This is the most studied field of concrete corrosion by salts and minerals [1;7]. The visual results of concrete destruction are disintegration of cement rock from aggregate and crumbling. Both of the processes can occur at the same time.
The disintegration of the cement rock from aggregate is a part of the artificial nature of concrete [2], because both of them are opposite by a density, linear coefficients of thermal expansions, modules of elasticity and rupture, water sorption ability, which cause an unpredictable level of durability by incompatibility in terms of temperature expansion also occurs rather often, especially in a climate conditions with frequent changes in ambient temperature and humidity. The crumbling of cement rock is the result of chemical reactivity of the elementary kation’s particles of cement rock with ions of sea water. The products of these reactions are the foreign bodies that cause the manifest in 3 to 5 years in the form of salt spots, angle rounding and cracking that make the structure service life shorter [1].
It is proven that the hardening of concrete depends on the features of the solvate membranes as a hydration product around of cement grains. Generally, these solvate membranes are hydro-sulfate-aluminates and are hydrosilicates of calcium. These membranes are important for equalizing the speed of cement hydration for homogeneity of the future concrete structure. Practically this is approachable by a high speed mixers and molding of the concrete mix by high pressure technology [8]. This concrete is economically unacceptable even for first class civil and industrial buildings.
Therefore, the regular concrete structure might be represented by three types of contacts between cement grainApplying sea sand and sea gravel as an aggregate to a concrete mix causes the more complicated process, that is shown above. Most of the sea salts are fast and completely dissociate with water into the salt solution that might cause the next changes in the process of hardening of cement rock, as follows:
1.Changes of the crystal phase of new growths from the weak salt solution to insoluble crystalline inclusions. This process is described by “carousel” exchange of kations and ion:
+ _
Ca(OH)2 ↔CaOH + OH - dissipation of alite (12)
+ _
NaCl ↔ Na + Cl2 - dissipation of salt (13)
Ca(OH)+ + Cl- + aq → CaOHCl aq [Ca(OH) CaCl2 H2O]; } hydroxochlorides (14)
[Ca(OH)2 CaCl2 12H2O]
Both of the phases are dangerous for durability of concrete under the outside conditions with frequent changes in ambient temperature and humidity.
2. Changes of the hardening speed, because belite solubility is higher in salt solutions than in water, which face a problem of fast growing, small, numerous crystals before forming a cement structure. Dissolubility of belite in salted water is 10 times higher than in top water. That’s why other processes go faster. The speed of formation of the structure depends on the speed of charge exchange.
The exchange of charges in belite is given by (15):
The dissolubility of belite in water and salt solution is calculable by Davise (5;6) equation [17]:
m+n ξs ξ =√ nⁿ (17)
Dissolubility of belite in a water is known [5] as ξ = 0.0019 mole/dm3;
Dissolubility of belite in 10% of NaCl-water solution by (17) is ξ = 0.01 mole/dm3
Therefore, the chlorides intensify early hardening of concrete with extremely tensioned contacts between particles of cement rock. These tensions are the reason for the sudden destruction even of the standard concrete structures on offshore and sea shelf locations.
3. Changes of the directed kinetic consecution of forming the concrete structure from the outside surface in the depth of concrete mass, even in the stochastic process, i.e., the centers of crystallization might appear in and on the surface of the concrete mass at the same time. That becomes the reason of disorganized, i.e. crumbled structure of concrete.
Therefore, the disintegration of concrete structure might be represented by the three consequent stages of destruction of contacts between cement grains, as shown on theFigure 5. The disintegration of cement particles by chlorides, provided by sea sand and sea gravel into concrete mix. Shown is the trigger mechanism of destruction of the concrete structure.
Obviously, both of the descriptions of osmotic oscillator and chemical disintegration of cement structure are two sides of the process named as the “White Death of Concrete”. The farther investigations prove that we are dealing not with a hypotheses, but a readable and controlled process.
Concrete Protection from Salt Corrosion.
