ATTACK OF CONCRETE - SULPHURE & MICROBIAL CORROSION
“Concrete sewer structures and pipes are corroded by sulphuric acid which
destroys the cement binder and ultimately results in corrosion of the
reinforcing steel. Sulphuric acid is produced in sewers by a complex chain
of microbiological and gas/liquid solubility stages which occur as the
sewage travels through the sewerage system.
These bacteria can create levels of sulfuric acid concentrations as high
as 7%. This acid diffuses into the concrete structure, destroys the cement
gel binder, and forming soft and soluble gypsum (calcium sulphate hydrate)” [1].
“KALMATRON® KF-A admixture to concrete mixes is a conceptually new
product patented in the USA (#5,728,428). This is an inorganic oxidizer of
micro/macro metal elements contained in cementitious materials providing
electro-chemical decay of cement grain by electrolysis between inversely
charged particles of electrolyte and cement grain.
KF-A falls under the classification of the following types of ASTM C 494:
• Type C – cement hydration accelerator;
• Type F – high range water-reducing admixture;
• Type S – specific performance admixture.
Decay-hydration reactions result in maximum hydration/decay of cement
grains and volume of cementitious paste as a continuous solid phase in
which the aggregates are embedded.
Any ingredient of the concrete batch with certain sorption ability is
vulnerable to any liquid/gas corrosion. The photograph at right shows
corroded coarse aggregate when cementitious paste protected by KF-A
was perfectly intact. Therefore, completed cement grain hydration by KF-A
admixture do not leave agential volume for any acidic reaction.
The attack on concrete's cementitious part takes place
mainly above the normal sewerage flow level. Sewage is
rich in sulphur containing materials, both organic
(protein, etc) and inorganic (sulphates, etc).
Above: concrete with KF-A applied on the floor of a zinc
plant, where the cementitious part of the concrete was
intact after one year but the dolomite-like aggregate was
eaten up by the sulfuric acid, and that floor looked like a
honeycombed surface. It was recommended to use a denser
type of aggregate.
Concrete specimens were placed into the sewage flows for six months to observe resistance of concrete to corrosion.
Trial specimen made with the same concrete mix design with added 12.5 Lbs/yd3 of KALMATRON® KF-A was observed almost intact.
SULPHURIC ACID 15%; Weight Loss:
KALMATRON® KF-A = 422 gr
SILICA FUME = 800 gr
HYDROCHLORIC ACID 15%; Weight Loss:
KALMATRON® KF-A= 110 gr
SILICA FUME = 180 gr
ORTHOPHOSPHORIC ACID 10%; Weight Loss:
KALMATRON® KF-A = 45 gr
SILICA FUME = 87 gr
KALMATRON® CHEMICAL RESISTANCE
Final examination of concrete specimens showed severe damages on the control concrete specimen (picture above).
DOES CONCRETE EXIST UNDER pH of 3?
YES, IT DOES WITH KALMATRON®!
This test procedure is based on comparison of building materials submerged in a solution of 1.00pH, which is close to battery acid.
Conventional concrete with added 17 Lbs/yd3 of KALMATRON® KF-A was tested also and survived 62 cycles with 4% of mass loss [5].
Information about control and compared specimens was not available.
We believe that pH =1 level is not suitable for any cement containing material. As it follows from the source [6], concrete is testable in a
range of acidity at 3pH to 6pH. The level of acidity over 6pH is a normal corrosive environment for concrete. Inversely, acidity below 3pH
is corrosive on a level of cement grain and not testable for cementitious materials. But it does work for concrete with KALMATRON®.
This is an example of the control concrete specimen deterioration in 10% acidic solution [3].
This sewer canal was built with KALMATRON® and has working for 12 years without any need for repairs. (Khabarovsk City, Central Sewer Facilities, Russia).
Repair of concrete manhole from inside. Spraying of KALMATRON® provided stable renovation to the structural strength, impermeability, and corrosion resistance.
Important economical issue is that the surface before application was not sand blasted and was not washed with acid solution.
The mass increasing type of concrete corrosion occurs in the salt, alkali, ligno-sulphate, and sugar containing environments.
The mechanism is simple, fast, and dangerous by unpredictable terms of structure exhaustion.
