority states that viable concrete can be made using multiple mix proportions, and no single method is best. However, it recommends obeying the rule of "6's" for preparing concrete: a minimum of six bags per cubic yard of cement, a maximum of six gallons of water per bag of cement, curing the concrete by keeping it wet for at least six days and a 6 percent air content.
The basic component ratios for preparing concrete depend on the maximum course aggregate size -- the size of the aggregate particles, whether crushed stone, gravel or sand, you are using, states Portland Cement Authority. Each aggregate particle is graded by size, generally ranging from 1/4-inch up to but not to exceed 2 inches. As the maximum course aggregate size is decreased, the cement content must be increased so that the necessary amount of cement paste can appropriately bind the aggregate elements. That being said, the amount of wet sand is not affected by aggregate size. The proportion is typically 2-1/2 parts wet sand for every 94 lbs. of cement, with 1 part equaling 1 cubic foot of material.
Once you understand the basic principles of how to compute the material proportions required to mix concrete, you can apply them to your specific project. For example, a 3/4-inch maximum course aggregate requires you to use 1 part cement mixture, 2-1/2 parts wet sand, 2-1/2 course aggregate and 1/2-part water -- together these material proportions equal 6-1/2 total parts. The actual total amount of prepared concrete is about 2/3 of the total of the component volumes needed to produce the mixture.