When the KALMATRON® KF-SEA composition is mixed with concrete, which contains sea sand and sea gravel, a number of consecutive and simultaneous reactions take place between the components of the composition and between them and cement components as follows:
CaO + H2O → Ca(OH)2 (18)
Ca(OH)2 + NaNO3 →↓Ca(OH)NO3+ NaOH (19)
Ca(OH)2 + Na2CO3 →↓ CaCO3 + 2NaOH (20)
Ca(OH)2 + Na2SO4 → ↓ CaSO4 + 2NaOH (21)
Ca(OH)2 + NaCl2 → ↓ Ca(OH)Cl2+ NaOH (22)
Free calcium oxide of cement forms calcium hydroxide when mixed with water (18). Calcium hydroxide then takes part in exchange reactions with sodium nitrate and calcium carbonate and sulfate, and with calcium chloride, to form low-soluble and hardly-soluble acidulation crystals of hydroxonitrates Ca(OH)NO3 that will continue to grow well after the completion of structure formation of the cement stone, by using free pore water and Ca ions released from the cement stone gel. These crystals have a micro-reinforcing effect on segregation within voids under the effect of temperature, shrinkage and corrosion. Therefore, a primary structure reinforcement framework is formed within the concrete mix as early as at the setting stage. This framework is built up in the direction of mass transfer of a diffusion flow.
Hardly soluble double salts of calcium sulfoaluminate 3CaAl2O3CaSO4•31H20 are crystallized at the same stage. The crystals are in the form of hexagonal syngonite-like structures or a package of parallel laminate with interstices filled with intercrystalline solutions. The density, volume and strength of the entire package depend on density of such solutions. When moisture gets into the interstices, the solutions are diluted, and the package volume increases. Given the conditions in the pore space of concrete, this is the explanation of an exponential decrease in permeability with time during test. If temperature decreases, the intercrystalline solutions break into crystalline hydrates and solutions of residual concentration. The volume of the interstices decreases, and density and strength of structure as a whole increase to ensure a high frost resistance.
During a further maturing stage, low-soluble double salts of calcium nitrochloroaluminate 2CaOAl2O3Ca(OH)Cl2•10H2O are formed on the primary framework in the form of the same hexagonal syngonite-like structures. However, concentration of the intercrystalline solutions is so high that their density does not almost change with an inflow of moisture from outside. High level of molecular bonds is explained by the effect of chlorine ions upon dipole water molecules. This phenomenon is similar to the case where water is magnetically treated before mixing in concrete components to improve concrete strength. The components of the salted concrete mix are in accordance with the following sequence:
Cl2>NO3>SO4 (23)
The chlorine ions from sea salt dissolved in water have a polarizing effect on dipole water molecules to lower the level of molecular bonds of water. Owing to weak bonds in the presence of calcium hydroxide, an alkali group is released into the water to protect calcium against dissolution at the maturing stage:
Tricalciumalumochloride formed as a result of reaction (24) forms hardly soluble solid phases when water is released for simultaneous hydration reactions. The alkali and the internal pore moisture form solutions inhibiting metal corrosion that also have a low eutectic temperature of -126°F (-70°C) at the stage of a stable phase condition of the cement stone. At the stage of unstable phases, owing to weak bonds of water molecules that are depolarized with chlorine ion and weak bonds of the reaction products (24), nitrate ions come to react, and the sequence of these reactions is determined by their inherent chemical activity, alkali level of the solution, and the intermediate reaction product - calcium aluminate - with which the following dissociation reaction is most likely:
This reaction yields a low-soluble double salt of calcium hydronitroaluminate with an increase in pH of the pore fluid. The stability of the reaction [25] is ensured by an almost simultaneous reaction of sodium sulfate. The consumption of starting components for another reaction [26] results in their shortage and in a one-way character of dissociation:
Therefore, if such an electrolyte is added at a concentration that insures a change in solubility of mineral binders without reacting with them, with a subsequent formation of hardly soluble complex compounds - calcium hydrosulfoaluminate, calcium chloroaluminate and tricalcium chloroaluminate from the resulting solution, the overall volume of the crystalline component of the structure increases all at once in parallel with the normal concrete cure (8).
