Superplasticizer (SP) and hydrogel are two important chemical admixtures of concrete. Superplasticizer or high-range water reducer is a dispersant for cement particles. Only a small amount of SP could greatly improve the workability of concrete, and make high performance concrete or self-compacting concrete possible. Sulfonated naphthalene formaldehyde condensates (SNF) and polycarboxylate polymers with long, comb-type side chains (PCA) are typical examples. Hydrogel or superabsorbent polymer is a crosslinked polymer which can absorb lots of water. It acts as an internal curing agent of concrete. When added into concrete, hydrogel in concrete performs as a water reservoir, which gradually releases water, supplements the water loss and maintains the humidity of concrete. Therefore, the resulting concrete shows reduced dry shrinkage and cracks. Poly(acrylic acid-co-acrylamide) (PAM) based hydrogels are typical examples. 

Up to now, most chemical admixtures used such as SNF, PCA and PAM hydrogel are anionic. In this presentation, an amphoteric copolymer PAC was prepared. PACs with proper reactant ration and molecular weight are more effective than SNF in dispersing cement particles. Separately, PAC hydrogel was also prepared. The water absorbency of PAC was measured in salt solutions. The effects of PAC on the material properties of mortars in terms of compressive strength and length change were determined and discussed.

Dr. Kung-Chung Hsu received PhD in Department of Chemical Engineering at The Penn State University, in 1985. He worked as a senior scientist in the R & D Department of China Steel Corp. in 1985-1990. He was an Associated Professor in 1990-1996, Professor in 1996-2020, and is now an Emeritus Professor in the Department of Chemistry of National Taiwan Normal University, Taipei, Taiwan. Dr. Hsu has research interests in (1) preparation and application of dispersing agents in ceramic materials, (2) preparation and development of superplasticizer and self-curing agents in concrete, and (3) preparation and application of nano powder and graphene/polymer composites. He has published more than 50 peer-reviewed papers and obtained over 25 patents so far.