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ConBlock MIC: Antimicrobial Concrete Admixture

Why choose ConBlock MIC?

 Break the Chain with Microbial Induced Corrosion Defense, ConBlock MIC!

Microbial induced corrosion (MIC) occurs in unique environments that develop because of a particular chain of events. During this chain of events, an acid generating bacteria – Thiobacillus – will grow on the surface of concrete. The excreted acid will begin to corrode the concrete, and harsher bacteria strains will continue to develop. ConBlock MIC breaks this chain of events by creating an uninhabitable environment to these organisms on the concrete’s surface, protecting the concrete from microbiological corrosion.

Whether integrated throughout the matrix of the concrete when used as an admixture and/or directly applied to the concrete as a surface treatment, ConBlock MIC inhibits the growth of bacteria, fungi, mold, and algae. The unique chemistry of ConBlock MIC creates a chain of molecules that are chemically bound to the concrete. Gram-negative organisms are attracted to the positive charge in the ConBlock MIC molecule resulting in a rupture of the organism’s outer cell. With a ConBlock MIC treatment the concrete surface becomes uninhabitable to microbiological organisms.

US EPA Registration No.: 87907-1


Brief overview of MIC and how ConBlock MIC breaks the chain

The performance history of underground infrastructure supports concrete’s long and reliable service in wastewater systems.  Concrete sewer pipes unearthed after centuries of use have been found in good condition.  The sustainable and resilient attributes of concrete are why concrete is the most widely used product for wastewater systems worldwide.  However, the alkalinity of concrete leaves it susceptible to an acid attack under unique biogenic conditions known as microbial induced corrosion.


Microbial induced corrosion, commonly referred to as MIC, is the biogenic process of microorganisms corroding concrete – most commonly found in concrete wastewater systems.  When environmental conditions allow, the Thiobacillus species of bacteria thrive and MIC to occurs in a defined, 3-phase chain of events.  This chain of events must take place before corrosion of concrete starts.

A graphical depiction of the different phases of Microbial Induced Corrosion.


The phases of MIC can be broken down into separate pH ranges of the concrete surface.  The first phase of carbonating the concrete surface starts immediately after production of the concrete.  This natural process only needs to affect the thin layer at the surface to allow the start of phase two – the growth of a biofilm.

Transitioning from Phase 1 to Phase 2

Phase two, the biofilm phase, provides the necessary colonization of organisms for harmful Thiobacillus to inhabit the concrete surface.  The first species of Thiobacillus excrete weak acids by consuming available hydrogen sulfide gas and oxygen in the aerobic environment of the wastewater system.  The excreted acid helps lower the concrete surface pH, enabling Thiobacillus species that produce stronger acids to inhabit the biofilm.  This process continues well into phase three, where concrete deterioration occurs.

Image Note: Thiobacillus can survive on concrete
with a pH of 9 or lower.  Turbulence releases
hydrogen sulfide from the wastewater providing
a source of food for the Thiobacillus.

Phase three, the deterioration phase of MIC, is only possible if phase two occurs.  Starting around a pH of 4, habitation of Thiobacillus species that excrete stronger concentrations of acid begins the deterioration of the concrete surface.  Severe corrosion occurs as the concrete surface pH drops below 1.  The damage occurs when the excreted sulfuric acid reacts with the free lime (calcium hydroxide) forming calcium sulfate, also known as gypsum.  The gypsum reacts with the alumina in the concrete to form ettringite, which expands in the presence of moisture.  This expansion causes the concrete to crack and spall, thus allowing for deeper penetration of acid and continuance of the damaging cycle.

Image Note: Damaging levels of corrosion
begin to occur when the concrete surface pH
drops below 1.

Environmental Attributes of MIC


  • Bacteria/Biofilm
  • Low dissolved oxygen in wastewater
  • Sulfates in the effluent
  • Warm temperatures
  • Turbulence
  • Moisture on the walls above the waterline
  • Reactive compounds in concrete
  • Low effluent flow


MIC produces rough concrete surfaces showing loss of mortar or aggregates along with general spalling of the concrete.  Damaged concrete surfaces can become soft to the touch, with missing aggregate and a gel-like texture at the concrete surface.  One of the first indications of MIC is the appearance of a white mass above the waterline in a concrete wastewater system.  This white formation is the gypsum formed in the reaction between the biogenic sulfuric acid and calcium hydroxide.


The Technology of ConBlock MIC

At the base of ConBlock MIC is a silane molecule.  The silane molecule serves two functions. First, it creates a covalent bond with the concrete – it cannot wash off or leach out.  Second, when applied at the proper concentration, the silane base of ConBlock MIC will polymerize into a layer of networked silane molecules – making it more difficult for water to absorb into the concrete.  In the center of this technology is a nitrogen atom with a positive charge.  Many bacteria are electrostatically attracted to the molecule because of this atom.  Finally, there is a molecular chain of carbon 18 atoms long.  As bacteria are attracted to the ConBlock MIC, the carbon sword will pierce their cellular membrane and the outer cell ruptures upon reaching the nitrogen ion.  This creates an uninhabitable environment for the bacteria; thus, breaking the chain of microbial induced corrosion.

Click here for more detailed information about MIC and how ConBlock MIC breaks the chain that leads to microbial induced corrosion.


Video Overview of MIC and ConBlock MIC Defense


Test Data


Thiobacillus sp.(): Untreated Control ConBlock MIC Treated
T. novella: +570% -99.4%
T. intermedia: +900% -98.5%
T. thioparus: +130% -93.5%

Testing was performed on concrete aged to a pH of 6.8-6.5.  The test method is ISO 22196 Modified Method for Concrete.

Click here for more detailed test data.