The concentration of aggressive media rises into the concrete, and results in the production of crystals with genesis respectively to dissolved agent. Physical tensions of crystals in the concrete causes massive and quick micro-cracking with consequent crumbling of the structure. Rebar looses its binding with concrete in the first few months.
The sugar-water solution is one of the fastest agents, because it is chemically active with cementitious elements. That’s why it was chosen for demonstration of KALMATRON® KF-A effectiveness, shown on the picture at right.
SUGAR 15% SOLUTION; Weight Increase:
KALMATRON® KF-A = 2 gr
SILICA FUME = 7 gr
Therefore, protecting the cement grains should be provided by completely hydrating of cement to assure binding of the concrete. KALMATRON® KF-A is designed to provide complete hydration of cement grain for concrete protection.
The most preferable way to repair damaged sewage concrete structures is by lining with a corrosion-proof repair coat containing KALMATRON® KF-A, seen as one of the few viable options for prolonging the service life of concrete sewer structures.
REFERENCES
[1] Fred Salome “Acid resistance assessment of concrete sewer repair lining” CTI consultants PTY LTD, Head Office: www.cticonsultants.com.au Postal Address: 4
Rothwell Avenue, Fax: (02) 9736 3287 PO Box 153, Concord West NSW 2138 Phone: (02) 9736 3911 North Strathfield NSW 2137
[2] Dr. Alex Rusinoff, KALMATRON® HPC, www.kalmatron.com
[3] Prof. Bacoss S.L. “Investigations into the effects of KALMATRON® admixtures on concrete properties”, UTS, Sydney, April 2000
[4] REDNER TEST. This test takes its name from John A. Redner, Departmental Engineer, Sewerage Department, County Sanitation Districts of Los Angeles
County, LA, California. He has published results of testing the acid resistance of many sewer lining repair coatings in a simulated sewer set-up. The Redner
test was developed to objectively assess the likely in-situ application issues and the acid resistance of coatings on concrete sewer pipes.
[5] Ryan Bailey, “KALMATRON® fully Submerged in 1 PH Solution.” GENEVA PIPE CO., 2004
[6] – A.M. Neville, Properties of Concrete, page 453, 3rd Edition, “Longman Group UK Limited”, “John Willey & Sons Inc.” 605 Third Avenue, New York NY 10158
MASS INCREASING TYPE OF CORROSION
Testing on the Central Sewer Station
Sydney, Australia
Test results from UTS laboratory [3]
KALMATRON® KF-A FOR BUILDING AND REPAIR OF SEWER STRUCTURES
MANHOLE REPAIR BY SPINNER & PLASTCRETE
Application of PLASTCRETE by Spinner brings multiple advantages such as shortest construction time and the most durable PLASTCRETE performance. Spinner is simple in the operation and gives highest possible superficial layer, which is over sufficiency of application by trowel.
Below are the photos of manhole repaired by the Spinner with PLASTCRETE. The surface is densifyed continuously, which is the base of durability and degree of corrosion resistance. Accessibility of Spinner allows to provide sewer pipes by trenchless technology. Economical issue is another advantage of technology combination with superior product.
Inventions of the 21-st Century
Therefore, completed cement grain hydration by the KALMATRON® KF-A admixture does not leave agential volume for any acidic reaction.
KALMATRON® is a cement hydration agitator which postpones* the molecular bonding of
Three Calcium Silicate. This results in complete cement hydration during the first 5 to 8 hours instead of 5 to 6 decades!
* - a similar process has been observed with magnetized water for concrete batching
At left and right are SEM photographs and a concrete cylinder made of concrete based on High Alumina Cement (A) as well as a concrete cylinder made of conventional concrete with KALMATRON® (B). Both concrete cylinders represent samples of the groups tested in Dionized Water (H2SO4), in accordance with the protocol of the Redner Test.
Comparing the two SEM photographs, the Integral Surface (IS) of "A" is smaller than the
IS of "B". This presupposes that cylinder "A" will corrode faster than cylinder "B".
While High Alumina Cement provides faster hydration, it also alters the kinematics of deformation in this particular type of composites, resulting in tensional cracks.
Mass loss of "A" is 6 times greater than the mass loss of "B". The change in coloration of "A" could be explained by belite decomposition in sulphuric acid.
