High Strength/High Performance Concrete (HPC) is characterized as a concrete mix design that sustains controlled batch workability with further adequate resistance to climatic and urban environments after application, i.e., performance durability. There is a multitude of admixtures on the market to achieve HPC features with the functions of densifiers, thinners, retarders, stabilizers, and agitators. All of them are functional substitutes for the natural cementitious gel performance.
KALMATRON® KF-A admixture 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. Decay-hydration reactions result in maximum volume of cementitious paste as a continuous solid phase in which the aggregates are embedded.
Extension of the gel surface classifies KALMATRON® KF-A with admixtures known as Type C – accelerating admixtures, and Type F – water-reducing, high range admixtures (See ASTM C 494).
RHEOLOGICAL ADVANTAGES OF CONCRETE WITH KALMATRON® KF-A
•Reduces shrinkage, 200÷300 micro-strains is a typical result. Just no cracks
•Increases compressive strength by 20 to 35%
•Exothermic heat is lower 30% to 50%
•No flakes, efflorescence, dusty spots, or slid areas
•Water impermeability is 100% starting at 50 mm or 2” concrete thickness
•Highest resistance to chemical and climate corrosions
•Increases frost-resistance up to 35%
•Tensile Resistance is higher up to 40%
•Contains approximately 3% macro and 97% micro pores
CONCRETE APPLICATION ADVANTAGES WITH KALMATRON® KF-A
•Accelerates cure without affecting working time
•Less heat build up when cured in mass. No bleed water
•Mixing up to 5 hours keeps batch revived with insignificant slump reduction
•Mixes are more cohesive and will not separate if vibrated, yet flow better
•Twice lower material loss on shotcrete application with build in one pass
•Early strengthening on 3rd to 7th day with higher compressive strength at 25%
•Metal parts of equipment are cleaner than usual
•Highest adhesion to most known porous materials
•Allows application from -5 ºC to 40 ºC without affecting the set time
•The need for concrete curing membranes is virtually eliminated
•Yield of concrete mix is higher by 3% to 6%
•Reliable “raw compaction” of concrete mix
•Pumpable concrete mix flow with slump at 2 ½ “ to 3”
ECONOMICAL ADVANTAGES OF CONCRETE WITH KALMATRON® KF-A
•Eliminates the use of any known admixtures and supplementary materials
•Setting-Accelerators and Air-Entrainers are applicable due to application
•Does not require curing compounds and heat/cold insulations
•Ready to use on 7th day of natural hardening for any structures except bending structural
elements. They have to be aged with project request
•Doesn’t need to be isolated for liquid containing structures. KF-A itself waterproofs concrete 24
hours after application
•Yield of batch is higher by 3% to 6% which is significant for precast industry
•Reduces labor time on vibrating and flattening by 15% to 20%
•One pass application for precast and stucco industry
KALMATRON® KF- A as an admixture transforms the most conventional concrete mix designs to concrete with stable High Performance features, while the cost is much lower.
A concrete mix contains a lot of structurally useful minerals, which are not used at all since the active agent is water only. Water is not active enough to involve them in hydration and hardening processes. KALMATRON® KF-A admixture provides agitation of cementitious mixes in chain reactions. The gradated solubility of KALMATRON® KF-A components sets up a sequence from first reaction to fourth, if the initial dosage of water is reduced enough and mixing done completely. Otherwise, as practice shows, the whole chain of reactions will be delayed by 30 days. But the final performance of this product will be the same as described below.
1. Dissolution of cement grain by speeded hydration. The stage when standard hydration speed increases due to weakening of molecular tensions of water with electrolytes formed by KF-A. The standard “reactive bawl” of a concrete batch has some potential energy which should be spent on hydration and structure formation. With KF-A part of this energy goes to the electrochemical decay of cement grains and after that on to hydration itself. The results of this reaction are:
• The chemical heat of hydration is lower. The tensional heat of water absorption subsides proportionally as the area of the cement gel surface increases. That means much lower exothermic reaction heat.
• Prolonged equalization of solution concentrations during the mixing and transportation of the concrete
mix give the best compaction, which results in low slump with high workability.
• Also, this retards the shrinkage dynamic in the first 60 days.
• Provides natural increase in structural strength by enhanced compaction.
