Modifying concrete matrices with beneficiated dredged material or other clayey constituents.

摘要

Conventional wisdom suggests that for concrete production no clay minerals should be used, which aside from sands and silts are the main components of dredged material. It was the main goal of this research to investigate the feasibility of modifying concrete with clayey components in spite of the initial reservations found in the literature.; The disposal of dredged material is a challenge most of the harbors worldwide have to face. Traditionally, the excavated material was dumped in the ocean or other places next to the dredging site. Today, most of the material is placed in landfills or specially designed facilities. Diminishing capacities of existing facilities, increasing volume of contaminated material, new regulatory restrictions, and rising public awareness towards environmental issues are applying pressure on the port authorities to search for alternative disposal methods. Ideally such techniques reuse or recycle the material as a valuable resource. In this work, methods of beneficiating dredged material for concrete applications were investigated.; The large fraction of sands and silts in dredged material suggested replacing regular fine aggregate with dredged material. However, the results were not very promising. In a second approach, dredged material was added as a filler, which introduced “undesirable” clay minerals as the main active component to a given concrete. Kaolin served as a model for these minerals. Concrete mixes were thus modified with untreated or treated dredged material, with natural or thermally activated kaolin, or selected combinations thereof.; It was found that the loss of workability of fresh concrete required the addition of a superplasticizer when clayey constituents were used as filler in concrete applications. However, such components prevented segregation and bleeding. The properties of fresh concrete, such as coherence, flow, homogeneity, compactability, and air content depend on the type of filler and superplasticizer. They relate closely to all physico-chemical and mechanical properties of the hardened product. The amount of dredged material used as filler can be adjusted to meet given requirements. The findings are encouraging and indicate that it should be possible to beneficially use dredged material and other clayey constituents in concrete production.