Granite, Limestone or Concrete - Which is better?

When it comes to construction, the topic of construction aggregates is never far behind. You might be wondering what they are. They are simply the most mined construction materials in the world!

Construction aggregates, otherwise known as aggregates, is a broad classification of coarse to medium construction materials that are grained particulate in nature. Some examples of aggregates are geosynthetic aggregates, recycled concrete, slag, crushed stone, gravel and sand.

Now that we know what construction aggregates are, let's discuss which construction material is better: granite, limestone or concrete.

The Importance of Aggregates    

Aggregates are key components of composite materials like asphalt and concrete. They are added to composite materials to reinforce their strength. Because of their high hydraulic conductivity value in comparison to soils, they are the preferred construction materials when it

comes to creating French drains, foundations, roadside edge drains, retaining wall drains and septic drain fields.

Construction aggregates are also the preferred base material under railroads, roads and foundations. They help stabilise the construction project, preventing them from settling under the building or road. They also serve as inexpensive extenders that bind well with cement or asphalt.

A concrete mix is made up of 60 to 80 per cent construction aggregates, providing the majority of the bulk to the mix. To make a good concrete mix, the aggregates must be hard, clean, and free of clay coatings, absorbed chemicals or other fine substances.

A careful choice must be made on what aggregate is best for a specific project. Different aggregates have different qualities and they are chosen solely for their material strength, durability and workability. They are divided into two categories; coarse and fine.

Coarse construction aggregates have a diameter of more than 4.75mm but the usual diameter range it is used is between 9.5mm and 37.5mm. Fine construction aggregates, on the other hand, have a diameter of less than 9.55mm.

The commonly used aggregate size in construction is 20 mm while 40 mm is commonly used in creating mass concrete. Typically, the larger the aggregate diameter, the lesser amount of water and cement is needed in the concrete mix.

What is Granite?    

Granite is a common type of igneous rock with phaneritic and granular texture. It is generally found in colours of white, pink or grey.

The word originates from the Latin word granum, meaning grain, which is a reference to its grained structure. By composition, it is made of 20% to 60% quartz by volume and 35% alkali feldspar. The term 'granite' is also used for other types of coarse and grained igneous rocks that contain feldspar and quartz.

What is Limestone?

Limestone is a sedimentary rock that is made up of skeletal particles from marine organisms like molluscs, foraminifera and coral. It is predominantly composed of aragonite and calcite, minerals that create the calcium carbonate crystal forms.

Limestone is a popular choice for construction aggregate because of its decreased likelihood to react with alkali-silica, considerable strength and minimal drying shrinkage in concrete.

What is Concrete?

Concrete is considered as the most extensively used man-made substance in the world, second only to water. The other major component of concrete is the binding medium which is used in binding construction aggregates together to form a tough composite substance. The most common concrete material nowadays is the chemical combination that results from mixing cement and water.

If you can see any city in the world, you can fairly conclude that the future of concrete is very bright. Because of the numerous satisfactory engineering features and affordability, concrete has become one of the most preferred materials for constructions projects.

As we have mentioned earlier, concrete is a composite substance made of fluid cement and coarse aggregates which solidifies over time. The majority of concrete used nowadays are lime-based (Portland cement concrete) or are formulated using other hydraulic cements (ciment fondu).

The concrete that is mostly used in creating roads, known as asphalt concrete, is also a type of concrete which uses bitumen as its cement material while polymer concrete, another type of concrete, uses polymer as its cement material.

The concrete that is mostly used in creating roads, known as asphalt concrete, is also a type of concrete which uses bitumen as its cement material while polymer concrete, another type of concrete, uses polymer as its cement material.

Whenever construction aggregates are mixed with Portland cement and water, it turns into a slurry that can be easily poured and moulded into specific shapes. The magic begins when cement is added with water. Once they are combined, a chemical reaction happens: it turns into a substance that is as hard as stone. To improve the strength of the hard matrix or finished material, additives like superplasticizers or pozzolans are included in the slurry.

As soon as the concrete is ready, it is usually poured with reinforcing components like rebar, producing a reinforced concrete.

Which is better?

The answer actually depends on what type of construction project you are going to do and what type of materials are needed to finish it.

Adding granite aggregates to a concrete mix is also a great option because granite demonstrates a high compressive strength while curing. This is due to the fact that granite is an igneous rock that is tough and strong. Its surface texture permits correct bonding between cement and construction aggregates, making it a stronger mixture than limestone and concrete.

If you need construction aggregates that have a reduced capacity for drying shrinkage when mixed with concrete, it is good to use fine limestone. Even the pore volume of the limestone itself is not substantial in the reduction of drying shrinkage.

Limestone's elastic modulus, density and hardness are the key factors in reduced capacity for drying shrinkage. However, if the limestone rock surface has many pores, the possibility of shrinking would increase because of the shrinkage effect and the adhered paste. The amount of water that is added into the concrete and limestone mix may bring about shrinkage when it evaporates out from the mixture.

It is also worth taking note that increasing the amount of limestone aggregate on the concrete mix will improve the strength, durability and elasticity of the final product.

Using concrete by itself for construction purposes is not advised. As you can remember, concrete needs to be incorporated with construction aggregates, cement, water and reinforcing components to produce a hard matrix that will improve its strength and durability. Therefore, concrete mixed with the proper type and amount of construction aggregate is the better choice than using concrete alone.