Finding a Good Concrete Supplier

Ultimately, if you are producing enough concrete then producing it yourself should be the next logical step. In the mean time it is important to have a reliable concrete supplier who will help you get the best out of your moulds and products. That means a good mix, a knowledgeable supplier, and flexibility.

In the free precast booklet ‘How to find a good concrete supplier’ (click to get all the booklets available to download) it aims to help you do just that.

Here is an extract:

Think about your mix
Once you choose a ready mix supplier, you will need to communicate your performance requirements for the concrete. The supplier can then work with you to provide a mix that will  achieve the desired results. Your supplier also needs to know the anticipated exposure and service conditions of the concrete once it has been delivered so that he can supply you with a material strong enough for the application and advise you on admixtures to use to enhance concrete performance, such as water reduces and air entrainers.

Other ingredients you might want to include in your mix recipe include fibres, colour pigments, decorative aggregates, or admixtures.

Understand mix design basics
You should know the basics of concrete mix design so if your supplier gets the formula wrong, you will at least have a basic understanding of how the components in a mix interact so you can help troubleshoot the problem. In some cases, even slight modifications can make a big difference in how the concrete performs.

Figure out how much concrete you require
Once you work with your supplier to come up with the best mix for your application, the next step is to order the right amount. Buying too much concrete is not only a waste of money,  but also necessitates finding an environmentally safe way to dispose of the excess. If you’re too conservative with your estimate and don’t buy enough concrete, you’ll be forced to put the project on hold until an emergency delivery arrives. Volumetric concrete suppliers are able to supply smaller amounts of concrete as they can produce fresh concrete on site to the
quantity required. This takes away any waste issues. Plan ahead to ensure timely delivery Ask the ready mix supplier how many days of lead time are necessary for an order and  whether the concrete can be delivered at the time of day you want it. Giving your supplier ample notice will help to ensure priority service and on-time delivery. For additional reassurance, be sure to confirm your order the day before the pour.

Hopefully that helps you to choose your ready mix supplier, for more tips, hints, help and information click here and download some of our helpful books.

Recycled Aggregates in Precast Concrete

Many people ask if recycled aggregates can be used in precast concrete.

Surely not, many of you will say, with the inconsistency in colour, type, size, shape etc, it surely is the worst product to use in precast concrete?

Click here to get our free downloadable booklets

Approximately 275 million tonnes of aggregates are used each year in the UK as raw construction materials with around 70 million tonnes derived from recycled aggregates. The UK has a dwindling natural reserve of sand and aggregates for use in
construction and the recycling of construction, demolition and excavation waste was identified to offer a solution to the shortage in supply of virgin construction materials. In the UK alone 25% of all aggregate demand is now fulfilled with recycled aggregates.

There is scope for these environmentally friendly options to be expanded even further. Potential for obtaining additional supplies already exists in construction, demolition and excavation wastes that are not currently being recycled and are being sent to landfill

Sustainability in Precast:

Reduces the amount of materials used and the toxicity of waste materials.

Precast concrete can be designed to optimize or lessen the amount of concrete used. Industrial wastes such as slag cement and silica fume can be incorporated into the mix, reducing the amount of cement, which in turn reduces the CO² emissions. As a manufactured product created under controlled conditions in the plant, precast concrete generates low amounts of waste and the waste generated has low toxicity.

Reuse and repair products

Precast concrete panels can be reused when buildings are expanded. Concrete pieces from demolished structures also can be reused in other applications. Recycle and use products with recycled content The British Standards which govern the
manufacture of precast products set performance criteria for products irrespective of individual components. Many precast products (for example, block pavers, and aggregate concrete blocks) can therefore incorporate a high recycled content
within both the aggregate and the cement binder without affecting the end product performance.
Approximately 25% of aggregates used in the precast sector are recycled or from secondary sources. The sector has set a
target to increase the use of additional cementitious materials.Precast products can often be re-used in their entirety.

Precast Concrete Production

The production of precast concrete has many environmental benefits, including:

• Less material is required because precise mixture proportions and tighter tolerances are achieved.
• Waste materials are more likely to be recycled.
• Hardened concrete is recycled.
• Sand used for finishing surfaces can be reused.
• Moulds can be reused.
• Precast recycling systems capture virtually all processed water, slurry, aggregates or cement and these can be re-used in the production process.

