Submitted to: Polymers and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 2004
Publication Date: January 1, 2004
Citation: Glenn, G.M., Klamczynski, A., Chiou, B., Wood, D.F., Orts, W.J., Imam, S.H. 2004. Lightweight concrete containig alkaline resistent starch-based aquagels. Journal of Polymers and the Environment, 12(3):189-196. Interpretive Summary: Lightweight concrete is destined to become a dominant construction material in the new millennium because of its lower density and unique sound-proofing and thermal properties. Starch-based lightweight concrete is a useful new building material but it may have very long and variable setting times compared to normal concrete. This paper identifies the cause of long setting times and demonstrates that a starch/polymer blend is more stable in concrete mixtures. The results will help engineers successfully use starch in making lightweight concrete.
Technical Abstract: Starch aquagel-based lightweight concrete has properties similar to those of other lightweight concrete products. However, starch aquagels are unstable in the strongly alkaline conditions typical of Portland Cement-based concrete and may interfere with the setting process. The effect of alkali treatments on the physical, mechanical, and functional properties of starch aquagels and aquagels from starch/polymer blends was investigated. Starch was blended with five different polymers to determine whether the blends improved alkaline resistance. Polymer blends containing 5, 15, and 30% of the polymer hydrated and formed aquagels when equilibrated in water for 24 hr. However, equilibrium moisture content was lower for the blends compared to the starch control. Aquagels equilibrated in 0.15 N NaOH swelled, lost compressive strength and had greater than 90 % moisture. The blend of starch and 30% PVOH absorbed less moisture and was more resistant to alkaline dissolution in 1 N NaOH than the other blends tested making it a more suitable material for aquagel-based concrete. The moisture content of starch-based aquagels and mixing time were critical factors in determining setting times. The size of aquagel blends had a minor effect on density and compressive strength.