Finding the right size of crushed stone for your construction project

Finding the right size of crushed stone for your construction project

Crushed stone aggregate comes in a variety of sizes and shapes that are suited to various applications in a construction project. Contractors cannot assume that any sized stone will work for their structures. They need to understand the key differences between the various types and sizes of aggregate needed for construction.

For example, you should use large stones for a smooth path, otherwise, the stones would make the surface bumpy and difficult to walk on. Likewise, using large stones were small stones are actually needed could increase the overall building costs unnecessarily. Large stones are heavier and more expensive to transport, so they are less practical for certain building projects.

Choosing the correctly-sized stone for the job will ensure that a concrete structure is finished to a higher quality and standard. These buildings will be stronger, more durable and keep their value for longer. When planning a project, be sure to choose the right size of crushed stone aggregate.

Types of crushed stone

  • Crushed and screened – This is the most basic type of crushed stone that you can get. Large granite rocks are crushed and the various chipped stones are fed into a screen filter that separates them into specific sizes. These stones are not cleaned or treated, so may carry some excess rock dust.
  • Washed clean – These are crushed and screened stones that are fed into a washer to remove the rock dust and any additional mud or debris. These stones are clean and do not have any contaminants that could affect dam projects or a concrete batch.
  • Gravel – This is a smoother form of crushed stone that is often used for landscaping projects and to make stone pathways. Gravel comes in a variety of sizes and is more suited to decorative purposes than functional building applications.
  • Quarry process – This type of crushed stone is also known as ‘dense-grade aggregate’. It is a combination of stone dust and crushed stone aggregate of various sizes. The stone dust makes the batch more dense as it fills the spaces between the stone chips.
  • Riprap stone – This is one of the largest types of coarse aggregate. Some of the pieces can be as large as 23 centimetres in diameter. These mini-boulders are often used in heavy concrete applications, such as high-rise foundations and bases for large roads.
  • Stone grits – These are fine particles of stone that are a by-product of the crushing process. They are 5 millimetres or less in diameter and are technically the smallest size of coarse aggregate available (before being classified as rock dust).

Crushed stone sizes and their uses

Small crushed stone (5mm or less) is often used as a functional surface layer on top of a compacted base for landscaping and decorative purposes. This size of stone is ideal for paths, driveways, patios, parking lots, water features and concrete pots.

Medium crushed stone (5mm to 2cm) is ideal for use as a layer on top of a larger crushed stone foundation. The medium stones will settle into the gaps between the larger stones and provide a stable and supportive layer for concrete. Medium crushed stone is also used in most general concrete applications for buildings.

Large crushed stone (2cm to 6cm) is ideal for foundations and filling sub-bases for roads, pavements and airport runways. These large rock particles give a strong and durable base support for concrete and bricks. Sometimes large crushed stone is used for decorative landscaping purposes or to build retaining walls with mortar.

Mixed crushed stone (variety of the sizes above) is often used to build solid foundations for most buildings. It can also be used to build semi-permanent roads and driveway surfaces, such as dirt roads to remote villages and walking trails. Mixed crushed stone is a dense and compact mix that creates solid surfaces as the smaller particles settle into the gaps between the larger particles.

These guidelines should help contractors to choose the right size of crushed stone for their needs. Not all crushed stone is the same, and certain structures call for a certain size of particle. Most general concreting jobs require medium crushed stone. The right size of aggregate can improve the quality and durability of concrete and building projects.

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LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges. 

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LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.

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At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.

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Follow us on Facebook, Twitter, LinkedIn and Pinterest for the best tips on construction, handy projects and the latest industry news. See our Instagram channel for more insights into our products.

Eight frequently asked questions about concrete

Eight frequently asked questions about concrete

Concrete is one of the most popular building materials across the globe. It is used in most construction projects, along with other cement-based materials such as plaster and mortar. Here are eight frequently asked questions about concrete that can shed some light on the material for people wanting to know more or become contractors themselves.

1. Are cement and concrete the same thing?

No, cement and concrete are not the same. Cement is a main ingredient of concrete and comes in a dry powder form. Together with water and aggregates (usually rock, gravel or sand) cement is used to make concrete. As a part of concrete, cement is the binding agent that holds the mixture together.

2. How long does it take for concrete to become hard, or set?

It takes 24 – 48 hours for concrete to set. Concrete will achieve 70% of its full strength seven days after it was laid. It will reach its full strength (100%) 28 days after it was laid. Concrete will become increasingly stronger over time because the cement forms bonds with surrounding moisture particles.

