Concrete
Concrete is a construction material with many attributes and disadvantages that should be carefully designed for good construction and rehabilitation work. Some defective concrete can be attributed to the addition of reinforcement steel since corrosion of imbedded steel is one of the most frequent causes of concrete damage. Concrete is highly alkaline with electrical resistant, which gives imbedded steel some corrosion protection. However it is a porous material and over time is not very resistant to acidic chemicals. Deicer chlorides and also chemical reactions within the concrete destroy the protection. In addition to other means there are two types of corrosion inhibitors attracting interest for concrete repairs. One, calcium nitrate, an admix for fresh concrete that has been used for several years with good results. Other inhibitors are applied externally on hardened concrete. They function by migrating through the concrete covering the reinforcement steel. Their effectiveness however is uncertain for the long term.
Evaluation
Concrete is a construction material with many attributes and disadvantages that should be carefully designed for good construction and rehabilitation work. Some defective concrete can be attributed to the addition of reinforcement steel since corrosion of imbedded steel is one of the most frequent causes of concrete damage. Concrete is highly alkaline with electrical resistant, which gives imbedded steel some corrosion protection. However it is a porous material and over time is not very resistant to acidic chemicals. Deicer chlorides and also chemical reactions within the concrete destroy the protection. In addition to other means there are two types of corrosion inhibitors attracting interest for concrete repairs. One, calcium nitrate, an admix for fresh concrete that has been used for several years with good results. Other inhibitors are applied externally on hardened concrete. They function by migrating through the concrete covering the reinforcement steel. Their effectiveness however is uncertain for the long term.
Evaluation
A thorough and logical evaluation of the current condition of the concrete in a structure is the first step of any repair or rehabilitation project. It mean,when the condition of a structure indicates that major repair or rehabilitation is probably necessary, a comprehensive evaluation of the structure should be conducted to determine the scope of the work required. Such an evaluation could include the following:
a) a review of the available design and construction documentation;
b) a review of the operation and maintenance records;
c) a review of the instrumentation data;
d)a visual examination of the condition of the concrete in the structure;
e) an evaluation of the structure by nondestructive testing means;
f) a laboratory evaluation of the condition of concrete specimens recovered from the structure;
g) a stress analysis; and a stability analysis of the entire structure.
Investigation
Collection and evaluation of information through inspection, document search, load testing and other testing.
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