The eight types of construction company

The eight types of construction company

There are many different types of construction company. Not all contractors specialise in the same fields and not all companies do the same construction work. Depending on the type of work they do, construction companies can be classified into the following eight types:

1. General contractors

A general contractor provides all of the labour, equipment, materials and services needed for the construction of the project. General contractors often hire subcontractors to perform part or all of the construction work on a project – especially those subcontractors that are specialists in their field, such as plumbers, electricians and roof tilers.

2. Owner-builder

An owner-builder takes responsibility for domestic building work done on their own land. They are legally responsible for the project from beginning to end. Owner-builders construct buildings for themselves, to sell once it is finished or to rent out and manage. Many owner-builders also act as general contractors as a secondary business.

3. Small renovation contractor

Small renovation contracts usually work on jobs with small budgets or that don’t require large amounts of capital. They do work that does not need a lot of estimations or require a large construction organisation. They usually do home renovations and alterations, as well as small commercial and office work. They often have their offices at home and do their paperwork in the evenings.

4.  Real estate developer

A real estate developer is a type of owner-builder who constructs property developments for personal ownership. However, they also build to sell before or after finishing a project. This category includes one- and two-family home builders. Most real estate developers will buy an empty plot of land and construct several independent homes for maximum resale value.

5. Package builders

Package builders both design and construct buildings. Their services often include buying the land as well as financing the project. Package builders can usually show prospective clients examples of similar buildings they have completed for previous clients. They often employ their own architects and engineers, as well as construction workers.

6. Professional construction manager

A professional construction manager is an individual or company who does all the required work on a building project, on behalf of or as an agent of an owner. The construction manager often supplies all the necessary personnel required. The management company outsources the construction work in the name of the owner and does all the necessary administration, supervision, safety regulation, requisitioning, paying of subcontractors, payroll reports and other work on the owner’s behalf, for a fee.

7. Sponsor builder

Sponsor builders often work in the field of government-aided or subsidised building, particularly in the housing sector. A sponsor-builder may be responsible for the planning design, construction, rental, management and maintenance of a project. A sponsor steers a project through the government processing and design stages. They also hire attorneys to deal with the various financial institutions, government agencies and real estate consultants.

8. Program manager

Sometimes, general contractors or construction managers broaden their services by offering program management. These services can include the demolition of existing buildings on the site, the acquisition of a new site, providing financial analyses of new buildings and the hiring of an architect on behalf of the owner. A program manager will also supervise all services, advertise for and receive bids from contractors for the new work, obtain tenants and help administer and manage the entire project.

These eight construction companies have various fields of expertise and specialise in different aspects of construction. When building a structure, it is important to first find the correct construction company for your needs and requirements, based on the services they offer and what type of company they are.

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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.

How to fix common concrete slab problems

How to fix common concrete slab problems

When working with concrete, contractors may encounter a few different problems. The following issues can sometimes occur when pouring concrete slabs. While some aspects of working with concrete slabs have changed over the years, many issues have not. Here are three common problems that come with pouring concrete slabs, and their possible solutions.

1) Excessive Bleeding

Bleeding occurs when the heavy ingredients in concrete (aggregate and sand) settle and push the extra water to the top of the slab. Concrete that bleeds for too long or too fast can cause problems like sand streaks in walls; weak horizontal construction joints; rock jams in pump lines; etc. Finishing a concrete slab before bleed water has evaporated can cause cracking, dusting, scaling and low-wear resistance.

Excessive bleeding can be avoided by not adding too much water to the concrete; placing concrete at the lowest possible slump (if you need a higher slump to speed placement, consider using a superplasticizer); using a more finely ground cement; adding more cement to the mix; blending in a fine blow sand or fly ash.

2) Curling

Curling happens when a slab rises up at corners and edges – or sometimes at a mid-panel crack. It happens when the top section of a concrete slab dries or cools faster than the bottom section. Curled concrete slabs can be fixed, but it is expensive. 

