A ratio of 1 part cement to 6 parts ballast yields concrete appropriate for roads, pathways, and patios, whereas a ratio of 1:8 yields foundation-strength concrete. For a normal-weight concrete driveway, you will need 200 pounds of cement and 100 pounds of ballast per cubic yard. Lighter colors require less cement but the same amount of ballast; darker colors require more cement but the same amount of ballast.
Cement is the main ingredient in concrete. It's a mixture of limestone powder and clay (or other minerals) that has been processed into a paste. When mixed with water, cement sets into a hard mass. There are two types of cement used in concrete: portland cement and blended cements. Portland cement is made from limestone powder and clay as well as various additives such as calcium carbonate, sodium carbonate, sulfates, and silica. The type of cement used affects the color and texture of the finished product. Blended cements are combinations of portland cement and other materials such as ground rice hulls, ground glass, or sand. They usually produce concretes with similar properties to those made with portland cement but can be cheaper.
Ballast is the second main ingredient in concrete and provides it with weight so it can be spread out over an area before setting.
Say it aloud: "Pause." In terms of "how many bags of cement to a ton of ballast?" there are normally 6 bags of 25kg (total 150kg) Portland cement to a ton of ballast by employing a one-part cement-to-six-parts-ballast ratio. A ton of ballast requires 7 bags of cement for a 1:5 mix, and 9 bags of cement for a 1:4 mix. Therefore, a typical mix for 1 ton of ballast consists of 250kg of Portland cement and 500kg of sand.
The exact amount of cement required depends on the type you buy. The most common types of cement are portland cement and concrete cement. Both have different ratios of calcium carbonate to silica. Concrete cement is typically higher in silicon dioxide than portland cement, so it can be used in more acidic environments.
Concrete cement is the type usually found in home improvement stores. It's suitable for most applications where portland cement would be used. It's available in pails with or without additives. If you add sulfur trioxide (SO3) gas during mixing, the resulting concrete will appear white instead of gray. This additive increases early strength and durability while reducing the risk of corrosion for internal steel reinforcements. Concrete cement leaves some room for variation depending on the brand; generally, 1 ton of this type of cement requires between 320 and 400kg of sand.
Portland cement is the type usually found in construction centers. It's suitable for most applications where concrete cement would be used.
Ballast for concrete is made up of coarse elements such as sharp sand, gravel, and limestone. The majority of the cement mix is made up of concrete ballast, often known as aggregates. Ballast is also made from recycled materials such as air-cooled furnace slag or quenched molten slag. These types of ballast are called reactive or supplementary ballast.
The main purpose of using ballast in making concrete is to increase the density (weight per cubic foot) of the finished product. This allows for reductions in the amount of cement used while still achieving the required strength. Reactive or supplementary ballast increases the amount of cement needed because it requires more than regular portland cement. However, if sufficient water is added during mixing, the ballast will hydrate and the increased amount of calcium carbonate will reduce the amount of cement needed.
In addition to increasing density, ballast also affects other properties of the concrete such as color and texture. Concrete with a high percentage of ballast tends to be gray instead of white. It may also have a gritty feel underfoot when dry.
Ballast can be mixed with concrete in two ways: before mixing with water or after mixing with water. Before mixing with water, the ballast should be covered with a layer of mortar (cement paste).
I'd say you'll need a little more than one 1 ton bag of ballast and about six bags of cement. A 1 ton bag weighs about 900 kg (approximately), therefore I'd imagine 40-45 bags weighing 25 kg apiece. A 1:4 ratio is fairly powerful; a 1:6 ratio would suffice, with 12 shovels of ballast to 1/2 bag of cement.
A common mistake made by people who don't know much about cement is to use the same amount as sand for their mix. This isn't good practice because if you add too much cement, then the mortar won't set properly; if you add too much sand, then the mortar will be too weak. A proper quantity of cement should make up 10% of the weight of the sand, but this depends on how hard you want the finished product to be. If you want it workable right away then less is better, whereas if you want it to last longer then more is better. There's no real right or wrong here, but depending on your situation you might want to go with either option.
As far as the length of time needed for the cement to dry, that really depends on the temperature where you are building this thing. In warmer climates you can get by with just a few hours, while in colder climates you might need a day or two of constant exposure to the sun. Cement doesn't evaporate so there's no way around this problem. The only way to speed up the process is by using a heat source such as an oven or stove.
10mm ballast is made up of 10mm gritstone and 10mm grit sand. It is used to mix concrete in tiny quantities when a finer mix is desired. This medium is also useful when you need a fast-setting concrete.
A common application for this material is as a base course in footpaths, driveways, and parking lots. The coarse aggregate in the 10mm ballast helps the concrete resist frost heaving while the fine powder helps it cure quickly.
This type of ballast is not recommended for use as a core sample material because the coarse aggregates will remain in the concrete after it sets. This could potentially damage any embedded metal objects!
The best part about using this type of ballast is the price: A 10-pound bag of 10mm grit stone costs around $20 and a bag of 10mm sand is less than $3. The total cost of these two items is only $23. That's cheaper than buying concrete mix on an average size project!
Also worth mentioning is that this type of ballast does not have a long life span. If it is not used within one year then it should be discarded. This is different from regular concrete where 5-10 years is typical.
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