How to Achieve The Very Best Concrete Floor Finish

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Polished concrete can have a stunning effect, this beautiful surface when polished to perfection not only provides durable floor space but adds a high-quality shine to any environment.

However, it is not without some challenges and in order to achieve this ultra sleek look, here is a list of issues that can occur when the correct controls are not in place.

A floor full of character where no two are the same

Preparing yourself for a naturally organic finish is key to being satisfied with the end result. Consider the amount of variables involved from composition to installation and then professional finishing, a well-planned step by step approach will give the best result but when variables change so can the final finish of the floor; these range from dark stains and imprints which naturally form within the concrete due to discoloration caused by the placement of the concrete. For some people, these patterns and colourings make for a unique space, for others not so much.

Let’s take a look at some common Issues and how to prevent them


1) Discolouration of polished concrete


Discoloration on Concrete Floor
What can happen?

During the polishing process, friction is used to grind the upper layer of the concrete. This can uncover a different colour underneath this surface.

Why does this happen?

This problem only usually occurs in fine ‘grid’ and ‘cream’ finishes.

The reason for discolouration is when water or calcium chloride added to the concrete mixture is not being evenly distributed.

The cement-water ratio contributes to the outcome of the colour.

How can this be prevented?

Using the liquid form of calcium chloride is preferable over the flaked product because the flaked type doesn’t dissolve well, leaving you with an uneven mixture.

Another option would be to dye the concrete after mixing to help get a more even coloration.

2) Varying Aggregate Exposure


What causes this problem?

Varying aggregate exposure happens when the surface level is uneven and forms high and low dips across the surface.

Why does this happen?

If the surface is not level when the concrete is poured, the machine is unable to polish the floor evenly, removing the mounds but not being able to polish low into the dips that form.

How can this be prevented?

Ensuring a smooth surface with a floor flatness Level of 40 or higher ensures the machine can cut the floor evenly and achieve that reflective shine

3) Don’t be haunted by ghosting


Ghosting Concrete Floor

What is Ghosting?

Ghosting isn’t as scary as it sounds, shadowing occurs when you remove a previous floor covering such as tiles, or VCT appears on your finish.

Why does this happen?

Contamination from the residue shows up on the surface as a smooth, translucent mark in the shape of the residue from the previous floor or other residues that remain.

How can ghosting be prevented?

To avoid issues with ghosting, its best to reduce the number of potential causes before pouring the concrete, some of the main culprits are:

* Tape
The sticky glue residue has to be one of the worst culprits, the glue remains, often unseen after the tape has been removed and this affects the outcome due to the sticky residue entering into the concrete and resisting sealer or stain. Leaving ghosting streaks.

* Vinyl Composition (VCT), Ceramic and Stone Tiles
The outcome will be slightly different from VCT and ceramic tile, mainly being the gaps between the vinyl tile are thinner and touching and the stone or ceramic tile have thicker grout lines.

* Wood
Ghosting can occur by either wooden flooring being left laid down or careless parts of lumber being placed on top of the concrete before it is set.

* Cans and Buckets
The types of containers left to sit on the concrete during the curing process can cause circular ring patterns on the final finish.

* Contamination
Spillages of some drinks can stain the concrete, usually, when the concrete is dry and not yet sealed, these stains are not very noticeable but can become very noticeable once the floor is sealed.

To avoid these issues make sure to prepare the area well, you can clean the area using a chemical cleaner to rid the floor from any sticky residue and be sure to keep the area clear of any debris before and after pouring.

4) Micro Pitting


Micro Pitting

What can cause micro pitting?

Pitting indicates an issue with the mix or curing stage, sections of concrete could be too soft therefore failing.

Why does pitting happen?

The most common reason is ‘sand loss’. If the concrete is very soft, deep grinding can leave tiny holes where the sand has worked free from the slab. These holes can reduce reflectivity.

How can micro pitting be prevented or repaired?

Specialist silicate hardening agents such as sodium or lithium can be applied to the area and will harden the concrete to stop pitting from occurring.

These holes can be filled with grout to help give a smooth reflective surface.

5) Crazing


Wavy Floor

What can happen?

Tiny cracks can appear across the surface, leaving the appearance of a dry, cracked effect in some areas or the entire surface.

Why does this occur?

These small cracks can appear when the slab has dried too quickly during the curing process.

How can this be prevented?

Taking care to cure the concrete correctly can prevent cracks from forming, taking into account the weather conditions at the time of curing, warm air can speed up the drying process and create crazing.

If the cracks have already appeared, they can be hidden with grout or by polishing the surface.

6) Excess Fibre


Excess Fiber

What can happen?

If the ratio of concrete strengthening fibre is not correct, this can leave the surface with a blemished outcome.

Why does this happen?

If the wrong ratio is mixed with the cement, the fibre will clump in certain areas and be less present in others.

How can this be prevented?

Always mix to the ratio of 1.5 to 2lbs of fibre per yard of cement (not concrete). This will ensure you can achieve the ultra shine you desire.

7) Footprints


Footprints Concrete Floor

What can happen?

If the surface is stepped on before the concrete has hardened sufficiently, indentations may occur.

Why does this happen?

The pressure from the weight bearing down can cause the cream to lower the surface level of the slab and leave the unsightly imprint of footwear or other objects.

How can this be prevented?
Ensure that no person steps on or places any objects onto the surface until it has completely dried out in all areas, to be safe it’s best to wait for approximately 5 hours after pouring until the surface is firm enough to withstand the weight.

8) Uneven Hydration


Uneven Hydration
What happens?

Uneven distribution of water that escapes the concrete slab via the surface.

Why does it happen?

If items have been placed onto the surface as it cures, this can result in watermarks left underneath the object.

How can this be avoided?

Be sure not to place any objects onto the surface until all the water has evaporated, if this mistake has already been made, the concrete will dry eventually, but this can take a year or so to completely dry out the marks.

9) Poor Edge Finishing


Edges Burned Compacted

What happens?

If the edges aren’t poured out with the same attention as the rest of the surface, it can leave a noticeable frame around the edges of the surface.

How can this be avoided?

An effort must be made to ensure the edges of the surface are well compacted in order to prevent a visible difference between the edges and the rest of the floor. If this is not achieved, polishing the area will not help to disguise the difference, if anything the added shine will accentuate it.

10) Foreign Material


Foreign Material Placed on Floor

What can happen?

Many foreign objects can be uncovered during the grinding process, everyday materials such as leaves, straw, cigarette ends, nails, paper and wood can be amongst the unearthed.

Why does this happen?

There are many reasons for this problem. Mostly it is down to carelessness within the pouring environment or leaves and other debris blown onto the surface via open windows or doors.

How can this be fixed?

These foreign objects are usually uncovered during the polishing process. Once the slab is opened up, the only way to rid the surface of these is to patch the area, (but these areas will be visible.)

11) Wavy Floor


Wavy Floor
What happens?

If the concrete slab is not installed correctly it can leave an undesirable wavy finish this is due to the laws of light refraction being the light will reflect from the varied angles.

Why does this happen?

If the concrete is not poured as flat as possible, you will end up with this wavy effect as the light refracts off the varying levels and looks as if it’s rippling in waves.

How can this be prevented?

The concrete slab must be installed correctly to achieve a flawless Polished Concrete floor.

To gain optimal light reflection, it’s important the concrete surface be as flat as possible.

Always remember – we can only polish what you give us.

For more information click here to view our Concrete Polishing Service Page


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