Before facing the problem of choosing natural stone, this seems one of the simplest on Earth. And yet, only people who already decided which natural stone best suit their projects can tell you how difficult this operation is. Of course, for the first time we have to decide on the color, but we cannot limit it to a single product, because we will not decorate that space with only one type of natural stone. So we have to consider that color as an integral part of a system that must have harmonies and suitable contrasts.
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We still have to choose the finish and tile size. But even now the selection is far from being complete, because, ultimately, we must also take into account the following parameters: water absorption, resistance to friction, physical resistance and durability. Let's take them one at a time.
Sealing
The water absorption of the stone is an extremely useful indicator that proves the resistance of the material to stains. A high water absorption means that the stone can stain because of liquids. The capacity of a stone to absorb water can vary greatly depending on the nature of the stone. Granite and marble have an absorption rate of less than 0.1%, while limestone and sandstone can record a rate of more than 10%. These figures speak for themselves about the characteristics of the material, and especially about the areas where the stones can best be used, as well as about natural stone aftercare.
From the table above, we notice that marble indicates a lower absorption degree, which would lead to the conclusion that marble is staining harder. Yet, this indicator does not reveal the whole phenomenon, because we still have to consider the stone composition. Some stains are caused by the chemical interaction between the components of the stone and the staining agent. For example, most of the limestones and marble contain calcite that is sensitive to reaction with acid solutions.
Thus, the wine spilled on one of these stones will leave stains not only by the deep penetration of the liquid into the pores of the stone but also by the superficial attack on the surface of the tile. Under these conditions, rocks whose composition is mostly composed of chemically inert (stable) minerals, such as quartz and feldspar (as found in granite), are more likely to withstand superficial staining.
Therefore, it is recommended that this type of inert mineral stones be used for flooring in risky areas from this point of view: bath and kitchen countertops, balcony balustrade, etc.
On the other hand, the aspect of the tile, determined by the internal structure of the rock, is also important. For example, a granite tile, whose composition is pigmented, can more easily "camouflage" a stain than a white marble tile. The case here is similar to a red wine stain on a red shirt compared to a red wine stain on a white shirt.
In conclusion, if the area where we install the natural stone is a very transitory and exposed to the risk of encountering frequent spills, it is advisable to choose a water-resistant stone and not to have minerals such as calcite. We will also consider a material that has a rich, variegated vein. Among the stones that meet these conditions we find granite, slate and marble with dense textures.
Very important! The rest of natural stone types that do not fit into this category can be used as bath and kitchen countertops if, for example, they are sealed and suitably maintained on time.
After all, the choice is made depending on everyone disposition to put more or less effort into the aftercare of that stone. We say this because there are materials that look absolutely fantastic, yet still many people use them in "risky" spaces.
Resistance to friction
This factor is especially important for stones used in interior design. A low friction resistance leads in time to a significant loss of stone gloss, scratches and a deeper texture degradation. Friction resistance (abrasion) is due to the hardness of the minerals that form the rock and the force between the particles that makes them stay together, to remain compact. Let's take a sandstone plate and a granite tile for comparison.
Both tiles contain quartz in a significant proportion. Quartz is a resistant and durable material, yet granite is considered more resistant to friction than sandstone. This different behavior is explained by the fact that particles in the granite composition are tighter, more compact, and in the sandstone their union is achieved by weaker forces and by a less durable clay. Through long-term friction, quartz granules can be displaced from the sandstone tile and on granite quartz granules allow the surface to gradually wear off.
A small index indicates low resistance to friction / abrasion. A number greater than 8 is an indicator that is usually considered sufficient, so that tile will be suitable for interior flooring in residential spaces. For commercial or public spaces, generally, if the tile is polished, it must have a friction resistance factor of at least 12. Such a factor will mean the stone's gloss will last longer. Obviously, this indicator needs to be higher for areas with high traffic.