Similarity to known: This type of reaction may be recognizable in the application of salts with some plasticizer. On the first 28 days it gives a huge increase in strength. But the consequences of such an application after 45 days are recognizable also since concrete gets dusty, cracked, and fragile because the ion-kation exchange is out of control. It means that concentrations of inter porous solutions are really high with immediate ability for self- crystallization before the concrete hardening process begins. That creates opposing tensions in the concrete body. Early crystallization means aging of concrete before maturing.
2. Oxidation of metal containing elements. Involvement of negatively charged artificial minerals provides magnetic reorientation of water dipole molecules and particles of cement grain. Weakening of their relations by reorientation causes ordered rotation with considerable freedom to be involved in the hydration reaction with a greater amount of cement particles. That’s why KF-A has higher effectiveness with lower quality cements. This reaction results in:
• Darker color of concrete because there is no lime emission during drying;
• Up to two times lower exothermic heat emission, since that energy is taken for oxidation;
• As a result of the above, porosity becomes milder in size of development from depth to surface of
concrete;
• Shrinkage is 1 ½ to 2 times lower than conventional;
• Electric conductivity increases because of metal oxidation. In concrete maturity stage it becomes
normal;
• KALMATRON® Concrete behaves as a High Alumina Concrete in respect to corrosion resistance, \
compressive strength, impermeability, and abrasion resistance, i.e., an “ironed concrete.”
• Cementitious paste volume increases by 10% and higher which depends on cement quality. That’s why
it worse cement is better KF-A performance.
Similarity to known: Actually, this reaction is similar to the function of magnetized water. The distinguishing part is that the KALMATRON® KF-A admixture provides a more stable residual polarizing effect. The followers of KALMATRON® KF-A created an admixture which only functions like this with well-ground magnetic materials. Test results are not stable and have never been applied in the field because natural concrete magnetic conductivity is random enough.
3. Colloidation of free molecules of water – the thickening of water by solutions with high concentrations. Since most cement grains are hydrated and the inter porous liquid-vapor part is represented by natural mineralogical cementitious solutions, then:
superficial vapor emission is slower; that reduces shrinkage;
concentration of solutions on the surface and inside the concrete body changes almost simultneously
osmotic pressure is very low and that’s why “hydrothermal” deformations are not significant;
number of pores is lower and different types of pores are fewer, i.e., ordered porosity.
Numerous mineralogical sediments become natural centers of cementitious solutions and densify until
crystallization. Solutions with lower concentrations stay diffuse to the close of the colloid phase in accordance with gradated concentrations. The speed of colloidation is slow and the whole process may take decades. This reaction results in:
• Homogeneity of concrete structure with considerable compaction of concrete aggregates;
• Increase in macro-structural density from 3 to 5%;
• Early strength on third or seventh day;
• Liquid impermeability is 100% in respect to initially targeted type of concrete;
• Oxide film resists rebar corrosion; that is observable by any detector pulled out from a batch;
• Physical resistance to freeze-thaw cycles and cycling drying-saturation types of corrosions because
of better compacted structure and ordered porous structure.
Similarity to known: This reaction is recognizable in natural hardening. The difference is that the KF-A admixture provides structural formation by hardening much faster and relatively more simultaneously from surface to depth.
4. Stabilization of the gel of the cement paste. Obviously, this is a result of naturally growing viscosity of solutions in cement paste. The approximate time of this process is from 7 hours to fourteen months, which is much longer than for conventional cement paste. The longer term of the gel phase’s presence in the concrete body results in:
Growth of micro-structural density;
Dynamic growth of liquid impermeability;
Increase of crystalline containing part by natural drying of cement gel;
Stable and predictable growth dynamic of compressive strength;
Dominant type of continuous porous system up to 97%;
Lower pore suction ability, below 5%, with reduced superficial tensions of saturation;
Creep of concrete is stable and indicative after 91 days.
Concrete batch with KALMATRON® KF-A where W/C=.41; slump 2 1/2"
This concrete is applicable with shotcrete providing high adhesion and waterproofing advantages.
A similar mechanism of concrete improvement can be observed when water treated in a magnetic field is added to concrete. In a magnetic field water molecules loose their attractive-repulsive forces and become oriented on a magnetic pole or electric charge. “Neutralized” molecules of water are much more easily attracted to numerous electrostatic fields naturally contained by cement grains. Hydration of cement is faster and more complete than with untreated water. However, on an industrial scale magnetic water treatment facilities would create environmental and economical disadvantages.