3. What are the ingredients of concrete?

Concrete is made up of cement, water and aggregates (sand or crushed stone). Cement is a dry powder made by LafargeHolcim Tanzania. Cement is the binding agent that holds the mixture together. Water is needed to form a chemical reaction with the cement. The water/cement ratio will determine the strength of the concrete. Aggregates can be either gravel, rocks or sand. It gives the concrete its structural volume and strength.

4. Can I lay concrete in wet weather?

Yes, it is possible to lay concrete when it is raining, but proper preparation is necessary. Precipitation (rain, snow, sleet, or hail that falls to or condenses on the ground) can lead to concrete becoming soft, which could reduce its strength. Constructing a protective enclosure of wood and plastic sheeting around the area where the concrete will be laid can prevent this type of damage.

5. What is concrete’s durability?

Concrete is extremely durable. It is a high-strength product and its traits make it suitable to be used in a number of ways, from industrial to domestic. Concrete has a lifespan of 40 years or more and it also hardens with age.

6. Is concrete an eco-friendly material?

Concrete is sourced from natural rock and often extracted on location, which means that minimal resources are needed to transport it to the required work site. At the end of its lifespan, concrete can be crushed and recycled. So, while it is not traditionally classed as an environmentally-friendly material, there are eco-friendly elements to concrete’s creation.

7. Will my floors be cold if they are made from concrete?

While concrete floors can be cold, they are not much colder than other often-used materials like natural stone flooring or ceramic tiles. During hot summer months, cooler floors can be a bonus and contribute to lower air conditioning costs – especially in a country like Tanzania where hot weather can be experienced all year-round.

8. How do I calculate the amount of concrete my project requires?

It is simple to calculate the amount of concrete needed for your project. Here’s an article that outlines the process of estimating the volume of concrete needed for any project, based on its area and volume.  

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LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges. 

___

LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.

___

At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.

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Follow us on Facebook, Twitter, LinkedIn and Pinterest for the best tips on construction, handy projects and the latest industry news. See our Instagram channel for more insights into our products.

What is a construction consultant and what do they do?

Construction consultant at work on site

A consultant is someone who offers expert or professional advice in a particular field. They provide this service of expertise to either a company or an individual client, charging a professional fee for their services. A construction consultant is an experienced expert in the construction industry who can offer clients valuable advice and share expert knowledge that the client may lack.

A construction consultant can work in various aspects of the building industry. This includes project management, contracts, surveying, architecture, analysis, construction management and so on. The administration of the consultant’s work contract is the responsibility of the client.

A construction consultant must offer his or her clients:

  1. A perfectly clear definition of the project and what it entails.
  2. Advice and guidance on how the project should be set up.
  3. Development and coordination of the project design.
  4. Collecting and preparing the product information and documents for tender.
  5. Inspection and correction of contractors’ work.

Consultants perform an extensive analysis of their projects

For example, civil engineering professionals provide their services as consultants for engineering consulting companies. These experts plan, design and execute buildings, highways, water treatment plants, airports, railroads and more. Civil engineering consultants must perform an extensive analysis of the structure that they will work on. They must also analyse environmental factors, ensuring that the final structure is safe, sustainable, functional and durable.

It is the consultant’s job to select the best, most economical materials and methods of construction in order to perform the project. Consultants must give priority to what the client wants, as well as take their views into account. The client chooses the consultant based on the type of project and its requirements.

Construction consultants are hired for their particular expertise

If the project requires the design of reservoirs and the maintenance of rivers and coastal areas, consultants in hydraulics civil engineering will be hired for their expertise. To create buildings that will safely perform its functions in all types of weather, structural engineers will consult on the project.

In order to be a construction consultant, you will need a graduation degree in civil engineering. You will also need to have sufficient knowledge of physics, maths, structural design and project management. It will also be an advantage to know the relevant software packages and to be able to develop structural drawings.

When they work as consultants, civil engineers earn a high income compared to civil engineers working in other industries or government agencies. Established construction companies also offer regular training and courses to keep engineers up-to-date with the latest innovations in the industry.

Once a construction professional has gained a sufficient amount of working experience, they can start a career as a freelance consultant working in the construction industry.

The following services are offered by civil engineering construction companies:

  • Structural design
  • Civil and environmental services
  • Site development
  • Surveying
  • Environmentally-safe construction
  • Energy-saving equipment
  • Energy-saving methods

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LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges. 

___

LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.

___

At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.

