Practical Guide: How to Remove Algae, Mould, Moss and Lichen from Concrete and Cement-Based Agglomerates

Outdoor surfaces made of concrete and cement-based agglomerates, such as concrete paving, interlocking pavers, concrete blocks, cement tiles, terrazzo aggregates and Palladian paving, are particularly vulnerable to the growth of algae, mould, moss and lichen, especially in areas affected by moisture, shade and poor drainage.

This guide explains when to carry out the treatment, which surfaces are suitable for this procedure and which cleaning system to use to effectively remove biological deposits and restore the original appearance of outdoor paving.

When This Treatment Is Recommended

This cleaning system is recommended when outdoor surfaces are:

• darkened or stained
• slippery underfoot
• contaminated by algae, mould, moss or lichen
• subject to persistent moisture

It is particularly effective against light, moderate and heavy biological deposits, including during colder periods of the year.

Surfaces and Application Areas

This system is suitable for cleaning:

• outdoor concrete floors and wall coverings
• interlocking pavers and concrete block surfaces
• cement tiles, terrazzo aggregates and Palladian paving
• courtyards, driveways, pathways and walkways
• outdoor areas exposed to rain, shade and frost

The Problem of Biological Growth

On outdoor cement-based surfaces, moisture and material porosity encourage the proliferation of microorganisms such as algae, moss and lichen.
Over time, these biological colonies can cause:

• widespread dark staining
• reduced slip resistance
• deterioration of the surface appearance
• greater retention of dirt and moisture

Treatments based on sodium hypochlorite often provide only a temporary and superficial effect, with limited long-term results.

Treatment Approach

For this reason, effective removal of biological contamination should not be limited to surface cleaning alone. Instead, the treatment should:

• act deeply on biological microorganisms
• promote the detachment of biological colonies
• allow the mechanical removal of degraded contamination
• deliver a more durable result over time

The system described below uses specialised products for outdoor surfaces, which remain effective even at low temperatures and are fully compatible with cement-based materials.

Recommended Cleaning System for Outdoor Cement-Based Surfaces

Step 1 – Stain Removal and Sanitising Treatment

Apply ALGANET®, a highly effective stain-removing cleaner specifically formulated to eliminate algae, mould, moss and lichen from outdoor concrete and cement-based agglomerate surfaces.

The treatment should be carried out using stiff brushes, BROWN BUFFER PAD or BROWN DISC, which help provide the mechanical action required to remove the most stubborn biological deposits.

ALGANET® penetrates deeply into biological contamination, remaining effective even at low temperatures and providing longer-lasting results than traditional sodium hypochlorite-based treatments.

Step 2 – Rinsing and Final Cleaning

After the stain-removal treatment, rinse the surface thoroughly and clean it with ECOMARBEC, a biodegradable degreasing cleaner used to:

• remove residues of degraded dirt and biological contamination
• eliminate any remaining traces of ALGANET®
• restore a uniform appearance across the surface

During this stage, the use of stiff brushes, brown buffer pads or brown discs is recommended, as these tools help complete the removal of biological contamination and improve the final result.

➡️ For dilution ratios, contact times, application methods and coverage rates, always refer to the relevant product data sheets.

Treatment Results

Once the treatment has been completed, outdoor surfaces will be:

• clean and visually uniform
• free from algae, mould, moss and lichen
• less slippery
• restored in appearance
• ready for any subsequent protective treatment

Frequency of Use

This system is designed for deep cleaning treatments, carried out as required or whenever new biological contamination appears.

In particularly damp or shaded environments, the treatment can be repeated over time without damaging cement-based surfaces.

Technician’s Tip

For the routine cleaning of outdoor floors, we recommend using ECOMARBEC, as it effectively cleans and degreases surfaces while remaining safe for surrounding plants when used correctly.

After deep cleaning with ALGANET®, and once the surface is perfectly clean and dry, you can also apply TIM®, a water-repellent and stain-resistant protector specifically designed for absorbent stone and cement-based materials. This treatment reduces the absorption of water and dirt, simplifies routine maintenance and helps limit the reappearance of algae and biological growth over time.