The latest advancement of using plastics as admixtures to improve the working and service properties of concrete comes from Germany. Previously researched polyisocyanates cannot be stirred homogeneously into an inorganic binder like cement, and they raise ecological concerns or require special high-speed mixers.
Although modified polyisocyanates do not require high-shear mising, their shelf life is too short.
A new invention by Hans-Joseph Laas, Jan Mazanek, Martin Brahm, Hermann Kober, Manfred Schonfelder, Dietbert Knofel, Karl-Georg Bottger, and Anke Reinschmidt received a U.S. patent. The new admixture uses isocyanate-functional admixtures composed of water-dispersible polyisocyanates rendered hydrophilic (i.e., they attract or are attracted by water) with nonionic chemical groups. It appears to improve concrete compressive and tensile strength.
Four samples using the new invention are compared for flexural and compressive strength at 7 and 28 days.