Work sequence in construction projects

Work sequence in construction projects

All construction projects should follow a set sequence of jobs in order to complete the building on-time and within budget. This work sequence is an important process for a number of reasons, but mainly because it helps to establish order between construction teams. 

By following the sequence, contractors can plan the project and know what to expect next. The major sequences of construction are marking, excavation, concreting, bricklaying, roof building and finishing. There are more minor steps in between these processes, which have been outlined below. 

Work sequence in building construction

1. Paperwork – Any construction project will begin with paperwork. This includes architectural drawings, planning permission, costings and outlining the project process. Contractors need to ensure that their paperwork is completed properly (in accordance with regulations and laws) and filed correctly. Documents need to be easily accessible when they are needed, so the filing is just as important as the completion of paperwork.

2. Marking and outlining – Once the building and paperwork have been approved, the contractors can start to mark the outline of the structure on the ground. The dimensions and orientation of the building are marked according to the architectural drawings. Once the outlines have been marked, the ground can be prepared for the next step.

3. Excavation – Now the building process can really begin. The foundations are excavated along the outlines drawn in the previous step. Excavations should be carried out according to the planning documents. Contractors should work carefully to match the exact dimensions of the trenches and floor spaces.

4. Foundation work – Building the foundations is a precise process that follows this sequence:

  • Compacting the ground – The trenches are dug and the ground is compressed using tampers and rollers.
  • Pouring concrete – Plain cement-based concrete is then laid on top of the compacted soil. The depth of the concrete depends on the nature of the foundation.
  • Footing reinforcement – Steel rebar is tied together and placed on the concrete base to form a skeleton for the foundations. 
  • Formwork – To achieve the proper shape of the concrete, formwork is constructed according to the planning documents. This formwork also helps to keep the concrete from coming into contact with the surrounding soil.
  • Footing – Concrete is poured into the formwork to create solid footings upon which the building will stand. Once the concrete is cured, construction can take place on top of the footing.

5. Column casting – Concrete columns are then built on top of the foundations. Formwork is built around steel rebar skeletons; wet concrete is poured into the formwork, around the rebar. The formwork is removed after 24 hours and the columns are left to cure.

6. Wall construction – Once the concrete columns are in place, they are connected by the construction of the walls. These walls can be made from concrete, wood, brick or composite materials. The base of the wall is built first using concrete. The height of the wall is determined by the architectural drawings. 

7. Lintel construction – Lintels are concrete beams that sit above gaps for doors and windows. These reinforced concrete beams are poured and set on the ground, then hoisted into place above door frames and windows using a crane. They need to be strong to support the weight of the walls above, without any support from below.

8. Roofing – Once the walls and bricklaying are complete, contractors can start building the roof. Whether concrete slabs are used, or wooden trusses and tiles, the roof is the final layer of any building. They will be built according to the planning documents.

9. Plastering – Once the basic structure is complete, contractors can now prepare the building for the final touches. Walls and ceilings can be plastered to give them a smooth appearance. Special mortar is used for plastering, such as TemboFundi. The thickness of the plaster should never be more than 2cm as it becomes heavy and prone to cracking. Leave the plaster to cure for seven days.

10. Installing doors and windows – Next, contractors can start to install the doors and windows beneath the lintels. The metal frames are installed first and then the doors or windows are attached to the frames.

11. Installing electrics and plumbing – The necessary wiring, lighting, piping and water outlets are then installed. These should be completed before painting and tiling.

12. Tiling and painting – Tiles need to be installed in the kitchen, bathroom and any other room that will not be carpeted. If the walls are being tiled too, complete the walls before installing the floor tiles. Then, the non-tiled walls can be painted using two coats of primer and two coats of paint. The paint is applied directly on top of plastered walls – inside and outside the building.

14. Miscellaneous projects – Once all of the above tasks have been completed, contractors can then worry about the minor jobs, such as terracing, landscaping, interior decorating and final installation of appliances and carpets. The planning documents should outline what these minor jobs entail.

By following this work sequence, a contractor can complete a project efficiently and orderly. It will also help to plan the teams of builders, painters, electricians, plumbers and tilers. This work sequence is widely used around the world, so it has been tried and tested.

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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.

What are the major causes of delays in construction projects?

