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CLEVA-Crete Tech Talk

If you have any questions about how CLEVA-Crete this is the place to come to.

This is an extensive knowledge bank for anyone involved in concrete for construction.

We are constantly adding to the articles contained within so add a bookmark in your browser so you can easily return whenever you need to.

If there are any questions you have that we haven't covered here please feel free to contact us (details are at the bottom of the page) and we'll do our best to answer your queries.

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Why should we request the use of CLEVA-Crete on our products?

CLEVA-Crete is cheaper to buy than anything else, it pumps easier than anything else and drops the pressure in the lines by 35% on average.

It is just as easy to spread, makes the bull floating process easier, doesn’t produce any annoying bleed water and enables you to finish off one to two hours earlier, saving time and money over and over again.

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Is CLEVA-Crete suitable for undercroft or underground carparks, cellars and lift wells?

Whether in-situ poured, precast or sprayed in, CLEVA-Crete enhanced concrete is incredibly good at keeping any groundwater out.

It will take hundreds of years for moisture with a solid hydrostatic pressure to get through CLEVA-Crete 842 W-P’s defence shield.

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How does CLEVA-Crete improve concrete strength?

CLEVA-Crete admixtures enhance low permeability and strength, while adding ductility and thus resultant durability to the life of concrete. ‘CLEVA-Crete’ technology works with the calcium hydroxide and the free water in concrete to produce additional calcium-silicate-hydrate (C-S-H) gel, the nano building block of concrete. This is an exact science, calculated using the proven ‘Powers’ calculation model that works out how much free water there is in your mix design. This permanently disrupts normal capillary formation, leading to ultra-low permeability and superior long-term shrinkage reduction.

CLEVA-Crete does not rob any hydration water in its process, rather it creates a non-hygroscopic, shrinkage and crack reducing concrete. This is mainly due to the fact that the usual osmosis effect on concrete as it is drying, is stopped and the moisture is retained in the slab where it forms nano sized pure C-S-H. The result is a tough, durable, strong C-S-H material that densifies, creating a stronger resultant concrete. There is a typical gain of 13-17% increase in MPa during the setting stage of concrete which is the first couple of days, then as the concrete cures through the 28 day process, strengths show a 4 to 11% increase in MPa overall and overtime.

Is it possible to minimise the steel cover in areas for concrete elements that will be exposed to extreme acid or alkaline?

For issues with edge lifter linking rebars not getting the full cover that engineers want, it is possible to minimise the steel cover in areas for concrete elements that will be exposed to extreme acid or alkaline for certain critical infrastructure projects.

However this is all very dependent on the size of the aggregate being used in the concrete and whether any steel or synthetic fibres have been used in the matrix, as moisture will travel through absorptive stone and long fibres.

The fact that CLEVA-Crete enhanced concrete makes the mortar extremely impermeable in concrete precast elements, piers and footings, some stakeholders in the industry are working with 10-12mm cover, especially where edge lifters are involved in structural elements.

In rheology, when using 5 to 7mm aggregate and no fibres, many involved in cellars, car parks and pools are reducing steel cover.

CLEVA-Crete 842 RP is specifically designed for where you have many low cover areas in precast or if you are pouring deep foundation piles where you know that integrity of steel around perimeter spacers could be compromised while being lowered into position, or going into aggressive environments.

CLEVA-Crete 842 RP is specifically designed as a reo protection product, hence the RP.

While such concrete is in its plastic stage there is a chemical reaction that takes place, permanently coating steel with a reo protection chemical and thereby double the life expectancy of the steel’s integrity due to the RP factor.

What do I have to do to get CLEVA-Crete specified for all future work?

Our CLEVA-Crete technical advisor is always ready to approach the specifying body looking after any of your future projects.

Please call and register your interest and we will assist you in every way we can.

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Does the slump stay the same when the concrete has CLEVA-Crete in it?

The slump is different from mix design to mix design, but CLEVA-Crete will generally increase the slump.

The gel created causes the stone to roll over very easily when the concrete is in its plastic stage and, because it is dynamic, it causes the mortar around the stone to be more even.

It is also one of the reasons why the concrete is 4 to 11% stronger after 28 and 56 days.

Please be aware that when the concrete truck rolls up to the pump and the concrete slump appears low, it likely does not require as much water as you might ordinarily add.

The slump is likely right where you want it, so be careful not to overwater.

How does CLEVA-Crete stop slab curl?

Slab curl is caused when the concrete has capillaries and moisture is moving in and out of it, just like a sponge, affected by any abutting surface temperatures and moisture levels.

If the substrate under a building or a road or a warehouse is wet, but it is dry on the top or inside, that slab will curl.

CLEVA-Crete doesn’t let any capillaries form.

Do I still need silica fume if using CLEVA-Crete?

CLEVA-Crete completely replaces silica fume.

It has the same blaine of >20,000 square metres per kilogram and, yet, produces a finer resultant gel that flows smoother, hangs up better and cracks significantly less than silica fume.

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How does CLEVA-Crete affect setting times?

CLEVA-Crete has a blaine of over 20,000, which gives it a mass of reactive surface area per kg.

It is not a cement, it is a pozzolan so it creates additional purer amorphite types of C-S-H. However this does not make the CCMC go off that much faster than control.

Silica fume also has a blaine of 20,000, yet would not go off a lot earlier. Silica fume just makes the concrete stickier and holds up well in rheology, whilst CLEVA-Crete replaces it, CCMC is not as sticky to work with or finish.

CLEVA-Crete modified concrete will have properties very similar to any other concrete you have batched. When it gets to site and is poured in place, screeded and being finished, it will set up the concrete a little bit earlier but it only means that the grano’s don’t need to wait around the normal typical 1-2 hours waiting for all the bleed water to come up.

Otherwise there is no real difference.

If CLEVA-Crete reduces line pressure by 35% does this also affect rebound volume loss and cold jointing from rebound material?

Yes, it reduces rebound by 35% so, in something as small as an 8 x 4 metre swimming pool with an average depth of 1.4 metres, you can reduce rebound material loss by up to 50%.

Also, if the mix has steel fibre in it, it causes less rebound, makes the mix stickier and dramatically improves workers' safety near the nozzle.

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Why do you require use of your special pump? Why can’t we use our normal pumps and a spare tank that we have at the batch plant?

CLEVA-Crete is an extremely high quality, super fine material and, when it dries in a normal rubber or steel impeller pump, there is the risk that it can cause damage to equipment and the impeller blade.

Our air driven, twin-diaphragm pumps have proven to be the most reliable option over the last 25 years.

Our fluid controller talks directly to your batch plant computer.

We will install our pump free of charge and, if you don’t have a tank available, we will install a type and size that will suit and fit into your plant. Many batch plants utilise normal IBCs.

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What price should we allow for using CLEVA-Crete on a project?

CLEVA-Crete has only one wholesale price and is only sold to all the major concrete suppliers.

As a fully-warranted product, on-site quality control is imperative and dosage is by computer either during the batching process, or on-site as requested, protecting you and your client.

As all states price differently, CLEVA-Crete does not set the price in stone, it’s best to contact your concrete suppliers direct to find out the exact price per cube.

CLEVA-Crete’s RRP for:

CLEVA-Crete 842 is $40 per cubic metre (Resolves moisture vapour egress)
CLEVA-Crete 842-WP is $80 cubic metre (Waterproofing to stop ingress/egress)
CLEVA-Crete 842-RP is $110 cubic metre (corrosion inhibitor plus waterproofing)

Is there any benefit to using CLEVA-Crete for smaller precast elements for civil infrastructure?

Many precast companies use CLEVA-Crete with smaller precast elements as you get the shrinkage reduction attributes plus there is no bleed water,.

Labour time is reduced as there is no need to work the bleed water back in.

When used in the manufacture of pipes, you can typically de-mould earlier than normal, with less break-outs.

What are the payment terms?

Payment terms are 30 days from the date of invoice.

How does CLEVA-Crete reduce pressure in lines and at the orifice of the nozzle?

CLEVA-Crete dynamically produces calcium silicate hydrate gel that acts like a lubricant and causes the finer aggregate in shotcrete to rollover easier and flow-through pipe systems much better.

CLEVA-Crete modified concrete typically reduces pressure in the line and at the nozzle by at least 35%.

Are there certain projects or situations where CLEVA-Crete shouldn’t be used?

In a word - no.

It gives a superior finish. It lessens the usual shrinkage. It lowers the heat of hydration. It reduces DEF and ASR and stops slab curl and surface dust.

Then, over the structure’s life cycle, it also stops or reduces carbonation, chloride and sulphide ingress from destroying the concrete.

Why are we required to give you our mix design?

CLEVA-Crete is normally dosed at about two litres per cubic metre for a lot of mix designs, but our trained dosing officers require the mix design including information on what SCMs are being used and at what percentages and - most importantly -it is essential to know the water/cement ratio of your mix design.

The technology only uses up the free water that is in the concrete matrix and does not require any additional hydration water during the dicalcium silicate hydrate and tricalcium silicate hydrate stages. Our lab will use the ‘powers model’ for getting the product balance exactly right so we do need cooperation with the full mix design. It is not uncommon for us to sign an NDA for certain projects, so that sensative information is protected and we are happy to discuss any such concerns.

How soon after pouring can installation of rubber backed carpet tiles or resilient vinyl occur?

Once concrete has turned from the original plastic stage and has fully set - usually 72 hours - there will little or no moisture egress.

Because CLEVA-Crete technology stops any capillaries from forming, it will not let out any moisture after the original tricalcium silicate hydrate stage sets in the matrix.

It will take the same time as normal concrete to cure, but all moisture will stop in 72 hours, meaning that you can lay all flooring and coating systems as soon as the top surface has reached the pH level of about 8.0 (as required by all the glues and bonding materials specifications).

This usually takes 10-14 days, depending on exposure for carbonation.

Fans may be used for jobs required to be finished 10 to 14 days after the concrete has been poured. Remove all large objects off floor areas and avoid gas heated air movement devices as these create some noxious gases in the air that slow down the process.

In hot and windy weather, does the concrete need to be kept wet to stop plastic shrinkage cracking?

Because CLEVA-Crete stops any capillaries from forming it typically doesn’t crack on top or shrink anywhere near as much as other concrete, but as there will be tension on the very top surface when drying quickly.

On a warm day there will be a lot less surface tension if it is kept wet in such conditions.

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How does CLEVA-Crete affect hollow-core precast elements?

For the most part, CLEVA-Crete does two things when used in hollow-core precast elements or planks.

Firstly, the gel produced causes the mortar to evenly spread around all the aggregate, so as it passes smoothly through the hollow-core formation machinery. This characteristic causes a smoother concrete and results in decreased noise levels and less wear and tear on machinery.

Secondly, the batchers have noted that, when the zero slump mixes for hollow-core planking is being batched, less water is required to get the same slump. This decrease in water required for zero slump mixes in a planetary mixer, resulting in a stronger MPa every time.

When there is CLEVA-Crete in concrete, does it made the concrete go off faster?

The concrete will set 13 to 17% quicker.

There isn’t any need to be concerned about this - a shorter morning tea is all it usually takes.

CLEVA-Crete just increases the setting time rather than decreasing it, like crystal growth technologies do.

Do CLEVA-Crete’s waterproofing abilities prevent bonding of glues and adhesives for roofing and coating systems or membranes?

Not at all. In fact the opposite occurs.

There have been many examples of bond testing boards snapping when being lifted off by hydraulic jacks, so CLEVA-Crete enhanced concrete is an exceptional material for bonding.

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What changes in finishing techniques will be evident when CLEVA-Crete is used?

As it cures from the inside out it is easy to get used to the change very quickly.

