Air-entraining agents are additives that introduce a large number of tiny, trapped and stable air bubbles into mortar or gypsum during mixing.

Why are they also commonly used in dry-mix mortars?

In wall putty, rendering mortars or tile adhesives, air-entraining agents offer the following benefits:

• Improved workability: Workers find the mixture ‘smooth’ to work with; it does not stick to the trowel, making the mortar easier to level.

Prevention of hollow spots: By improving the cohesion of the mortar or gypsum, it reduces shrinkage after hardening.

Lightweighting: In certain formulations, the appropriate amount of air-entraining agent can reduce the material’s density and increase the coverage area.

In construction, self-levelling mortars or flowable mortars produce a large number of unstable large, harmful bubbles during mixing. The primary function of a defoamer is to eliminate these large bubbles, ensuring the material’s density and aesthetic quality.

1. Why must defoamers be used in construction materials?

To improve strength: Large bubbles can turn into voids, severely weakening the compressive strength of concrete or mortar. Defoamers can significantly improve the material’s density.

• Improved appearance: Prevents ‘honeycombing’ or pinholes from appearing on self-levelling floors and exposed concrete surfaces.

2. Common types of defoamers for construction

• Polyether-based: Extremely popular in dry-mix mortars (such as self-levelling compounds). It is resistant to high temperatures and strong alkalis, offers long-lasting defoaming, and does not leave oil stains.
• Silicone-based: These defoam extremely rapidly, requiring only a very small amount to break bubbles; however, if added in excess, they may affect the recoatability and adhesion of coatings or mortars.

3. Main Application Scenarios

• Cement-based/gypsum-based self-levelling compounds
• High-strength grouts

Anti-efflorescence agents are specially designed functional additives primarily used in cement-based materials. They prevent calcium hydroxide (alkali) from migrating to the surface through a dual chemical and physical mechanism.Efflorescence essentially occurs when calcium hydroxide (an alkaline substance) in cement is carried to the surface by moisture, where it reacts with carbon dioxide in the air to form white calcium carbonate crystals, resulting in white patches on walls or floor tiles.

2. Key Advantages

• Exceptional efflorescence inhibition performance: It is specifically optimised to inhibit both ‘primary efflorescence’ and ‘secondary efflorescence’.
• Improved colour uniformity: In coloured grouts or decorative mortars, it significantly reduces colour variation, resulting in a richer and more uniform surface colour.
• Excellent dispersibility: As a spray-dried powder, it can be pre-mixed very uniformly into dry-mix mortars and rapidly releases active ingredients upon contact with water.

3. Working Principle

Reaction Inhibition: It reacts with the hydration products of cement to reduce the content of free alkali.

Hydrophobic Effect: It forms a hydrophobic layer on the walls of the mortar’s capillaries, blocking the ‘pathways’ through which water carries alkali ions to diffuse outwards.

4. Recommended Applications

• High-end coloured grout/decorative grout (cement-based).
• Coloured rendering mortar and decorative mortar
• Exterior landscape bricks, artificial stone

Cement shrinks in volume as it hardens; this phenomenon is known asshrinkage. It is the cause of cracks, delamination and leaks in buildings. Shrinkage Reducing Agents (SRAs) are additives designed to prevent shrinkage following water loss.

Core principle: reducing surface tension

Shrinkage Reducing Agents are typically surfactants (such as polyethers or alcohols).

They penetrate the water within the capillaries, significantly reducing the surface tension of the water. When the water evaporates, the inward tensile force acting on the capillary walls is reduced, thereby substantially minimising drying shrinkage deformation.

This operates on a different principle to expansion agents, which counteract shrinkage through ‘micro-expansion’, whereas Shrinkage Reducing Agents suppress shrinkage by ‘reducing tensile force’; the best results are achieved when the two are used in combination (dual compensation).