The advantage of KF-SEA complex additive is explained by the fact that, although the rate of formation of double salts is lower than in the case of a single additive (which is due to the consumption of calcium aluminate of the liquid phase for hydration), cement components can react at a lower reaction constant. Moreover, a protracted reaction allows the ion force of free water (which later becomes the pore fluid) to become stronger so as to form saturated solutions form additional double hydrate salts. The use of fillers containing a chloride insures a better use of the potential of alite 3CaO SiO2 C3S. Chloride ions that are still in the liquid phase are products of displacement. They form solvate shells at the boundaries of kation fields, thereby preventing free calcium from leaving the structure-forming reactions. At the same time, nitrate ions accumulate in the free water polarized with chlorine ions to form solutions of increasing ion strength. These solutions will, in turn, accelerate hydration of alite. The manifest, relay-like character of these processes allows alite to develop to a greater extent into a symmetrical three-dimensional conglomeration with isotropic properties.
This allows also the group of belites β2CaOSiO2 (β-C2S) that are lagging in their development in comparison with alite to cause an exponential increase in the group of calcites and silicates that failed to be attached in previous hydration reactions. With further curing of the concrete mix, no sulfoaluminate is formed, and this results in an improved sulfate resistance of concrete, a better strength and frost resistance.
Involvement of electrolytes by sea fillers results in intensification of chemical reactions and a better solubility of cement clinker minerals in water. They also accelerate the exchange reactions. The resulting products of hydrolysis and hydration, which are in the form of crystals and gel, actively coagulate. It should be noted that gel expands due to the absorption of a large amount of water. This enhances adhesion of the aggregate of the mix and results in clogging of pores and compaction of the concrete stone.
Therefore, the relay-like character of the reactions results in rapid formation of a primary framework of acicular crystals of calcium hydroxo-salts at the stage of concrete setting. This framework is overgrown with lamella crystals of calcium sulfoaluminate, calcium nitrochloroaluminate and calcium hydrosilicate. The formation of hardly-soluble crystalline structures raises the density of the cement stone and acts like a micro-reinforcement. These structures reduce permeability of concrete and preserve its compressive properties.
It has been found that the use of fillers containing chlorine ions should be in strong proportion to the respective components of the concrete mix design and in accordance to recognition of the consumption of KF-SEA by test results on local raw materials.
We had got stable test results of compressive strength during 90 days. These tests were provided by the standard concrete mix design with sea fillers. Obviously, every sea-filler from different places has a different salt concentration. That’s why it is impossible to propose the versatile consumption of KF-SEA for every case. Because of this we have to propose the recognition of KF-SEA consumption by testing compressive strength with three levels of additives at 13 Kg/m3, 16 Kg/m3, and 19 Kg/m3. Preferable time of testing at 3, 14, 28 to 45 days and 90 days.
The main goal of KF-SEA testing is the evaluation of the capability of sea sand and sea gravel to be the filler for the concrete mix by comparison with regular control specimens cured in top water, the same cured in salted water and specimens with KF-SEA admixture cured in salted water. Now we have to choose the right criteria for the right application [9]. Actually, the testing under these conditions is the evaluation of concrete resistance to sea salt corrosion with and without KF-SEA admixture. Therefore, the chosen criteria might be:
•Lower than control compressive strength even at 28 days. Later, that data will grow until to target or higher
level. Early strengthening is dangerous in this case, because characterizes the domination of salts’ new
growths and further collapse of concrete structure.
•Flexural strength and resistance to rupture are higher for all of the testing time.
•Sorption ability is close to control specimens.
•Impermeability is much higher than in control specimen.
We recommend the application of KALMATRON® KF-SEA for concrete structures with central and equally loaded structures. The wide spread of this technology is obvious economy and makes great environmental sense because it is straight application of natural resources.
Dr. Alex V. Rusinoff
President and Chairman of “KALMATRON® Corporation”
1. S.V.ALEXANDROVSKY, The creep of concrete. Stroyisdat, Moscow. 1975
2. P.C. KREIJEGER, Inhomogenity in concrete and its effect on degradation: a review of technology, Protection of concrete, Conference of Dundee, Scotland,UK,p.p.31-52 (11-13 September,1990)
3. A.RUSINOFF, The phenomena of osmotic oscillator by absorption of the atmospheric salt solutions by surface layers of exterior building walls. Collection of scientific works. Khabarovsk Railway Engineering Institute, Russia, pp. 59-63, (1988).