Polished surfaces are more sensitive to friction and the traces occurring especially on tiles with monochrome and homogeneous textures can be seen more easily. However, proper care (permanent removal of dust, pebbles and soil accidentally) can reduce the risk of scratch marks. Considering these data, it is advisable to use honed, brushed, tumbled or bush hammered tiles in heavy traffic areas.
Pressure resistance
Pressure resistance (generally called "resistance") is denoted by MPa and describes the minimum required force at which the stone breaks under pressure or flexion (buckling).
If we try to break a 23 x 11 cm limestone brick with a 4 MPa pressure resistance, we will need to apply a force of 101,000 Newton, equivalent to approx. 10 tons.
Bending resistance
Bending resistance is another factor that is extremely relevant for thin and large tiles, such as slabs and half slabs (with lengths ranging from 290 cm to widths of 70 cm). These tiles have a great visual impact on landscaping and are therefore increasingly recommended by architects and designers. Also in this category, where the resistance to flexion is relevant, are also included large stone tiles, slate panels, kitchen countertops and bathroom countertops.
Here are some examples of flexural strength values for some of the most famous natural stones:
As you can see, all types of stone have a fairly high flexural strength spectrum, but even so, figures can predict the chance (the failure!) that the product breaks or cracks during transportation or installation. Another detail, closely related to this flexural strength index, is the size of the product. Suppose we have a 30 cm wide, 120 cm long and 1 cm thick granite tile, which has a flexural strength of 10 MPa.
We can place the board on two bricks at a distance of 110 cm between them. If we begin to put weights on the tile, when we reach 36 kg it breaks by half. The same material, with the same pressure resistance index, but 2 cm thickness, will break in half to a weight of ... 150 kg. So double thickness, 4 times higher flexural strength.
In fact, such a situation cannot happen in real life, the example is given purely to demonstrate the different material response according to thickness, but with the same degree of elasticity, flexion. Some of the conclusions that come out of the above demonstration: a double width of the tile doubles the risk of it bursting, a twice thicker tile will break at a four times the weight and the more resistance high on flexion, the harder it will be for the tile to break or crack.
Careful! These are just transport and installation situations. These risks are excluded when the tile, regardless of size, thickness or flexural strength, was suitably installed horizontally or vertically.
Durability
When we talk about sustainability, we must always think about the resistance of ancient buildings, such as the Parthenon, the Pyramids, and many other temples or theaters that withstand the test of time. The meteorological phenomena that most affect the stone are acid rain and the freeze-thaw cycles.
There is a test, especially for sandstone, where the stone is immersed in salt water, then dried in the oven. The stone is subjected to this cycle 15 times. The amount of eroded stone is weighed, resulting in a percentage of the residue that the stone loses from these cycles. The weight loss percentage of the tile subjected to the test is based on the estimates in the table below:
A natural stone that belongs to Grade A can be used for exterior cladding of walls, alleys or pool coping around swimming pools. The stones used in the pool design must have a high degree of durability, so an equivalent value of A or even higher is required.
Durability is associated with resistance. Both resistance to pressure and flexion are determined by the link between rock minerals. A tight bond between the mineral particles makes the stone more durable to the mechanical forces created by the crystallization of the salts and processes generated by water freezing. If these mechanical forces born from infiltration of water in the rock are larger than the forces that hold the particles together, the stone may be damaged or chipped.
Water absorption is also an indicator for the stone durability. High-level absorption can allow access to dangerous solutions for naturel stone such as salt or acidic water. These solutions can act chemically or physically on the internal structure of the stone. An aggravating factor in AA or A-grade atmospheres is the distribution and the size of the pores: the more pores and the larger the pore size, the greater the risk that the particular stone is affected by the climatic changes described.
However, if a durable stone (resistance to the salt-rich environment) is required, then we have to choose a stone product with these properties: a small percentage of weight loss following the test described above, a degree of waterproofing and high resistance.
Consequently
All these data presented in the article make us understand the complexity of natural stone used for interior and exterior decoration. Perhaps for some it seems complicated, but any field is complex if you analyze carefully all its details. On the other hand, knowing the details is to master the domain so that we can request the most relevant information at the time of purchase or even before, when we are looking online for the most suitable natural stone for each project individually.