Bad weather can cause delays for construction projects

Delays on construction projects are not only frustrating; they can also be incredibly costly. There are many factors that can lead to delays in building projects. These factors will vary from project to project, as each job is unique. Here are a few of the most common causes of delays in construction schedules:

Access to construction sites

Problems gaining access to the site of construction can cause delays to the project schedule.

  • Issues with access. For example, the owner of the construction site did not provide the necessary information for the contractor to obtain the permits needed to access the construction site.
  • Issues with security. This could create dangerous conditions for the contractor, or create problems with access to the site, leading to delays.
  • Unfinished work. If the previous contractor had not finished their work on the site, it can cause issues with access and could lead to delays in the construction schedule.
  • Environmental issues. If environmental issues had not been resolved prior to work commencing, it could also lead to delays in construction as a result of a lack of access. 

Site conditions

If the on-site conditions differ from those described in the plans and specification contract documents, it can lead to delays. Delays can also occur when there is a difference between current site conditions and site conditions that are usually encountered at the location of the project.

Uncontrollable events

Uncontrollable events are unpredictable and unavoidable – there is nothing contractors can do about them. Examples of these events include severe weather, earthquakes, floods, as well as man-made events like war. Usually, delays caused by uncontrollable events are seen as non-refundable; the contractor can regain lost time, but not the costs. If the owner is the cause of the delay, compensation can be claimed.

Adverse weather conditions

Most construction projects are sensitive to weather and influenced by adverse weather occurrences, like heavy rains and storms. The levels of sensitivity to weather of the various construction stages and construction activity are also very different. A construction contract should state what the procedure would be, in order to make up time lost due to adverse weather. 

The contractor must also clearly show how the detrimental weather affected the project and how it exceeded the expectation of the contractor, leading to delays in the construction schedule. Weather delays are considered excusable but non-compensable, as neither the owner nor the constructor has any control over weather events.

These causes of delays in the construction industry are some of the most common. Contractors always need to be prepared for these events and have stringent contingency plans to deal with the effects of these delays. They should also include a budget for the delays that can be used to minimise the impact on the final costs of the building project 

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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 install windows in a brick wall

How to install windows in a brick wall

Every house, office and shop needs windows. Any space that will be used by people will need natural light and a breeze. Windows are a vital component of any structure as they brighten up the interior and allow fresh air to enter the building. Every contractor will need to know how to install windows in a brick or concrete wall.

Firstly, the wall will need to be built and the lintels installed. If a contractor wants to create a window in a solid brick wall, they will need to remove some bricks and insert steel reinforcement pillars to hold the bricks up above the window opening. A concrete lintel can then be created and placed above this opening.

Making a hole for windows in a solid brick wall

  1. Mark out the position of the window on the brick wall using a tape measure and chalk.
  2. Look for any hidden obstacles in the wall that could pose a problem, such as internal wiring, plumbing and air vents.
  3. Remove a few bricks at the top of the marked area to make a small opening where the window will be placed. Make sure that the wall is strong enough to support the weight above the window hole before removing too many bricks.
  4. Remove bricks from the top to the bottom of the opening.
  5. As you remove more bricks, install metal jacks or use wooden planks to support the weight of the bricks above the opening.
  6. Cut the bricks that jut into the opening with a circular saw to create straight edges that are perpendicular to the plane of the brick wall.

Construct the lintel for the top of the window opening

  1. Remove about 20cm of the top three layers of bricks at the top of the window opening. This is where the lintel will be installed.
  2. Measure the length and width of the lintel space – it should be 40 cm wider than the rest of the window gap.
  3. Create a wooden formwork of the same length and width. The formwork must be three bricks in height.
  4. Mix some concrete and pour it into the formwork to create a solid concrete lintel. Leave it to set for 24 hours.
  5. Remove the formwork once the concrete has set and leave it to cure for another seven days. Remember to keep the concrete lintel damp during this curing phase.
  6. Use a crane or a pulley system to hoist the concrete lintel into place at the top of the window gap. Use some mortar to secure the lintel in place. It will now support the weight of any bricks above it.