4. A.RUSINOFF, Exterior Walls In Extreme Climates, Protection of concrete, Conference of Dundee, Scotland, UK, p.p. 541-547 (11-13 September, 1990).
5. MOSES J. The practicing Scientist’s Handbook. A Guade for Physical and Terrestrial Scientists and Engineers. N.Y. Van Nostrand Reinhold Company.1978.
7. CABRERA JG and LYNDSDALE CJ Measurement of chloride permeaboloty in superplasticized ordinary Portland cement and Pozzolanic cement mortars. Proceeding of the International Conference on Measurements and Testing in Civil Engineering, Lyon, Franc, vol 1, 13-16 September, pp279-291.
8. GOWRIPALAN N., CARBERA JG, CUSENS AR and WAINWRIGHT PJ. Effect of curing on durability. Concrete International, Vol. 12, No 2, February 1990, pp 47-54.
9. LEVITT M.The philosophy of testing concrete. Concrete. December 1985, pp 4-5.
Area of H2O molecular penetration and accumulation into concrete structure from 1 mm to 150 mm. No salts deposits has been observed on the dried cut of concrete specimen.
Area of chloride ions penetration and accumulation into concrete structure. The depth (height) of salts penetration is unlimited. See the dried salt crystals deposits on the dried cut of concrete specimen.
Figure 1. Dried cut of a concrete surface, preliminary saturated by water-salt solution at the bottom of specimens.
A. The coagulation contact particles, separated by dispersed water.
B. Increasig of coagulation during evaporation and water hydration.
C. Consolidation of cement particles and beginning of crystallization from solutions.
A. The passive diffusion of cement particles with ions of chloride. Dispersed water between particles becomes a water-salt solution with high electric conductivity. It proves the electrochemical connection for inversely charged particles.
B. The compacting of cement particles by the attraction of inversely charged kation of solvate membranes and ions of chlorides. The intrusion of ions into membranes and inclusion of ions by kation begins Concrete structure is under compression tension and the compressive strength test result is very high.
C. The disintegration of cement particles by equalized charges of ions and kation. The forces of consolidation are weak at that moment. That's why the expansion of new growths is dominating with pressure at 5 MPa until the next equalization of charges. Concrete structure is under bursting tension and the compressive test result is very low.
A. The passive diffusion of cement particles with ions of chloride and kation KF-SEA additive. Dispersed water between particles becomes a water-salt solution with low electric conductivity. It proves the weak electrochemical connection for inversely charged particles.
B. The compacting of cement particles is provided by coagulation and attraction of inversely charged kation of solvate membrane and ion chloride is weak. The intrusion of ion and inclusion by kation is delayed because of ion-chlorides are weakened by connection with KF-SEA kation additive. Compressive strength is close to the standard concrete.
C. The stabilization of particles by equalized charges of ion-chlorides and KF-SEA kation additive. The low conductivity of that electrolyte and delaying intrusion of ion-chlorides into solvate membrane, force the process of consolidation of new growths. The significance of the data test is stability of characteristics. This is the criteria of durability.
Dr. Alex Rusinoff, Ph.D., S.P.
Application of sea sand and sea gravel as filler into concrete mix is known as a risky technology, because sea fillers contain chlorides, which destroy concrete and rebar in a short time. This type of corrosion has the dramatic name of “Concrete cancer” or “White Death of Concrete”. The impressive thing is the existing of ancient structures such as bridges, tunnels, palaces, temples and roads, which were built from rocks on cement-lime based mortar, containing sea sand and other salted fillers. It was a mortar with long term hardening, sometimes with additive of chicken eggs, and mineral organic binders such as manure. Electro-chemical analyses of the ancient building mortars show that the negatively charged ions of chlorides Cl- are balanced by positively charged kation of minerals such as Ka+, Mg+, Na+, etc.