When the hydration reaction is entirely complete, the highest performing concrete rheological features are measurable simply by the density which results from the ingredients’ structural compaction. The petrography analyses in this case show the unusually high contents of a densely integrated cementitious paste.
Fig. 1 shows a hardened cementitious paste with areas like melted and opened shells, which are the hydrated cement grains. The combination of hydration and electro-chemical decay of cement grain results in a maximally densified concrete structure. We never found an intact cement grain but still call it an almost completed process.
The maturation of a concrete batch begins from simple evaporation of excessive water from the surface. For conventional concrete it is the first step for superficial cracking and aging. KF-A added to the concrete mostly contains liquid electrolytes, which have a very slow evaporation speed that helps to prevent not only shrinkage, but allows the formation of macro pores.
THE MODEL OF CONCRETE MATURING
Fig. 3 “Model Of Concrete Maturing” shows the principle of concrete structure formation in the distribution of cementitious phases during hardening time. Obviously, the dominance of the cement gel is preferable there to increase the ratio of micro pores and reduce the self destructive nature of concrete. This is the function of KALMATRON® KF-A.
Below is a description of concrete maturing stages from the surface of evaporation to the depth of gel crystallization. Remarkably, the diameters of capillaries of every phase comprise 4Å of a water molecule, which means that physically densifying the concrete structure alone doesn’t improve water resistance.
CONSUMPTION OF WATER AND CEMENT HYDRATION
Modern admixtures and supplementary materials for the concrete mix are dedicated to improving applicability and concrete rheology. Hydration of cement relies on the amount of water and mixing time only. Relative to cement hydration, all this amount of water and admixtures work as thickeners or thinners of the water-cement solution, which creates concrete structure independently from compaction of aggregates within the cement dough.
No enhancing chemical reactions occur with the hydration of cement grains in this case.
It is known that unhydrated cement grains present a major problem in new concrete structures (Fig. 2). Even the final product of the cement clinker has a lot of foreign inclusions in the frame of the cement structure. During hydration of Portland cement, approximately 25% to 30% of the hydration products form calcium hydroxide, which is also known as free lime. This has no cementitious value by itself. It is soluble in water and is the cause of the powerful conduction of liquids through the concrete body. However, 30% of cement in a concrete mix becomes not only useless, but also harmful for the durability of the concrete structure.
What it takes to hydrate a cement grain is described in the source [1], page 14. “For instance, after 28 days in contact with water, grains of cement have been found to have hydrated to a depth of only 4 m, and 8 m after a year. Dr. Powers calculated that complete hydration under normal conditions is possible only for cement particles smaller than 50 micrometer, but full hydration has been obtained by grinding cement in water continuously for five days.” The size of a regular cement grain is over 90 micrometer.
Concrete mix with KF-A needs 10% to 30% less water than the standard concrete mix design. Nevertheless, workability is even better with lower slump. KALMATRON® KF-A hydrates almost all of the cement grains, which effectively produces good workability at a lower slump of only 2 ½” ÷ 3 ½” (65mm÷90mm). The entire reduced amount of water is used to hydrate all of the cement grains, leading to complete compaction of concrete structure.
There is no extra water added to provide workability and there is no bleed water because all of the water is effectively utilized.
SLUMP AND WORKABILITY
Modern concrete technology controls concrete batch performance by major parameters such as water to cement ratio, properly entrained air by admixtures, and high-range water-reducing admixtures to increase slump. The Slump Test by ASTM C 143-78 “does not measure the workability of concrete, but is very useful in detecting variations in the uniformity of a mix of given nominal proportions” [1, p. 208]. However, over 30% of water from the weight of cement that is poured into a concrete mix is aimed at providing “moveability” for the concrete batch, where compaction of concrete ingredients is a missing feature.