Grinding can level out the edges, and grout can be used to restore support to the slab. The best way to avoid curling is to control it before it happens. There are a number of material choices, construction practices and design decisions that will help prevent curling from happening in the first place.

3) Thin slab

All concrete slabs have varied thicknesses – some parts of the slab are thicker than others. When it comes to thin slabs, the thinnest sections may be too thin to retain their strength and may be prone to crumbling. In such cases, the contractor needs to decide how thin is too thin.

They must decide whether to make the slabs thicker for the sake of giving additional strength and durability to the concrete slab. Contractors should also pour thin slabs very carefully and ensure that the depth of concrete is even throughout the slab.

These are three of the most common problems that can arise when working with concrete slabs. They are easy to fix; taking care while pouring the concrete and being precise with measurements is the best way to avoid these problems in the first place.

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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 concrete bleeding?

What is concrete bleeding?

Concrete bleeding is a problem that can affect any batch of concrete that has been improperly measured and mixed. It is the movement of water to the surface of the concrete after it has been poured. Water collects on the surface of a concrete slab or structure when the water-to-cement ratio of the mix is too high (when too much water has been added to the batch). 

Bad proportioning of materials in a concrete batch is the main cause of bleeding. Too much water causes the concrete to segregate – a phenomenon where the heavy aggregates sink to the bottom of the mix, leaving the cement, sand and water at the surface of the structure. The water then seeps to the surface of the slab or structure, which creates big problems on the resultant integrity of the concrete.

When the water travels to the surface of the structure, it carries the fine particles of cement with it. This leaves a deficiency of cement within the rest of the structure. Since cement is the main binding material, the rest of the structure dries without much bonding between materials. Bleeding causes a weak, crumbly and dry concrete structure that cannot support any weight.

Bleeding affects the workability of concrete

There are two categories of concrete bleeding; normal and excessive bleeding. These are determined by the amount of water lost through the surface of the concrete structure. Both normal and excessive bleeding can affect the final quality of the concrete and the overall durability of the structure.

Normal bleeding is that which often occurs in all concrete projects. When you see freshly-poured concrete, it will often have a very thin layer of water on its surface. This is nothing to worry about and can actually enhance the workability of the mixture. The improvement in workability makes it easier to pour and work with before it sets. It also gives the concrete a smooth finish.

Excessive bleeding is an abnormal amount of water loss through the surface of the concrete. The mixture is usually too wet before it is poured. Contractors should keep an eye on their concrete batch and add more cement or dry aggregate if they think the mixture is too runny. Excessive bleeding leads to a high loss of water and a dry, brittle concrete structure.

Concrete that has suffered from excessive bleeding may also have large voids in the centre of the structure where heavy aggregates have moved the fine particles out of their way as they sink. This creates air bubbles and empty pockets that can severely affect the strength and durability of the concrete.

The best way to prevent concrete bleeding is to use the required amount of water, as printed on the bag of cement. Contractors can also carry out a slump test to check the mixture has the correct ratio of dry to wet ingredients. Bleeding is a normal occurrence with concrete, but excessive bleeding creates long-term problems that cannot be easily repaired.

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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.

The importance of having a schedule for a construction project

The importance of having a schedule for a construction project

Construction projects are delicate operations that need to run on time in order to stay within the allocated budget. As soon as a project is delayed, it costs the contractors and building owners more money. Having a strict schedule is important as it keeps the project on time and allows all workers to know when to expect certain deliveries and deadlines.

A schedule is the process of assigning tasks, activities, milestones and deliveries to a construction project – basically setting deadlines that everyone will work towards meeting. The schedule will be used by all construction teams on the project, as well as the suppliers, to finish the building on time. It outlines the pace of work and how the tasks are supposed to be executed, but it also outlines how the team should deal with changes in the plan and delays. 