On large slabs finishing can happen around an hour earlier than normal due to setting 13 to 17% faster.

When you do get to finish off, you will seldom need any water to do so, even though there will be little to no bleed water.

There will be no need to work up a finishing cream and you will get the concrete very flat, in less time than normal.

You can get a nice hard burnished finish on the concrete just the same and, in many cases, on large slabs, you can cut the control joints on the same day as the pour.

Is there anything in this material that an environmentally conscious construction business should be concerned about?

There is nothing in CLEVA-Crete or in the process of manufacturing, handling or dealing with it that is at all carcinogenic, toxic, poisonous or hydrocarbon rich.

Instead, it is VOC-free and ideal for ISO14001 certified companies.

How do engineers respond to CLEVA-Crete in the mix design?

CLEVA-Crete provides a superior finish, increased MPa, less shrinkage, lower heat of hydration, controlling ASR, slab curl and dusting.

These attributes provide project specific durability and longevity - factors that are important to most engineers, and they are embracing this global technology.

Engineers know that hydrophobic type water-proofers like caltite work very well, but they also realise that their hydrophobicity causes additional problems in that it slows down or delays effective hydration of the cementitious materials in the concrete, so generally concrete strengths are compromised in some cases up to 35% less compressive strengths, requiring more cement (and cost) to compensate for this.

As crystal growth technologies are reactive, they only work after moisture has come into the concrete and reacted with the crystals.

Engineers also know that once moisture comes into the capillaries of the concrete matrix, that you immediately you start off your process of lowering the pH around the steel, leading to eventual catastrophic failure.

If CLEVA-Crete provides higher early setting strengths after 8-10 hours, is it possible to strip and deform much earlier?

CLEVA-Crete increases early setting times by up to 13 to 17%, sometimes more.

It heavily reduces edge chipping and thus saves patching labour hours.

It reduces shrinkage, controls plastic shrinkage cracking, reduces heat of hydration, stops slab curl and normal dusting, so is an extremely good value proposition for precast.

When making the decision to use it purely for increased strength and possibly using decks twice in a day to double production, it works out that unless you excessively use steam setting techniques, it usually does not enable this.

What are your delivery arrangements?

We bulk deliver to batch plants daily.

To ensure a next day delivery the office or your rep in your state must have your purchase order by noon, the day before.

Does the MPa take a hit? Do you get earlier strength or is there a delayed setting time?

CLEVA-Crete enhanced concrete starts curing from the inside out, not the outside in.

Instead of waiting for a couple of hours CLEVA-Crete will increase the set times by about 13 to 17%, allowing finishing work to start about an hour earlier.

You should find that working with walk behind or ride-on helicopters, the concrete will become flatter quicker than normal and you can be finishing up usually 1 to 2 hours earlier than normal.

In winter, where with most other technologies, the slowdown of setting times are delaying finishing by hours, this will keep things on time and generally early if there hasn’t been too much H²O added in.

Does CLEVA-Crete help with delayed setting times?

Yes, it does.

When poured in limestone it can increase the set times by up to 20%.

It’s good to note that if customers request a rumbled top finish, which takes time to create and manoeuvre, you will find that if you get onto it straight away you will still have plenty of time to get great looking finishes.

If it is a concern to you, some have found that using a very small amount of Super P in the mix gives them an extra hour or so to play with textures and desired results.

Do you deal with builders direct or just with batch plants?

Our business model is to work directly with the concrete companies and their batch plants so that we can provide the very best quantified construction material through your primary nominated concrete supplier.

However, please don’t hesitate to contact us directly for more information or to answer any questions.

How does CLEVA-Crete affect the setting and curing time of the concrete?

CLEVA-Crete creates and adds more of the right type of calcium silicate hydrate, as it decreases setting times by 13 to 17% on average. It is typical to see 7 to 10 day strengths after 24 to 72 hours from being poured. After approximately 72 hours, there should be no moisture released out of the slab. Full curing time of the concrete usually occurs at the same time as normal, at or soon after 28 days, as with any other concrete or control mixes. At this point there is typically no more than 4 to 11% increase overall after 28 days.

The densifying process of the surface hardness is dependent on weather conditions and humidity. In recent testing, after 28 days of a taber-rotary-abraser test, CLEVA-Crete showed to be a little softer than control, however this all changed after 90 and 120 days. Using the same taber-rotary-abraser test, CLEVA-Crete showed a lot harder and denser than control and all other densifying products tested.

Because of this many engineers are signing off for early stripping, typically four days earlier per each floor.

With good planning, this may bring each project forward based on how many levels in the building and your capacity of your trades to keep up with the concrete pours plus, if vinyl layers can be screeding levels and putting down floors typically after day 14, this also brings a project forward.

On projects in the US using this technology, 20 storey project finishing times have been brought forward by 9-11 weeks.

Do concrete finishers have to use aliphatic alcohol or other types of curing agents?

All CLEVA-Crete admixtures are not the same as an AS 3799—1998. liquid membrane-forming curing compounds.

When an AS 3799—1998. liquid membrane-forming curing compound is specified for concrete, CLEVA-Crete would recommend that you use one. Combinations of high temperatures, winds and low humidity would require placement planning that include ‘Hot Weather’ considerations with concrete placement and finishing.

Whilst in optimal weather circumstances the answer to this question may be no, we recommend all standard procedures for pouring in cold weather and for pouring in hot windy weather as advised by Cement Concrete & Aggregates Australia, should be adhered to. This means that many concrete finishers will choose to use a curing agent, or simply keep the top surface wet till sundown at such times. In normal temperatures and when it’s not a windy day CLEVA-Crete doesn’t normally require any kind of curing agent on top because it cures the concrete from the inside out, and if it’s not a 35° day with high and low RH, it fares very well.

As far as densifiers, CLEVA-Crete is one of the best densifiers available. As it creates masses of nano sized particles of a very pure amorphous style calcium silicate hydrate gel it goes very hard after about two months, so these are not normally required.

How does CLEVA-crete change conrete's behaviour?

CLEVA-Crete provides concrete with a greater quantity of C-S-H gel.

Instead of the type of gel that is created from fly ash or silicon fume, this gel ‘sets up’ the concrete slightly higher but slumps well as, while the concrete is in its plastic stage, it enables the aggregate to rollover much easier.

This means that you immediately have plenty of working cream when you start screeding and using edging tools.

There is little to no bleed water, so bull floating is made easier and the surface gets very flat.

You can get on to finish it earlier with helicopters and final finishing techniques much sooner.

How old is the technology and when was it first used in Australia?

CLEVA-Crete technology is thousands of years old.

It was re-visited 100 years ago for the Hoover Dam project by the American Army Corps of Engineers.

They used it in a powder form, which worked very well for them however, with modern batch plants, we have found that this technology in a dry powder form competes for the water at the batching process, so CLEVA-Crete was formulated in a liquid.

This can go in with the head water or it can go in last, just prior to being utilised on site.

This technology has been used in Australia for over eight years now, on projects including large scale warehouses, aquariums, hospitals, aged care facilities, levee banks, many schools, day care facilities and high-end residential buildings.

How is CLEVA-Crete different to crystal growth technology?

All CLEVA-Crete modified concrete behaves very differently.

CLEVA-Crete makes the mix setup sticky, as if you have silica fume in the mix, and retains moisture so it will issue the finished concrete to have minimal - if any - cracking

Your finishers will notice extra finishing cream from the gel that enables a superior smooth, aestheticlt pleasing finish.

All of this will be achieved in record time, without putting pressure on your cutters and finishers.

Where shotcrete is being installed in full sunlight, on a very hot day, your cutters and finishers will spend less time standing around waiting for the concrete to go off. They will be able to begin their work earlier than normal, soon after the nozzle operator has sprayed each section rather than waiting around for hours.

If CLEVA-Crete sets earlier, is it harder to clean out the agitators?

CCMC cleans off easier than normal concrete because the gel that is created delays the paste from going rock hard.

