Subgrades and subbases for slabs – suitable materials and techniques that provide a solid foundation

/in , /by

The soil support system beneath your concrete slab is critical to a successful job. Brisbane’s experienced concrete suppliers understand that a well-compacted subgrade and subbase is the key to a solid concrete slab. Therefore, if you place concrete on an unstable soil support system, you will either waste the concrete or end up with a thin floor. Placing concrete on an inconsistent foundation results in cracking because the ground is not solid and stable.

What is a subbase / subgrade for slabs?

The subgrade is the soil that is usually compacted when preparing for slab installation. Thus, you find this soil at the bottom of the slab system. The subgrade may refer to the native soil or the improved soil delivered from a different source.

The subbase refers to the layer placed on top of the subgrade. Thus, the subbase features an easy- to-trim granular fill that remains stable and supports the slab. Therefore, the subbase and subgrade comprise the soil-support system for the slab. So, how do you ensure suitable materials and techniques for a solid foundation?

Here are essential considerations to bear in mind when working on subgrade or subbase.

  • Slits cannot be compacted in thick layers. Only granular soils can compact appropriately in thick layers. However, note that slits can be compressed at the optimum moisture content.
  • Soiling soil can expand and contract with moisture variations. The contraction and expansion of swelling soils affect the slab integrity. Therefore, avoid using swelling soils when working on subbase and subgrade.
  • Talk to Brisbane concrete suppliers for the right chemicals and materials for controlling the subbase and subgrade.
  • The subbase materials consist of naturally occurring coarse-grained soil or blended and processed soils.
  • Where possible, avoid the use of materials with more than 15% fines.
  • The subgrade and subbase thickness depends on the type of materials, compaction equipment, and construction method. However, the bottom line is that the subgrade should be thick enough to withstand the load on it.

What are the advantages of adding the subbase /subgrade layer?

  • The subbase or subgrade layers provide strength and support to the overlying pavement.
  • They provide proper drainage and ensure adequate frost protection
  • A compact subbase and subgrade prevents settlement to the pavement and the slab on a grade.
  • Subbase and subgrade compaction keeps the construction workers out of the mud and creates a workable surface before placing the concrete slab.
  • Overall, a well-laid subbase and subgrade reduces construction costs.

Subgrade soil is classified under four broad categories.

  1. Gravel—a coarse material featuring little or no fines and hence provides cohesion of materials.
  2. Moorum — the product of decomposition and weathering or rocks, similar to gravel.
  3. Silts— finer than sand and brighter in colour compared to clay, while they exhibit little cohesion.
  4. Clay—a type of soil that exhibits stickiness and features high strength when dry.

The types of subbase for flooring come in four categories:

  1. Cementitious— a lean concrete with a lower cement content that binds stone aggregate and sand.
  2. Granular—a popular alternative for cementitious
  3. Hill earth—a unique material used as a subgrade.
  4. Polyurethane foam insulation— a unique situation subbase material encountered in cold storage applications.

Conclusion

We have looked at the different subgrade and subbase materials. Now you know to ensure your site is compact before laying concrete. Talk to Reocrete for concrete delivery. We are theleading Brisbane concrete suppliers.

Understanding Slump

/in , /by

Slump refers to the measure of concrete fluidity and consistency, and it shows the flow and workability of premixed concrete. When mixing concrete, figuring out slump quality should be a priority because it directly affects the ease or difficulty of working with the concrete. It is essential to clearly understand slump, including what it is, how to test it, how to interpret the results, and many other facts. This article will help you learn more about the slump of concrete.

Slump Test

The test is done using a slump cone, usually in the shape of a conical frustum. The cone is open-ended and has handles attached to both sides of it. The cone has a diameter of around 3.6 inches at the top and 7.8 inches at the bottom. The height is about 12.1 inches. At the start of the test, the cone is placed on a hard surface that is not absorbent. Fresh mini concrete is put into the cone in three stages.