Why a construction schedule is important

The schedule is a vital planning document that outlines the following points:

  • It assigns dates and deadlines for the project’s activities.
  • Contractors can see whether these deadlines are obtainable or not and whether delays can be avoided.
  • The schedule allows contractors to estimate preliminary costs or tender bid estimates.
  • It can be used to plan the necessary resources (such as equipment, materials and labour) to meet the work tasks and deadlines.
  • The schedule provides a sequence of tasks so the project manager and all teams know what they need to be working on and what tasks they need to be prepared for.
  • It can improve the safety performance of a project by sequencing activities to ensure maximum protection for contractors.
  • It enables teams to set their own goals and work towards achieving these.
  • It outlines how delays can be dealt with in the smoothest and most efficient manner.
  • It eliminates problems of production bottlenecks, where many deadlines fall on the same day.
  • The schedule ensures that the project is completed at the soonest possible date.
  • It gives the building owners a target date by which their building should be ready for use.
  • It can be used post-completion to evaluate the contractors’ performances and to assign responsibility for any delays or overspending.

The building schedule is one of the most important documents for project managers, contractors and building owners. It keeps a project running on time and within budget. However, the schedule needs to be realistic and the estimations need to be achievable in order for it to be a valuable resource for the 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.

The four phases of project management

The four phases of project management

All construction projects require input from a team of various experts. Architects, contractors, project managers and suppliers have the most important roles to play in the creation of a new building. The project manager is the link between all of these teams. It is their job to ensure the project runs smoothly, on time and within budget.

The project manager needs to be organised and keep an eye on all aspects of the building’s progress. To do this, a project manager will need to use a phased process. There are four phases of project management that will ensure the building is completed efficiently and to a high quality. 

1. Defining and organising the project

The first phase of project management is to define the task at hand – what are the objectives of the project and whose expertise will be needed to help you complete these objectives successfully. Identify the competing demands of each team working on the construction site and plan how to overcome these conflicts while keeping all teams satisfied.

Organising the project requires the manager to define the roles and responsibilities of each team. The project manager should create a detailed estimate of the costs and timeframe in which the building should be completed. This organising phase will help to keep the project on schedule for its entire duration.

2. Planning the project

The planning phase of project management is based on the previous step. In the planning phase, the project manager will assemble a team of contractors and suppliers and assign tasks to individuals. The budget can be adjusted if necessary once the plans start to take shape. The project manager must also finalise the deadlines for the construction project during the planning stage.

A communications plan is also required, so the project manager can draw one up and distribute it to each team. This will ensure that all teams know who to communicate with and what the appropriate channels of communication will be. This is the last chance to make any final changes to the plan before the actual construction process begins.

3. Executing the construction project

This is the main phase of a project – the period where the construction takes place. Each team is required to monitor and control their own costs according to the budget set out in the previous step. They must also work to meet the deadlines assigned to the project. The project manager must now oversee all the teams and ensure that everything is running smoothly.

If the project falls behind schedule or is starting to creep over the budget, the project manager must take the necessary steps to fix the situation. Remember that time is money; the longer a project takes, the more it will cost. The project manager must keep strict control over deadlines but still ensure that the quality standards are met. This phase is the most stressful for all teams involved.

4. Finishing the project

At the end of the construction process, when the last interior fittings are being installed and the walls are being painted, the project manager must evaluate the performance of all teams involved. The project manager can use a variety of documents and records to analyse the construction process. This phase will also help the manager to decide whether they are satisfied with the teams’ performances and whether or not to use them again for projects in the future.

These four phases of project management will ensure that a construction job runs on time and within the allocated budget. They will help to align the goals of the various teams and the project manager. The overall result is a well-built structure that is completed to a high degree of quality.

___

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.

Improving the earthquake resistance of small buildings

Improving the earthquake resistance of small buildings

Tanzania is prone to earthquakes and earth tremors. The country has experienced five serious earthquakes since the year 2000. These natural disasters often result in widespread damage and even death. Small buildings and old structures are most at risk when an earthquake strikes, so it is important to improve the resistance of this infrastructure.

Small buildings can be made safer and stronger by taking certain precautions throughout the construction process. The earthquake resistance of buildings has improved dramatically over the past few years. Tanzanian architects and contractors can use some of these tips to make their small buildings more resistant to ground tremors.