Certainly this article is a good start in solving the problems of everybody with natural stone decoration project. For more information, you can write us an at , or give us a call at +.222.333.
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Crushed stone is an essential material used for various purposes in the construction and landscaping industries. It is made by crushing large rocks into smaller stones, which can be used for different projects or sold to the public. However, not all crushed stone is created equal - some types of stone are harder than others and require more crushing power and specific equipment for effective crushing. Learn different techniques and equipment used for crushing stone and their various applications.
There are two critical factors influencing choice of crushing techniques and equipment. Hardness of the rock and abrasiveness. Hardness of the rock is typically measured using the Mohs scale, where talc is rated as 1 (softest) and diamond as 10 (hardest). This scale helps determine what type of rock crusher is needed for the job. Harder rocks require more powerful crushing power from machines like jaw crushers and cone crushers, while softer rocks may be crushed effectively using less forceful equipment.
Understanding the most common rock types used in crushed stone production is essential for selecting the proper crushing process and rock crushing equipment. Here are some of the most common types:
Granite: With a Mohs hardness of around 6 to 7, granite is one of the most common rock types used in crushed stone production. It's durable, perfect for high-traffic areas like driveways and pathways.
Limestone: Ranging from 3 to 4 on the Mohs scale, limestone is softer and often used for decorative purposes in landscaping and building facades. It's also a popular choice for enhancing soil conditions.
Basalt: This rock type falls between 6 and 7 on the Mohs scale, similar to granite. It's highly durable and resistant, ideal for road construction, and a base material for construction projects.
Sandstone: With a hardness rating of 6 to 7, soft rocks like sandstone are often used in landscaping projects for their aesthetic appeal.
By correctly identifying the rock type and understanding its hardness, operators can choose the most efficient crushing technique and equipment, reducing wear and tear and maximizing production efficiency.
Crushed stone is a versatile material used across numerous industries, each benefiting from its durability and aesthetic appeal.
Road Construction: Crushed stone provides a stable base for roads and highways, ensuring durability and resistance against weathering and heavy traffic.
Agriculture: It improves soil drainage and aeration, enhancing crop growth and health by preventing waterlogged soil.
Drainage Systems: Acting as a reliable filter, crushed stone separates water from various materials, preventing erosion and protecting infrastructure.
Roofing and Heat Reduction: Roofing reflects sunlight, reducing heat absorption in buildings and contributing to energy efficiency.
Erosion Control in Bridge Construction: It stabilizes soil and prevents erosion around bridge abutments, contributing to the structure's longevity.
Concrete and Soil Layering: Crushed stone is a critical component in concrete production and is used for layering in soil to improve stability and drainage.
Decorative Landscaping: Beyond its practical uses, it also serves decorative purposes, enhancing the aesthetic appeal of outdoor spaces with its natural beauty.
In each application, crushed gravel and stone are invaluable, offering both functional benefits and enhancing the visual landscape. The demand for crushed stone is primarily determined by the level of construction activity and the demand for construction materials.
Choosing the right equipment to crush rock is essential to maximize efficiency, minimize maintenance, and produce high-quality crushed stones suitable for various applications.
Jaw Crushers: A jaw crusher is immensely powerful, making it ideal for crushing large, hard rocks like natural stone, granite, and basalt. They work by applying compressive force, which breaks down large materials into smaller pieces, making them the first choice for primary crushing stages where large rock sizes are encountered. Jaw crushers are also used for rock such as sandstone as this aggregate is extremely abrasive. The exception though, is that small/mini jaw crusher while perfect for concrete, block, and brick, should not be used for hard rock.
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Impact Crushers: Impact crushers offer efficient crushing capabilities for soft to medium rock types, such as limestone and less abrasive materials. These machines operate by hurling materials against hard surfaces to break them down into smaller pieces, which makes them particularly suitable for creating well-shaped particles for construction projects.