When each layer is added, it is tamped about 25 times with a long bullet-nosed metal rod. In stage three, the concrete is levelled off at the top of the mould. Then the mould is carefully lifted vertically to avoid disturbance of the concrete cone, and the concrete subsides. The distance from the top of the slump cone to the top of the slumped concrete is measured.

Interpretation of Slump Test Results

The profile of the slumped concrete determines the shape it is considered in the results of the test. The categories of the results are a true slump, collapse slump, or shear slump. An excessively wet mix is called a collapsed slump. For the shear slump, the top portion of the concrete shears off and slips towards the sides.

A 0-25 mm slump is considered very dry and used in construction projects such as road construction. Concrete with a slump of around 10-39 mm has low workability and is used for light reinforced foundations. A 50-91 mm slump has medium workability and is used as typical reinforced concrete. High workability concrete has a slump of above 100. This type is used to fill tight spaces for reinforcements and concrete that needs to flow long distances.

What Happens If the Concrete Slump Is Too High or Too Low?

If the slump is too high or too low, it means that the concrete has low workability. The workability makes it hard to handle. When the specified range is exceeded, shrinkage may occur. The concrete slump should be maintained at a workable range depending on the type of project you are doing.

Conclusion

The slump of the concrete is significant when using concrete during construction. It is essential to understand concrete slump clearly so that no mistakes are made when completing a construction project. This information can also help you make your projects more durable.

Quick tips to cut and bend steel reinforcing mesh into shape

/in , , /by

Steel reinforcement has emerged as crucial for many construction projects. To use it, you need to cut and twist steel to mould into the desired shape to support the planned loads. This strengthens the structural integrity of the project. You can contact Brisbane’s reinforcing mesh experts for your entire steel reinforcing requirements. It is important to seek professional help because most people lack the required expertise to use it correctly. You should also follow set standards pertaining to cutting and bending steel.

Here are some tips below that you may consider:

Bolt cutters for cutting steel mesh

Bolt cutters are used widely for cutting steel mesh. Bolt cutters have emerged highly useful when you need to cut steel rods. The pressure produced by bolt cutters will offer a smooth and fast-break as well as giving you great precision.  However, the circumstances under which you may have to use this method may be quite limited. The method has proved to be quite an effective one in the right situations. You can contact steel bar Brisbane specialists to procure top quality steel bars.

Circular saw for cutting steel mesh

You can also opt for a circular saw that is equipped with a metal cutting blade. A circular saw can make precise and straight cuts in steel mesh. It has also become one of the most popular power saws and can slice precisely. You will find several blade sizes depending on the projects. The kind of blade you choose will help in deciding the depth of the cut. Also, it has become one of the most reliable solutions while handling an off-site prefabricated cut.

Manual saw for cutting steel mesh

If you can’t find a powered circular saw, you may have to rely on a manual saw. It will also execute the task effectively. You should speak to leading steel suppliers in Brisbane as they will help in producing exact results as long as the metal is held strongly in a place. The only problem that you may face with this option is that it may be a little time-consuming.

Bend steel mesh with a pipe and bar

You may also fix the steel into place and then opt to use a bar to knock the end down. This will produce a bend in the steel with the least effort. You will also be able to decide an angle to create a desired shape for the specific job. This has become a common onsite method now. But, if steel cannot be bent to the right angle, it may compromise the integrity level of steel.

Use your hands

When working with thin steel pieces, you can bend the rod by hand. It will test your physical skills and may prove to be tough to bend the road by hand. However, when a fast solution is sought and correct tools are unavailable, it can be a last resort.

Conclusion

The above tips will help you cut and bend steel reinforcing mesh into the desired shape. You can contact premix concrete Brisbane to get the job done.

Different Proportions to Consider for Concrete Mix

/in , , /by

As your construction project progresses smoothly, it’s quite important to consider the right concrete mix proportion. But, as the slurry gets prepared with the addition of cement, sand, and water, the ratio totally depends on the construction project. However, based on prior experience, the building codes offer standard ratios for onsite construction. If you are worried about quality, then you should opt for premix concrete in Brisbane from Reocrete. But, if you are not sure about the ratio, then you should read ahead to learn more about the proportions.

