The new concrete recipe of Professor, Yaghoob Farnam from Drexel University can now withstand the deterioration of road salt.
Mr. Farnam created a method for using fly ash, slag and silica fume — leftovers from coal furnaces and the smelting process — in a new concrete mix that is more durable because it doesn’t react with road salt.
Calcium chloride salt – also known as “deicer” – reacts to the calcium hydroxide in commonly used cement, thus causing degradation.
By adding the new ingredients to the concrete, the rock showed no reaction to road salts.
The research proves that by using alternate cementitious materials to make concrete, they can avoid the destructive chemical reaction and continue to use calcium chloride.
The goal of Farnam’s work is to produce a concrete mix as strong as the ones currently used to build roads that contains less calcium hydroxide — the ingredient that reacts with road salt to form a compound called calcium oxychloride. This chemical tends to expand when it is formed, and when that reaction happens in the pores of cement it can cause degradation and cracking.
Farnam’s research led him to the conclusion that these “supplementary cement materials” could be substituted into the mix with a better result when they come in contact with calcium chloride deicing salt.
The study also revealed that higher concentrations of calcium chloride produce more calcium oxychloride when it reacts with concrete. So, theoretically, using lower concentrations of calcium chloride on roads could help extend their life, but it would also make it less effective as a deicing agent.
Image source: drexel.edu