Workability can be defined as ”…the amount of useful internal work necessary to produce full compaction (of concrete mix)” [1]. The test, known as the compacting factor test, was developed at the Road Research Laboratory and is described in BS 1881: Part 2: 1970 and ACI Standard 211.3-75. Therefore, the Workability Test lets us recognize the suitability of the present concrete mix for a particular job, but the Slump Test can only show the complete list of ingredients for the targeted concrete mix design. There are two main distinctive groups for slump recognition
STANDARD CONCRETE MIX
LOW SLUMP The application of a standard concrete mix with low slump from 1” to 2” (25-50 mm) needs less cement fine aggregates and simpler curing because the slump is stable. But it also needs more labor time for vibration and flattening because the workability is very low.
Field of application: roads vibrated by power-operated machines, floors and light-loaded shallow foundations.
MEDIUM SLUMP The application of the same standard concrete mix with medium slump 2” to 4”
(50-100 mm) needs less labor time for vibration and flattening because the workability is really good. But it needs more cement and fine aggregates and takes time to get full slump, which causes insufficient volumes for casting, additional concrete batches, and another extension of labor time for targeted filling of mold and curing to avoid heating, shrinkage, bubbling, cracking, etc. as prescribed for the standard concrete mix.
Field of application: roads vibrated by hand-operated machines; mass concrete foundations; vibrated reinforced concrete slabs, beams etc.
CONCRETE MIX ENHANCED BY KF-A
WORKABLE SLUMP The application of the same concrete mix with 8.5 to 17 Lbs/cu. yd. (5 to 10 Kg/m3) of KF-A varies with slump, needs less water and does not depend on cement quality and fineness of aggregates. With slump ranging from 2 ½” to 3” it has the same workability, casting sufficiency and pumpability. It needs less labor time for vibration and flattening, reduces time for equipment cleaning and eliminates labor time for curing.
Field of application: limitations not known due to the stable nature of HPC performance.
Therefore the most economically effective High Performance Concrete mix with the widest field of application and the best combination of features should provide:
1. Low slump for one step technology of application (precast, stucco, etc.)
2. Workability with stable viscosity of concrete mix until hardening will begin.
3. Early strength that matches targeted compressive strength appears on 7th to 10th day.
4. Liquid impermeability in 24 hours and growth during another 90 days.
5. Slowly growing flexibility during the first 45 days.
The dynamic performance of a conventional concrete mix with KALMATRON® KF-A provides:
• Batch pumpability equals that of a mix containing high cement with medium slump
• Hardening of concrete is dynamically close to that of Cement Type IV concrete mix
• Because of high early strength, concrete performs like a concrete batch with Cement Type III
• In maturity stage, high resistance to chemical and climate corrosions with high liquid
impermeability, performing as a High Performance Concrete.
TRANSFORMATION OF CONCRETE BY KALMATRON® KF-A
The most widely known way to improve concrete quality is increasing the cement content or applying fine-grained cement in an attempt to achieve a higher volume of cement gel. Increasing the cementitious volume of cement paste with KALMATRON® KF-A results in some specific performances of the concrete mix.
Tests were conducted to evaluate concrete specimens with Silica Fume and KF-A for resistance to chloride permeability [2]. We found that the standard test procedure wasn’t suitable because even with water-saturated concrete specimens, the electric conductivity of specimens with KF-A was much higher. What occurred was a functional change of concrete class from “low content alumina cement” concrete to “high content alumina cement” concrete without changing the initial amount of alumina content.
The chloride permeability test procedure is based on the electric conductivity of concrete specimens saturated with water and salt-water solutions. On the diagrams of present tests readings we can see that specimens with KF-A have higher electric conductivity even in a water test, up to 40 times. Even without any salt saturation, concrete with KF-A is more electrically conductive during concrete structure formation, as shown by the given electrochemical activity.
For testing KF-A, we’re asking to keep both control and trail specimens in different baths. Otherwise, test results would be very close for both groups of specimens because even a light water solution of KF-A chemicals improves control specimens significantly by exchange through the curing water in the same bath.
During present testing, researchers [2] noted that some blue film appeared on the surface of concrete specimens with KF-A (Fig. 6). That blue film has a very high electric conductivity due to its metallic nature. Obviously, after complete oxidation of metal-containing elements in concrete, the dominant remainder of metal oxides was dispatched to the surfaces of pores and capillaries with visible sediments appearing on the outside surface.
According to the source [1], measurements of Portland Cement paste in water show higher electric conductivity, up to 21/2 times greater than ordinary Portland Cement concrete.
