For centuries, stones have been used as essential elements in construction due to their toughness and durability. While some stones like granite and basalt are known for their superior strength and durability, others like gneiss are often used for decorative purposes. It’s important to know which one best suits your type of project with several stones to choose from.
There are many types of stones used in construction. Stones with high compressive strength like basalt, granite, and sandstone are ideal for massive construction projects like dams and bridge piers. For minor construction and decorations, stones like travertine, gneiss, quartzite, and Marble are ideal.
While some are perfect for constructing walls and foundations, others are best suited for decorative purposes. Read on as we take a look at some of the main stones used in construction. And to provide further guidance, the article will also highlight the essential requirements for good construction stones.
1. Basalt Stone
Also known as traps, basalt stones are igneous rocks formed when the molten rock solidifies under pressure. Basalts are known for their strength and compactness, which explains their heavy projects and decorative purposes.
Basalts have a fine texture that, at times, shows pores and cavities due to the escape of gases when lava cools. You’ll find that most basalts are light-dark or dark in appearance due to their abundance of ferromagnesian minerals.
With a compressive strength ranging from 200 MPa to 350Mpa, basalt is strong and compact, making it perfect for large construction projects. Basalt is highly resistant to water, wind, and other weather elements. However, the high compressive strength makes basalt very difficult to shape or dress to tiny slabs.
Besides being considerably durable, granite boasts a compressive strength of between 100MPa to 250 MPa. The presence of quartz, feldspar, and mica in graphite contributes to the stone’s strength and toughness, thus making it ideal for both small and heavy construction projects.For heavy-duty construction, granite can be used to make retaining walls, stone pillars, curbs, railway patience, exterior wall cladding, coarse aggregate in concrete, and dams.
Granite stones are well known for their reduced porosity, low absorbance value, and solid weathering properties. Despite having a low score in fire resistance, graphite can take glossy, fine finishes, thus making it ideal for use in interior decorations. Granite will also last long when used in acidic environments because it comprises quartz and feldspar, both of which are resistant to acid rain.
Sandstone consists mainly of quartz particles that eroded from neighboring rocks (often granite) over time. The quartz particles then mix with minerals found in natural cement before forming a solid whole.
Due to the presence of accessory minerals such as feldspars, micas, and even dark minerals, you can find sandstone in a wide array of colors ranging from grey, white, yellow, brown, red, dark gray, and even buff. Sandstones have a specific gravity that varies from 1.85 to 2.7 and a compressive strength ranging between 20 MPa and 170 MPa.
In combination with high-quality silica cement, sandstones are often used in the construction of large structures. Sandstones also come in handy in constructing dams, river walls, bridge piers, and several masonry work types.
Slate is a metamorphic rock (fine-grained) formed when sedimentary rocks are subjected to high pressure. Among the best slate features is its ability to be split into sheets with relative ease, thus justifying its use in most roof coverings.
Besides being used in roof coverings, slate is also perfect for pavements and slabs due to its versatility. The rock is too strong and is among the best stones for resisting potentially destructive weather elements.
Although not as capable of holding large loads as graphite, slate stands out due to its versatility. The stone can be split into appropriately-sized slabs along its foliated planes, which allows for its use in roofing works, floorings, damp proof courses, and partitions, among other uses.
There are several types of limestones, some of which aren’t ideal for use in construction. The best limestone to use in construction should be compact, dense, fine-textured, and free from cracks and cavities. Undesirable limestone types are usually soft and rich in clay content, which makes them unsuitable for use in construction.Limestone is known to contain calcium carbonate. It also contains calcite, which is obtained from marine organisms over time. The presence of calcite means limestone has fossils as part of the components, making it easy to polish or hone.
Widely used as a raw material for cement, limestone is also used to make ceilings, floors, sidewalks, cladding, bathroom wall tiles, and vanity tops. Construction engineers also fancy using limestone in the fabric of structures such as pillars, cornices, facades, and a host of other decorative features.
Disclaimer: Limestone isn’t ideal for use as a facing stone due to its susceptibility to industrial gases’ pollution. In coastal areas, limestone as a facing stone can lead to a rustic, unsightly look over time due to regular attacks from salty winds.
Laterites are sedimentary rocks consisting mainly of aluminum oxides with varying amounts of iron oxides. The rock is known to form due to igneous rocks’ chemical decomposition (alkaline) due to the leaching of some basic components, which often results in a spongy or porous texture.