Installing the windows in the brick wall

  1. Decide whether you want to build a window sill. If so, place some bricks along the bottom of the window opening at 90-degrees to the rest of the bricks in the wall. Using mortar, secure these bricks in place at a slight angle, so that any water on the outside of the window will run off the sill.
  2. Next, install the metal window frame in the opening in the wall. Use mortar and self-tapping concrete screws to secure the frame in place. Fill in any bigger gaps between the frame and the bricks with mortar.
  3. Leave the mortar to dry and set for 24 hours before installing the window glass. 
  4. Carefully insert the glass panel into the metal frame, starting with the bottom edge first. You may need to gently tap the window along the edges to make sure that they sit level with the frame.
  5. Apply window putty along the four edges of the window. While the putty is still mouldable, scape off the excess at an angle to make it look clean and smooth. Leave the putty to dry properly before painting the window frame or opening any windows.
  6. Check the waterproofing of the window by spraying it with a hose once everything is dry and set. Any leaks along the frame will need to be sealed with more putty or with silicone sealant.

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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 costs of a construction project

How to estimate the costs of a construction project

Working out all the costs involved in a construction project is very complicated and requires many factors to be considered. This skill of estimating costs takes a lot of time to learn. Studies, the right training, as well as practical experience is required in order to become efficient at estimating costs for construction projects.

There are many aspects of a building project that can influence the costs. The cost estimator should be familiar with all these factors. All aspects should be evaluated in detail before finalising a construction cost estimate. It is important to do the relevant research and to familiarise yourself with all of these factors before making a cost estimation.

Important factors to consider when estimating construction costs

  • The cost of similar projects – It is very helpful to study the cost estimates for similar projects. Study the final cost items and related expenses of other projects, similar to the project you are working on – it will be of tremendous help.
  • The costs of materials – The cost of supplies and materials, as well as their transport, must be calculated before you start the estimation process.
  • Inflation – If you are using previous, similar projects as a starting point for estimating costs, always remember to factor in inflation (the price increases and the decrease of the purchasing value of money over time).
  • The cost of labour – Work out the labour costs for your project in accordance to local labour rates, or as stipulated by your local government.
  • The conditions at the site – This can include things like the environmental sensitivity of the area, poor soil conditions, the presence of groundwater, archaeological sites or contaminated materials, as well as conflicting utilities, like buried pipes, cables, overhead lines, and so on.
  • Timing of the bid – Things like the seasonal time of year, as well as conflicts with other bid openings, can have a big impact on the cost of the project.
  • Plans and specifications – It is very important that all plans and specifications are well prepared, with every detail and aspect of the layout and design executed and fully described.
  • Project schedule – The timeline of the project is a critical factor. If it needs to be completed very quickly, this will generally make the project more expensive – in particular if a liquidated damages condition for failure to complete within a specified deadline is included in the contract.
  • Project engineer – Working with an engineering firm or project engineer that has a good reputation in the industry will ensure a smooth-running project, but might increase the costs. Keep in mind that, if a contractor enjoys working with a certain engineer or firm, the project will be more cost efficient and also likely run smoother.
  • Size of the project – The larger the project, the more bidders will likely be involved and the higher the costs. The size of the project will determine whether local contractors will have the capacity to do the work.
  • Granting agency – If a granting agency is involved in providing funding for a project, this will be taken into consideration when a contractor is preparing his or her bid. This might involve extra administration and paperwork, which can increase the cost of the bid.
  • Location of the work site – The location of the construction site is a big factor in working out a realistic cost estimate. If the location is remote, enough labourers to do the work may be scarce and labour will have to be imported, so driving up costs.
  • Contingency factors – Usually, a 10% contingency amount on the construction total is added to cover unforeseen costs that may arise as the project progresses. When inflation is at a high, or essential construction materials are limited, it may be best to play it safe and increase the contingency amount to 15% or 20%.
  • Regulatory requirements – Certain conditions in regulatory agency approvals can be costly. To reassure potential bidders, it is recommended to include all regulatory approvals in all bidding documents.
  • Value engineering – Certain agencies require that high-cost projects perform a value engineering review, before the design is finalised or before the bidding process proceeds. The estimator must be aware of this factor early on in the process.
  • Insurance requirements – A contractor’s general liability, performance bonds and payments are general insurance requirements, as well as normal costs of doing business. However, certain projects require additional coverage. Such insurance premiums (for supplemental policies) add to the cost of the project and must be factored in right from the beginning.

Cost estimation research is essential

Sound technical judgment is of utmost importance during the cost estimation process – this will come with experience, as well as from the mentoring of other experienced industry role players. It is imperative that research is undertaken to take all relevant factors into account when drawing up a cost estimate for a construction project. A detailed and thorough cost estimate will result in a smooth-running operation with the best possible outcome for all parties. 