___

Follow us on Facebook, Twitter, LinkedIn and Pinterest for the best tips on construction, handy projects and the latest industry news. See our Instagram channel for more insights into our products.

How to waterproof concrete structures

How to waterproof concrete structures

Waterproofing concrete structures can help to protect them from the weather and keep them in optimal condition. This is especially important in areas prone to flooding, heavy rainfall and constant ocean vapour. Water can penetrate concrete over time and affect its strength, so waterproofing is a good way to keep a building strong.

There are numerous ways to waterproof a concrete structure. Contractors can apply paints and bitumen felts to the exterior of the building, or they can use concrete admixtures to prevent water from penetrating the surface of the structure. For optimal waterproofing results, the design, workmanship and building materials should conform to the correct standards and codes of construction.

Concrete waterproofing admixtures

Certain admixtures make concrete impermeable to water and moisture. These chemicals can be added to the concrete or plaster batch during mixing. They reduce water permeability in the concrete by reducing the size and number of pores in the surface. They also line the surface with hydrophobic materials that prevent the absorption of water.

These admixtures react with the calcium hydroxide in the cement to create a hydrophobic layer. Examples of waterproofing admixtures include animal fats, stearic acid and some vegetable oils. These admixtures can also be mixed with plaster to line the surface of a wall. This acts like a layer of waterproof paint that repels rain, standing water and mist in the air.

Waterproofing concrete with bitumen coating

Another way to make concrete structures waterproof is to place a layer of bitumen on the exterior surface. The concrete first needs to be cleaned and sanded to give the bitumen a rough surface to stick to. Contractors should pour hot bitumen (about 1.5kg per square metre of concrete) onto the surface and spread it evenly. 

Once the first coat had dried and cooled, the second coating (1.25kg per square metre) is applied in the same manner. Immediately after the application of the second coating, contractors should spread sand over the surface. This is then left to dry and cool. The sand will give the surface a non-slip texture and improve the durability of the bitumen.

Certain concrete structures need to be waterproofed internally, such as concrete tanks and reservoirs that will store certain chemicals and liquids. Waterproofing a concrete structure will maintain its strength in the face of exposure to water and other liquids. It will prevent concrete rot and protect a building from heavy rains, flooding and salt moisture from the ocean.

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LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges. 

___

LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.

___

At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.

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Follow us on Facebook, Twitter, LinkedIn and Pinterest for the best tips on construction, handy projects and the latest industry news. See our Instagram channel for more insights into our products.

How to minimise concrete wastage on-site

How to minimise concrete wastage on-site

In any construction project, there is likely to be concrete wastage – a small percentage of the concrete that gets dropped on the floor, left on the mixing bed or left unused. These small amounts of concrete wastage still add up to some loss in costs for the contractor, so they need to be minimised as much as possible.

Around three to five percent of concrete is usually wasted on an average building project. However, even this amount can increase the cost of the project. Proper planning and taking extra care when mixing and working with concrete are the best ways to reduce wastage on-site. However, there are several other steps that contractors can take to minimise concrete loss.

Pre-pour checks can minimise concrete wastage

Firstly, pre-pour concrete checks should be conducted to ensure that the site is prepared properly. There should be minimal travel distance between the site where concrete is mixed and where it will be poured. This will reduce the chances of spillage on the way to the pour site. 

Concrete pour cards should be completed as this will inform workers exactly how much concrete needs to be prepared for the job. These cards will ensure that no extra concrete is mixed, which will go to waste when it is not needed for the project. Contractors need to calculate the volume of concrete needed, as accurately as possible, before the pour takes place.

Steps to take during the pour

While the concrete is being poured, contractors should aim to match the speed of mixing with the speed of pouring. In other words, new concrete batches should be mixed just in time for use, when the old batch runs out. This will reduce any waiting time between pours, where the concrete will start to set before it is used.

Towards the end of the concrete pour, the contractors who are mixing the batches need to be informed. This will allow them to stop mixing new concrete in time and to avoid extra concrete supply that will go to waste. Communication is a key factor in minimising concrete wastage during the pour.

In situations where unexpected delays and issues stop the concrete pour, the supervisor needs to have a plan for the concrete being mixed. Using mechanical mixers can help in these situations as they continue to churn the mix and prevent it from setting. Manually mixing concrete can be affected by delays in a pour.

Contractors should always aim to use any leftover concrete elsewhere on the site in order to avoid wastage. This is why planning, communication and timing are such important factors on any construction project. Steps need to be taken before and during a concrete pour to minimise the wastage on-site.