Main applications

• Ultra-flat floors and self-levelling mortar: Prevent the formation of mesh-like cracks or warping in large floor areas.
• Shrinkage-free grouting material: Ensure the grouting layer adheres tightly to the equipment foundation without gaps.
• High-performance concrete (HPC): Used in projects such as bridges and tunnels where durability and crack control are of the utmost importance.
• Repair mortar: Ensure that the interface between new and old surfaces does not detach due to shrinkage.

Coagulants are additives specifically designed to speed up the hydration reaction of cement, shorten setting time and improve early strength. In the formulation of self-levelling mortar, the selection of a coagulant is a highly precise process, as it must strike a delicate balance between ensuring sufficient flow time (working time)andenabling rapid hardening (walk-on time).

Key Functions

Reduced setting time: Enables the mortar to transition rapidly from a plastic state (slurry-like) to a hardened state, accelerating the construction schedule.

• Enhancing early strength: Significantly increases compressive strength within the first 6–24 hours, facilitating subsequent processes (such as formwork removal, grinding or foot traffic).
• Ensuring low-temperature application: In winter or low-temperature environments, where cement hydration is extremely slow, the coagulant maintains reaction activity, preventing the mortar from suffering freeze damage.

Main Applications

• Self-levelling mortar: Ensures the surface is walkable within 4–6 hours after application, or that the top coat can be applied the following day.
• Repair mortar: For rapid emergency repairs to roads and bridges, where strength must be restored within a few hours.

Combining Coagulants with Retarders

In actual production, it must be used in conjunction with retarders:

Retarders (e.g. tartaric acid, sodium metasilicate): Responsible for ‘suppressing’ the reaction during the first 20–30 minutes after mixing, ensuring the mortar flows like water.

Coagulants (e.g. lithium carbonate): Responsible for rapidly hardening the mortar once the levelling process is complete.

Thixotropic Lubricant Agent is a composite functional additive. It serves to reduce friction during application whilst maintaining the cohesion of the mortar. It makes the mortar as easy to spread as ‘cream’, yet prevents it from sticking to the trowel or running.

• Function: They are distributed throughout the mortar like ‘micro-balls’, reducing friction between the aggregates (sand).
• Texture: Provides an excellent silky smooth feel, particularly in thick-layer rendering or mechanically sprayed mortar, significantly improving pumping and levelling efficiency.

Why is it needed?

Cellulose Ether (HPMC): Primarily relies on ‘stickiness’ to retain water, but if too sticky it will ‘stick to the trowel’, making the work tiring for labourers.

Thixotropic Lubricant: It makes the mortar as smooth and silky as cream, making levelling very easy and preventing it from sticking to the trowel.

Typical Applications

• Machine-applied mortar: Ensures smooth machine application.
• Lightweight render: Provides superior encapsulation for mortars containing vitrified microspheres or polystyrene particles.
• Thick-layer wall putty: Improves levelling efficiency during large-scale applications.

In self-levelling mortar, the suspension agent’s primary function is to address“settling and segregation”and“surface bleeding”. Self-levelling mortar is required to flow like water; however, as the mortar contains heavy sand (aggregate) and light powder (cement, fillers), if not properly controlled, the heavy components will settle to the bottom, resulting in uneven strength after hardening, whilst the lighter components (water and fine powder) will rise to the surface, causing a pitted or powdery finish with low surface strength.

Core Function:

The suspension agent forms an extremely weak three-dimensional network structure within the mortar, acting like countless tiny hands to support the sand and stone powder, ensuring they remain evenly distributed throughout the flow process.

Why must self-levelling compounds contain a suspending agent?

• Prevent settling: Without a suspending agent, all the sand would settle at the bottom, causing the base layer to become too hard and crack, whilst the surface layer remains too soft and powdery.
• Eliminate colour variation/floating pigments: Ensures even distribution of pigments in coloured self-levelling compounds, preventing patches of varying shades.
• Improve flatness: Prevents localised water separation and pitting, ensuring a mirror-smooth surface once fully cured.