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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 global initiatives

LafargeHolcim Group global initiatives

LafargeHolcim is a worldwide leader in building materials and construction solutions. As such, the group strives to ensure that it is a responsible and ethical business in every single country in which it operates, including Tanzania. LafargeHolcim is a member of several global initiatives and alliances that are intended to develop surrounding communities and the business environment.

Sustainability is one of the core values held by the LafargeHolcim Group and is one of the initiatives that we endorse fully. This creates added value and has numerous benefits for our operations, shareholders and communities. Some of the other global alliances and initiatives are outlined below.

Global Reporting Initiative (GRI)

The LafargeHolcim Group is a member of the Global Reporting Initiative (GRI) community and supports the goal of GRI to empower leaders and decision-makers around the world. The GRI has set Sustainability Reporting Standards that encourage business leaders to push for sustainable business practices and unlock the economic potential that comes along with it. The information in LafargeHolcim’s annual Sustainability Reports and website is prepared in accordance with GRI standards. 

United Nations Global Compact (UNGC)

LafargeHolcim aims to embrace all of the United Nations Global Compact (UNGC) principles through our integrated approach to sustainable development. There are 10 UNGC principles and we strive to use them as the basis for advancing responsible corporate citizenship. The UNGC also enables LafargeHolcim to push its own programmes and processes in the areas of human rights, labour standards, the environment and anti-corruption.

Global Cement and Concrete Association (GCCA)

LafargeHolcim partnered with eight other multinational companies in the cement and building materials industry to launch the Global Cement and Concrete Association (GCCA) in early 2018. The GCCA is a progressive association that is dedicated to developing the industry’s contribution to construction. The association focuses on driving advancements in sustainable construction, as well as working to enhance the cement industry’s contribution to a number of global social and developmental challenges.

FTSE4Good

The FTSE4Good index was launched by the global index provider FTSE Russell. This index series is intended to measure the performance of companies that demonstrate strong environmental, social and governance practices. The FTSE4Good indices are used by a range of market participants to create responsible investment funds. FTSE Russell confirms that LafargeHolcim has been independently assessed according to the FTSE4Good criteria and has met the necessary requirements.

Dow Jones Sustainability Indices (DJSI)

LafargeHolcim was included in the 2018 DJSI European Index and was one of two Europe-based multinationals in the building materials industry to be included in this index. DJSI are the longest-running global sustainability benchmarks and are considered to be the reference point for sustainable practices.

Carbon Disclosure Project (CDP)

LafargeHolcim reports on its carbon statistics every year – the results are graded by the Carbon Disclosure Project (CDP). In 2018, the CDP scored LafargeHolcim with a B-grade rating in carbon emissions, which is above the industry average.

Task Force on Climate-Related Financial Disclosure (TCFD)

LafargeHolcim has been a member of the Task Force on Climate-Related Financial Disclosure (TCFD) since July 2017. The TCFD is gathering voluntary, consistent and climate-related risk disclosures from companies around the world. This information is then used to inform investors, insurers and stakeholders about the performance of the participating companies.

Global Alliance for Buildings and Construction (GABC)

LafargeHolcim is a founding member of the Global Alliance for Buildings and Construction (GABC). The alliance is an initiative that was launched at COP21 as part of the Lima Paris Action Agenda. It aims to mobilise all stakeholders, including member states and non-state actors from the building and construction industry, to scale up climate actions in the sector.

These are some of the global initiatives and alliances in which LafargeHolcim is a member and participant. They encourage ethical, responsible and developmental business practices with real accountability. We are proud to be part of these initiatives around the world in order to advance the building materials industry and our worldwide operations.

___

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 plaster on masonry surfaces

How to plaster on masonry surfaces

Plaster is a thin layer of smooth mortar that is applied over bricks or concrete to act as a protective and decorative cover. It also provides an ideal surface for the coats of paint that will be applied to a wall. LafargeHolcim Tanzania manufactures TemboFundi – a masonry cement that can be used to plaster walls and other masonry surfaces. 

A masonry surface can be made from brick and mortar, stone, slate, tile or concrete. The masonry surface should be a bit rough before the plaster is applied – smooth surfaces do not hold the plaster as well and this can result it chips being formed. Here are the steps to plaster on surfaces:

Prepare the masonry surface for plastering

  • Keep all the mortar joints on the surface rough. This acts as a good bonding surface that holds the plaster.
  • Clean all the joints on the masonry surface with a wire brush to remove oil, grease and soil.
  • Fill any deep holes or cavities with mortar before plastering.
  • If the masonry surface is smooth, or if it has been plastered already, then chip out the surface to a depth of 12 mm to create a rough surface to which the new plaster can bond.
  • Spray some water on the masonry surface and keep it damp for at least six hours before the plaster is applied.