Unfortunately, this “miracle” of the ancestors works for massive constructions and for homogeneous building materials only. Concrete is not homogeneous; even if concrete were a homogeneous material, we can’t allow to build the huge walls, beams and columns. In other words, we can’t provide a “negative capacity” from minerals against chlorides by the thickness of structure. We developed the admixture to any cementitious mix KALMATRON® KF-SEA that provides stable protection from chlorides with outstanding structural performance.
By conceptual nature KALMATRON® KF-SEA is membrane with selectively organized passing ability for molecules and ions through the “molecular sieve” of artificial minerals. In the present issue we will discuss the principal of the thermodynamic mechanisms of KF-SEA.
Salt and Concrete
Sea water is a complicated solution of minerals such as magnesium, aluminum, zinc, gold, semi-metals, acids, chlorides, alkalis, etc. Everything is harmful for cement. Consistence of chlorides is at 20% to 40%; that is why the chlorides have a more powerful influence on concrete structures than other minerals. This very high concentration of water-salt solution has its own mechanism of crystallization. The artificial nature of concrete hardening has never been in accordance with the mechanism of crystallization of new-growths like salt crystals. Obviously, the reaction of concrete hardening has a different speed and volume that salt crystallization.
The use of sea fillers for preparing a concrete mix creates two incompatible reactions, which are hydration of cement rock by salt water and independent crystallization of salts. These reactions have different speeds, volumes and time of maturity of the final products. Equalization of these reactions and neutralization of crystallization prevents dissipation of cement ingredients as foreign matter and destruction of concrete by separation of the filler’s particles
Distribution of the Salt Ions in the concrete structure
We will describe the destruction of concrete by sea salts under the proposition that concrete is already has salt
ions in the concrete structure. The initial penetration of salted solution into concrete, provided by capillary suction,
diffusion with free water into concrete structure, osmotic penetration, and difference of the temperatures on the
opposite sides of structure. Which factor has the greater influence on penetration of salts into concrete, depends
on various combinations of reasons. But distribution of salt ions into concrete has not random but strong thermo
dynamic law of nature (3).
After theoretical investigations we confirmed them by long term experiments (4). For studying of salt distribution we prepared the concrete cylinders with ø50mm and height of 300mm. After 28 days of natural maturing, we put they bottoms in 10% natrium chloride water solution on the depth of 10 mm. After 14 days we had cut them across the longer side and dried during 6 days. Fig. 1 shows a dried cut of a concrete cylinder that was saturated with 10% of NaCl salt solution at the bottom end. It can be seen that the suction area at the bottom does not contain salts, and an intensive salt release zone is clearly apparent above this area. Obviously, we can see the sieving effect, when a molecule of water accumulates in a bigger capillary space of concrete and can’t move up to the micron size capillary space of the wet gel of cement. Only ions of smallest size and highest kinetic energy, will be able to go through gel and unformed crystalline bodies into concrete.
Definitely, the ions of the salts are accumulated deeper into the concrete structure than molecules of water. Increasing of the concentration of salt causes crystallization. The solidity of salt crystals is 10 times higher than in crystalline bodies of concrete, that’s why increase in the volume of salts causes the destruction of concrete from inside. The depth and square of destruction depend on density and age of concrete at the moment of destroying. The chemical side of these processes consists in dissolution of calcium hydroxide by its transformation to chloride hydroxide.
Figure 2. Apparatus “osmotic box” for monitoring Rusinoff’s Osmotic Oscillator. This is hermetic plastic box with hermetical divisions into two equal volumes by a cement-sand mortar 10mm plate. Both sides of the plate were provided with mechanical indicators with units of measurements 2x10-3 mm. One volume was filled by tap water and the other with a water solution of 20% sodium chloride. The maximum meander of the plate’s central axes is » 0.1 mm. The time of the plate’s semi-oscillations is 8 months.