Plastic Expansion Agent is an additive designed to act specifically within cement pastebefore it hardens (during the plastic stage). Its primary function is to generate tiny air bubbles whilst the cement is still unhardened and has a ‘slurry-like’ consistency, causing the volume to expand slightly, thereby offsetting the early plastic shrinkage caused by water evaporation.

Why is it a standard component in ‘grouting materials’?

In equipment foundation grouting or bridge grouting, the mortar must adhere 100% to the steel plates or duct walls above.

Ordinary mortar: Once dry, it shrinks downwards, causing gaps (voids) to appear at the top.

With plastic expansion agent added: The grout ‘pushes’ slightly upwards, ensuring every gap is filled and achieving full-contact grouting.

Plastic Expansive Agent vs Post-Hardening Expansive Agent (UEA, etc.)

Plastic Expansive Agent (early-stage action): Addresses shrinkage within hours of mixing, preventing early settlement.

UEA Expansive Agent (late-stage action): Addresses drying shrinkage several days or even weeks after hardening, preventing late-stage cracking.

The Perfect Pairing: High-performance grouting materials typically combine both to achieve full-cycle volume compensation.

Main Applications

• Shrinkage-free grouting material: Installation of large equipment bases, grouting of steel structure column bases.
• Grouting of prestressing ducts: Ensures that bridge prestressing tendons are completely encapsulated by the grout, with no air voids.
• Wall repair/reinforcement: Ensures that newly added cementitious materials do not separate from the original structure.

In the field of building materials, nano-reinforcing agents fundamentally alter the microstructure of mortar or concrete by intervening in the hydration process of cement at the atomic/molecular level, thereby enhancing the strength and water resistance of these materials.

Core Principle: Why does the nanoscale make a difference?

• Seeding Effect: Nanoparticles act as ‘seeds’ for hydration products, inducing rapid crystallisation on their surfaces and accelerating hardening.
• Filling Effect: They fill the minute pores (gel pores) between cement particles, blocking water penetration pathways.

Dust suppressants possess excellent dust-adsorbing properties. Following physical mixing and homogenisation, they can significantly reduce dust emissions during the use and mixing of mortar, resulting in a more environmentally friendly, low-dust mortar.

Their unique molecular structure ensures that, whilst providing highly effective dust suppression, these agents do not affect the shelf life of cementitious materials. They also have minimal impact on mechanical properties such as compressive and flexural strength, and are effective in significantly reducing mortar shrinkage.

The dust suppressant is mixed with fine powders such as sand and cement. Following physical mixing and homogenisation, it significantly reduces dust emissions during the use and mixing of mortar, resulting in a more environmentally friendly, low-dust mortar.

Pregelatinised starch, commonly known as ‘cold-water-soluble starch’. In dry-mix mortars for the construction industry, it is a highly cost-effective binder and thickening agent. It is typically used in neutral-base putty (usually referring to interior wall putties that use talc or calcium carbonate powder as fillers and contain no Calcium Hydroxide or cement).

Core Function: The “low-cost binder” in neutral-base putty

• Auxiliary thickening: It significantly increases the viscosity of neutral-base putty, making the material feel “thicker”.
• Improved workability (smooth texture): It imparts an excellent smooth texture to neutral-base putty.
• Enhanced adhesion: As a physical binder, it helps provide a certain degree of surface hardness and initial tack once the neutral-base putty has dried.

Why do neutral-base putties “prefer” it?

• Acid-Alkali Neutrality: Pre-gelatinised starch is most stable in environments with a pH close to neutral. In strongly alkaline mortars such as cement or Calcium Hydroxide, starch is prone to degradation or loss of efficacy; however, in neutral-base putties, its performance remains most stable.
• Ease of sanding: Wall putty containing an appropriate amount of pregelatinised starch develops sufficient hardness upon full curing whilst retaining moderate flexibility, making it very easy to sand with sandpaper at a later stage.