The quantity of iron in laterites usually determines the color, with most laterite stones having brown, yellow, red, or gray shades. Although not the strongest stones, laterites are known to become stronger the longer they’re seasoned.
While laterite is usable in construction as a building block, the exterior must be coated for the stones to hold their weight. The stone occurs both as hard or soft varieties and is often used in pavement construction and several masonry projects.
Often characterized by its unique crystal-like features, Marble is among the most commonly used ornamental rocks. The stone is predominantly composed of dolomite or calcite crystal and often forms its crystal-like appearance due to combined pressure and heat over time.Marble is a metamorphic rock that’s both compact and strong, which explains its wide use in construction projects. The stone comes in a variety of colors, with most ranging from dense black to pure white. Similar to other stones, the color of Marble greatly hinges on the content of minerals and impurities, especially during formation.
Marbles are known for their reduced porosity, uniform texture, and ability to be polished. These features make Marble an ideal ornamental stone. You’ll find Marble used in bathrooms, floor and wall tiles, work surfaces, shower trays, cladding, and even staircases.
Marble can also make kitchen work surfaces. However, it is usually more susceptible to staining, wear, and tear than granite.
Gneiss is commonly used in ornamental stones, flooring, gravestones, and facing stones of structures. However, since the stone has strong varieties, it can also be used in light construction work.
Gneiss usually comes in different colors like purple, grey, pink, dark grey, and greenish-gray, depending on the minerals or impurities present at the formation time. Some gneiss stones are strong and durable enough to be used as dimension stones. They are sawn or seared into slabs and blocks before being used in a variety of curbing, building, and paving projects.
Despite lacking the compactness and resilience of granite, crushed gneiss can be used in light construction projects, stone pitching, and even rough stone masonry. It’s not the most popular stone out there, but it can add that bit of extra edge and transform the appearance of structures.
Compared to granite, quartzite is more resistant to staining and scratches, thus explaining why it is often preferred for kitchen countertops. Quartzite is also ideal for use in floor tiles, walls, and stairs. The stone is vital in industrial silica sand production and makes a great option for railway ballast.
Quartzite boasts of a fine to coarse grain and is mostly branded and granular. You can find quartzite in a wide range of colors, including yellow, gray, and white. The stone isn’t the best for heavy construction but is known to make an excellent (albeit pricey) option for interior decoration.
Travertine usually has troughs and pitted holes on its surface, thus making it highly porous. However, its internal properties make the stone easily polishable, which is advantageous when used as an ornamental accessory for interior decorations.
The stone is a type of limestone and is formed through calcium carbonate’s rapid precipitation. Granted, you cannot use travertine for heavy construction, but you can still use it in light projects like flooring, wall cladding, facades, shower trays, vanity tops, stands, and basins.
Alabaster has been used in construction for several centuries, with the stone commonly used in altars, effigies, tombs, and religious carvings during the medieval period. However, the stone is now widely used for light to medium fittings due to its translucence.
Unfortunately, alabaster isn’t weatherproof and can disintegrate considerably if exposed to elements like heavy rainfall, strong winds, and snow over time. Some people even use alabaster to make windows due to its translucence.
Therefore, due to its softness, alabaster can be easily carved into different shapes. Please note that alabaster is highly sensitive to water, and prolonged exposure to moisture will make the stone dull, rougher, and less translucent than normal.
The Main Requirements of Good Construction Stones
Not all stones are ideal for heavy construction. Similarly, for internal (or external) decoration and finishing, you’ll need aesthetically appealing stones that are easily transformable into different shapes and patterns.
Let’s take a look at some of the crucial things to consider when purchasing construction stones.
Strength of the Building Stone
Building stones should be strong enough to resist both dead and dynamic loads. For large construction projects, it is highly advisable to use stones with high compressive strength. Using stones with reduced load capacity means the structure won’t be strong enough to hold the overall weight, leading to structural integrity concerns.
The ideal strength of a building stone used for large projects (including foundations for homes) is within the range of 60-200N/mm2. Be extra careful to select a stone that’s strong enough to handle your desired structure’s weight and compact enough to withstand years of dead and dynamic loads.
Stones are constantly exposed to elements such as rain, wind, sun, and even vibrations due to earth movements. As a result, you should choose strong and durable enough stones capable of withstanding the destructive effects of the mentioned agents.