The difference in conductivity between Portland Cement concrete and both Rapid Hardening concrete and High Alumina concrete is 10 to 15 times.
The cementitious value of concrete is clearly measurable by electric conductivity, based on which quality control and even the field of application can be established. As proven by many applications of conventional concrete with KF-A for corrosion resistance, this is very important for evaluating further concrete durability.
It can also be regarded as a measure of a material’s homogeneity [1]. Obviously, the bigger the volume of the cementitious paste, the higher the homogeneity of the concrete batch. Cementitious paste has the highest electric conductivity and contains moisture longer than other concrete ingredients. In a post maturing concrete age, the gel and liquid phases are responsible for concrete resistance to industrial and climate corrosions. The present test demonstrates that KALMATRON® KF-A is a concrete class-upgrading admixture for conventional and High Performance Concrete that was proven in numerous practical applications.
Capillary-porous forming process
The maturing concrete mix develops a capillary-porous system during cement hydration and gel hardening. Actually, these voids are trace-ways of gas-bubbles from the exothermic reaction of cement hydration. The longer the time of hardening, the longer it takes a bubble to escape from inside the cement dough up to the surface. That is why slump and shrinkage are so high there. Of course the diameter of capillary-porous voids will be higger when the exothermic reaction is longer. This is one of the reasons why retardation of concrete hardening causes structures to crumble and have low resistance to liquid permeability.
The same results occur with fast hardening and high speed strengthening concretes, where bubbles are captured in the cement paste and create inter structural tensions that are generally directed from inside to outside of the concrete body. Further development of tensions causes an increase of micro cracks, with consequent reduction of compressive strength. Resistance to liquid permeability is unstable, resulting in unpredictable and abrupt leakage.
Concrete with KF-A admixture has advanced resistance to liquid permeability 2 to 4 times greater in comparison with control specimens because of its dominantly continuous porosity. It prevents the formation of hydraulic thresholds in the structure and forced migrations of inter porous moisture that increase the sorption ability of water from outside.
The pressure of inter porous gases might be as low as possible, as described by equation (3), which is integrated by three independent functions “n”, “V”, and “t”.
R t nni Vi ti
P = = - R ∫ ndn ∫dV/V∫tdt = 0.5R • (n²o - n²i ) • ( t² o - t² i ) • Ln [Vi / Vo ]; (3) V no Vo to
Wherein:
no; ni – number of cement grains at the beginning and after hydration, respectively; since ni <<no the integral will get a negative sign and finally no → 0;
Vo; Vi – volume of cement gel produced from cement grains at the beginning and after hydration;
t i; to - final and initial temperatures of exothermic reaction, respectively;
R – Gas Constant;
________
ε = √t²i - t²o – entropy of cement hardening, where the volume of cement gel has been represented by equation (4): R 2
R 0.5 • no² • ε
Ln Vi = 0.5 • n²o • ε; or : Vi = e P ; (4)
P
i.e., the volume of cement gel has an exponential relationship with the complex of straightly and inversely related parameters. This is the answer to how to increase the volume of cementitious paste. Since the number of cement grains “no” and the entropy of cement hardening “ε” are constants in equation (4), we have to reduce the inter porous pressure of exothermic gases “P”. KALMATRON® KF-A was developed for this.
Further integration of equation (4) will show a factorial growth of “no!” which in thermodynamic terms means that active surfaces increase during the decay-hydration process. But it will not affect previously accomplished processes.
The mechanism of concrete waterproofing by KF-A
Hydrothermical and barometrical balance between outside humidity and moisture in the concrete subsurface is the best hydroseal, as it works in natural rock. In regular concrete, the free molecules of water are involved in hydrothermical and barometrical migrations in the capillary-porous system of concrete and passively depend on outside changes. Because of this, even the sorption ability has a slowly growing dynamic through time.
During the hydration of cement gases are produced, and as the gases are released they create pores that mark their passage through the still plastic concrete. In normal Portland cement the gas produced is carbon dioxide; this gas must build up a bubble of a certain “critical mass” before it is able to rise to the surface. As a result, the pores formed are large and are known as macro pores. The exothermic reaction provides enough heat for macro pores to be produced and may even be dominant in the porosity forming process.