Building plans should be symmetrical

Architects need to be aware that symmetrical buildings are more stable and safer during earthquakes than asymmetrical structures. Simple, square or rectangular building plans are more sturdy than ornate designs. Avoid L-shaped and T-shaped houses as these can crack at the corners during an earth tremor. Rectangular buildings should not have a length more than twice the width – this will maximise the earthquake resistance.

Site selection is important

Contractors should avoid building small structures on unstable ground, especially near embankments that are prone to collapse during earthquakes. Sloping or uneven ground should be excavated and graded before any foundations are laid. Similarly, wet soils near river banks and wetlands can also shift and resettle during ground tremors, which could affect the foundations of small structures.

Solid foundations are key

One of the biggest factors affecting earthquake resistance is solid building foundations. The width of a small building’s foundations should be 75cm or more for single-storey houses and 90cm or more for double-storey homes. The depth of the building foundations should be 100cm or more in soft soil and sand, or 50cm in rocky ground. Before the foundations are laid, remove any loose materials from the trenches and compact the ground as much as possible. After the foundations are laid, back-fill them properly and compact once again.

Choose high-quality building materials

The best building materials are high-quality ones that come from reputable companies. LafargeHolcim Tanzania makes a variety of cement products that are strong and durable. Use properly-burnt bricks or well-formed concrete blocks. Brush the top and bottom faces of the bricks and blocks before laying to ensure a clean bond with the cement mortar. 

Use river sand for the mortar and concrete as it is the cleanest and best fine aggregate available. Avoid using a coarse aggregate over 30mm in diameter. Aggregates should be well-graded and angular for the best bond with cement. Dry mix the cement and aggregates thoroughly before adding the water. The length of brick walls should not exceed six metres in small homes – use intersecting partition walls to separate long exterior walls for maximum safety during a ground tremor.

Doors and windows can affect stability

Walls with too many doors and window openings are more unstable than solid walls. This means that having too many windows and doors on a wall will make it prone to early collapse during an earthquake. The total width of all the openings should not exceed one-third of the length of the wall. Avoid building doors at the end of a wall – they should be at least 50cm away from the edge of a wall.

Building a solid roof is important

In structures with a roof span of over six metres, use proper wooden trusses instead of rafters. These are far stronger and more durable than simple rafters. Small buildings with four-sided sloping roofs are stronger than two-sided sloping roofs. This is because the gable walls are prone to cracking and collapsing during an earthquake.

Retrofitting ensures stability in small buildings

Retrofitting is the process of building a structure such that all elements act as integral units of stability. It is the best way to achieve the maximum safety of a building. Examples include:

  • Anchor roof trusses to the walls with metal brackets.
  • Strengthen gable walls by inserting a sloping belt.
  • Strengthen corners of the building with seismic belts.
  • Anchor floor joists to the walls with brackets.
  • Provide vertical reinforcement between different floors of a building.
  • Encase wall openings with reinforcements.

These tips will help architects and contractors to make their buildings more resistant to seismic activity. Earthquakes and ground tremors often result in building damage or total collapse – neither of which are desirable for the safety of the people living inside the structures.

___

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.

Common terms and definitions for brick masonry

Common terms and definitions for brick masonry

The following words are commonly used in brick masonry and construction using cement and concrete blocks. Contractors should understand these definitions and terms in order to complete a project with high quality. Knowledge of common building terms will help contractors to communicate properly with suppliers, engineers and architects.