Cone Crushers: Suited for secondary and tertiary crushing stages, cone crushers are designed to crush medium-hard to hard materials. They are particularly effective in achieving fine material grades. Their design allows them to crush materials by compressing them between an eccentrically gyrating spindle and a concave hopper.
Hammer Mills: Hammer mills can be a practical choice for softer rock types like sandstone. They use the principle of impact to fracture materials, with hammers attached to a spinning rotor impacting the rock at high speeds, breaking it into smaller pieces.
Beyond the primary stone crusher and secondary crushers, screeners play a vital role in the stone-crushing process by grading the crushed material by size.
Screeners, or screening equipment, are integral to this process. They work by sorting crushed stones into various size categories using vibrating screens or mechanical separators. Thus, sorting large, medium, small, and stone dust into separate piles can help simplify the project and ensure that the desired results are achieved.
Here are a few notable types:
Vibrating Screeners: These machines combine gravity and vibrations to separate crushed rock into fractions of different sizes. They are versatile and can handle a wide range of materials, from hard rock to softer stones.
Rip Rap Trommel Screeners: Though most Trommels are intened for things like soil and mulch, Rip Rap Trommel screeners are useful for screening larger pieces of crushed stone. They consist of a rotating drum with screen panels around it, through which different-sized materials can be sorted.
Grizzly Screeners: Grizzly screeners are an excellent choice for separating soil and rock. They allow smaller particles to fall through the gaps while larger stones remain on top.
The ability to accurately separate and aggregate crushed stone into specified sizes ensures that a construction project meets specifications and can achieve the desired aesthetic. Furthermore, the efficiency of screeners in sorting materials helps to minimize waste and improve the overall sustainability of stone-crushing operations.
Selecting the right equipment to crush large rocks is crucial to ensure efficiency and cost-effectiveness in clean stone production. Factors to consider when choosing the right machine include:
Understanding the type of rock being crushed is essential in selecting the appropriate equipment. Different rocks have varying properties, such as hardness and abrasiveness, affecting how efficiently they are crushed. Limestone, dolomite, granite, and traprock are the most commonly crushed rocks in stone production.
Crushed stone serves as an essential component in various construction material uses. It is primarily used as an aggregate, and it's crucial to consider the intended use of the crushed stone when selecting equipment. Different applications, such as road construction or landscaping, may require different sizes and shapes of crushed stone.
The desired production capacity also plays a significant role in equipment selection. Crushing large quantities of rock will require more powerful machines than smaller-scale operations.
Maintenance is an unavoidable part of equipment ownership, and it's essential to consider the maintenance requirements of different types of machines before selecting. Some equipment may require more frequent maintenance, which can affect production efficiency.
Understanding the various types of crushers and screeners available and their uses and benefits is vital to making informed decisions that will ultimately contribute to the success of stone-crushing operations.
Crushing stone efficiently requires a well-designed process and the right combination of crushing equipment and screeners. By understanding the options available and their specific uses, operators can ensure that crushed stone meets project requirements while minimizing waste and improving sustainability.
In addition, regular maintenance of equipment is crucial to maintaining efficiency, reducing downtime, and ensuring cost-effectiveness in production. With these factors in mind, crushing stone can be a highly effective and valuable process for various industries.
So, it is essential to carefully consider the options available and select the right equipment for each specific application to achieve the best results.
At GrinderCrusherScreen we understand that the heavy equipment industry can be difficult for our customers to navigate alone. With over 50 years of experience our team has the expertise needed to help our customers make informed decisions and the industry experience and longevity to assist in sourcing the right machine and financing for your business.
What is Lime Mortar?
Lime mortar is a combination of lime (hydraulic or non-hydraulic), aggregate (sand, grit etc) and water. Due to the introduction of Portland Cement in the 19th Century, the use of lime declined. For the past 150 years modern, artificial cements have slowly been replacing traditional lime based mortars and plasters, to such a degree that now virtually all construction is carried out using only modern materials. Whilst many of these materials are perfectly suitable for modern buildings they have been found to be incompatible with the construction of old buildings.