In concrete containing KF-A and the same cement the gas produced is Acetylene (15) and it is released as soon as it is formed. The result is that the gas bubble is very much smaller and so is the resulting pore diameter, hence the pores are known as “micro pores”. Due to lower exothermic heat, the process of pore formation goes much slower. The smaller pore diameter means higher gas/vapor inter porous pressure, which prevents water from penetrating the concrete.
Conventional concrete contains approximately 70% macro and 30% micro pores. Concrete with KF-A contains approximately 3% macro and 97% micro pores, making concrete far more resistant to water ingress.
We can hypothesize also the dominating presence of “dead-ends” and closed pores. According to the test results, water resistance of specimens with KF-A grows after repetitive cycles of hydraulic pressure, but the structural content of moisture is the same and stable. This is proof of the “structural hydraulic lock” which is a usual property of natural rock characterized by superficial moistening only.
Further development of equations (2) and (4) results in the marvelous mathematical picture of a perfect concrete structure matrix. KALMATRON® KF-A makes that picture closer to reality.
REDUCTION OF CONCRETE CORE TEMPERATURES WITH KALMATRON® KF-A
The temperature of concrete delivered to a site in hot weather should not exceed 29°C (85°F). Cements with a limited rate of heat evolution are known as Portland Cement Type IV, Portland blast furnace Cement Type P and IP with a specific surface of about 320 m2/Kg and heat of hydration of 300 Joules per gram (80 cal/g). These cements, developed for massive concrete structures such as dams, have low initial cracking. Early strength of concrete with these cements is very low but the ultimate strength is unaffected.
According to research [2] of core temperatures for a hardening concrete mix, KALMATRON® KF-A provides a noticeably lower concrete core temperature of cement hydration in concrete mix. The conclusion is based on a reduction of exothermic temperature in the concrete mix with KF-A shown in Fig. 9.
At 1000th minute we can see the drop of tempe-rature to 5.25°C (41.9°F) relative to the control specimen. This is about 25% from the highest exothermic peak. For the trial specimen itself the readings range from 31.5°C (88.7°F) to 27.75°C (81.95°F).
For the control specimens these figures range from 33°C (92°F) to 30.5°C (86.9°F). This is significant entropy for such a process as the hydration of cement in a sampling volume.
Compared with control specimens in the same time frame, the temperature of specimens containing KF-A is more than twice as low.
The low heat feature is achieved by limiting lime content after correction for lime combined with SO3. The limit is:
CaO
------------------------------------------------------------- < or = 1 (6)
2x4(SiO2) + 1x2(Al2O3) + 0.65(Fe2O3)
The heat of hydration consists of the chemical heat of reactions and the heat of eater absorption on the surface of the cement gel formed during the hydration process. These processes are consequent.
In the first hours of hydration regular cements give heat indication, up to 500 joules per gram (120 cal/g). The heat of absorption is approximately 25% of the summary heat indication, which is relevant to the current measurements mentioned above.
With some delay, the heat of absorption will dominate until the final setting time. The delay is explained by the difference between the high heat energy of cement hydration and the low heat energy of absorption is the entropy of concrete structure formation. Obviously, KALMATRON® KF-A reduces entropy by reducing hydration heat emission that equalizes both reactions' speeds.
FORMATION OF CONCRETE STRUCTURE WITH KALMATRON® KF-A
The next equations are examples of the most probable reactions of KALMATRON® KF-A with a concrete mix during different stages of structure formation. However, abundance of water will cause discontinuance of (11), (12) and (17) reactions with apparent retardation of effectiveness until the concrete batch naturally desiccates after 30 days. That is why for KF-A application we recommend less water to produce a workable concrete mix.
Free calcium oxide in cement forms calcium hydroxide when mixed with water (7). 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 acicular crystals of hydroxonitrates Ca(OH)NO3 (9) that will continue to grow well after the complete formation of the cement stone structure 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 effects of temperature, shrinkage and corrosion. Therefore, a primary structure reinforcement framework is formed within the concrete mix as early as 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 x31H20
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 inters crystalline solutions. The density, volume and strength of the entire package depend on the 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 spaces of concrete, this explains the exponential decrease in permeability with time during tests. If temperature decreases, the intercrystalline solutions break into crystalline hydrates and solutions of residual concentration. The volume of the interstices decreases while the density and strength of the structure as a whole increase to ensure high frost resistance.