Materials used for preparing concrete

Among the basic materials, concrete always has cement as one of its constituents. While shale, limestone, and other ingredients are burnt to form clinker, the grinder grinds lump to obtain a fine powder. You may come across blended cement at some sites however, this is ideally used for masonry work, ideally for plastering. Apart from cement, aggregate and sand are also major constituents. The ingredients not only enhance structural integrity but also increase compressive strength.

Different types of proportions

  1. Nominal Mix ratios: Many years ago, the ratio of the constituents for concrete was actually based on the amount of cement and aggregate. Since this was considered a fixed ratio, such types of ratios were known as nominal. Ideally, the nominal ratio is 1:1.5:3 for M20 grade concrete and 1:2:4 for M15 concrete. To learn more about concrete prices in Brisbane contact Reocrete today!
  2. Standard Mix ratios: As the contractor may vary the nominal ratio, the overall constitution may differ to some extent. Even though the ratio may enhance strength, the cement may not be suitable for the onsite construction work. Hence, in order to maintain minimum compressive strength, concrete is based on a standard ratio. While you purchase concrete, you may come across different grades like N20, N50, N32, and N25. But, for grades more than 50, the contractor may require special class concrete for the work. Regardless of the concrete mix, every grade is different with respect to its compressive strength.
  3. Designed Mix Ratio: When dealing with a Designed Mix Ratio, an experienced professional determines the precise proportion of the constituents. Moreover, concrete suppliers in Brisbane may follow a rational approach to figure out the proportion with the unique characteristics of the materials. It’s completely normal to use standard or nominal mixes for short-duration jobs. The ratios, in this case, don’t matter when there isn’t any need to carry out control testing.

Finally, for increasing the strength of hardened concrete, it’s important to maintain the water to cement ratio; fine aggregate can be added only when the person is preparing a sticky mix.

Contact steel suppliers in Brisbane at Reocrete, if you have any questions or need any assistance deciding on the right concrete for your construction project!

How to Determine the Tensile Strength of Concrete

/in , , /by

When a contractor plans to execute a construction project, it’s important to firstly determine the overall strength of the concrete. Due to various effects and the applied load, the structures built from concrete are prone to tensile cracking. But, on the other hand, it’s advisable to use steel reinforcing mesh Brisbane when the contractor needs to reinforce concrete slabs. So, let’s get into two different kinds of tests and the procedure of measuring the tensile strength of concrete.

1. Split-Cylinder Test

A split-cylinder test is known as a standard test, which enables the contractor to find out the tensile strength indirectly. As the expert starts off with the test, a concrete specimen dipped in water is placed between the loading surfaces of the testing machine. While the load is applied uniformly along the diameter, the testing machine is set to a range between 0.7 to 1.4 MPa/min.

It’s important to note that a plywood strip has to be placed on the lowermost plate. Moreover, the expert shouldn’t forget to place another strip above the specimen. Later, the pressure needs to be applied relentlessly until the concrete specimen starts cracking along the diameter. At this instance, the expert has to record the reading which is nothing but the breaking load. He then has to use a formula for calculating the tensile strength of the specimen. Typically, the tensile strength may lie between 1/8 and 1/12 of the compressive strength. If you’re using mini concrete Brisbane, then you should be mindful of the time for which the specimen is exposed to water.

2. Flexure Test

The flexure test is yet another test that can help you determine the tensile strength of concrete. Before proceeding with the following steps, first pour fresh concrete into the moulds to create samples. Rather than coming up with just one sample, create three specimens for the test. Keep the hardened concrete in the water at a temperature between 24 and 30 degrees Celsius for two days.

