Corrosion Protection
Posted by David on December 28, 2006
I am working in the Delhi area of India. Very hot summers, flat typo. sewers normally fail after 15-20 years, corrosion of crown of pipe. Are their any admixtures that can effectively be added to concrete used for pipes that can reduce corrosion. What additional service-life can be gained from such admixtures and at what costs. Other solutions available?
David,
There are several options to protect steel in concrete from corrosion. Using concrete made with low water to cement ratio and containing slag or fly ash is good amounts will offer good resistance against corrosion. The cementitious content of concrete should contain atleast 25% Class F flyash or 40% slag for good results. Addition of a corrosion inhibiting admixture to the concrete will also offer resistance to concrete. A calcium nitrate based admixture is the most widely used corrosion inhibitor in concete. You can use a plasticizer or superplasticizer to compensate for the loss in workability due to low w/c ratio. Using epoxy coated steel will also help.
Lowering w/c ratio and using materials like flyash and slag will not only protect the concrete from corrosion but also a host of other durability issues such as sulfate attack, lower permeability, alkali silica reaction etc. and make the concrete really long lasting.
There are several protective coatings available in the market to protect pipes made with only steel. You should contact a local construction chemical company and tell them your problem, they should be able to recommend you the chemicals admixtures and coatings for your need.
If you are a small producer and do not want to add fly ash and slag in the concrete separately, there are also cements available in the market which already contain either flyash or slag in them, you can use these cements.
Check prices with 2-3 suppliers to get an idea about the cost.
Good-luck
