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 prevent dampness in a building

How to prevent dampness in a building

Dampness in a building may occur due to faulty construction, the use of poor-quality building materials or bad architectural design. Dampness affects the lifespan of a building or structure, but it also creates unhygienic conditions. Mold and fungi love to grow in damp conditions, so it is best to fix any signs of wet concrete as soon as possible.

The measures taken to prevent water from leaking into a roof is usually called waterproofing. The treatment given to a structure to keep its basement, floor and walls dry is called damp proofing. Some of the problems caused by dampness in a building include the disintegration of bricks, stones, tiles; the softening and crumbling of plaster; the corrosion of metals; the warping, buckling and rotting of timber; the presence of termites; deterioration to electrical fittings and the bleaching and flaking of paint with the formation of coloured patches.

What causes dampness in a building?

The absorption of moisture by building materials is one of the main causes of dampness. This can be caused by faulty structure design, bad workmanship or the use of defective structures or materials.

Sources of dampness in buildings include the rising of moisture through the foundation walling; splashing rainwater which rebounds after hitting the wall surface; penetration of rainwater through unprotected tops of walls, parapets or compound walls; gutters which allow rainwater to descend through the top supporting wall. In the case of buildings with flat roofs, inadequate roof slopes, improper rainwater pipe connections and defective junctions between roof slabs and parapet walls can also cause dampness.

How to prevent dampness in a building

1. Membrane Damp Proofing

This involves placing layers of water-repellant materials between the source of dampness and the structure. This type of material is commonly known as damp proof course (DPC). It could be made from materials like plastic or polythene sheets, cement-based concrete, bituminous felts or asphalt. Applying DPC in a basement is usually referred to as tanking and can prevent ground moisture from seeping into the concrete walls.

2. Integral Damp Proofing

This form of damp proofing involves adding certain waterproofing compounds to the concrete mix to increase its impermeability (resistance to absorbing moisture). The compounds made from sand, clay or lime help to fill the voids in concrete and make it waterproof. Compounds such as aluminium sulfate, calcium chlorides and alkaline silicates chemically react when mixed with concrete, producing waterproof concrete.

3. Surface Treatment

This type of treatment involves filling up the pores of the surfaces subjected to dampness. Water repellent metallic soaps such as calcium and aluminium oleates and stearates are often used for this purpose. Cement coating, transparent coatings, paints, varnishes and bituminous solutions also fall under this category. Another economical option for damp surface treatment is lime cement plaster. This effectively prevents dampness in walls as a result of rain.

4. Guniting

For this type of damp-proofing, a cement gun machine is used to deposit a layer of rich cement mortar over the surface. The surface must be completely cleaned of dirt, dust, grease or loose particles by wetting it properly. Cement and sand (or fine aggregates) are then fed into the machine. This mixture is finally shot onto the prepared surface under a pressure of 2 to 3 kg per square centimetre by holding the nozzle of the cement gun at a distance of 75 to 90 cm from the working surface.

5. Cavity Wall Construction

This form of damp-proofing consists of protecting the main wall of a building by an outer wall, leaving a cavity between the two walls. The cavity prevents moisture from spreading from the outer to the inner wall.

These five methods of damp-proofing will help to protect concrete structures from excess moisture, which can lead to mold, fungus, rot and damage to buildings. Contractors and homeowners must always inspect their buildings for any signs of stress and damage, such as dampness, which could affect the integrity and durability of the structure.

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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.

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.

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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.

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.

___

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.

___

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.

Guidelines for fire protection of high-rise buildings

High-rise building on fire

Fire safety is an important factor for any building’s design and construction. The architect and engineers need to work together to ensure that buildings comply with safety standards and meet the necessary fire protection regulations. High-rise buildings present a particular challenge when it comes to fire protection and safety.

Tall residential buildings and office blocks have longer evacuation times, more restricted firefighter accessibility, greater smoke containment and more difficult fire control. In many high-rise buildings, the only fire escapes are staircases – occupants cannot use the windows to escape the flames and smoke. 

Making high-rise buildings safe from fire

Here are some guidelines for constructing high-rise buildings with good fire protection mechanisms:

  • The national building code should be followed when designing and constructing tall buildings. This document will outline all the procedures and regulations that need to be followed, including fire escape guidelines and emergency evacuation procedures.
  • Any high-rise structure should have at least one staircase that is designated as a fire escape. The doors should be linked to a fire alarm and kept closed (but not locked) to prevent people from triggering the alarm unnecessarily. The closed doors will also isolate the stairwell from the smoke and external open air space, which could speed up the spread of the fire.
  • The high-rise building should have access to its own water supply in the case of a fire. If no municipal fire hydrants exist nearby, the building should have its own borehole or underground water tank to supply water for firefighters. This water supply needs to be connected to accessible fire hoses on every corridor of every floor.
  • Smaller, dry-powder fire extinguishers should be located in convenient and accessible places throughout the building. Security personnel should also be given access to fire extinguishers and they must be trained in firefighting techniques.
  • A detailed plan of the building should be accessible to all occupants. This plan will highlight fire escape routes, as well as the locations of fire hoses and extinguishers.
  • Another building plan should also be made available to local firefighters that describes where external fire hydrants and water pipelines are located. They can use this plan to see the cross-sectional layout of the building and plan their firefighting strategy accordingly.
  • The electric circuits in a high-rise building should be separated from one another. Two lighting circuits should be installed – one for regular use and one at floor level in case of smoke and flames. The elevators should run on a separate circuit that can be disabled if a fire breaks out. 
  • All tall buildings over the height of 25 metres should have backup generators that can switch on in the case of a power failure due to fire. Lighting is essential in an emergency evacuation event.
  • All the requirements outlined in the building code should be signed off by the building owner, the architect, contractors and local council. The government can request further building plans and drawings as they see fit.

These guidelines will help to make high-rise buildings safer in the event of a fire. In any apartment block or office space with hundreds of occupants, the risk of fire is increased – especially in high-rise buildings with multiple homes and kitchens. All architects and contractors must be familiar with their national building code and ensure that structures are built in-line with these regulations.

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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.

Finding the right size of crushed stone for your construction project

Finding the right size of crushed stone for your construction project

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

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

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

Types of crushed stone

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

Crushed stone sizes and their uses

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

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

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

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

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

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

___

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.