Concrete is a building material known for its marvellous strength and wide range of applications. Its usage worldwide (weight for weight) is twice that of wood, steel, plastic and aluminium combined. When mixed concrete hardens, it gives a stone-like finish that is extremely useful in construction. However, how is concrete produced, and how is the right mix achieved? In this article, we will enlighten you about the correct concrete mix ratio using ballast.
What Is Concrete Made Of ?
Mixed concrete is made up of basically two materials:
- Cement, the binder which holds other materials.
From rapid hardening cement to portland cement, natural or synthetic, cement is made of finely ground powder which hardens when it reacts with water. Water is crucial in the production of cement. Water-cement mix sets through a chemical process known as hydration.
Additives are added to give concrete other desired properties. Accelerators hasten the hydration process, and plasticisers improve the workability of concrete. Also, corrosion inhibitors minimise corrosion.
- Concrete ballast or aggregates, which provide the bulk, increases the strength of the concrete and improves its properties to suit its application.
Ballast for concrete comprises of coarse materials like sharp sand, gravel, and limestone. Concrete ballast or aggregates make up the bulk of the cement mix. Recycled materials such as air-cooled furnace slag or quenched molten slag are also used in ballast. The amount and particle sizes and distribution of concrete ballast added to a cement mix significantly affect the strength and the amount of cement used in the cement mix. Sometimes decorative stones such as river stones, quartzite and shattered glass are added for a more elegant finish known as an exposed finish.
More Ado About Concrete
High strength concrete has relatively high compressive strength. This strength is measured in megapascals (MPa) or pounds per square inch (psi). The compressive strength gives a measure of how well a material resists load due to compression. This high strength makes it suitable for roads, patio, bridges and other structural uses. Steel reinforcement is added to make it stronger. A wide range of concrete grade is used for different applications.
Low strength concrete has a strength of about 14MPa. It is often made by adding foam or using lightweight ballast mix. Concrete with over 35MPa in strength is regarded as commercial-grade concrete and is used in road works, foundations, support and structural beams. Concrete greatly exceeding 40 MPa is used in bridges and other heavy construction. The strongest of concrete grades used for super rigid structures generally exceed 100 MPa in strength.
Need Aggregate Suppliers – Call: 01702 200 119
One of the most important factors in making concrete with your required strength is the cement to water ratio. Using less water makes the concrete stronger, and using excess water will make the concrete less workable. Also, using too much water leads to segregation of the sand and aggregate particles and cause microscopic pores in the concrete. This process is called bleeding, and it makes the concrete weaker than it should be.
Generally, your water to cement ratio should be between 0.35 and 0.6. If you need to mix concrete more than once for the same project, you should ensure that all batches of the concrete mix are consistent. More importantly, adjusting the cement to ballast ratio gives you varying concrete strength.
Ensure that the concrete is blended expertly to maintain its properties and for better workability. The aggregates and additives should be added after the water and cement have been mixed to achieve maximum strength.
Mixing The Right Amount of Ballast
For making a cubic metre of cement with 20 MPa strength, mix 320 kg of cement, 600 kg of sand with 1200 kg of aggregate. This can be easily scaled down to whatever amount you require. This concrete mix can be used on driveways and paths and other domestic purposes. The right amounts of ballast or sand-aggregate can also be expressed in simple ratios. So for the concrete mix mentioned above, your cement: sand: aggregate ratio should be 1:2:4 or ballast to cement ratio of 6 to 1.
For a low-grade concrete with 10MPa strength, the perfect ratio should be 1:3:6. For 30MPa concrete use 1:0.75:1.5. The cement to aggregate ratio should be increased to produce concrete with higher strength.
Getting the right concrete mix ratio can be a tricky thing, but something else can be much more inconvenient, and that is transporting all the materials. You need professionals who will put you first at all times. At TJC Transport, we offer a wide range of aggregates which can be delivered to you. You can also choose to come to collect them. Contact us today!