Improved Compressive Strength of Concrete and Mortar Containing Fly Ash

Invented by: John Liskowitz, Methi Wecharantana, Chai Jaturapitakkul, Anthony E. Cerkanowicz

Field(s) of Study: Civil Engineering, Engineering
Patent Category: Architecture, Construction, Energy, Environmental, Transportation

  • Patent #US5853475

  • Filed on May 19, 1995 Granted on Dec 29, 1998
  • Website

New Jersey Institute of Technology
Newark, NJ 07102

“Improved Compressive Strength of Concrete and Mortar Containing Fly Ash” is a relatively easy innovation with great implications on construction across the globe. As the name implies, the patent deals with improving the overall strength of concrete and mortar used in construction projects. What is unique about this invention is that it gives a method of a mixture that includes fly ash and cement. This new method of combining fly ash and cement together results in achieving greater compressive strength than other materials that contain only concrete. Moreover, it gives engineers the ability to predict the strength of the concrete containing fly ash before it hardens. This is utterly important in planning for any project but especially large scale buildings. Thanks to the formula provided by John Liskowitz, Methi Wecharantana, Chai Jaturapitakkul, and Anthony E. Cerkanowicz, the compressive strength of concrete containing fly ash can now be predicted before the mixture hardens.

This method can significantly reduce construction costs that accompany major construction projects. The masterminds behind this patent were able to produce concrete with about 15% to 25% fly ash as a replacement to expensive cement. Not only did they save about a quarter of the production cost by doing so but also they still met the design specifications required for buildings and even highway construction. Cheaper production with maintained quality is the formula for success in construction, and these inventors out of NJIT have found the successful formula.

Under government supported research, the inventors – the majority of whom were affiliated with the Department of Civil and Environmental Engineering at the New Jersey Institute of Technology – were tasked with building a concrete that is sturdy and sufficient enough to be used in buildings and transportation projects, but also affordable. The inventors went a step further and came up with a formula that is cheap, highly durable, and environmentally friendly. The use of fly ash as a substitute in concrete mixtures has the ability to reduce the carbon footprint on the environment. First, the use of fly ash, also known as “pulverized fuel ash”, in concrete mixtures cuts down the use of cement – and that in itself can cut cement and carbon waste by 25%. Secondly, the production of fly ash used to be an environmentally messy procedure. Fly ash is created when coal is burned. The ash is then removed and used to be just thrown away into the air. Thanks to environmental protection laws in the US, fly ash now must be stored either in coal plants or landfills. But storing massive amounts of ash can be difficult and takes up a lot of space. For example, in 1988 the U.S produced about 50 million tons of fly ash that had to be stored. Thanks to this invention, about 43% of those stored ash heaps can become useful again in concrete.

However, there are some downsides to using this method. For starters this fly ash method requires a lot of time in order for it to be successful. To be exact it requires 90 days for the fly ash to become inert and to increase the compressive strength in most cement mixtures. Although, 90 days isn’t that long when it comes to most construction projects, it is a significantly undue burden when trying to pave a road. A second downside to substituting fly ash in cement mixtures is that not all fly ash is made the same way or composed of the same quality. As previously mentioned, fly ash comes from all different sources, and there is no set standard quality that is used in composing fly ash. This uncertainty in the composure of fly ash can lead to different outcomes in cement, and that is a risk that can’t be taken all the time in building projects.

Although this method has some flaws, “Improved Compressive Strength of Concrete and Mortar Containing Fly Ash” has great implications that can benefit the construction community. With more pressure on construction projects to find cheaper alternatives for accomplishing the same task, substituting fly ash can be incredibly helpful. Since its publication date in 1998, there have been 46 other patents that built upon the same general idea initiated by this patent. The most recent was in 2011. These patents range from other methods to save money in cement mixtures and methods in shortening the wait time needed to accomplish this feat. These 46 other patents would not have been possible if it wasn’t for the work done by these four inventors out of the New Jersey Institute of Technology.

By Michael Tadros