Durability of concrete with addition of dry sludge from waste water treatment plants

This paper evaluates the use of dry sludge as an additive for concrete, for which it must be guaranteed that the resulting concrete has the appropriate mechanical strength and durability.In earlier work on the subject, it was shown that the addition of sludge reduces the mechanical strength of concrete. With the addition of 10% sludge in proportion to the amount of concrete, the mechanical strength decreases significantly, making it unsuitable for medium- to high-strength reinforced concrete.One possible area of application would be in the preparation of low-strength mass concrete that could be used for bases and subbases of roads with light traffic, as filler, etc.We subjected the concrete specimens to different types of accelerated attack in order to evaluate long-term performance and compare them with the reference concrete (not containing sludge).The following tests were made:

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Combined wet-dry cycles using fresh water, seawater and water containing 5% sulphates

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Accelerated ageing in an autoclave

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Accelerated carbonation

The performance of the concrete containing sludge was acceptable and comparable to the results obtained for the reference concrete not containing sludge.