Lay the groundwork for the plaster

  • The aim to get a uniform thickness of plaster across the entire masonry surface. To do this, fix dots of plaster to the wall at regular intervals. These dots should be 15 mm across and about 10 mm thick.
  • Fix the dots horizontally across the masonry surface, then vertically to create a grid of plaster. The gaps between dots should be about on metre.
  • The thickness and alignment of the dots can also be checked using a plumb-bob or weighted string.
  • After fixing the dots, lay a vertical strip of plaster between them. This is called a screed. The screed will serve as a guide for maintaining the thickness of the plaster across the entire masonry surface.

Apply the base coat of plaster

  •  If the masonry surface is brick and mortar, the first coat of plaster should be 12 mm thick. If the surface is concrete, the plaster should be between 9 and 15 mm thick.
  • Make the plaster mix with the appropriate ratio of cement, sand and water.
  • Apply the first coat of plaster in the spaces between the screeds. Use a trowel to achieve a smooth surface.
  • Level the surface using a wooden float or a straight edge.
  • After levelling, leave the first coat to set. Then, scratch it with a tool to form a rough surface in preparation for the second coat.

Apply the finishing coat of plaster

  • The thickness of the second coat of plaster should be between 2 and 3 mm.
  • The ratio of cement and sand for the finishing coat should be between 1:4 and 1:6.
  • Damp the first coat of plaster with a quick spray of water. There should be no drops of water when the finishing coat is applied, just a damp surface.
  • Apply the last coat of plaster using a trowel and smooth it with a wooden float.
  • The final coat should be applied from the top of the masonry surface to the bottom. Do this in one operation to prevent joining marks.

Leave the plaster to cure

  • After the two coats of plaster have been applied, keep the surface damp with a sprinkle of water. This surface should be kept moist for at least seven days in order to cure properly.
  • If the plaster is left to dry out or if it does not cure properly, it can lead to cracks and the formation of efflorescence on the surface.
  • Keep the surface of the plaster clean before applying any coats of paint.

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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 fine aggregate affects the mix design of concrete

Fine aggregate concrete mix design

When it comes to aggregate in a concrete mix, contractors can choose to use fine sand or coarse stone. This decision depends on the application of the concrete mix – whether they want a smooth and binding concrete mix or a sturdy and durable structure. Concrete mix design depends largely on the size of the aggregate used.

Fine aggregate can affect the water content of the concrete mix – it determines how much water needs to be added to the mix to create a workable texture. Other factors, such as the specific gravity of fine aggregate and its silt content, will affect the mix design of concrete. These factors are outlined below.

Fineness of aggregate

The fineness or particle size of aggregate is one of the biggest variables that contractors need to consider. It determines how much sand will be needed in the concrete mix to achieve a strong and workable mix. This affects the overall ratios of the cement to sand to water.

The overall particle size of sand is determined by the fineness modulus, which is found by sieve analysis. The fineness modulus of sand varies between 2 and 4 – these numbers allow contractors to determine the size of the average grain of sand in a batch. Fine aggregate requires more water in a concrete mix than coarse aggregate as it has a larger surface area.

Moisture content of fine aggregate

The moisture content of sand is a crucial factor in determining the water to cement ratio. All aggregates contain some moisture, but sand is able to retain more moisture than crushed stone, for example. Contractors often keep their aggregates damp so that they do not absorb too much water from the concrete mix.

Fine aggregate can be purchased with different moisture conditions; oven-dry (OD), air-dry (AD), saturated-surface dry (SSD) and wet. Only OD and SSD sand correspond to a specific moisture state and can be used as reference points for calculating the moisture content of fine aggregate.

Fine aggregate is frequently sold in a wet state with a moisture content of up to five percent. This is known as ‘bulking’ and needs to be taken into consideration when proportioning the cement and water to the sand. Wet aggregate will absorb less water from the concrete mix, so less water will be needed to achieve a workable mix.