During a further maturing stage, low-soluble double salts of calcium nitrochloroaluminate 2CaOAl2O3Ca(OH)Cl2 x10H2O are formed on the primary framework in the form of the same hexagonal syngonite-like structures. However, the concentration of inter crystalline solutions is so high that their density does
not change with an inflow of moisture from outside. The great number of molecular bonds is explained by the effect of chlorine ions upon dipolar water molecules. This phenomenon is similar to when water is magnetically treated before mixing concrete components to improve concrete strength.
Adding metal oxide ions to compounds dissolved in water has a polarizing effect on dipolar water molecules to lower the number 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 (13) 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 ºF (-70 ºC) when the cement stone is in a stable phase stage.
At a stage when phases are unstable, owing to the weak bonds of water molecules that are depolarized with chlorine ions and weak bonds of the reaction products (8), nitrate ions react, and the sequence of these reactions is determined by their inherent chemical activity, the alkali levels 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 hydro-nitro-aluminate with an increase in pore fluid pH. The stability of the reaction (16) is insured by an almost simultaneous reaction of sodium sulfate. The consumption of starting components for another reaction (10) 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 parallel with normal concrete cure.
The advantage of complex additives 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 from additional double hydrate salts.
Calcium electrolytes containing calcium accelerate hydration and hardening of silicate phases of cement owing to a higher probability of formation of three-dimensional germs of a new phase. These electrolytes also disperse the products of hydration through dissociation with anion-kation groups:
Ca(OH)2 + Na2CO3 → CaCO3 + 2Na+ + 2OH- (21)
The above-described processes insure a high hardening rate and a fast rise of concrete strength. The use of KF-A additive insures a better use of the potential of alite 3CaOSiO2C3S. Ions of electrolyte that are still in the liquid phase are products of displacement. They form salvation 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 the 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.
Involved Na+ and SO- also participate in exchange reactions similar to (13). However, it should be noted that these components used as herein disclosed decelerate dissociation of ions because of accumulation of alkali in the aqueous solution in the presence of calcium hydroxide.
This allows the group of belites β2CaOSiO2 x (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.
As the components causing the formation of calcium sulfoaluminate are well soluble, and sulfate ions are present in the solution at a high concentration after displacement, the aluminate available in the system is fully bound into sulfoaluminate during the setting of the structure. With further curing of the concrete mix, no sulfoaluminate is formed, and this results in an improved sulfate resistance of concrete, lower shrinkage, a better strength and frost resistance.
Adding electrolytes results in intensification of chemical reactions and a better solubility of cement clinker minerals with 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 the clogging of pores and compaction of the concrete stone.
It should be noted that the presence of lime-based elements in cement improves the isotropy of a concrete structure. It is known that a scatter of test results is mainly associated with, and depends on, ambient temperature and mixing water temperature. These temperatures affect the rate and completeness of the above-described reactions. Also, it
stabilizes the local temperature field of the mix during the lime based elements quenching. A stable quenching reaction is insured by making a specific choice of particle size and moisture content of those elements and also of the water/cement ratio.
Therefore, the relay-like character of the reactions results in the rapid formation of a primary framework of acicular crystals of calcium hydroxo-salts at the stage of concrete setting. This framework is overgrown with lamellar 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 the permeability of concrete and preserve its plastic properties.
RESISTANCE OF CONCRETE WITH KALMATRON® KF-A TO CORROSION
Resistance of concrete to chemical corrosion depends on its liquid and gas conductivity and dynamic wetting ability. Liquid-gas conductivity can be determined by evaluation of macro and micro pores, where a domination of micro pores is preferable. The dominance of micro pores in the cement stone gel with diameters of 15 Å provides absolute liquid-gas impermeability by high inter porous pressures of gases and vapors as the products of concrete batch hydrothermic reactions.
KALMATRON® KF-A as an admixture to concrete mixes provides stable resistance to the chemical corrosion of aggressive liquids and gases. Due to increased cementitious gel because of KF-A reactivity, the concrete body obtains 97% micro pores, which are the best hydraulic lock in itself. Almost complete hydration of the cement grains before concrete application gives no chance for wetting conductivity.