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LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges. 

___

LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.

___

At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.

___

Follow us on Facebook, Twitter, LinkedIn and Pinterest for the best tips on construction, handy projects and the latest industry news. See our Instagram channel for more insights into our products.

How to estimate the number of bricks needed for a project

How to estimate the quantity of bricks needed for a project

Before any brickwork construction can begin, the contractor first needs to order the building materials (bricks, cement, sand, etc.) and have them delivered to the site. To do this, an accurate estimation will need to be made of the volumes of building materials that will be required. The contractor has to consider how many bricks are needed for the total area of the building.

When making estimations, contractors often work out the number of bricks needed to fill a space of one cubic metre. Clay bricks tend to have a standard size (roughly 222mm long by 106mm wide by 73mm high). For one cubic metre of standard-sized brick masonry, a contractor will need 494 bricks. This equates to about 60 bricks per square metre of single-brick wall or 120 bricks per square metre of double-brick wall.

The contractor needs to calculate the volume (for a double-brick wall) or area (for a single-brick wall) by multiplying the width, length and height. This can be done according to the architect’s drawings. Once the contractor knows the area of the wall, they can use the above guidelines to place an order. They can multiply the area by 60 (for a single-brick wall) or by 120 (for a double brick wall).

Once the number of bricks has been calculated according to the size of the wall, contractors should always add a 10% allowance on top of that number. This takes into account any additional bricks needed for verges, pillars or to replace broken ones. It is always better to have a few extra bricks than not enough.

The contractor will also need to estimate the quantity of mortar needed for one cubic metre of masonry. On average, buildings will require between 0.25 and 0.3 cubic metres of mortar per cubic metre of brick. This means that between 25% and 30% of brickwork consists of mortar (or sand and cement).

Contractors can use these estimations as a guideline to know how many bricks will need to be ordered and what volume of sand and cement to have delivered. Running out of building materials will cause time delays and cost the contractor money. However, builders do not want to have hundreds of bricks leftover at the end of a project either.

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LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges. 

___

LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.

___

At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.

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Follow us on Facebook, Twitter, LinkedIn and Pinterest for the best tips on construction, handy projects and the latest industry news. See our Instagram channel for more insights into our products.

Direct and indirect costs of a construction project

Direct and indirect costs of a construction project

All construction projects consist of direct and indirect costs. Together, these form the total cost of construction and they must be factored into the budget. Direct costs are easier to estimate, while indirect costs can vary widely from project to project. Contractors need to keep an eye on the progress and minimise any delays and mistakes as these will add to the indirect expenses of the building.

There are three main costs of a building project; fixed expenses, time-related costs and quantity-proportional costs. Examples of fixed expenses include the once-off purchase of equipment, machinery, supplies and materials. Time-related costs are those that accumulate over a period of time, such as salaries, wages and rent. Quantity-proportional expenses depend on the quantities of materials needed for the project, including cement, aggregate, bricks, steel and glass.

Direct costs of a construction project

These are the expenses that are fixed upon a product, function or facility. In construction projects, the direct expenses include workforce labour, building materials and equipment – so fixed costs and quantity-proportional costs are included in the overall direct expenses of a project.

These costs are developed as estimates before the project starts. Detailed analyses of the construction methods, site conditions, available resources and building contracts are performed in order to accurately estimate the direct expenses. Contractors need to factor in any subcontractor payments and equipment rentals into their direct cost budget.

Indirect costs of a construction project

These are expenses that are not directly fixed – they can vary depending on each project’s requirements and situation. Indirect expenses can include time-related costs due to delays, additional security, administration and extra personnel costs. These expenses do not have a direct connection with the building project and can grow over time. The longer a project takes, the higher the indirect costs can be.

Indirect expenses can also be classified as overheads; whether project overheads or general overheads. Project overheads are those expenses that are related to the actual project but cannot always be directly allocated, such as parking fees, office rentals, workshop facilities and safety costs.

General overheads include supporting expenses such as electricity tariffs, water tariffs, architect fees, directors’ and managers’ salaries and supplier fees. All overheads can be estimated and factored into the budget before a project starts. Most contracting companies make use of checklists and forms to help them develop these estimates. These overheads can account for 5% to 15% of the total project cost.

It is vital that accountants and contractors estimate these direct and indirect expenses as accurately as possible. This will allow the team to set a realistic budget for the construction project and build in some leeway for indirect costs that might creep up. An accurate budget can also help to secure funding from the government or private businesses.