Specific gravity of fine aggregate

Specific gravity is the ratio of the solid density of sand particles to the density of water. Bulk specific gravity is the measure of the volume occupied by the aggregate and the voids between the particles in the concrete mix. This determines the proportioning or ratio between cement, aggregate and water. A high specific gravity means that the sand particles are heavier and more densely packed, resulting in a dense concrete mix. On the other hand, a low specific gravity of sand will result in a low-density concrete mix.

Silt content of fine aggregate

The silt content of sand affects its fineness, and in turn, the amount of water needed in the concrete mix. The silt content can be determined by wet-sieving the sand. Any particles that pass through a 75-micron sieve are classified as silt. These are super-fine particles that can give concrete a smooth and silky texture, but they also require more cement and water in the concrete mix. Silt also lowers the strength of concrete – it makes for better screeds and plaster but is not suitable for high-strength concrete applications.

These properties of fine aggregate will determine the final quality and strength of a concrete batch. The fineness, moisture content, specific gravity and silt content of the aggregate all influence the final concrete mix in various ways, so contractors need to keep an eye on these variables.

___

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 coarse aggregate affects the mix design of concrete

Coarse aggregate concrete mix design

When it comes to aggregate in a concrete mix, contractors can choose to use coarse stone or fine sand. This decision depends on the application of the concrete mix – whether they want a sturdy and durable structure or a smooth and binding concrete mix. Concrete mix design depends largely on the size of the aggregate used.

Coarse aggregate, such as crushed stone and gravel, occupies a large portion of a concrete mix but it also adds strength to the final concrete batch and reduces its water demand. The properties of the coarse aggregate, such as angularity and strength of the material, can affect the concrete in numerous other ways, which we will outline below.

Size of coarse aggregate

The maximum size of the coarse aggregate dictates how much water will be needed in the concrete mix. It also determines how much fine aggregate will be needed to produce a workable mixture and cohesive concrete batch. The bigger the size of the aggregate, the smaller its bondable surface area becomes for cement, sand and water. This means that less water and fine aggregate is needed with concrete mixes that contain coarse aggregate.

The size of the coarse aggregate determines the cement to water ratio. Less water means a stronger mix, but it also becomes less workable. One important factor that contractors need to consider when it comes to the size of aggregate used is the spaces between steel rebar. The aggregate needs to be smaller than the space between internal reinforcements. This will allow the aggregate to pass between the rebar and settle evenly throughout the structure.

Grading of coarse aggregate

The grading of aggregate is the average size of the particles, from the smallest to the largest. It is important that the grading is kept constant for concrete batches with the same application. The aggregate particles need to be a consistent size for an even grading and a cohesive and dense concrete mix.

Grading is directly linked to aggregate size, so it also determines the workability, pumpability and durability of concrete. Proper grading of coarse aggregate will minimise the possibility of segregation of the concrete mix. By using aggregate particles that are similar in size, the concrete is more cohesive and uniform throughout.

Shape of coarse aggregate

Coarse aggregate may be round, angular or completely irregular in shape. Rounded aggregates, such as gravel, have the lowest water demand due to their lower surface area. They also have the lowest cement requirement. This makes rounded aggregates more economical, however, the bonds formed are not as strong as angular aggregate.

Angular coarse aggregate requires more water and cement because they have a higher surface area. This can make a concrete batch more expensive, but it is also stronger and more durable. Irregularly-shaped aggregate has similar properties to angular aggregate, but if the particles are too flaky or elongated, it can result in segregation in the concrete.

Strength of coarse aggregate

The strength of the actual material of coarse aggregate will determine the final strength of the concrete mix. Some rocks and stones are stronger than others – they have a higher resistance to cracking and crushing. Granite, for example, is far stronger than limestone. Therefore, it is a common aggregate used by contractors.

Coarse aggregate water absorption

Aggregate absorption is the amount of water that the crushed stone soaks up in the concrete batch. Dry aggregates suck up any water in the concrete, which can lead to a dry and brittle mix. That is why contractors keep their aggregates damp before mixing a batch of concrete. Coarse aggregate can absorb water up to five percent of its weight. This means that contractors need to add extra water to a concrete mix if the aggregate is dry.

These properties of coarse aggregate will determine the final quality and strength of a concrete batch. The size, grading, shape, strength and water absorption of the aggregate all influence the final concrete mix in various ways, so contractors need to keep an eye on these variables.