But, we have also the logarithm for the concentration Ln½Ca½, which is supposed to increase the density
of concrete by filling porous concrete with salt crystals:
μ ln|T| / PVh
Ca = e ; (2)
Wherein:
Vh - remainder of water in concrete after hydration; (cm3);
P - osmotic pressure of Vant-Hoff, (Kg/cm2 ),
which is right during the filling of a porous volume. Salted concrete specimens have a very high
compressive strength at the first stage. Moreover, that concentration grows with reduction of water
Vh for hydration and evaporation in accordance with equation (3):
|μ/mRT + ln|Vf||
Vh = e 0 ; (3)
Wherein:
Vf - whole volume of water in a concrete mix; [cm3]
R - Thermodynamical Gas Constant;
m - mass of KF-SEA per concrete mix; [Kg]
That’s why the chemical potential "μ" is always regressive data:
μ = n/v RT ln |Vh/Vf| < 0; Vh << Vf; μ→0; (4)
Wherein:
n- dissolved moles of KF-SEA; [mole]
Vh/Vf - ratio of reminder and whole volumes of waters;
Despite the laminar characters of all the above shown equations, Vant-Hoff’s pressure is not linear during the whole process. We can see it by figure 1, where the field of Vant-Hoof’s pressure is not flat on the different spots. Concentrations are different on different places and in different stages of the process, which is described by equation (5):
P = μ ln |Vh / Vf| ln |Ca/Cs| ln |T|, →σ (5)
Obviously, we can get a model of Vant-Hoff’s pressure’s physical behavior on different stages of initial Ca and consequent Cs concentrations. Actually, all of the situations with concentrations are processes of equalization by osmotic diffusion.
Before, we have to agree, the consequent concentration is able to get the highest level of as much as 1 (6):
Cs = 1 (6)
which is right for matured or old concrete. So, for this case, logarithmic ratio of initial Ca and consequent Cs concentrations will be less than zero:
Ln |Ca / Cs| < 0; P < 0; (7)
which means, that equation [5] will get a negative sign, which also means that concrete will get a compression tension. Concrete structure has been pre-compressed by inner tensions and the current compressive test result is very high on that moment. This stage is always mistakenly taken as the increase of compressive strength. Farther increasing of the Cs concentration until the crystallohydrate of salt destroys the concrete structure. As a rule, it happens suddenly, after integration of micro-cracks.
Figure 3. Apparatus for monitoring Rusinoff’s Osmotic Oscillator. These are the specimen-holders for monitoring of behavior of concrete cylinders, provided by sorption of 20% water-salt solution from the bottom of the cylinders. Every cylinder was also provided by 16 indicators for monitoring horizontal oscillations and one for vertical.
Another case is the opposite, when Cs represent a low level of concentration, less even than initial one (8):
Ca > Cs; (8)
and then : Ln |Ca / Cs | > 0 ; P > 0, (9)
which means, the concrete structure takes a bursting strength. The steam of osmotic diffusion is directed into the depth of concrete, i.e., from high concentration (outside) to lower concentration (into structure), which is right for initial stage of sucking salted water into the concrete porous system. Or, this also reflects the stage of concrete hardening by hydration of salted water. During the process, the concrete structure takes a tremendous amount of slowly developing micro-cracks until the concrete structure is destroyed completely.
The ideal condition for the durability of concrete is a balance of concentrations from both outside and inside of the concrete structure (10):
Ca = Cs; (10)
and then : Ln |Ca / Cs| = 0; P = 0, (11)
Obviously, dynamically reading the equations [7], [9] and [11] during a period of time will show the character of a cycle of the whole process.
Under condition (11), concrete in a permanently drying condition, will work for around 120 years, as sources (1) say, but after that period concrete will destroyed anyway by the natural drying of the gel of cement rock. But for permanently dampened concrete, it is different.
A remarkable thing we saw was in the Japanese Sea, where the underwater part of the concrete pillar was at the age around 200 years. The ideally smooth and solid surface of the probe is unscratchable, with a compressive strength up to 800 Kg/cm2. Extracted water from a specimen showed the same salt concentration as sea water on a particular depth (see equation (11)). But above that depth, where sea water has lower salt concentration, concrete was destroyed a very long time ago (see equation (9)).
