Most buildings in Spain are built using steel reinforced concrete. There are many reasons why damage can occur: poor design and specification, overloading, movement due to ground movement and fire to name a few.
Decennial Insurance Policy: the 10 year Builder’s Guarantee
Prevention is better than cure (mas vale prevenir que curar). It’s very important if you are building in Spain that you insist on the 10 year guarantee that protects you from damage during the first year of the structure’s life. These guarantees are compulsory for professional developers and optional for self builders. However we strongly recommend that self builders opt in for very good reasons.
It means that an independent professional from the insurance company monitors the pouring of the cement. That focuses the attention of your contractor and means the job is done properly.
It also protects the value of your house because any purchaser, properly advised, will want to see the guarantee. Even if the ten years have expired they will still want to see it. If it doesn’t exist it raises questions, doubts, delays, it may put them off if there are any cracks in the building or ground movement in the area and ultimately all this affects the price they will pay and the value of your asset.
A Commonly Held False Belief
Many people think you can simply remove the damaged material and replace it with any kind of mortar but this not the case.
What is the Cause of the Damage?
This is the first thing to establish.
The reinforcing steel ribs within the concrete are protected by an iron oxide film that protects it from corrosion. This protective film forms during hydration. There are two things that may disrupt this protective film and expose the steel to corrosion: carbonation and chloride attacks.
Carbonation is the chemical reaction between the CO2 in the air, and the water and calcium found in the concrete. It results in the formation of calcium carbonate. The protective film of the rods is neutralised. The concrete discolours anything from grey to orange. The rods swell to up to 6 times their volume. The concrete cracks and breaks away.
This happens when the concrete is exposed to de-icing salts, marine salts or contaminated raw materials. Again the chloride penetrates the concrete and attacks the rods protective film. A symptom is a black coloured rust.
Guide to Repairs
When you understand the cause and severity of the damage you can decide on a range of repairs from patches to replacement. The repair will involve some of the following principles
1. Protection against ingress
2. Moisture control
3. Concrete restoration
4-5. Structural strengthening
6. Resistance to chemicals
7. Preservation or restoring passivity
8. Increasing resistivity
9. Cathodic control
10. Cathodic protection.
A Note of the Design and Specification of Reinforced Concrete
It’s clearly important that the design takes into account the purpose for which the structure will be used and the environment it is in. The water content, porosity, compaction, spacing of the rods must all be considered in the optimum solution. Concrete structures require on going maintenance.
A Note on Concrete and the Environment
We know concrete is not an environmentally friendly product as it produces a lot of carbon dioxide in its manufacture. But for many people it’s the only practical or economical solution.
You can certainly make a concrete framed building energy efficient and that way make up for the Co2 used in the house construction.
The embodied energy calculation of any structural system whether concrete, timber or steel, will depend on the exact circumstances of the material’s production. It will take into account many different factors including the distance the material has to travel and all the energy that goes into its production over what can be many years.
Author: John Wolfendale
Bio: John is a founder of Eco Vida Homes and is passionate about bringing modern design and construction practices to Spain. He believes a home which is warm in winter and cool in summer is largely a matter of design and selective use of materials. He is British and a Chartered Surveyor with over 22 years experience living and working in Spain.