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LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges. 

___

LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.

___

At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.

___

Follow us on Facebook, Twitter, LinkedIn and Pinterest for the best tips on construction, handy projects and the latest industry news. See our Instagram channel for more insights into our products.

LafargeHolcim Group cement is carbon efficient

LafargeHolcim Group cement is carbon efficient

The global LafargeHolcim Group manufactures some of the most carbon-efficient cement products in the world. Since 1990, the group has reduced its net carbon emissions per tonne of cement by 25%. This represents the highest reduction of all cement companies worldwide since 1990.

This carbon emissions reduction was achieved by reducing our clinker content in cement and by using alternative fuels to fire our cement kilns. Alternative fuels release less carbon dioxide than the traditional fuel (coal). This means that LafargeHolcim consumes less energy per tonne of cement produced, making our production process more efficient than it was 30 years ago.

The group has also managed to reduce carbon emissions by one percent since 2017, which currently exceeds our year-on-year targets. This initiative puts LafargeHolcim on-track to meet its 2030 objective of reaching an emissions level of just 520 kilogrammes of carbon dioxide per tonne of cement produced.

We currently produce 576 kilogrammes of carbon dioxide per tonne of cement produced. The group has an interim target in 2022 of 560 kilogrammes of carbon dioxide per tonne of cement produced. These ambitious targets are within our reach and we aim to lead the way in carbon efficiency.

Clinker substitution

The production of clinker – the main component of cement – is where the majority of carbon emissions result. This is an unavoidable process during the chemical reactions but we can work to reduce these emissions as much as possible. Replacing the clinker in our cement products with alternative mineral components, such as pozzolana, fly ash and slag, will help to minimise our carbon emissions.

Many of the alternative minerals are byproducts of other industrial processes. We can recycle them into cementitious materials as replacements for clinker and to serve as a viable end-market for waste products from other industries. In certain countries with favourable markets, LafargeHolcim has replaced up to 50% clinker with alternative minerals.

Waste-derived fuels for kilns

Another major way to reduce our carbon emissions during cement production is to use waste-derived fuels to fire our kilns. The combustible materials serve as replacements for fossil fuels, such as diesel, natural gas and oil. LafargeHolcim Tanzania uses a combination of rice husks and coffee husks from nearby agricultural facilities as an alternative source of fuel for our kilns.

Carbon efficiency

Being carbon-efficient also means becoming energy efficient. Cement production is an energy-intensive operation. Improving our energy efficiency will also help to reduce the carbon intensity of the manufacturing process, lowering production costs at the same time.

The LafargeHolcim Group has reduced its overall energy consumption per tonne of clinker produced from 4532 megajoules in 1990 to 3518 megajoules in 2018. This represents some of the lowest energy rates in the global industry. Since 1990, LafargeHolcim has increased its cement production by 75% while our annual energy consumption has reduced by 18%.

Becoming more carbon-efficient is one of the main goals of the LafargeHolcim Group. We will continue to push to minimise our carbon dioxide emissions while manufacturing world-class cement products at a reduced cost. The group is on its way to meeting the 2030 targets for energy efficiency and carbon reductions.

___

LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges. 

___

LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.

___

At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.

___

Follow us on Facebook, Twitter, LinkedIn and Pinterest for the best tips on construction, handy projects and the latest industry news. See our Instagram channel for more insights into our products.

Moisture changes can affect concrete

Moisture changes can affect concrete

Moisture changes or the incorrect water content can affect concrete. It often leads to small cracks that are caused by the shrinkage of the concrete as it dries out. Concrete is slightly porous – meaning that it can absorb and lose water fairly easily, even moisture from the air. This results in the expansion and contraction of the concrete, depending on the moisture changes.

Concrete is most affected by moisture changes in its early stages of setting and curing. That is why it is so important to keep concrete damp for the first few days while it cures. During this phase, the concrete can undergo irreversible changes if it is left to dry out completely, such as cracking under shrinkage.

Types of cracks in concrete resulting from moisture changes

1. Initial shrinkage cracks in concrete

Initial shrinkage causes small cracks when there is not enough moisture during the setting process (the first 12 hours after pouring). These cracks are partly irreversible and they occur in all cement-based building materials, such as concrete, mortar and plaster. This initial shrinkage is one of the leading causes of hairline cracks in concrete structures, but it can be avoided.

