Date of Graduation

2015

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Roger HL Chen

Committee Co-Chair

Fei Dai

Committee Member

Radhey Sharma

Abstract

Self-Consolidating Concrete (SCC) is a relatively new type of concrete mixture that does not require external compaction during placement. Compared to traditional vibrated concrete (TVC), SCC is much more fluid, which gives it the ability to flow and fill formwork without the need for any external compaction efforts. Although the increased cement content and chemical admixtures found in SCC typically results in a higher material cost, the potential for cost savings in reduced construction time and labor are significant. The potential of this relatively new type of concrete have yet to be realized due to a lack of regulation and full understanding of its material behavior which radically differs from traditional concrete mixes. This thesis outlines a research study performed on SCC for cast-in-place (CIP) applications, which includes a comprehensive literature review, the current practices and regulations of 25 state agencies, as well as experimental findings related rapid fresh water-to-cement ratio determination and the effects of pumping SCC on segregation resistance and air-void properties.;Due to SCC's relatively high sensitivity to changes in water content, the development of on-site quality control measures to determine the fresh w/cm could be beneficial to the implementation of SCC for CIP applications. The Standard Test Method for Water Content of Freshly Mixed Concrete Using Microwave Oven Drying (AASHTO T318-02) was evaluated for potential use as an on-site quality control measure in the determination of fresh w/cm. Two testing procedures were investigated using AASHTO T318-02 which included the use of concrete samples and sieved mortar sample. Both methods predicted the w/cm for delivered concrete and laboratory batched SCC within reasonable accuracy. The average difference (taken as calculated w/cm minus the actual w/cm ratio) for concrete and sieved mortar samples were found to be 0.012 and 0.013, respectively.;The relatively low viscosity of SCC allows for the use of innovative construction methods such as pumping from various locations on the formwork. A previous research project at West Virginia University performed in 2010 proved that SCC could be pumped from the bottom of the formwork with the casting of a 12-feet SCC column. Due to the low viscosity of SCC, some researchers have suggested that the stability of the air void structure as well as the segregation resistance may be lower than traditional mixes. Adequate segregation resistance and air-void structure within a concrete structure is necessary to ensure acceptable material behavior. An image analysis was performed to evaluate the segregation resistance and air-void structure of the pumped SCC. Five concrete samples were cored along the height of the hardened SCC column. The hardened aggregate analysis showed that the pumped SCC exhibited segregation behavior at various locations within the column. Of the specimens analyzed, half did not meet the ASTM C457 recommended value for specific surface to resist moderate freeze-thaw cycling while none of the samples met the ASTM C457 recommendation of spacing factor less than 0.20 mm for structures exposed to moderate freeze-thaw conditions. Additionally, changes in the air-void size distribution were observed along the height of the pumped SCC column. The increased pressure and agitation from pumping the SCC may have resulted in reduced segregation resistance and air-void stability within the SCC.

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