Types of inspection for concrete structures

Inspection of concrete bridge

Inspecting concrete is a necessary step in the proper maintenance of buildings and  structures. It allows contractors to find any faults, such as cracks and salt damage, before they become bigger problems. Inspections will provide assurance that the concrete is structurally safe at any given period, so they need to be performed once every couple of months at least.

During inspections, any defects or problems need to be recorded. This allows contractors to keep an accurate record of when issues occur and how they are resolved. This information can also help engineers and architects to plan the repair work and strengthen the concrete structure.

Types of concrete inspection

There are three main types of inspection that need to be performed on concrete structures. These are; routine, detailed and special inspections.

  1. Routine inspection – This is the examination of concrete structures at regular intervals. Routine inspections are usually quick and they only look at the general condition of the structure. Each examination is recorded in a book. The inspector will make a visual assessment and use simple tools to determine the condition of the concrete. The purpose of routine inspections is to find cracks, chips, delamination, spalling, salt build-up, rust streaks and deformation in the concrete.
  2. Detailed inspection – This is a thorough examination of a concrete structure that takes longer than a routine inspection. A detailed inspection requires the assessor to closely examine the concrete and use specialised tools to accurately determine the state of the structure. These inspections need to be carried out by trained engineers who can plan comprehensive repairs.
  3. Special inspection – These examinations are done in special circumstances or after unusual events. They are usually performed when a building is being extended vertically, when reinforced concrete pillars show signs of stress, when a foundation starts to collapse, after earthquakes or ground tremors, after a fire, after a flood and after accidents. Any of these circumstances or events will require an engineer to perform a special inspection, which looks at very specific aspects of a structure’s integrity.

These three inspections ensure that buildings and other load-bearing concrete structures remain in perfect condition. Routine inspections must be carried out regularly, white detailed and special inspections are more needs-based – they are carried out as and when necessary. All concrete inspections must be recorded and performed by trained engineers and contractors.

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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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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. 

___

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.

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.

___

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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The role of calcium chloride in concrete

The role of calcium chloride in concrete

Admixtures are chemicals that are mixed in with the cement, aggregate and water in a concrete batch. These chemicals have various effects on concrete; some make it waterproof, others make it more workable. Calcium chloride is an admixture that speeds up the hydration process and makes the concrete set quicker with high initial strength.

This can have various benefits. By speeding up the initial setting time, building projects can progress at a more rapid pace. It also allows contractors to build on top of new concrete within a number of days. This is ideal for load-bearing structures, such as columns and beams.

How to add calcium chloride to concrete

Calcium chloride can be purchased as flakes, pellets, granules or as a liquid. All forms of this chemical are soluble; they can dissolve in water, so it is recommended to use the liquid form. No more than two percent of a concrete batch should be calcium chloride. 

The chemical reacts directly with cement, not the other ingredients in a concrete batch, so it cannot come into direct contact with cement until a concrete batch is being mixed. Contractors should dilute the calcium chloride in the water for the concrete batch and then mix it with the sand and crushed stone. The cement can then be added to the mix.

Effects of calcium chloride on concrete

As mentioned before, calcium chloride speeds up the setting time of concrete and allows it to develop high initial strength. This admixture can be used in low-temperature conditions where concrete would normally take a few days to set. When using calcium chloride, contractors need to make sure that the concrete does not set before they have finished working with it.

Calcium chloride does not affect the water ratio required for a concrete batch. However, it can cause the mix to become stiff, so contractors may need to add a bit more water to keep the mix workable. This admixture also reduces bleeding in concrete once it has been poured, which can sometimes increase drying shrinkage. Contractors need to keep the surface of the concrete damp to prevent it from cracking.

In some cases, calcium chloride can cause a white deposit to form on the surface of the cured concrete. This efflorescence does not happen in every case, but it is not the same as salt damage – contractors do not need to be concerned. These white deposits cannot be washed away with water, so contractors must dilute hydrochloric acid with water and pour it over the surface of the concrete. Brush the diluted acid away with a broom and always wear rubber gloves.

Advantages of using calcium chloride in concrete

  • Development of high initial strength.
  • Reduced initial and final setting time.
  • Reduced bleeding.
  • Improved workability in cold conditions.
  • Fast work turnaround.
  • Cost-effective

___

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.

Ideal building orientation in hot and dry climates

Ideal building orientation in hot and dry climates

Buildings should all face certain directions, depending on their location in the world – in the Southern Hemisphere, they should ideally face north. The reason for this is to provide residents with comfortable living conditions throughout the year. This is done by optimising on the sun’s warmth during winter, which shines from a more northern point in the sky.

In hot and dry climates, which generally occur at latitudes between 0 and 30 degrees, the daytime temperatures in summer can peak above 45 degrees Celsius. Tanzania falls within these latitudes, but is located just south of the equator. These climates do not receive excessive rainfall during the year and the humidity can be quite low.

The buildings in these climatic zones should be orientated so that they receive as much sunlight in winter and as little sunlight in summer as possible. The ideal orientation is north-facing. This means that the main windows should face in a northerly direction in order to allow light and warmth into the house during the cold of the winter. 

In summer, the sun is further south. This means that no sunlight will enter the main windows and doors, keeping the building cooler during the heat of the day. The building orientation depends on the architect and building contractors, but it can have a big impact on the internal temperatures of the rooms, throughout the year.

Typical features of buildings in hot and dry climates

1. Building layout – Different rooms should occupy different positions in a house. Long walls with windows should face north to maximise solar exposure during winter. The kitchen should be placed on the downwind, or leeward, side of a house. This will prevent hot air and the smell from the kitchen blowing through the house. Bedrooms can be located centrally to keep them insulated from outside temperatures.

2. Windows and openings in the walls – Large windows and openings in the walls should face north and west. This will allow the warmth from the sun to enter a building in winter and at sunset. During summer, the sun won’t shine through north-facing windows, but it will still shine through west-facing windows at the end of the day, providing a bit of warmth for the night. 

3. Layout and building of walls – The thickness of the wall plays a big role in heat insulation. Buildings in hot and dry climates should have thick outer walls to act as an insulating barrier, keeping the house cool in summer and warm in winter. Houses should be painted light colours in hot climates to reflect the sun’s heat. The paint should also be smooth and glossy to further insulate the building.

4. Layout of the roof – The roof of a house in a hot climate should be well-insulated and slope in a windward direction. This will allow the roof to cool as the wind blows directly over it. The insulation will also stop the heat from the roof entering the house during hot summers. Ideally, roofs should be tiled with concrete or clay tiling, not tin. Tin roofs can get extremely hot during summer, whereas concrete is a better heat reflector and insulator; concrete tiles will keep a house cooler in the summer and warmer in the winter.

5. Vegetation around a house – The trees and bushes around a house play a big part in its thermal properties. Large trees cast shade over windows, walls and roofs. These should be planted on the south side of the house to provide maximum shade during summer. Make sure that the roots do not grow into the building’s foundations.

In hot and dry climates, such as Tanzania, building orientation is important. It determines how warm a home can be in winter and how cool it can stay in summer. Architects and contractors should pay attention to the orientation of a building when designing and constructing it.

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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 test the workability of concrete on-site

How to test the workability of concrete on-site

There are a few ways to test the workability of concrete at a construction site, but three of the most common methods are the Vee-Bee test, slump test and compaction factor test. Different concrete mixes will have various values for these tests, depending on their applications. So, what is the workability of concrete?

The workability describes the ease or difficulty of the handling of a concrete mix. It is the dryness or liquidity of concrete that determines how easy it is to mix, transport, pour and place in formwork. The workability is an important factor for a concrete mix for a couple of reasons.

If the mixture is too wet, the coarse aggregates will sink and settle at the bottom of the concrete structure. As a result, the concrete will be non-uniform and have weakened integrity. If the concrete mixture is too dry, it will be hard to mix and place in position. It will also be prone to cracking.

Tests for the workability of concrete

As mentioned before, there are three common tests for concrete workability. These include:

  • Vee-Bee consistometer test
  • Slump test
  • Compaction factor test

The slump test is the only one that can be performed on-site. The Vee-Bee test and compaction factor test are usually performed in a laboratory or specialised facility.

How to perform a concrete slump test

A concrete slump test is performed on-site to determine the correct workability of a concrete mix. Contractors will use a cone-shaped mould that is 30cm high with a top diameter of 10cm and a bottom diameter of 20cm. The test is performed in the following steps:

  1. Place the slump mould on a smooth, flat, non-absorbent surface.
  2. Mix the dry ingredients of the concrete and then add the required amount of water, according to the instructions on the bag of cement.
  3. Fill one quarter of the slump mould with the concrete mix.
  4. Compact the concrete 25 times using a tamping rod.
  5. Place some more concrete in the mould, filling it half-way. Compact it again.
  6. Place more concrete in the mould, filling it three-quarters of the way. Compact again, 25 times. 
  7. Fill the mould completely and compact again. The tamping rod should penetrate all the layers to ensure maximum compaction and no lines of separation between layers.
  8. Scrape off any excess concrete from the top of the mould, using a trowel.
  9. Flip the mould over and place the concrete on the flat surface. Remove the mould in an upwards direction.
  10. Watch the concrete slump and settle. Once it has stopped moving, measure the subsidence (or how much the concrete sinks from its original 30cm height) in millimetres. This will tell the contractor how much the concrete will settle and how easy it will be to handle on-site.

Recommended values for the slump test

The slump test should only be used for concrete that is supposed to be of high or medium workability (i.e. stiff or semi-dry mixes, not dry mixes). The following table outlines the recommended slump value for various concrete applications:

Concrete applicationSlump
Road construction20 to 40 mm
Walls, slabs, piers, curbs40 to 50 mm
Normal reinforced cement concrete (RCC) work80 to 150 mm
Mass concrete20 to 50 mm
Concrete to be vibrated and compacted10 to 25 mm

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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.