We did the special experiments to approve the theoretical hypothesis about the cycling character of concrete destruction under salt conditions. Figure 2 is the photo with the apparatus of our experimental investigation. This is a hermetic plastic box that is also hermetically divided into two equal volumes by a cement-sand mortar 10mm plate.
Both of the sides of the plate were under control by mechanical indicators with readability of 2x10-3 mm. One volume was filled by the top water and the other with a water solution of 20% sodium chloride. The box was sealed hermetically and data from indicators were taken every hour for 5 days, and subsequently four times a day. The constancy of the temperature and humidity of the room air were also monitored.
We’ve got the phenomenon of the cycling movements of the cement plate, which has been called the “Rusinoff’s Osmotic Oscillator” [5]. During of the first 50 days, the maximum amplitude of the plate central axes had achieved about 0.1mm. This is 10% from the 10mm thickness of the cement plate! For massive constructions, this is the biggest deformation that is theoretically possible even in bending beams.
Teillation’s box” (Fig.2) show the meander of the plate’s central axle as small as 0.37%. This is 27 times less than of the control cement plate. The time of oscillation was 30 days only. This is 8 times less than the time with control cement plate.
During the next 5 months, these amplitudes were reduced slowly until zero. Another test procedure was provided by the investigation of concrete cylinders in the special specimen holders with 17 mechanical indicators for each specimen (Fig 3). The results of both experiments were convincingly approved. The results of these investigations were performed in the Scotland University and published by the Academy of Science in London [4].
After numerous tests, we’ve got the stable result of reducing oscillation’s meanders and the speed of new growths crystallization by the chemical additive KF-SEA into plate’ mortar. This chemical compound has very high chemical potential (positively charged ions’ force) and very low electrochemical conductivity. It means the KF-SEA can’t be involved in reaction of hydration with the standard concrete mix. For this case KF-SEA works like a powerful plastisizer only.
The Cl- ions are perfect conductors for any electrochemical reactions. That’s why KF-SEA works with salted concrete mixes as a stabilizer of structure without developing new growths. KF-SEA is a semi-electrolyte with very low conductivity. KF-SEA becomes a complete electrolyte after mixing with sea salt containing raw materials and works for homogeneous hydration of cement. Therefore, with KF-SEA, the sea salt works as a co-agent in the hardening process.
Kinetic Mechanism of Destruction of Concrete by Sea Salts.
Saying with care, the reason for concrete destruction is combination of over volume of new growths and chemical dissipation of cement structure. This is commonly known and looks clear except the one thing. This is the circular character of the destruction of structures. Commonly known also, is that testing of salted concrete specimens for compressive strength, periodically shows very high or very low test results. Finally, the same group of specimens suddenly shows the falling down of all the structural features at an unpredictable time. We will describe this process apart from the erroneous belief in a leading importance of high compressive strength of concrete against salt corrosion.
Equation (1) is showing the dynamic character of development of any crystalline structure. Obviously, at an early stage, the crystal growing into porous concrete gets a tension "σ" , which is already used by archaeologists for cleaning fossils in water-salt solutions. Extra pressure of salt crystals at 5MPa, grown on the border between fossilized matter and rock, detach them by slices. Concrete structure can resist a crystal’s tension of rupture at 0.55 MPa, i.e. 10 times less. However, increasing of tension in the concrete structure (or porous) reduces integral density:
μ
Dt = --------- ln| Ca| ln |T|; (1)
σ
Wherein:
Dt - integral density of concrete including new growths and concrete structure ( Kg/cm3)
μ - chemical potential of KF-SEA electrolytes dissolved in concrete mix (J)
σ - tension applied by new growths of sea salts (Kg/cm2)
Ca - concentration of KF-SEA electrolyte into concrete (Kg/Kg)
T - temperature of the whole mix (Celsius).
Figure 4. The standard compacting
of cement particles during hardening.
Figure 6. The protection of cement particles by kation-additive, provided by additive of KF-SEA into concrete
mix containing unwashed sea sand and sea gravel.
Figure 5. Disintegration of particles by inter-particles' tensions.
Changes of the crystal phase of new growths from the weak salt solution to insoluble crystalline inclusions. This process is described by “carousel” exchange of kations and ion:
