User Guide: Mortar and Concrete Additives

Solutions & Applications · Concrete and Mortar Additives

A cubic ton of concrete is mixed in the concrete mixer. The additives determine how much water will be required, how dense the mix will be, whether it will crack during the initial curing stage, and how many years the reinforcement will last. The guide starts with the problem you want to solve, explains what each additive does, how it is incorporated into the mix and where it is used — and what happens when the concrete has already deteriorated.

First the problem, then the solution

What you need	Addendum	How to enter
Less water with the same workability; pumpable concrete; concrete placing in hot weather	TECNOS 95 superplasticiser	Liquid, added to the mixing water or to an already wet mix
Water-impermeable concrete throughout the entire mass	SINTOMIX SM N mass waterproofing	Liquid, added to the mixing water or to an already wet mix
Protection of reinforcement against chlorides and sulphates	MuCis ad 19/L corrosion inhibitor	Liquid, during the production of concrete
Fewer hairline cracks in floors	PP Fibres 18 mm polypropylene fibres	Solid fibres, in the aggregates, in the concrete mixer or in the drum
Bonding new to old; more elastic mortar	SINTOPLAST SBR latex resin	Liquid, as a cement slurry or mixed into the mortar

Why mixing water is key

Cement requires a specific quantity of water to hydrate. Any excess added to make the mixture ‘workable’ later evaporates, leaving behind pores — the pathways through which water, chloride ions and carbon dioxide to the reinforcement. The superplasticiser allows for less water without compromising workability; the mass-sealing agent seals the remaining pores. That is why adding water to the mix on site negates the benefit of the additive you have paid for.

The additives, one by one

TECNOS 95 — superplasticiser

A liquid plasticiser made from synthetic polymers, chlorine-free, in accordance with ASTM C-494 types B, D and G — that is, it reduces the water content whilst simultaneously slowing down setting. It reduces water demand by 20–30% whilst increasing workability, improves initial and final strengths, and produces a homogeneous mix without segregation.

Where: ready-mixed and pumped concrete at great heights, large-scale concreting and at high temperatures, heavy-duty industrial floors 10–25 cm thick, flowable cement screeds, cast mosaics, precast and exposed concrete.

SINTOMIX SM N — mass waterproofing compound

It acts within the microporous structure and intercalates between the aggregate grains, rendering concrete and mortars impervious to water penetration; it also functions as a superplasticiser. It contains no chlorides and is therefore suitable for reinforced and prestressed concrete.

Where: foundations, basement walls, ground slabs, tanks, channels, collectors and hydraulic works in general.

MuCis ad 19/L — reinforcement corrosion inhibitor

It is added during the production of concrete and does not act solely on contact with steel: it diffuses through the porous structure to the reinforcing bars and inhibits both anodic and cathodic corrosion. It is based on organic components, does not alter the physical and mechanical properties of the concrete, and remains effective in the presence of chlorides and sulphates.

Where: structures adjacent to or in the sea, bridges, reservoirs, aqueducts, cooling towers, refineries and industrial plants, exposed fair-faced concrete facades.

PP Fibres 18 mm — polypropylene fibres

They limit hairline cracks caused by plastic shrinkage and drying shrinkage, and increase cohesion and resistance to impact and abrasion. Dosage 0.6–0.9 kg/m³ — the 600 g pack corresponds to 1 m³.

Method: mix with the aggregates at the factory, directly into the concrete mixer drum or the mixing drum prior to laying. This is followed by mixing at maximum speed for at least 5–7 minutes (approximately 70–80 revolutions of the drum), to ensure no lumps remain. During finishing, the fibres ‘settle’ within the mixture. They do not replace the structural reinforcement.

Where: industrial and stamped floors, floor slabs, unreinforced concrete, prefabricated elements.

SINTOPLAST — SBR latex resin

Fine-particle styrene-butadiene emulsion. It improves the bond between new and old concrete, imparts flexibility to mortars, reduces the water-to-cement ratio and, consequently, shrinkage and cracking. It is resistant to the constant presence of water, oils, fuels and most acids.

How: as a Portland cement-based screed, applied to the substrate before the new mortar, or within the mortar itself. Where: joints between old and new structures, repairs and levelling of floors, walls, beams and columns, and gutters.

Combinations by application

Application	Additions	What does this combination offer?
Flooring & basement walls	SINTOMIX SM N + TECNOS 95	Low water-to-cement ratio and closed pores — with waterstops at the joints
Industrial flooring	TECNOS 95 + PP Fibres	Strength, workability and control of shrinkage cracks
Ground-level slab; stamped	PP Fibres	Fewer surface cracks during the initial drying stage
Reservoir · coastal project	SINTOMIX SM N + MuCis ad 19/L	Waterproofing and protection of reinforcement against chlorides and sulphates
Summer or large-scale concrete works	TECNOS 95	Setting retardation and workability retention
Repair · joining old and new sections	SINTOPLAST	Adhesion and flexibility of mortar

When more than one additive is used, compatibility and the order of addition must be checked against the technical data sheets prior to concreting — and ideally by means of a test mix.

When the concrete has already deteriorated

Additives act as a preventative measure. If the reinforcement has already rusted and the coating has delaminated, restoration is carried out using a repair system in accordance with EN 1504-3:

1. Removal of loose concrete from behind the reinforcement and cleaning of the bars to remove rust.
2. Corrosion protection with SINTOCRETE AntiCorr ST — a single-component cementitious product that inhibits corrosion and also acts as a bonding layer (≥ 0.5 kg/m²).
3. Wet the substrate thoroughly with plenty of water.
4. Cross-section repair using fibre-reinforced thixotropic mortar: SINTOCRETE Basic (class R3) or SINTOCRETE (class R4, non-shrinking, impermeable even under pressure, sulphate-resistant, ≈ 2 kg/m²/mm).
5. Wet curing: 6–24 hours for R3 and 24–48 hours for R4, longer in hot and dry conditions.

Correct use on site

1. Dosage as per the technical data sheet — usually as a percentage of the cement weight. Excessive dosage may alter the setting time.
2. Liquid additives should be added to the mixing water or to a mixture that has already been moistened — never to dry cement.
3. Fibres: mix for at least 5–7 minutes at maximum speed.
4. No additional water is added to the drum to ‘loosen’ the mixture — workability is adjusted using the fluidiser.
5. Compatibility checks when additives are combined.
6. Vibration and wet curing as specified in the design.

Mistakes that cost

Incorrect	Consistency
Water in a barrel on the building site	More resources, lower strength — the additive is cancelled
Mass waterproofing without waterstops at the joints	Water passes through the expansion joint, not through the structure itself
Fibres used in place of structural reinforcement	The fibres control shrinkage cracks, not loads
Fibres with brief mixing	Lumps and uneven distribution
Repair without anti-corrosion treatment of the reinforcement	Rust continues beneath the new mortar and causes it to flake off
Repair compound for dry substrates	The substrate ‘soaks up’ the water from the mortar — poor adhesion and cracks

Concrete and Mortar Additives

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