01664294

Component

There are a variety of concrete applications that place unique demands on the material that must be overcome by utilizing a combination of admixtures and changes to the mixture design. Conventional high early age strength concrete can be achieved by using a mix with low water to cement ratio and accelerating admixture, but some adjustments associated with increased early age strength can cause the concrete to become more brittle, undergo increased shrinkage and likely crack under shrinkage strain. Shrinkage reducing admixtures (SRA) can reduce shrinkage in concrete but they can also cause reduction in early age and long term strength. Micro-fibers can control the formation of plastic shrinkage cracking as well as increase the early age strength of concrete. The research results herein report the impact of shrinkage reducing admixture, accelerating admixture, and three volume doses (0.1%, 0.3%, and 0.5%) of high elastic modulus micro-carbon fiber on 24 hour compressive strength and restrained shrinkage. The results showed that overall, increasing carbon fiber dose increased the 24 hour compressive strength of concrete for the volumes tested. Although increasing micro-carbon fiber volume showed no real trend with regards to changing the amount of shrinkage or shrinkage rate, no mixes with carbon fiber of any dose cracked during the 28 day test while the control mix with accelerating admixture cracked at approximately 15 days. Results suggest that micro-carbon fiber is effective for preventing shrinkage cracking in concrete subject to drying shrinkage induced stress, and can significantly increase the 24-hour compressive strength of concrete. The combination of SRA and accelerating admixture in concrete showed compatible effects and the advantages of increased early age compressive strength and reduced shrinkage rates.

This paper was sponsored by TRB committee AFN10 Standing Committee on Basic Research and Emerging Technologies Related to Concrete. Alternate title: Assessment of Strength and Restrained Shrinkage Behaviors on Micro–Carbon Fiber–Reinforced Concrete with Binary Chemical Admixtures

18-06356

English

8p

2018

Transportation Research Board 97th Annual Meeting

Digital/other

Figures; References; Tables

Accelerating agents; Admixtures; Carbon fibers; Compressive strength; Cracking; Fiber reinforced concrete; Mix design; Modulus of elasticity; Shrinkage

Carbon microfibers; Shrinkage reducing admixtures

Highways; Materials; I30: Materials

Transportation Research Board Annual Meeting 2018 Paper #18-06356

TRIS, TRB, ATRI

Jan 8 2018 11:38AM