Does CLEVA-Crete challenge concrete finishers in any way?

All concrete finishers will find that it is slightly different to what they are used to with several benefits.

First of all, it pumps a lot easier than normal concrete with the same slump as the gel created makes it good to handle.

It also lowers the pressure in all pump lines by around 35 to 40%, which makes it easier to pump long distances and up a number of storeys.

Secondly, it also grabs all the excess bleed water and turns it into a gel, so there is no excess bleeding to wait around for, meaning less labour time on the squeegee, wiping the bleed water off of the slab.

Finally, because it starts curing from the inside out, it will increase set times by about 13- 17%. This allows concreters to start finishing with helicopters about an hour earlier on the flatter, level areas, saving around one or two hours on the job.

This is a huge benefit, especially in winter where, with most other technologies, the setting and drawing out of finishing times are often delayed by hours.

Can you still get a burnt finish when CLEVA-Crete is in the concrete?

Yes, you can.

The reason end-users often want a hard-burnished finish is so that the concrete turns out a lot denser.

CLEVA-Crete is a great densifier for concrete, more than many on the market.

The nano-sized particles of calcium silicate hydrate produced fill any void in the concrete’s matrix with a resultant dense hard finish that you would ordinarily only achieve by burnishing the top.

When putting a concrete roof on top of a building, how soon can bonding materials and sealers be used?

It is fine to seal up any time after the top surface has reached a pH of around eight (typically, 10-14 days).

Anything will bond extremely well to CLEVA-Crete enhanced concrete.

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How does CLEVA-Crete compete or behave with similar waterproofing options?

CLEVA-Crete creates a beneficial gel for the concrete without turning into pots of jelly that take time to go off.

Compared to crystal growth options, finishing will occur one to two hours earlier, as opposed to two to four hours later.

When compared to Caltite, it is different in that it is not a hydrocarbon, is not toxic or carcinogenic and has no offensive odour.

Why does CLEVA-Crete require an approved mix design?

The mix design is different for each building and application and the dosage rate varies accordingly.

Also critical is water to cement ratios and how much cementitious material is utilised so, in the early stages of this process, we require that the builder take care of the necessary paperwork so there is no discrepancy.

As the only water-proofer that provides a 25 year warranty and with our $30 million product liability insurance, we know you will be happy with the end result.

Do concrete finishers have to use aliphatic alcohol or other types of curing agents?

CLEVA-Crete admixtures are not the same as an AS 3799—1998, liquid membrane-forming curing compounds.

When an AS 3799—1998. liquid membrane-forming curing compound is specified for concrete, CLEVA-Crete would recommend that you use one.

A combinations of high temperatures, winds and low humidity would require placement planning that include ‘hot weather’ considerations with concrete placement and finishing.

Whilst in optimal weather circumstances, the answer to this question may be no, we recommend all standard procedures for pouring in cold weather and for pouring in hot windy weather as advised by Cement Concrete & Aggregates Australia, should be adhered to.

This means that many concrete finishers will choose to use a curing agent or simply keep the top surface wet till sundown at such times.

In normal temperatures and when it’s not a windy day, CLEVA-Crete doesn’t normally require any kind of curing agent on top because it cures the concrete from the inside out. If it’s not a 35° day with high and low relative humidity, it fares very well.

Is CLEVA-Crete added at the batch plant or on site? Will you be required on-site?

Ideally CLEVA-Crete will go into the mix with the head water at the batch plant, using a special delivery diaphragm type pump that talks directly to the batching computer, removing all opportunity of human error from dosing on site.

Having said that, on a lot of small projects CLEVA-Crete is put in the concrete agitator onsite, with one of the CLEVA-Crete dosing vans or trucks.

These will dose the agitator five minutes before they reverse up to the pump.

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Want to learn more about how CLEVA-Crete can obliterate concrete cancer and save you thousands?

Call the CLEVA-Crete tech team on 1300 503 929 for more information

or send us a message

Call us on 1300 503 929

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