The durability of construction stones usually relies on the stone’s chemical composition and the immediate atmospheric surroundings’ chemical elements. Additionally, stone texture also plays a role in determining a stone’s durability.
To be on the safe side, go for close-grained and crystalline homogeneous stones that have dense structures. These stones hold their weight pretty well and are strong enough to resist gradual deterioration due to wind, rain, or other elements.
Hardness and Toughness
In addition to checking for durability, you should also consider the hardness of stones, especially if they’re meant for use in high traffic areas. Stones used in floors, bridge aprons, and roads should be hard and tough enough to resist abrasive forces resulting from friction and gradual wear.
It’s advisable to use the Mohr’s scale of hardness to determine the toughness and hardness of stones you intend to use in your construction. You can also scrap the surface of the stone to determine its hardness. Hard stones rarely show any scratches after intense scraping.
As a rule of thumb, the higher the specific gravity, the stronger and more capable the stone is to withstand enormous weights. Therefore, stones with high specific gravity are best if you’re working on heavy-duty construction projects like dams, docks, harbors, and retaining walls.
Porosity and Absorption
Did you know that the porosity of stones usually depends on the parent rock’s structural formation and mineral constituents? Therefore, it is crucial for construction projects (especially exposed stones) to use non-porous stone as they’re usually tougher and more resistant to gradual disintegration.
Stones with high-porosity ratings tend to absorb water than their less porous counterparts. This explains the need to use solid, non-porous rocks in heavy-duty construction projects. Rainwater often freezes inside the pores in cold environments, leading to disintegration as the stones become more porous.
Therefore, it is highly advisable to conduct porosity tests to determine how porous a stone is before using it in construction. Please note that, in construction, porous stones should only be used in strategic locations, especially where they aren’t likely to encounter rain, frost, or excessive moisture.
Seasoning and Dressing
The best construction stones should be well seasoned and free from quarry sap. You can get rid of quarry sap by placing the stones inside a shade without walls to allow for gradual drying and air circulation. Disclaimer, seasoning duration differs between rocks, with lateritic stones needing at least months to season after quarrying.
You should also check on the dressing ability of a stone before using it in a construction project. The stones should be easy to cut into blocks and square as per the measurements. You’ll need tools like a hammer, puncheon, ax, and chisel to season your stones. The dressing cost of stones during construction can go considerably high, exactly why you should consider stones that are easy to season.
It is always advisable to check the appearance of stones before making a purchase. Ideally, the color of stones should complement your primary design. And as most architects can confirm, houses and commercial buildings usually look better when they match the immediate surroundings.
When selecting colors, going for lighter shades instead of darker ones is highly recommended. This is because lighter shades are usually less susceptible to fading over time. However, the strength of stones should not be judged by appearance, which means you`ll need to check for both features separately.Appearance matters more when it comes to stones meant for face works and other decorative purposes. Before choosing a set of decorative stones for your interior or exterior décor, check on the color coordination, attractiveness, and quality of the shades to ensure you get a durable product.
Fire-resistant stones enhance property value, especially since the building or structure is more capable of resisting fire and other extreme conditions. Building with fire resistant stones also helps homeowners to get favorable home insurance rates.
Therefore, when shopping for fire-resistant stones, be sure to choose products that are free from oxides of iron, calcium carbonate, and minerals with different thermal expansion coefficients.
The cost of stones is an important consideration that should be made well before construction. Some stones cost more due to their versatility, strength, and durability, while others tend to cost less.Overall distance to the quarry also plays a crucial role in determining the total cost of the stones. The closer a quarry is to the building or structure you’re constructing, the lower the total cost due to reduced transport costs.
A stone’s texture indicates the alignment of its constituent minerals. As such, a good building stone should have a homogenous structure. This is because stones with crystalline and homogenous textures are usually compact and hard compared to their open-texture, non-crystalline counterparts.
Stones meant for use in large construction projects should be free from cracks, patches, cavities, or even loose material. For ornamental carvings, you should ensure stones are fine-grained in order to achieve your desired aesthetics.
Good stones shouldn’t weather even after prolonged exposure to elements such as rain, sunlight, wind, and even snow. And to determine the weathering properties of a particular stone, inspecting ancient buildings made from similar materials is highly recommended. You should examine structures in an environment similar to where you’re planning to construct.
If the old buildings you examine have retained their sharp corners and edges, chances are the stone will also work well despite prolonged exposure to rain, intense sunlight, and strong winds.
