Evaluation of Self Consolidating Concrete and Class IV Concrete Flow in Drilled Shafts
-
2019-10-01
-
Details:
-
Creators:
-
Corporate Creators:
-
Corporate Contributors:
-
Subject/TRT Terms:
-
Publication/ Report Number:
-
Resource Type:
-
Geographical Coverage:
-
Edition:Final Report 01/16-10/19
-
Contracting Officer:
-
Corporate Publisher:
-
Abstract:The term “mattressing” is a relatively new term coined by a joint task force formed by the Deep Foundation Institute and European Foundation Federation Committee (DFI/EFFC). Mattressing is defined as a pattern of creases on the surface of drilled shafts or slurry walls where the pattern reflects the reinforcing cage layout and which gives the appearance of a quilted mattress top. The presence of creases does not substantially affect the volume of placed concrete and therefore is not detected by routine drilled shaft inspector logs where the anticipated/theoretical shaft volume is directly compared to the as-placed volume. The presence of creases, when found, was thought to be an unusual occurrence caused by out-of-spec concrete flow (low or borderline slump) or slurry heavily laden with suspended soil particles (high sand content). Two studies leading up to this work identified that (1) concrete flow is radial and not vertically rising in the cover region, and (2) creases always formed when mineral slurry was used in large-scale laboratory shaft specimens where the concrete was tremie-placed and slurry displacing. This project was tasked with identifying the extent to which creases have formed in both laboratory and field conditions and the effect of their presence. Laboratory findings showed that use of mineral slurry significantly affected rebar bond/development length requirements and corrosion resistance/durability provided by the cover concrete. Polymer slurry showed similar rebar bond effects but less frequently affected durability. The presence of water at the time of tremie-placing concrete had no adverse effect on rebar bond or durability. Underwater inspection of selected in-service bridges showed similar results to the laboratory findings where the concrete surface behind removed casing coupons was visibly distressed for shafts using bentonite slurry, partially distressed for shafts using attapulgite slurry, and little to no distress for shafts using water.
-
Format:
-
Funding:
-
Collection(s):
-
Main Document Checksum:
-
Download URL:
-
File Type: