Development history - VISCO TOP

Wondering if there was a way to solve the problem of segregation and fluidity in concrete, Koji Koyanagi, a researcher at Kao Corporation came up with the idea of using micro-molecules instead of the macromolecular polymer thickeners used as admixtures to date. Harnessing the surfactant technology that forms one of Kao’s core technologies should yield the desired result....And so, this unprecedented development got underway with no real direction.After a bit of experimentation, I started to focus on the rheological properties of wormlike micelles because of their unique behavior compared to spherical or layered forms.Gaining inspiration from the unknown possibilities of wormlike micelles, different in shape from spherical or layered micelles that had been used in existing products, such as shampoo and conditioners, Koyanagi discovered that he could control the viscoelasticity by adjusting the length of the wormlike micelles and how easily they could be unraveled. This gave birth to VISCO TOP, created from two liquid solutions, “100A” and 100B”.

Although both 100A and 100B solutions are thin and flow easily, mixing them changes the shape of the micelle, achieving a high viscoelasticity. If A and B low viscosity solutions are force-fed through separate hoses and are mixed immediately before construction, it is possible to achieve a uniform and strong concrete, while eliminating stress when it is time to pour. Feedback from customers commenting on how well it flows despite its high viscosity and how it doesn’t separate in water is testimony to its performance and low environmental impact.

Koyanagi's research results have garnered high acclaim, receiving the "21st Century Invention Incentive Award" at the National Commendation for Invention. However, this came with an unexpected request.This was a request to make VISCO TOP, a product comprised of two separate liquids, into one single solution.The reason behind this request being that it was open to the risk of human error on construction sites, carelessly using only one of the liquids or miscalculating how much of each liquid was required."Of course, in the laboratory, we were conducting tests by mixing amounts measured in grams, however on construction sites they are using massive amounts in the area of several hundred liters. The scale is different, so even if you tell people to mix them before use, there is room for error."This marked the beginning of the development of VISCO TOP from a double solution to a single solution.

VISCO TOP was originally developed to achieve high viscosity by mixing two solutions, A and B. However, to develop a single liquid, it was necessary to achieve low resistance through the pump line with low viscosity while at the same time, maintaining a high concentration with a mixture of both liquids. In order to maintain the performance of concrete, it is not viable to reduce viscosity by dilution. Based on the hypothesis that we need to achieve low viscosity through the use of additives, we looked to develop an optimal additive.We repeatedly faced defeat, unable to achieve the desired viscosity. It was then that another "epiphany" from Koyanagi gave rise to the solution.When an additive is added to a single solution (the key to controlling viscoelasticity) the worm-like micelle change in length, becoming shorter and lower the viscosity. It was based on this idea that I believed that if the additive disappeared when mixed with the slurry, the worm-like micelles might regenerate.This discovery of this special additive led to the development of VISCO TOP 200 LS-2 that enabled the use of a single liquid with the performance of two liquid solutions. Either a single solution or two solutions can be used depending on conditions at the construction site, further expanding the range of applications.

Currently, Kao is working on the development of new materials and construction methods using VISCO TOP to meet a variety of requirements, such as soil improvement, seismic reinforcement of ports and harbors, and measures to counter the liquefaction of soft soil."From the development phase to the present, we have continued to make improvements, and the quality of VISCO TOP as a product has increased considerably. But there is no end goal to our research. We will continue to pursue other applications, such as energy harvesting, as well as improvements in usability."VISCO TOP has provided a dramatic breakthrough in concrete construction. We will continue to take on the challenge of further innovation to protect all forms of life and to make construction and civil engineering beneficial to the natural environment.