The need to understand the different technology involved in historic and modern structures is essential if successful repair and maintenance programmes are to be carried out.
Lime has been the primary binder used in mortars and plasters for thousands of years and the vast majority of all buildings constructed before used lime. Despite this, in many cases today lime is ignored, so why Lime.
Modern cements are harder and less permeable than lime mortars, the general aim when selecting a traditional mortar or plaster is that it should breathe more freely than the material which it is applied to and that it should have less composite strength than the substrate with which it is used. This is essential if you are to prolong the life of the historic fabric.
Different Types of Lime
Non-Hydraulic Lime
Non-Hydraulic Lime Putty - Although traditionally this type of mortar was used internally and externally, today it is generally used for internal plasterwork & cornice etc, pointing, bedding and renders in sheltered areas.
Non-Hydraulic With pozzolan - All of the above plus the ability to withstand more exposure to the elements.
Production
Limestone is burnt in a kiln using temperatures of around 900C to produce lump lime, Calcium Oxide (CaO).
The production of lime putty is a hazardous procedure and should only be carried out by suitably trained personnel. This is not a procedure to be carried out on site where the work cannot be monitored and controlled.
The lump lime/burnt limestone (calcium oxide) is immersed in water. The mix is raked vigorously to aid the breakdown of the lump lime. When the resulting mix is the consistency of milk, the lime is then sieved to remove any un-slaked particles. The operatives should take great care as the mix reaches a very high temperature due to the chemical reaction taking place. The resulting material is called lime putty (calcium hydroxide).
This material is left to de-water/mature for at least three months in a bulk container known as an ark. The material will take on the appearance and consistency of cream cheese. Lime putty can be stored indefinitely in this state provided it is not exposed to air. When Carbon Dioxide, which was burnt off in the kiln, is reabsorbed back into the mortar/lime, this causes it to return to its original state, calcium carbonate.
Storing the lime putty in airtight containers allows the putty to mature and any un-slaked particles will have sufficient time to slake. The longer the putty is allowed to mature the better the finished product. Traditionally in Italy the best quality work was carried out using lime putty allowed to mature for generations.
Having manufactured and left the lime putty to mature for at least three months then this material can be used for mixing with suitable aggregate to make mortar. The best method of manufacturing a lime putty based mortar is to mix the ingredients in a mortar mill. The resulting mortar is of a high quality and very workable. No extra water should be necessary during the mixing process.
The amount of lime putty needed to bind the aggregate is determined by the amount of void space between the grains of sand, which needs to be filled. Most mixes use a ratio of two and a half parts aggregate to one part lime putty. This can vary slightly depending on the aggregate selected.
Health and Safety – Lump lime (calcium oxide) is a caustic alkaline. When it comes in contact with eyes or skin, it will cause a chemical burn. Wash the affected area with a solution of sugar water immediately and seek medical assistance. When working with lime the operative needs to wear personal protective equipment (eye protection, gloves, overalls and dust mask).
Non-Hydraulic
Non-hydraulic lime mortars were generally speaking the most common type of mortar used in the construction of historic buildings, these mortars were often a mixture of lime, earth, shells, crushed stone, pit or beach sand. The aggregate used basically depended on what was available locally and was often the direct result of years of local knowledge being passed down from generation to generation, as opposed to formal teaching techniques. These mortars performed and do perform in a very different way from modern cement or gypsum based mortars.
Non-hydraulic limes, sometimes called “fat limes” are limes which are very pure with regard to their calcium carbonate (CaCo3) content. The purest forms of this material can have upwards of 95% CaCo3, these “fat limes” have no or little chemical set in the way that modern materials harden, they harden by a process called carbonation i.e. reaction with the air.
The carbonation process is a slow ongoing reaction which can take weeks, months and to a degree years to complete. The mortars and renders therefore need good protection from the elements whilst carbonation is taking place.