After the specimen undergoes curing, it has to be placed carefully between the loading points. After some time, a load equivalent to 2% to 6% of the ultimate load has to be applied steadily. Mesh reinforcement Brisbane is essential for concrete slabs at the construction site.

Towards the end, as soon as you calculate the loading rate, find out the modulus of rupture. This figure is nothing but the extent at which the concrete cracks when it is subjected to continuous load or pressure. Post test, set the testing machine to a configuration for cylinder testing. Also ensure you discard the specimen and clean the testing machine thoroughly.

Once you have decided on what type of concrete you need, you can find suitable tools online. If you are concerned about completing the construction project, you should contact firms dealing in concrete delivery Brisbane  such as Reocrete Brisbane.

How to Speed Up Concrete Drying Time: Pre-Pour & Post-Pour Tips

/in , , /by

In applications like flooring, one needs to wait for a long time to let the concrete dry properly. During this time if anything is rushed, it may result in flooring issues. The flooring may crack later. In order to avoid this, the ideal drying time set is around one month.

Here are some pre-pour and post-pour tips that will help to achieve maximum efficiency and strength of concrete. Also, it will boost the drying process.

Pre-Pour Tips
Follow these pre-pour tips to fasten up the concrete drying time:

1. Reduce Water Quantity:
It’s an obvious solution here. If you add a lot of water to the mixture, it will take more time to dry up. It’s advisable to add a little water to speed up the drying process of concrete. However low water-cement ratio can make the mixture too thick.

Still, if you are skeptical about the right water-cement ratio, you can consult concrete suppliers Brisbane for that matter.

2. Add Self-Desiccation Agents:
Chemicals like calcium chloride hydrate the mixture quickly and attain enough moisture. It reduces the drying time of concrete to a great extent. So instead of adding more cement, you can add chemicals like these before pouring to accelerate hydration. A good alternative to this is to use ready-made premix concrete Brisbane.

3. Add Warm Water:
Water added when it’s hot fastens the reactions in the mixture and therefore the drying time also. Adding hot water accelerates the concrete mixture to attain hydration quickly. However, do not add blazing hot water as it can have its own repercussions.

4. Choose the Right Weather:
If it’s not urgent, avoid laying down floors in cooler months. In winters, the concrete drying time becomes much more than in the summers. Always go for hot sunny weather as it will quickly dry out the mixture without compromising on strength and efficiency.

Post-Pour Tips
Follow these post-pour tips to fasten up the concrete drying time:

1. Trowelling Technique:
High intensity trowelling should be avoided after the mix of concrete has been prepared. Hard trowelling loses the ability to let moisture dry. The vents or capillaries somewhat sealed off prevents the moisture to vaporize. It remains inside and thus slows down the drying time.

2. Dehumidification:
This process is often used to dry out the concrete slab much quicker. The method is quite simple; you just need to reduce the dew point of the air surrounding the concrete Brisbane slab. This helps in evaporating out the moisture through the surface of the concrete. This process is most commonly used in the building industry.

3. Use a Dryer or a Heater:
If the weather is acting against the drying time of concrete, use heaters. But never overheat the concrete mixture as it may end up creating more problems; just heat in the right intensity. You can also use heating mats for this purpose.

Wrapping Up:
These were some of the pre-pouring and post-pouring tips to improve the drying time of concrete. Since the natural drying time is not always good enough, these tips become necessary to set it quickly and attain the desired strength. Apart from this, readymade concrete delivery Brisbane is also available which has the right amount of chemicals added to it!

Pouring Concrete in Hot Weather – What Do I Need to Know?

/in , , /by

Excess heat can have a devastating effect on the quality of freshly mixed concrete. It is recommended to store newly prepared concrete at a lower temperature than 77 degrees Fahrenheit. Thus, Concrete Brisbane strongly recommends that you should have proper arrangements for placing, finishing, and curing of concrete if you wish to use it as the planning material for your building.

Pouring concrete in hot weather can be a little tricky as it does not take too long for the quality of concrete to break down in hot weather conditions. From the loss of entrained air to the surging demand for water, here is a list of what can happen to the concrete if the temperature exceeds 90 degrees Fahrenheit.

Effects of Pouring Concrete in Hot Weather

  • During the hot weather, the temperature is very high and calls for more water. This is the reason for which the water-cement ratio increases and leads to enhance the potential strength of the concrete.
  • Hot weather also accelerates slum loss and may even cause loss of entrained air.
  • Weather plays a crucial role in setting time of concrete. If the weather is hot or the concrete is poured in high temperature, then the concrete sets quickly and requires more rapid finishing.
  • In hot weather, the temperature is usually high, which increases the rate of evaporation due to which the surface water removes very quickly. Surface water plays an important role in hydration.
  • High temperature further escalates hydration of cement due to which thermal cracking of the concrete can be observed in many concrete structures.

Whether your concrete would show the signs of all these effects or not, it would depend on its quality. The material from reliable providers, such as concrete suppliers Brisbane, can resist a higher temperature without showing any sign of the deterioration of quality to a certain extent.

While there is no denying the fact that you may need to spend a little more on a quality product, it does not mean spending a fortune. For instance, if you are based in Brisbane, there are ways to keep concrete prices in Brisbane within your reach.

Furthermore, you can consider taking certain steps to keep things under your control. For getting desired results while pouring concrete in sultry weather conditions, consider taking the steps given below.

Measures to be taken during Pouring Concrete in Hot Weather

  • At first, you need to erect temporary windbreaks which limit the wind velocities and try to keep fix sunshades in order to reduce concrete surface temperature.
  • You can add cool aggregates and mixing water to the concrete mixture which will reduce its initial temperature to a smaller extent.
  • Ensure that you have enough workers to minimize the time to place and finish the concrete, because hot weather conditions mostly decrease the setting time of concrete.
  • Try to perform the concrete process in the foggy area which helps you to raise the relative humidity and also satisfy moisture demand of the ambient air.
  • Also, provide authentic cutting method after the completion of the concrete placement.
  • Always use a concrete consistency which allows rapid consolidation and placement.

Takeaway

No matter how hard you try, the fact remains that hot weather conditions will have a negative effect on your construction material in some way or another. You can keep the effects down to a certain extent by choosing a reliable supplier such as Concrete Brisbane.

By choosing such providers, apart from getting quality material, you can also expect to have proper concrete delivery in Brisbane for the construction of your project.

How to Lay Concrete Like A Pro

/in , /by

Looking to do some DIY concreting? Creating a good concrete slab is not that difficult to do. Once you know how, you’ll be able to create great floors for your garden, patio or shed.

But first things first – materials. Get hold of some pre-mixed concrete, steel pegs, reinforced mesh and formwork (the mold into which your concrete will be poured). Talk to us for advice on materials and your project.

You’ll also need measuring tape, a spirit level, shovel, concrete edger and rake, float, levelling screed and stringline.

Once you have everything ready, these are the steps to follow to create a pro-looking concrete floor.

  1. Dig out a level to match your formwork. It should be at least 100mm deep. Dig the area that you wish to place the formwork in and add an extra 50mm in thickness for the formwork. Make sure all of your measurements are square and that your ground is even by using a spirit level.
  2. Secure your formwork using steel pegs. Make sure they’re firmly hammered into the ground.
  3. Lay down some reinforced steel meshing. This stops your concrete from cracking over time. Make sure you have at least 25mm of concrete covering the mesh.
  4. Even out your concrete. Use a rake and screed to spread the concrete evenly and flatly. Tap the outside of the boxing with a hammer or use a concrete vibrator inside the boxing to eliminate porous finish once boxing is removed.
  5. Smooth the surface. Use a steel trowel and wooden float to create a smooth surface and your concrete edger to add a nice finish.
  6. Take away your formwork. Remove the formwork after 3 days to reveal a perfectly constructed concrete slab.

For more information and advice, contact us today.