How To Clean Concrete and Asphalt Paths and Driveways

Including cleaning of:

• Smooth or Exposed Aggregate Concrete.
• Concrete Paving and Cobblestones
• Concrete Block Walls
• Unpainted Concrete Plaster
• Concrete Infrastructure

Should I water blast clean or use an exterior cleaning solution to clean Concrete or Asphalt?

Water blasting concrete to get rid of fungal, moss, and lichen growths may harm the surface by removing the cement and sand, leaving a rougher and more porous surface.

When it comes to asphalt, water blasting is even more destructive than it is to concrete and will leave deep gouges in the surface.

Furthermore, water blasting is a time consuming, expensive, and ultimately futile way to clean these surfaces: concrete and asphalt may look clean by blasting them with high pressure water, but when they are not sterilised in tandem, the spores within the concrete and asphalt will quickly regenerate and discolour the surface in quick time.

The best method for cleaning and maintaining concrete and asphalt is exterior cleaning solutions. We highly recommend the use of Bio-Shield®.

A good exterior cleaning solution not only is easy and faster to apply, but can provide protection for an extended period of time.

Once the surface has been cleaned with Bio-Shield® regular light applications of the solution can be used at the first sight of regrowth. The maintenance applications are very quick, done in minutes and are extremely effective in removing new light regrowth, affecting a cleanup in 24 hours in some cases.

Preparation

If you choose to do-it-yourself over hiring a professional contractor, there are a few things you need to do to get the most out of your exterior cleaning solution. Preparation is crucial for a successful do-it-yourself project. 

Following these easy guidelines will provide a beautiful finish and long-term protection against lichen and moss growth.

Remove loose debris such as tree leaves, dirt etc, from the surface.

While concrete can have an exterior cleaning solution applied when damp or dry, asphalt is better suited to being as dry as possible to ensure that the maximum amount of the solution is absorbed into the surface and the base of the moss or lichen growth.

Application

If you have a respirator, put it on now, as well as gloves and soft-soled shoes or long pants. If you don't have a respirator, try to stay upwind when applying the solution. On a warmer day, the solution will evaporate, producing vapour that should be avoided where possible.

This should be done on a cloudy day at any time of year, or during the morning and late afternoon in summer if there is a warm sunny day forecast. This reduces evaporation and speeds up the process.

Follow your chosen exterior cleaning solutions instructions to fill your sprayer or plug in your Jet-Stream® hose end applicator.

Dividing the area to be treated into sections makes application easier.

Carefully and slowly spray the solution onto the surface in even strokes. To ensure uniform and complete coverage. 

To penetrate to the deep roots and achieve a good kill, any moss growth growing in the joints or cracks will need to be saturated with your exterior cleaning solution.. The Jet-Stream® Applicator applies a high volume of solution so saturation of this moss is much easier than a pump up garden sprayer.

Aim for the surface to stay wet for 5 to 10 minutes after application.

With Bio-Shield® you can see results within minutes as the treated concrete surface shows a brown discoloration. This discolouration will fade in 24 hours and you will notice the surface beginning to clean up in a few weeks.

Avoid over-spray on plants, if in doubt flush the plants with clean water.

Maintenance

Over the next few months, if the area is exposed to rainfall, the treated surface should clean up; nevertheless, it's not uncommon for particularly dirty surfaces to take 6 to 12 months to clear up.

The more rain the surface receives, the faster it will clean up.

Your exterior cleaning solution should be reapplied as soon after re-growth has appeared as possible. This will generally fall between 1 and 2 years apart. The best approach would be to re-treat just as the growths become visible again. It'll be easier, faster, and use a less diluted solution; any new growths will die off and the surface will clean up quickly.

Once the surface is clean, most exterior cleaning solutions will give optimal results with regular removal treatments. This will prevent the build up of moss, fungal and lichen growths and keep your home, building or infrastructure assets clean and protected.

How to clean Concrete and Asphalt - Bio-Shield® Application Instructions

Preparation
For a successful DIY job, preparation is the key. Following these simple steps will ensure a professional looking finish and long lasting protection against fungal and moss regrowth.

Remove loose debris, tree leaves, dirt etc, from the surface.
The concrete surface can be either dry or damp. Asphalt is better treated when dry to maximise absorption of the Bio-Shield by the lichen growths.

Check the weather forecast, or rain radar - brief showers after application on a porous surface will assist the action of Bio-Shield® Air temperature above 10 degrees C° will help to accelerate bio-cidal action.
Premix the Bio-Shield® 1 part to 20 parts water in the sprayer or a larger bucket.
Spread rate for diluted Bio-Shield on concrete will be 3 to 5 m2 per litre depending on the condition of the surface.
Spread rate for diluted Bio-Shield on asphalt will be 3 to 4 m2 per litre depending on the condition of the surface and how much lichen is present.

Bio-Shield Mixing Ratios

Application
If you have a respirator, now is the time to put it on, along with a pair of gloves and soft soled shoes and/or a pair of long pants. If you don't have a respirator, try to stay upwind during application. Evaporation of the solution on a warmer day will generate vapour that should be avoided where possible.

Application is best done on an overcast day at any time of the year, or early morning and late afternoon in summer if a warm sunny day is forecast. This slows evaporation and speeds the treatment process.

Fill your sprayer with the premixed Bio-Shield® solution and pump it up to pressure.
Dividing the area to be treated into sections makes application easier.
Begin application to the surface in slow, even strokes. Allow the following stroke to overlap the previous stroke by 50% to ensure even and complete coverage.

Any moss growth growing in the joins or cracks will need to be saturated with Bio-Shield® to ensure penetration to the deep roots and achieve a good kill. I do this by placing the nozzle of the sprayer directly into the moss and injecting it into the clump.

When you have finished treating the section, look back over it and respray any patches that have dried out. This drying out can be caused from the application not saturating the surface.
Aim for the surface to stay wet for 5 to 10 minutes after application.

If you have achieved correct coverage the runoff should have an orange-brown colour - this is a good sign and indicates that the Bio-Shield® has penetrated the cell walls of the fungal growths and that their death is unavoidable.
Avoid too much over-spray on plants, if in doubt flush the plants with clean water.

Success!
Any leftover Bio-Shield® solution will keep indefinitely and can be kept aside to use as a spot spray to touch up any areas that need it.
Over the next few days the orange-brown colour will fade and the moss growths will begin to turn brown as they die off.
2 to 3 weeks after application the moss growths should be entirely brown and any lichen present will have undergone a slight color change. The black fungal growths will not change color, but will simply fade away.
If there are any green patches in the moss growths, the Bio-Shield® was applied too lightly to saturate the growth to the roots.
 Spot spray these areas with the leftover Bio-Shield®.

Maintenance
The treated surface may clean up over the next few months providing it is exposed to rainfall; however it would not be unusual for a dirty roof to take up to 12 months to fully clean up.
The more rain the surface receives, the faster it will clean up.
It is best to reapply Bio-Shield® at the first signs of re-growth. Typically this will be every 2 to 3 years.
Best practice would be to have the roof re-treated just as the growths become visible again.
Application will be easier, faster and use less diluted solution; any new growths will die off and the roof will clean up quickly.

Once the surface is clean Bio-Shield® will give optimal results with regular treatments. This will protect the cement-based color-coating from damage and premature erosion caused by a build up of moss, fungal and lichen growths.