You might also need to consider the weight of stones when working on construction projects. Heavy stones are known to have high specific gravities besides being compact and less porous than lighter varieties.
Heavy stones are ideal for heavy-duty construction such as docks, barrages, dams, and retaining walls. But for light construction like domes and roof coverings, lighter varieties of stone tend to work best. Therefore, the weight of the stones you use should depend on the nature of the construction.
Classification of Rocks/Stones
There are three main ways to classify rocks: geological, physical, and chemical classifications. Rock classification usually plays an integral role in determining the characteristics of a particular stone. Below is a brief discussion of the main classification of rocks,
When it comes to geological classification, stones are usually recognized by the physical changes, such as melting, cooling, gradual erosion, compacting, and eventually deforming. Here are the three types of rocks based on geological classification.
Sedimentary rocks are usually formed from pieces or sediments of other rocks or organic material. The pieces or sediments form as neighboring stones continue to erode over time. The sediments are then transported by weather agents like wind, gravity, frost, and water.
After piling up gradually, the sediments then form layered structures, thereby resulting in sedimentary deposits. The main types of sedimentary rocks include clastic, organic, and chemical sedimentary rocks.Organic sedimentary rocks form from biological materials like shells, plants, and bones, a great example being coal. Contrastingly, clastic sedimentary rocks (like limestone) form when pieces or clasts of other rocks weather over time. Chemical sedimentary rocks usually result from chemical precipitation and often form stones like halite, flint, and limestone.
Igneous rocks form when magma solidifies below the earth’s surface. Igneous rocks will only form when magma fails to erupt and consequently cools and solidifies beneath the surface. Normally, the strength of igneous rocks tends to vary based on the depth or location of the magma at the time of solidification.
When magma hardens deep below the earth’s surface, the resulting rocks are called plutonic rocks and usually feature a coarsely grained crystalline structure, an example being granite.
Similarly, magma that hardens at an average depth forms hypabyssal rocks with finely grained crystalline structures. Finally, rocks that form closest to the earth’s surface are called volcanic rocks and are usually fine-grained.
As the name suggests, metamorphic rocks form through gradual metamorphism over time. Metamorphism usually occurs when stones change their characteristics as a result of pressure and heat. The pre-existing rocks could either be sedimentary or igneous. Gneiss, Slate, Marble, soapstone, and schist are some common examples of metamorphic rocks.
There are three main types of rocks based on physical classification: stratified, unstratified, and foliated rocks. Below is a brief description of the above rocks.
Stratified rocks usually have different layers, with the layers separated by cleavage planes. The cleavage planes, also called bedding planes, are more often than not the point of weakness where the rocks can be easily split up. Common sedimentary rocks include limestone, shale, and sandstone.
Unstratified rocks tend to have a crystalline structure. These rocks usually feature a uniform structure throughout their entire body. You’ll find that most igneous and sedimentary rocks can be classified as unstratified rocks, with granite, trap, and Marble making the best examples.
Foliated rocks usually possess a banded or layered structure that stems from prolonged exposure to heat and pressure. Contrary to stratified rocks, foliated rocks can be split in a single direction only. Metamorphic rocks like gneiss, slate, and schist tend to fall under the category of foliated rocks.
Rocks are also classifiable based on their chemical content. From a chemical perspective, there are three main types of rocks-argillaceous rocks, calcareous rocks, and siliceous rocks, as discussed below.
Argillaceous rocks contain clay as the predominant content, consequently making the resulting stones softer and more likely to crumble. Laterites, slate, and shale are common examples of argillaceous rocks.
Calcareous rocks usually have calcium carbonate as the main ingredient. Although generally hard, the durability of calcareous rocks often hinges on the constituents of the surrounding rocks and plants. Examples of calcareous rocks include limestone, dolomite, and Marble.
Siliceous rocks contain silica as the predominant content. The presence of free silica (in abundance) makes siliceous rocks hard and durable, and resistant to gradual weathering. Quartzite, chert, and granite are common examples of siliceous rocks.
As observed in this reading, there are many types of stones used in construction, with each having its unique set of characteristics.
The best stone for use in construction should be one that suits your building needs. For instance, you’ll need heavy stones with high specific gravity and minimum porosity for large projects. Ornamental rocks like Marble usually come in handy when looking to beautify or decorate your structure.
Therefore, as you choose construction stones, it’s best advised to consider some of the key factors such as seasoning, dressing, appearance, strength, durability, porosity, and specific gravity.