The biggest problem with painted concrete is its ability to chip and flake (aka, spalling). Sadly, once this starts there is nothing you can do to stop it.
The reason being water.
Well laid concrete bases will have a plastic vapor barrier laid down first before pouring. This is simply to stop the moister rising up through the solid concrete to come out on top. The paint cannot cope with this effect and falls apart in chips and flakes.
Water will always try and migrate up through the earth to the surface. So unless there is a vapor barrier in the way, it will always get through. No matter how thick the concrete, the water will always get through. Even studies on concrete bunkers laid down in the Second World War, have shown signs of vapor penetration, due to capillary action. Any chemical bond between the paint and the concrete will be broken, due to the baking effect of sunlight upon the paint surface.
The best guarantee of success, is to have the concrete foundation laid by a professional. Most staining on concrete, and the subsequent failure of the material, is do to the concrete foundation never having had water barrier.
Another problem, with painted concrete, is the safety hazard it might pose. The surface becomes very slippery, and can give concern from health and safety quarters, on behalf of the public.
One method of counter acting this, is to mix the paint with fine sand or other crushed materials. However, this is not easy to do and it is hard to achieve a uniform finish across the whole surface area of the concrete.
Manufacturers have tried to combat this with various products, and some degrees of success have been achieved. This results in textured epoxy paints. Solving some, but not all of the problems.
Painting concrete walls can be achieved by preparing the surface first, and cleaning it of any grease and dirt, which might break the bond. One of the best methods of preparing a concrete wall, is to let nature take its course and leave it to weathering. This is to reduce surface alkalinity.
But this is not always practical, for new constructions. So one solution is to use 100% acrylic latex paint. This only requires 4 weeks of aging, due to the resistance to surface alkalinity.
The staining of cement is achieved by using a solution made from acid, water, inorganic salts and the natural reaction of minerals already present in the concrete. It is a coloring process, which takes place on a cementitious surface.
Many people think at first it is a type of paint, but the results are achieved by manipulating these effects, to give the impression of colors. If, it is protected by a sealer or wax, it can be very enduring, and Acid stained concrete has been used with great effect both inside and out.
People are often surprised by the results achieved with the effects of acid stained concrete. These can be anything from a marble look, to a variety of earthy browns. Many builders achieve this by mixing their own shades at different rates. One thing they quickly find, is that no two pieces of concrete are ever the same. Each surface is unique, so the resulting reaction is always different.
This gives acid staining such a useful and popular range of applications, that is can be seen in everything from living rooms, to driveways.
The biggest problem faced by engineers and builder, when it comes to acid staining, is the condition of the concrete surface. Age may not come into it, but the condition certainly does. If the surface is Spalled, the aggregate stones may be showing through the concrete surface. They may be cracked or flaking, and this will mean the acid staining will never really take on the surface.
Another reason for the acid staining not working, could be due to the surface previously being acid etched. This is because the aggregate stones do not react with the acid stain, and what you are seeing is only from a reaction with materials in the concrete paste.
Whereas, where the concrete has been stamped overlaid or textured, a very effective depth of color and realism can be achieved.
Concrete Foundation Repair
Concrete foundation repair can come about due to the slabs settling and moving as a result of what is below them. Clay and soil have to be carefully prepared before any building work can be undertaken upon the surface. So if this work was carried out badly, or not enough research was undertaken before building, the concrete can only fail.
Most ground foundations move slightly with time. They may be clay, or filled in with soil, and the builder will take this into account, when designing the structure, which is going to stand on it.
But even the best planned projects run into trouble, and concrete foundations can move or sink. Underpinning is the commonest method provided by engineering firms when it comes to repairing a foundation with problems.
At first this can be a traumatic time for anyone facing the problem of repairing a building with a failing foundation. As it strike at the heart of why the building was put there in the first place, and many contractors could be facing ruin.
The good news is, that modern technology has come so far, the solutions are not impossible.
The two commonest methods of tackling this problem, are Slabjacking and Piering.
Slabjacking is the process of pumping grout beneath the beam or slab, to produce a lifting force, restoring the desired leveling. This is often used when the concrete slab has simply sunk into the earth. But can be used, when engineers find a structure to be uneven. One of the commonest uses can be found in stabilizing, when cracks start to appear in a pavement or driveway.
Filling with pressure grout is one of the best methods of stabilizing a structure, when a void has been found beneath the site. These voids often occur due to water running beneath the surface. So cement slurry can be pumped in to fill the gap and divert away any unwanted water.
Piering is the method of driving steel pipe pilings into the ground to counter-act the results of a failing structure. A hydraulic ram will drive a section of Galvanized or epoxy-coated steel pipe into the soil. They can also be screwed into the ground with Helical Piers via a torque motor.
The idea of this is to find a stratum suitable enough to bear the weight above.
Concrete angels, statues and ornaments are created using rubber moulds. These moulds are an effective way of creating many things, but are especially effective when pouring concrete.
Rubber or latex moulds are used because they reproduce details in an object to a very high standard. They have proved to be more flexible than any other casting material, such as plaster because they are easier to remove from the object you have cast.
In terms of production, they are very popular because the mould can be used many times, in a production cycle.
When it comes to making concrete Angels, there are 3 methods of making a rubber mould. Pouring, spraying or brushing on with liquid rubber.
With Polyurethane rubbers, they can be brushed, poured or sprayed on a model. These are idea for concrete angels, as they are easy to use, have a good resistance to abrasion, and are fairly cheap. But they can be more adhesive than other rubber types of mould, so they can be difficult to remove from the model.
The model is placed in a containment field, and made secure. It is then covered with a releasing agent, which allows it to be more easily removed from the finished mould. The rubber is poured into the containment field, then allowed to harden. Finally the finished mould is pulled away from the model.
Another technique is brushing. Here the model can be coated with several layers of rubber by brushing it on. Letting each dry before applying the next. The same is true when it comes to using a sprayer to do the same job. These are often used when it comes to dealing with very large objects. Often used on churches, where the Angels cannot be easily moved or may crumble. The good thing here, is that the workers can have access to the model they are to copy, without having to take it away. What is more, spraying the coating on, can ensure a more even surface than using a brush. The only down side, is the expense of the sprayer, which might be costly.
One of the biggest problems faced by any piece of concrete is the effect water will have on it. The most obvious sign is staining. This can result in algae or black spots, and can lead finally to cracks. So the only way of combating this, is to use a concrete sealer.
If a concrete surface is not treated, and is subject to weathering, it can break up and results in what is know as Spalling. This is where the aggregates in the concrete come through and begin breaking back down.
The effect of water on concrete can be described in two ways. Positive, is from rain fall, and Negative is from ground water. Either way, the moisture and vapor will transmit itself through the concrete. Concrete behaves like a sponge with water. The water will always travel through it, seeking the dryer areas, until it reaches the air. Finally the only way of stopping it, is to form a membrane across the surface.
The way water can break down a piece of concrete is not complicated. Basically it undergoes alkali disintegration, which lies dormant, and no longer reacts with the Portland in the cement. As the water hydrates, the alkali begins to react with the cement around it to turn back into a powder, or efflorescence.
When mould takes hold of concrete it can lead to sever health problems for those living near it. Mildew and mould can produce a fungus which releases Myotoxins. These can be deadly if taken inside the body. Sealing the concrete is one very good solution.
One of the chemicals used in concrete a sealant, is Polysiloxane. This is used as curing agents with epoxies to generate flexible, moisture and weather resistant coatings.
These can result not only in saving a concrete surface, but can make a pathway or drive easier to keep clean.