Utilization of Rice Straw Fibers as an Internal Curing Agent for Concrete, 2016

 

Project Leader

Feraidon Ataie, program coordinator, Concrete Industry Management Program, CSU Chico

The goal of this two-year project was to determine whether rice straw fibers could be used as an internal curing agent to decrease concrete dry-ing shrinkage. Objectives for year two of the study included:

  • Investigate impacts of rice straw fiber addition on concrete shrinkage cracking.
  • Find an optimum level of rice straw fiber addition in concrete.
  • Characterize impacts of warm water-treated rice straw on concrete shrinkage cracking.

All experiments were conducted at California State University, Chico. Rice obtained from a local farm was ground to produce fibers at two different particle sizes. The fibers were added to concrete at four different dosages (1%, 2%, 3%, and 5% of cement weight). Rice straw fibers were washed and dried to make sure they didn’t absorb water from concrete. Twenty different concrete mixes were made.

Results indicate that the addition of rice straw fibers has negative impacts on concrete properties. Concrete containing rice straw fibers had higher drying shrinkage and lower strength. Retreating rice straw with water did not help solve this problem. Using finer rice straw fibers did not help reduce drying shrnkage or increase concrete strength.

The idea for this research project was that rice straw fibers would act as an internal curing agent to reduce concrete drying shrinkage. However, rice straw fibers were squeezed during concrete mixing, causing them to release water when mixed. This increased the water content of the concrete, reducing concrete strength and increasing drying shrinkage.

More experiments will be made by adding dry rice straw fibers to concrete. Although not funded, the project leader believes it is important to complete this part of the research.