Understanding SikaPaver® HC-200, Weber ADMIX CMU 100 and Weber ADMIX SD PLAST 110

In Part 1, we looked at something every block manufacturer understands:

broken blocks cost money.

But how can an admixture actually help?

The answer starts with what happens inside a semi-dry concrete mix.

Water Is Not Always the Solution

When a block mix becomes difficult to compact, there can be a temptation to solve the problem with one instruction:

“Add some more water.”

It may appear to make the mix easier to work with, but water is part of the concrete mix design—not simply a convenient lubricant.

Changing the water/cement ratio can influence the properties of the concrete.

A properly selected plasticising or compaction admixture gives the producer another tool:

improve dispersion, lubrication and compaction without depending only on additional water.

For machine-made semi-dry concrete products, this can contribute to better mould filling, particle packing, cohesion and density.

Let’s look at three products designed for this type of production.

1. SikaPaver® HC-200

SikaPaver® HC-200 is positioned for semi-dry/no-slump concrete production, including products such as:

• building blocks and bricks;
• paving blocks;
• kerbstones;
• concrete pipes; and
• other machine-made concrete products.

Its stated benefits include improvements in areas such as cement and fine-particle dispersion, mould filling, compaction and green strength.

For a block manufacturer, those technical improvements can matter commercially.

A denser and more consistently compacted unit with better early handling characteristics has a better chance of surviving the journey from:

machine → stacking area → truck → customer.

Sika also associates the technology with reduced density and strength variation and opportunities for more economical concrete production when the mix is properly optimised.

Typical dosage

Sika Ghana’s technical guidance should always be checked for the current product requirements. A range of approximately 0.3%–1.2% by weight of cement has been specified for SikaPaver® HC-200.

For 50 kg of cement, that corresponds to approximately 0.15–0.60 kg, with the optimum dosage established through trials.

Do not simply select a number from the range and make it your permanent factory dosage.

Trial first.

2. Weber ADMIX CMU 100

Weber ADMIX CMU 100 is formulated for concrete masonry and precast applications such as blocks, pavers and architectural concrete products.

It acts as a plasticising admixture for semi-dry concrete.

Manufacturer information associates it with benefits including:

• improved cohesion;
• improved placement and lubrication;
• reduced water demand;
• improved green strength;
• increased ultimate compressive strength;
• lower moisture absorption;
• reduced efflorescence;
• improved appearance and texture; and
• improved productivity.

That makes CMU 100 particularly interesting where a manufacturer isn’t concerned only about whether a block survives transportation, but also about appearance, absorption and consistency.

Typical dosage

A recommended starting range of approximately 3–5 litres per 100 kg of cement has been given in the technical information.

Again, the word starting matters.

Your materials and factory determine the optimum dosage.

3. Weber ADMIX SD PLAST 110

Weber ADMIX SD PLAST 110 is developed for dry and semi-dry vibrated and pressed concrete products, including masonry blocks, bricks and interlocking pavers.

One of its particularly relevant benefits for block manufacturers is the manufacturer’s reference to reducing damage during operations such as handling, strapping and palletising.

Those are exactly the stages where many factories experience losses.

Other stated benefits include:

• improved compaction;
• better dispersion of cement and fines;
• lower water/cement ratio;
• increased green strength;
• increased ultimate compressive strength;
• improved cohesion;
• better consistency;
• improved surface texture;
• reduced moisture absorption;
• reduced efflorescence; and
• potential improvements in production efficiency.

Typical dosage

Technical information provides an approximate range of 1–5 litres per 100 kg of cementitious material, with the optimum dosage to be established through production trials.

Which One Should My Factory Use?

There isn’t one universal answer.

Think in terms of your production objective.

SikaPaver® HC-200 may be considered where the focus includes high-performance compaction, mould filling, green strength, reduced early handling damage and strength development in semi-dry/no-slump production.

Weber ADMIX CMU 100 may be relevant where water reduction, cohesion, early strength, absorption, appearance and efflorescence are important.

Weber ADMIX SD PLAST 110 may be considered where compaction, production efficiency, green strength, handling resistance and reduced manufactured-product losses are key objectives.

But product literature alone cannot tell you which one will be most economical in your factory.

Why?

Because your:

sand is different;

aggregate grading is different;

cement may be different;

machine is different;

vibration is different;

moisture conditions are different;

production cycle is different.

That’s why controlled trials matter.

An Admixture Cannot Fix a Bad Block Factory

This is extremely important.

Don’t expect any admixture to compensate for:

• unsuitable or dirty aggregates;
• uncontrolled aggregate moisture;
• poor grading;
• inconsistent cement measurement;
• uncontrolled water;
• poor vibration;
• worn moulds;
• inadequate curing;
• premature handling; or
• poor quality-control procedures.

An admixture is a tool for optimising a controlled concrete production process.

It is not magic in a bottle.

And Don’t Automatically Reduce Your Cement

Manufacturers naturally become interested when they hear that admixtures can contribute to more economical mix designs.

But this must be approached correctly.

DO NOT REDUCE CEMENT SIMPLY BECAUSE YOU HAVE ADDED A PLASTICISER.

First optimise the mix.

Produce trial blocks.

Cure them correctly.

Test them.

Confirm the required strength and other performance characteristics.

Only then should cement optimisation be considered as part of a controlled and verified production mix.

In Part 3, we’ll show how to conduct a simple factory trial and answer the question that ultimately matters:

Is the admixture actually making me more money per 1,000 saleable blocks?

Technical note: Always consult the manufacturer’s current Product Data Sheet/Technical Data Sheet before use. Dosage ranges are starting guidance and do not replace production trials or engineering requirements.