We have many helpful booklets online and free to download at – http://www.armcon-online.com/pre-cast-user-guides/

Warm Weather Precasting

One of the biggest influences when precasting is the temperature, and knowing how to handle different temperatures is key to ensuring you maximize the production value of your concrete.

Here is part of our booklet on warm weather concreting, for the full booklet or a booklet on cold weather click here

So lets explore:

The most important phase in concrete’s life cycle is the curing phase; this is when the concrete will start to develop  properties that will directly affect its ability to perform the task for which it has been designed. During the curing phase, maximum strength and durability are affected by the weather. To ensure that both these properties reach their expected level it is important to maximize the hydration of the cement. How this is done will depend on which temperature extreme is  present.

Warm weather affects concrete mainly due to higher curing temperature and a loss of water through evaporation. When the internal temperature of concrete exceeds 200C, the hydration reaction (the reaction that causes the concrete to set )  increases. This can lead to a premature stiffening and loss of consistence (workability) in the mix. The rise of the internal temperature will make the risk of cracking higher. Loss of water can also occur due to a higher ambient temperature, low
relative humidity, high wind velocity and heat radiation.

A loss of workability will make the concrete difficult to place, compact, increase the risk of cracks forming during big concrete pours and make the concrete difficult to finish. The exposed surface of the concrete is prone to moisture evaporation and
therefore is the most vulnerable part of the concrete.

Remedies:

When pouring/producing concrete in warm conditions it is vitally important that there is little or no delay in placing it. If the concrete needs to be transported or is left unplaced it will start to stiffen and suffer a loss of consistence. For example a 30 minute delay in warm conditions can reduce the slump value of a concrete up to 50mm, a reduction in slump is increased as the cement content of the mix is increased.

To stop this rapid hardening and loss of slump use a retarding admixture, but great care should be taken with these  admixtures as over dosing them will cause problems like long cure times and possibly segregation. Another way to reduce the effects caused by warm weather is to use a blended Portland Cement that contains GGBS (Ground Granulated Blastfurnace Slag) or PFA (Pulverised Fuel Ash) but both a blended cement and retarding admixtures will reduce the possibility of a quick rate of hydration that leads to thermal cracking.

– To see more of this and other booklets please see – http://www.armcon-online.com/pre-cast-user-guides/

Blemish Free Precast Concrete

Blemish free concrete can be a difficult and frustrating goal at times. The hard work is mastering the method, once you have mastered it, then repeat, repeat, repeat. To start with make your life easier by using the right materials, use the correct release agents, aggregates, and admixtures in the right proportions, skimping on materials is never a good way to go, the money you save on materials, you often lose on failing concrete, having to over use cement, or… blemished concrete.

The points to look at when producing concrete are:

· Aggregates – Use a good clean aggregate, that is free of contaminates. Make sure you use a dust free aggregate if possible this will save you on cement, as well as ensuring you don’t over dose on the water (dusty aggregates are thirsty) that ultimately causes blemishes.

· Water – Make sure you are using the correct amount, if water sits on top of the concrete when it is setting; you’ve probably added too much, this in turn can create blemishes as well as weaken concrete against frost.

· Admixtures – Use a plasticiser to reduce the amount of water needed and to ensure an equal colour through out.

· Curing – Allow the concrete to cure correctly, so protected from the elements, and with enough time, this is not always possible, but things like wind, water and sun when curing can cause stains, cracks and discoloration.

· Vibration – Use a good table or poker to vibrate all the excess air out of the concrete, over vibration is always better than under vibration – under vibration is one of the primary causes for blemishes in concrete, including blowholes, bad finish, and unsightly concrete.

· Consistency – Ensure a consistent mix and process. This ensures there are no changes (although consistent aggregate can be hard to find, and variations in cement and aggregate colour is common) in the finish and colour that can be caused due to changes in the mix.

· Mould cleanliness – Ensure your moulds are clean and free of any muck or general debris – this is vital to ensure you don’t have blemishes, your moulds stay in good condition and your products are quality.

· Mould type – Certain moulds need to be treated differently – If your mould has a negative taper, then you may have to vibrate longer, or move the mould, testing different methods is always best. For example if you are producing a sphere mould, make sure to add extra vibration and turn the mould around to help the air escape.

· If using colour then make sure to mix the concrete thoroughly and to add the pigment at the right time – with powdered pigment this is when the cement is added.

· For how to reduce lime bloom/ efflorescence have a look at our Reduce lime bloom booklet found here.

Water Proofer in a Modern Precast Concrete Works

With so many admixtures available for the concrete industry, I though we could focus on the Water Proofer, which is often over looked, when it could be an integral part of your process.

Below is an extract from one of our booklets that you can download for free here

Benefits of Water proofer in a modern precast concrete works:

There is a wide range of admixtures available to the precast industry today but their use is often misunderstood or worse still ignored all together. Waterproofer is an essential admixture for a wide range of precast concrete products.

Why use waterproofer?

Many architectural precast products are made using a “dry-cast” process and are required to have waterproofer added to comply with building regulations. It ensures your concrete is protected from water penetrating the concrete. Example of a product made with waterproofer demonstrating how water sits on the surface and does not soak into the concrete.

Example of a product made with waterproofer demonstrating how water sits on the surface and does not soak into the concrete.

Benefits of Waterproofer

· Reduced permeability means less water penetration
· Improved durability means increased resistance to frost attack
· Reduced aggregate transparency effects means product consistency
· Improved colour retention in pigmented mixes means higher quality
· Reduces efflorescence effects means higher quality finishes
· Hardened surface finishes stay cleaner means higher quality finishes

Typical Applications

· Paving blocks
· Concrete bricks
· Concrete blocks – dense, ash and lightweight
· Cast stone and semi-dry pre-cast concrete
· Semi-dry in-situ concrete work
· Mortars requiring permeability reduction

Remember to never mix admixtures in the same storage tank, always keep separate until they are added to the mix.

Demonstration of reduced permeability on treated concrete.

To download this and other booklets please go to http://www.armcononline.com and click downloads or click here

Stone Blocks

At this time of the year when the cold weather is at its worst, it’s great to receive some fantastically warm photos, these are the cast stone blocks, in the Philippines,

The mould that produced them is highly durable, flexible and produces an easy to install, single piece, mortar free walling system component. The integral retaining edge interlocks each staggered course, with the natural stone front surface of the finished wall sloping gently backwards (19mm in 100mm). Ideal for retaining walls, terracing, tree rings and planters.

Here is an equally sunny photo of the mould itself:

If you want to see a video of them being demoulded – http://youtu.be/9Zf2hq-K58w

And finally the beautiful pictures themselves.

For more information please go directly to Stoneblocks (click the link) or go to our website www.armcononline.com

Thermal Blankets

Thermal Blankets are an ideal way of cutting down on your heating costs, in winter time they help your concrete cure, and in summer they help protect the concrete from outside elements.

Our Thermal Blanket is Quilted, Stitched and Welded, to ensure not only durability, but also flexibility. Made from Heavy Duty Terylene reinforced PVC, filled with 2 layers of polyester fibre, this blanket ensures minimum heat loss, 95% heat retention, and at least 25% improvement on next day strengths.

Read more about our Thermal Blankets by going on our website and downloading a booklet

 

Top Tips:
· Use a fitted blanket to your concreting beds if you can
· Concrete creates its own heat so any blanket is better than nothing
· Use a specific concrete blanket if you can – hard wearing and heat retaining
· Never pour concrete in temperatures under 0° Celsius

Overview
A lot of concrete has not had a chance to properly cure. A cover helps create an environment in which the concrete has the chance to cure as ‘thoroughly’ as possible, which is vital, especially in those  early key stages of curing. Good curing means that the concrete is as hard as it possibly can be, it means that the cement you have used in your concrete is being used to its full potential. Ensuring your concrete cures well means that you can save money by using less cement, whilst achieving the same strength as the concrete was before using a blanket.

