Early-age hydration and shrinkage of cement paste with coir fibers as studied by Nuclear Magnetic Resonance

Abstract

• Coir fibers at the adopted dosage have a negligible influence on cement hydration kinetics. • Internal curing effect of saturated coir fibers. • Water competition introduced by dry coir fibers. • Saturated coir fibers decrease autogenous shrinkage and drying shrinkage of cement materials. • NMR can be used to track water transportation and shrinkage in cement materials. Nuclear Magnetic Resonance (NMR) is used to study the early-age hydration as well as autogenous shrinkage and drying shrinkage of cement paste with the addition of coir fibers. The dosage and water content of coir fibers are evaluated. The results show that added coir fibers have a negligible influence on cement hydration kinetics. However, the internal curing effect of saturated coir fibers and water competition induced by dry fibers are visualized. As the saturated fiber content increases, autogenous shrinkage and drying shrinkage decrease due to the internal curing and reinforcing effects of fibers. Dry fibers generate more autogenous shrinkage but less drying shrinkage than saturated fibers of the same dosage due to the introduced water competition. NMR is proven able to track water transportation and shrinkage in cement composites.