  • Back – The inner surface of a wall that is not exposed. The material used to create the back of the wall is called the ‘backing’.
  • Bat – The portion of brick that is cut across the width.
  • Bed – The bottom surface of bricks in each course.
  • Bevelled closer – The portion of a brick in which the whole length is beveled for maintaining half-width at one end and full-width at the other.
  • Blocking course – The top-most course of bricks immediately above the cornice to prevent the tendency of the cornice to overturn. It also adds to the aesthetics of the cornice.
  • Bond – The method of arranging bricks so that the individual units are locked together. Bonding is used to eliminate long vertical joints in the wall.
  • Closer – The portion of brick that is cut across the length.
  • Coping – The course placed upon the exposed top of an external wall to prevent the seepage of water.
  • Corbel – The extension of one or more courses of bricks from the face of a wall to serve as a support for wall plates.
  • Cornice – A projecting ornamental course near the top of a building or at the junction of a wall and ceiling.
  • Course – A horizontal layer of bricks or stones. A brick wall will have many courses.
  • Face – The exterior of a wall that is exposed. The material used to create the face of the wall is called the ‘facing’.
  • Frog – An indentation or hole on the top face of a brick, made with the purpose of forming a key for the cement. Frogs reduce the weight of bricks too.
  • Header – The brick that lies with its greatest length at right angles to the face. Any course that lays with all the bricks as headers is known as the ‘header course’.
  • Hearting – The interior portion of a wall between the facing and the backing.
  • Jambs – The vertical sides of an opening for doors and windows. These may be plain or recessed to receive the frames of doors and windows.
  • Joint – The junction between two or more bricks. If the joint is parallel to the bed of bricks in a course, it is called the ‘bed joint’. If the joint is perpendicular to the bed, it is called the ‘vertical joint’.
  • King closer – The portion of brick that is obtained by cutting off a triangular piece from the corner of the brick.
  • Lintel – A horizontal concrete, wood or iron beam that sits above a door or window opening. The lintel gives support to the bricks above a gap in a building.
  • Plinth – The horizontal course of bricks at the base of a wall, above the ground level. It is the first visible layer of a brick wall and protects the building from dampness.
  • Queen closer – The portion of brick that is obtained by cutting a brick into two portions lengthways.
  • Reveals – The exposed vertical surfaces left on the sides of an opening after a door or window frame has been installed.
  • Side – The surface forming the boundary of bricks in a transverse direction to the face and bed.
  • Sill – A horizontal member of concrete, wood or bricks that sheds water off the face of a wall, underneath a window. It also gives support to the window frame.
  • Stretcher – The brick that lies with its longest side parallel to the face of the wall. The course of bricks that is laid as stretchers is known as the ‘stretcher course’.
  • String course – A horizontal course of bricks that projects out of the face of a wall for shedding rainwater.

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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 set out a building plan on the ground

Architects building plan

Before contractors can begin a construction project, they first need to lay the building plans on the ground. This is the process of making the outline of the structure, to the exact dimensions, on the location of where it will be built. The building plan will show contractors where to dig and lay the foundations for the building.

The building plan is often marked by pegs and string, but some contractors like to use white paint on the ground. Pegs are hammered into the ground and attached by a string along the centreline of walls. Contractors need to make sure that the pegs and string follow the architect’s drawings perfectly. 

Steps to laying a building plan on the ground

  1. Clear any long grass and rocks from the construction site where the building will stand. Remove any debris and skim off the topsoil. This will make the marking process easier and clearer.
  2. From the architect’s drawing, start by hammering a peg into the ground at one of the corners of the building (call it point A). Measure the distance of the wall, using the architectural plan as a reference, and place another peg in the ground where the next corner of the wall will be (point B). 
  3. Place a peg two metres away from point A and point B and connect these two pegs with the string. These pegs (call them A1 and B1) will help contractors excavate the foundations later without having to move the string or corner pegs.
  4. Repeat this process of placing pegs at all the corners of the walls (points C and D) and placing additional pegs two metres away. Attach all the outer pegs with string. Each corner point should have two pegs (corner A will have peg A1 joining B1 and A2 joining D2). Where the strings cross will mark the exact corner of the walls.
  5. To make sure that the corners are 90°, the centre points of the rooms needs to be calculated. Measure the distance between opposite corners (point A and point C) on the architect’s drawings. Make sure that the real distance between the pegs at point A and point C match the distance on the drawing. You may have to move the pegs a bit to make these diagonal measurements are exact.
  6. Where the diagonal strings cross is the centre point of the room. The opposing walls (AB and CD or AD and BC) should be the same distance from this centre point.
  7. Once all the strings are laid, the contractors can start excavating the foundations. The extra two metres of string at each corner will allow the contractors to dig the foundations without having to excavate any corner pegs. The strings will be used as a guide for the centreline of the walls.
  8. Some contractors like to spray white spray paint on the ground or use lime to demarcate the path of the wall underneath the strings. This just helps to dig the foundation more accurately.

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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.

Why concrete strength tests are performed after 28 days

Concrete cylinders for strength tests

Contractors often rely on the strength test result of concrete conducted at the age of 28 days. The strength results at 28 days are considered standard and contractors rely on these to determine the integrity of the resultant structure.

Concrete gains strength over time. It can take anywhere from a few weeks to a few years for different concrete mixes to reach almost 100% strength. Contractors generally perform strength tests four weeks after pouring – or 28 days. During this time, all concrete batches will have cured and strengthened rapidly. After 28 days, the rate of strengthening slows down.

How concrete gains strength over time

Standard grades of concrete will generally gain 16% of its strength after the first day, 40% after three days, 65% after seven days, 90% after 14 days and almost 100% after 28 days. This is why compressive strength tests are performed after 28 days. The concrete will be near-optimal strength and is unlikely to change much more after four weeks of curing.

The figures above clearly show how rapidly concrete sets and cures during the first four weeks. After this time, the rate of strengthening slows down considerably, gaining just one more percent of strength in a number of months after being poured. After the first two weeks, concrete only gains nine percent strength in the next two weeks, so the slowing of the rate begins after 14 days.

Concrete takes about 12 months to reach almost 100% strength

Most concrete will reach 100% strength about a year after pouring. Contractors only need to wait for 28 days before performing strength tests as it is close enough to maximum strength to form reliable results. The basis for evaluation is so close to perfect after four weeks that there is no point waiting for another 11 months to do the strength tests.

Although all concrete mixes are different in terms of how rapidly they cure, 28 days has become the standardised length of time to wait. Some rapid-setting concrete mixes may cure within half the time, contractors should still wait for four weeks to perform tests on the structure unless time is extremely limited and deadlines are threatening the project.

___

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.

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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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How to expose aggregate on concrete floors

How to expose aggregate on concrete floors

Some concrete projects call for smooth gravel stones to be exposed for textural and decorative purposes. There are several ways of exposing aggregate on concrete floors. It all depends on the desired appearance and size of the project. Only the top of the stone is revealed, while the rest remains permanently embedded in the concrete. Usually, surface mortar is removed to a depth of no more than one-third of the diameter of the aggregate particle.

1. Brushing and washing

This method doesn’t require special tools or chemical retarders and is the oldest and simplest way of exposing aggregate on concrete surfaces. The thin layer of surface mortar covering the aggregate is simply washed away by spraying with water and scrubbing with a broom until the aggregate is exposed to the desired depth. 

The timing of doing this is very important. Begin as soon as the surface mortar can be removed without overexposing or dislodging the aggregate – the concrete will need to have started setting already, so wait an hour or so after pouring. You can do a test by lightly brushing the surface mortar away in a small area with a stiff-bristled broom.

2. Using a surface retarder

Most contractors use a chemical surface retarder to expose the aggregate. They do this by spraying the retarder onto the slab surface immediately after placing and finishing the concrete. Doing this delays the setting of the concrete and allows them to remove the cement paste a day or so later. This can be done by either pressure washing or scrubbing the concrete surface. Exposing the stones this way can be very useful when working in hot weather or working on large jobs such as pavements and long pathways.

3. Abrasive blasting

Abrasive blasting allows the aggregate to be exposed after the concrete has set and hardened. Either shot blasting or sandblasting can be used. A disadvantage of this method is that it can dull the aggregate’s appearance due to fracturing the surface of the smooth stones. If you want to preserve the shape and full color intensity of the aggregate, this is not the best method to use. 

These three methods of exposing aggregate on a concrete surface allow contractors to create textured and decorative structures. The most common application of this building method is on concrete pathways, parking lots and pavements where the stones give added grip and a pleasing look to the grey concrete.

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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.

___

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.