To download this booklet and many more go to http://www.armcon-online.com/pre-cast-user-guides/ 

 

How to precast?

On this blog I talk a lot about specifics and give you links to books, but recently I was told that we give out too much information and that it was too much to take in.

So where to start? Well… Yup a booklet… Setting up a precast yard, is a good place as any, it sets out what you need, from there you can then get into specifics. You can see the booklets here.

Here is an extract – its only short, but it gives you an idea:

What will I need?

Precast yards depending on their size and the production capabilities need a variety of products.

First of all, ask yourself what is it that I want to produce?
The precast industry has a huge range of different products, and deciding which one is suitable for your market is an important question to ask before considering all the options. Precast concrete can mean ornamental (gnomes etc) or paving, fencing, bridges, architectural concrete etc.

Once you have decided on the products that you want to produce, say fencing or paving as these are a staple of the precast world, then you need to work out how you are going to produce these. For this you need to take into consideration:
· Space
· Moulds
· Mix
· Machinery
· Men
· Review
Space: Do you have the space needed to set up your precast works? I’ve known huge sites that are the size of 10 football pitches, and I’ve know yards that would fit in your front room.
The key things to consider when choosing a yard is; Will you fit all your machinery, moulds and you need in your yard, and will you be able to store your products.

 

There are loads of booklets all on precast concrete, if you are precasting, take a look, at http://www.armcon-online.com/pre-cast-user-guides/ or get in contact, its always good to hear from you – online@armcon.com

Summer Concreting

Summer is here, and with it comes the warm weather that is ideal for fast concrete production.

Or is it?

Anybody who works with concrete will know that the warm weather speeds up concrete set times. One of my customers in the middle east was using the same mould 3 times in one day! That’s fill and demould 3 times in 24hours, not that I would recommend doing this, as hot weather can  be as much of a problem as cold weather.

If your concrete sets too fast the following problems can happen:

– Thermal Cracking

– Less workable (less slump)

– More water = weaker concrete

– Poor surface finish

So how do you combat these and make the most of the warm weather:

Here are my top tips (you can download the full booklet here)

Top Tips
· Cover any exposed concrete surface during warm conditions to help prevent loss of moisture at the surface (reducing the risk of cracking).
· If the temperature exceeds 350C it is not advised to pour concrete unless special precautions have been taken.
· Cover aggregates that are to be used in the concrete to stop them drying out and becoming warm enough to raise the concrete temperature.
· Always double check retarding admixture dosages before using them.
· Try not to have any delay between producing concrete and placing/compacting it.

 

Read the full booklet here

There are lots of booklets to download here and if you have any precast queries just let us know, we are always happy to hear from you.

 

 

Magnablocs – Keep your formwork in place with no nuts and bolts!

Magnablocs as the name suggests, are magnetic blocks. (the blue blocks in the picture) They are used to ensure accurate form work that is easily constructed and modified. ‘MagnaBloc is comprised of a high impact, polymer body containing powerful magnets and a release screw.’

In place, the unit gives up to 400 kg force, and provides a stable vertical surface with two 8mm fixing holes for attaching timber or metal shutters. Any steel bed or plate can be speedily adapted for variable casting dimensions, without any drilling or welding damage.

The key thing is just how easy the magnablocs are to place and move around, they save time in man hours and materials.

I have known them to be placed on a vibrating table meaning the concrete in the form work is vibrated.

This system is ideally used with a steel base that allows the magnets to attach to the base. The 400Kg force means that the form work is firmly fixed in place.

Doser in a Precast Concrete Works

This is one of our customers assembly lines, he uses the foot pedal to dose the concrete into the moulds.

Having the doser means consistency of product. That means the same sized product every time, that means happy customers with standard sizes, it means less breakages due to perfect sized items, it means time and concrete saving.

You can also use the timer to dose exact amounts into your moulds. So should it take 3 seconds to fill your mould, simply set the timer to 3 seconds and press the button. It is that simple.

In this case they fill the concrete into the hopper by using a fork lift and a pan mixer, it is possible to use a volumetric to fill the doser by feeding directly into the doser hopper meaning continuous accurate production.

For more information go to http://www.armcon-online.com/shop/doser/