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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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A contractor’s role in preventing building fires

Preventing building fires

Houses and buildings can sometimes catch fire, whether it is an accident in the kitchen, faulty wiring in the roof or a sooty chimney that ignites. Luckily, there are measures that can be taken by contractors when building a house that can prevent fires and limit the damage caused by heat and flames.

The contractor has a big role to play in preventing household fires. Using the right building materials is the first step to flame prevention. Concrete and bricks are fire-resistant materials, so houses built with these products will be better off than wooden structures if an inferno breaks out.

Measures that contractors can take to prevent household fires

1. Start with the roof – Most household fires start in the roof. The common causes of roof combustion include fireworks, lightning strikes, chimney heat, sparks from bad wiring and burning embers from nearby fires. Most roofs are built with wooden trusses and paper-lined ceiling boards – both of which are dry and combustible materials.

By using materials that are fire-resistant, such as fibreglass trusses, concrete tiles and metal brackets, the contractor can prevent fires from spreading through the roofs of homes. Recycled rubber tiles are also fire-resistant materials that are becoming a popular building choice.

Homeowners can help to prevent roof infernos by trimming branches from nearby trees and bushes, maintaining clean gutters to remove dead and dry organic materials, as well as cleaning the chimney regularly to remove combustible soot and ash.

2. Detached garages and sheds – Many household fires begin in garages and storage sheds. These buildings often house flammable materials such as oils, petrol, fertilizers and wood. Contractors should build these structures separate from the main house – at least 10 metres apart. This will prevent flames from spreading to the house if they break out in the garage or shed. 

3. Treat wooden structures with fire-resistant coatings – Contractors should always coat wooden structures with fire-resistant coatings. Wooden decks, roofs and floors should be treated with fire-proof paints and sealants. Ideally, these wooden structures could be replaced with fire-resistant materials, such as concrete. This will further protect a home from flame damage.

4. Screen possible airways – Fires are fueled by air and oxygen. Contractors need to carefully think about where they build ducts and air vents. These airways should be constructed from metal, such as aluminium or steel, and have corrosive-resistant shutters that can block the airflow in the case of a fire.

5. Use insulated concrete forms (ICF) – Insulated concrete forms are becoming a popular material for residential homes. They are precast concrete forms that can be installed quickly to create a durable structure in a short space of time. ICF is a better material for homes than wood as concrete is an extremely fire-resistant material with low heat transfer properties. These act as insulators against heat and flames, which could prevent a fire from spreading from room to room. ICF walls can withstand flames for up to four hours.

These are a few of the measures that can be taken by contractors to protect homes from fires. Investing in fire-resistant materials could save lives and will save money in the future. Using concrete as a building material is the best way to minimise inferno damage and the spread of flames and heat. Other fire-resistant materials should also be used where possible.

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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.

Three untrue myths about concrete

Three untrue myths about concrete

There are many myths and beliefs about concrete in the construction industry. Some contractors may believe these myths and, as a result, shy away from using concrete in a project, in favour of other less adequate building materials. Concrete is a strong, resilient and cost-effective building material, so take note of the following three myths.

1. Adding lots of water to the concrete mix will be better

Many contractors believe that the more water you add to the concrete mix, the better the results will be. In truth, the correct water to cement ratio is absolutely vital to the final quality and strength of the concrete. By adding too much water, you actually weaken the bonds between the materials in the concrete mix. This can lead to brittle concrete that is prone to cracking. It also makes the concrete slump and runny, which means that it can leak out of formwork easily.

2. All concrete will crack

This is simply untrue! If the concrete is mixed, poured and cured correctly, it should never crack. Any cracks in concrete are the result of improper building practices or shortcuts being taken. If a contractor does not use the right ratios of cement to water to aggregates, then the final concrete structure can be compromised. Not allowing the poured concrete to cure properly afterward can also result in a weaker structure. Concrete will not crack if due care is taken throughout the entire process.

3. Concrete does not require maintenance

Many homeowners believe that concrete requires no maintenance. While concrete is incredibly durable, it does need to be looked after. Concrete structures and surfaces should be cleaned regularly, inspected once in a while and repaired as soon as any defects present themselves. Homeowners need to look after their concrete surfaces as they are an asset and can impact the value of the home.

These are the three most common myths about concrete that can mislead contractors and homeowners. Concrete is a versatile and useful building material, especially when it is used properly and looked after in the decades following. Contact us for more information about our cement products and concrete building tips.

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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.