Hot Lime
This is the most traditional method of preparing mortar in Ireland. This process combines slaking and the mixing of the aggregate in one operation. This method was most commonly used in the preparation of mortar for the construction of rubble stone walling. The mixing took place on or very close to the construction site.
The aggregate was normally spread in a circle and the lump lime was added to the centre of the heap, water was added and the mixture was turned a number of times. The end product is a very workable and “plastic” mortar that is ideal for rubble wall construction. You can use this fresh or it can be stored and reworked at a later date. Traditionally the mixing of mortars was carried out in the winter and they were left to sour out in pits until the building season started in the spring.
When producing hot lime mixes judging the correct ratio of lime-aggregate is rather difficult. Lump lime increases in volume when it slakes. In general, a useful rule of thumb is to use four parts aggregate to one part lump lime.
This type of mortar is unsuitable for plastering as it may contain un-slaked particles. These un-slaked particles tend to blow and give the plastered surface a pock marked appearance.
There are many health and safety issues to be addressed when working with hot lime mixes and great care should be taken. Skilled operatives who understand the process and the dangers are essential when working with hot lime mixes.
Storage
In the past lime mortar was heaped up and allowed to stand with little more protection than a sheet thrown over it, and in many cases no protection at all, the outer skin hardened and the mortar underneath remained moist with just occasional wetting down. The reason for allowing the mortar to stand or mature is to allow a better bond to take place between lime and sand. When using large amounts of mortar the best way of storage is to construct large timber mortar bins, three sided, which will allow the mortar to drain off any excess water and with little more than a polythene sheet keep the mortar air tight, wetting the top in warm weather. When using small amounts, sealed plastic tubs offer the best way of storage.
Natural Hydraulic Limes (NHL)
Feebly Hydraulic Lime NHL 2 - Some internal/external work, pointing, bedding, rendering on soft brick or stone backgrounds in sheltered locations, grouts.
Moderately Hydraulic NHL 3.5 - External rendering, pointing, bedding, some moulded work in normal exposure conditions.
Eminently Hydraulic NHL 5 - Areas of extreme exposure on hard dense stonework, sea defences, canal work, coping, pointing (very strong mortar).
Production of Natural Hydraulic Limes
Natural Hydraulic limes differ from non-hydraulic limes in that they have a chemical set as well as the process of carbonation. The limestones from which natural hydraulic limes are formed naturally contain a varied range of minerals of which silica and alumina are the main ones for creating NHL. When these limestones are heated in a kiln at temperatures of around ℃, the resulting lime has different properties. From the pure limestone, silica and alumina combine with the lime to form active compounds. These compounds combine with water to create a chemical set. The percentage of silica and alumina contained in the limestone will determine the main characteristics of the lime and of course the resulting mortar or plaster.
The main characteristics:
Strength
Setting time
Durability
Frost resistance
Workability
Colour
Sand Selection
Sand and larger sized aggregates make up the larger proportion of most mortars. Colour, texture and overall strength are all strongly affected by the choice of aggregate.
The aggregates most commonly used with hydraulic lime are sand and grit, although for the purpose of matching historic mortars various impurities may have to be added. A good sand should be a washed, sharp sand with angular grains to ensure good bonding qualities. Soft building sands should be avoided as their rounded grain shape can result in excessive shrinkage.Sands used should be well graded with a range of grain sizes, which for most plaster, render and mortar work will range from 5mm down to 75 micron. Larger sized aggregates may be used in some mortar or pointing work. As a rule of thumb for pointing, the maximum size of aggregate should be no bigger than one third of the joint width. Sands, which contain a clay or silt content of more than 4% should be avoided, as these will inhibit the contact between lime binder and aggregate.
Sands which have a high fines content should also be avoided as the larger surface area of these will require more water in the mixing. This higher water content will induce shrinkage and can affect flexural and compressive strengths. Monogranular sands should be avoided as they will possess poor workability qualities and will inhibit good vapour exchange i.e. the ability to breathe.
Water
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