Precast

How does CLEVA-Crete affect hollow-core planks?

It does two main 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 through the hollow-core formation machinery, this characteristic creates a smoother concrete and results in decreased noise levels and less wear and tear on the machine.

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

when edge lifter linking rebars do not have the cover that engineers require, is it 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?

Yes, 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 CCMC 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 7 mm aggregate and no fibres, many involved in cellars, car parks and pools, are reducing steel cover.

CLEVA-Crete 842 RP is specifically designed for situations 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 Rio Protection chemical and thereby double the life expectancy of the steel’s integrity due to the RP factor.

If CLEVA-Crete provides higher early setting strengths after 8-10 hours, what kind of value proposition is it, given that it is possible to strip and deform much earlier?

CLEVA-Crete decreases early setting times by up to 13 to 17%, sometimes more. It heavily reduces edge chipping and thus saves patching time. It reduces shrinkage, controls plastic shrinkage cracking, reduces heat of hydration, stops slab curl and normal dusting so is an extremely good value proposition in these ways 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 appears that steam setting techniques, in many cases enable this.

Is there any benefit in using CLEVA-Crete for smaller precast elements used for civil infrastructure works?

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

We use pozzolan admixture to assist in speeding up the setting times. Does CLEVA-Crete modified concrete (CCMC) replace pozzolan admixture?

CCMC creates a purer form of pozzolan from the CLEVA-Crete admixture, and negates the need for any additional pozzolan admixture.

We use a biodegradable form release agent, would we need to change?

CLEVA-Crete creates a concrete that neither egresses moisture or ingresses any liquids or solids, so there is no requirement for your factory to instigate any change to what you are currently using when it comes to release agents used on your form work and decks.

Would you sell CLEVA-Crete direct if we have our own on-site batch plant?

If you do have your own on-site batching facility, you can purchase from CLEVA-Crete direct, exactly the same way as the leading concrete batchers. Contact our office on 1300 503 929.

When pouring 2-3 metre thick precast elements, do I need to have sacrificial cooling manifolds throughout the mass of concrete for cooling HOH and minimising DEF?

This can only be answered on a case-by-case basis. On a recent major infrastructure project we anticipated reducing the HOH by 10% but when test results came back, CCMC had reduced the HOH by more than 25% over control. Going by this reduction in HOH, it is reasonable to say it reduced the incidence of DEF in these 1.2 meter thick slabs. It is a case by case situation as to whether you should decide to eliminate internal cooling manifolds.

Does CLEVA-Crete react differently if white cement and titanium dioxide rich SCM's are utilised?

CLEVA-Crete works very well with it and we generally find an increased MPa when using white cement instead of the typical 13 to 17% increase. We have witnessed up to 35% increase in early strength in concrete where the cementitious material is white cement.

Do Ny-loc fibres assist with fine shrinkage cracks on precast elements?

The nylon fibres are extremely good for plastic shrinkage cracking and the tensile strength that these fibres attain are astounding and will improve all aesthetic cracking.

does CLEVA-Crete work in with coloured concrete? Can it assist with coloured panels which tend to dry out a bit patchy?

It works extremely well with colours. Due to the dynamic active nature of creating C-S-H gel, on a nano sized level, it seems to cause all oxides to fully integrate in CCMC. The resultant colours gained are more true to character and are thus distributed evenly throughout the panel. In most cases, unless batches are completely different, it creates a very even distribution of colours on high spec panels.

Do you have any further questions? If so, please contact us at info@clevacrete.com.au.

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