Firstly, contractors need to make sure that they are using the right cement-to-water-to-aggregate ratio. Follow the instructions on the cement bag for the optimal ratios to use. This will ensure that there is enough water to prevent the fresh concrete from drying out and cracking. Proper curing for the first seven days after pouring can also prevent initial shrinkage cracks.

2. Plastics shrinkage cracks

Cracks that appear on the surface of concrete during the curing phase are a sign of plastic shrinkage. A few factors can cause plastic shrinkage, including rapid evaporation of surface water. This causes water on the surface of the structure to dry out, which then creates cracks in the surface layer of the concrete.

Plastic shrinkage is more likely to occur in hot and dry climates when the water on the surface of the concrete evaporates rapidly. Contractors need to keep the surface of concrete wet during the first seven days on concrete curing. This is the best way to prevent the concrete from drying out and, therefore, plastic shrinkage.

3. Plastic settlement cracks

Plastics settlement cracks are similar to plastic shrinkage cracks. They are caused by the settlement and separation of heavy aggregates in the concrete mix. As these aggregates sink to the bottom of the mix, it leaves a concentrated cement and water mix near the surface of the structure, which then cracks. Some reinforced concrete suffers from plastic settlement cracks too. As the aggregates sink, they hit the steel reinforcing but it forms small voids above the aggregate particles. These voids can then create cracks in the structure.

These causes of cracking on concrete structures are all linked to moisture changes. That is why it is so important for contractors to use the right amount of water in their concrete mix and to keep the structure damp during the initial setting and curing phases. Moisture changes are an important aspect of construction, but knowing what to look for can help contractors prevent their structures from cracking.

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LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges. 

___

LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.

___

At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.

___

Follow us on Facebook, Twitter, LinkedIn and Pinterest for the best tips on construction, handy projects and the latest industry news. See our Instagram channel for more insights into our products.

How to speed up concrete drying time

How to speed up concrete drying time

Much of the time spent on a construction project is spent waiting for the concrete to cure and dry. However, this is an absolutely vital process as concrete that does not set, cure and dry properly will be flawed and prone to structural failure. The structure needs to be given enough time to harden properly before more work takes place on top of it.

In order to maximise the efficiency of the construction project, contractors can use several techniques to speed up the drying time of their concrete structures. This will help to keep the project on schedule without compromising the structural integrity of the concrete. These methods will allow contractors to maintain safety on-site, as well as meet upcoming deadlines.

Pre-pour tips for speeding up concrete drying time

  • Choose the best weather – Contractors need to keep an eye on the weather forecast. Concrete dries faster in dry and warm conditions. Luckily, Tanzania is warm and sunny for most of the year. Extremely hot weather can have several effects on concrete, so keep this in mind. If a project is running on a tight schedule, avoid pouring concrete in the rain as this will slow down the drying time.
  • Add warm water to the mix – Water is a key ingredient of concrete and is essential for the curing reaction to take place. Contractors can use warm water in their concrete mix to help speed up the curing process. The water can be left in a bucket in the sun, or added from a hot tap – it should not be boiling or too hot to the touch as this can damage the concrete.
  • Add calcium chloride to the mix – Calcium chloride is a concrete additive that can be mixed with the cement, water and aggregates. This chemical compound accelerates the process of hydration and helps the concrete to dry faster.
  • Reduce the amount of water in the mix – The more water you add to a concrete mix, the longer it will take to dry. Using less water will reduce the drying time, but be careful not to remove too much water from the mix. A dry concrete batch can crumble once set, so always use enough water to make a workable mix.

Post-pour tips to speed up concrete drying time

  • Trowelling technique – Avoid hard-trowelling as the increased pressure on the concrete can cause densification and collapse internal vents. This prevents moisture from evaporating from the concrete mix when drying. It will extend the drying time significantly.
  • Cover the concrete with a plastic sheet – Curing requires moisture on the surface of the concrete. It sounds backwards, but a damp concrete surface actually dries faster and with greater strength. Cover the concrete surface with a plastic sheet to prevent too much moisture from evaporating. The plastic sheet will also prevent excess atmospheric moisture from being absorbed into the concrete.
  • Use a heater – If the weather is overcast and cold, contractors can use heaters or heating mats to warm up the structure and decrease the drying time. However, take care not to overheat the concrete as this can bake the surface and cause it to crack. A gentle heat will help the concrete to dry faster.

These tips will help contractors to speed up the drying time of their concrete projects. They can be used before the concrete is poured and afterwards. A construction project that runs on-time will save money. So use these tips to speed up the process and meet all the required deadlines.

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LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges. 

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LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.

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At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.

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