Therefore, the most chemically resistant part of the concrete structure is the cementitious stone gel. We have excellent results of KF-A application on the floor of a zinc plant, where the cementitious part of the concrete was intact after one year but the aggregate was eaten up by the sulfuric acid, and that floor looked like a honeycombed surface (Figure 12).
It was recommended to change the porous aggregate to a more durable type.
We have also the results of comparative applications of concrete with KALMATRON® KF-A and High Performance Concrete (HPC) made with High Aluminum Cement, where after nine months the aggregate above the deteriorated HPC is exposed (Fig. 13).
Products were applied to the floor of an acid room where electrolysis occurred with solutions of 30% sulfuric acid and copper sulfate. This photo was taken after 9 months. There is the intact surface of concrete with KF-A (above) and the deteriorated surface of HPC with the filler appearing.
HP CONCRETE AS IT IS
What happens if we pour some “oil” into the concrete batch? Obviously, slump and workability will be great, and even the initial properties of concrete will exceed expectations, but retardation of hydration will occur and the final concrete structure will be fragile, or became fragile under cycling temperature/ moisture or chemical corrosion. We can observe the same effect with other hydration retarders such as:
•Super fine fillers (fly ash, sandy dust, volcanic dust, etc.).
•Soluble organic fillers (kaolin, lignite, etc.).
•Plasticizers based on organic soluble minerals (lignosulfates).
•Premixed accelerators for hardening, which need much less time than
required for hydration.
•Organic retarders of hardening which prevent hydration itself.
•Any “crystal growers” based on “fast blowing minerals.”
On the pictures shown at right are the comparative tests results of traditionally enhanced concrete mix designs with regular concrete mixes transformed to High Performance Concrete by KALMATRON® KF-A. Twice bigger looses of aggregates are obvious with control specimens.
Most concrete features depend on the volume and speed of hydration of the cement grain. High Performance Concrete must be designed with a maximum of rheologically uniformed ingredients to allow the performance of natural materials’ properties. The cementitious part should act like glue among natural aggregates. KALMATRON® KF-A is designed to enhance the natural performance of cementitious paste, its volume and original properties.
KALMATRON® KF-A was tested, specified, and applied for structures that come in contact with aggressive media, such as ammonia, alkalis, sugar, sulfates, chlorides, sea-water, and distillate petroleum products. Other fields of successful application are sewage systems, zinc plants, uranium mines, food processing plants, wineries, sea structures, airports, roads, etc.
Controlled setting time, high compressive strength, absence of cracks, high tensile and flexural strength, impermeability, sulfate and alkali resistance, frost resistance and low labor efforts for preparation and use - those are the main characteristics of the concrete mix with KALMATRON® KF-A.
It is proven that KALMATRON® KF-A as an admixture to concrete mix provides stable high-cementitious effects on different stages of the forming concrete structure; it can’t be identified otherwise than the performance of cured High Performance Concrete.
Dr. Alex V. Rusinoff
President and Chairman of “KALMATRON® Corporation.”
2. S.L. BAKOSS, R.SRI RAVINDRARAJAH, H. KINCSES, Investigations into the effects of KALMATRON admixtures on concrete properties, UTS Centre for Built Infrastructure Research, University of Technology, Sydney 2000.
3. Dr. R. Sri Ravindrarajah, H. Kincses, and Professor S. L. Bakoss, A NEW SHRINKAGE CONTROLLING ADMIXTURE FOR STRUCTURAL CONCRETE, Second Asia/Pacific Conference on Durability of Buildings Systems: Harmonized Standards and Evaluation, Bandung, Indonesia, 10-12 July 2000
5. Graham Vankan “ KALMATRON, “On Solid Ground Limited”, New Zealand, 2002
6. Dr. 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).
7. Dr. A.RUSINOFF, Exterior Walls In Extreme Climates, Protection of concrete, Conference of Dundee, Scotland, UK, p.p. 541-547(11-13 September, 1990).
8. T.S. Do Minh Dgo. XU LYCAT, 2001, Vietnam
9. T.S. Do Minh Dgo. THONGTIN KINH TE, KHOA HQC KY THUAT, 2001, Vietnam
10. Dr. Robert Usher. METALLURGICAL INSPECTION REPORT Examination of Concrete Samples, -Ex Pasminco, Port Pirie, Australia, April-July 2001.
11. P.C. KREIJEGER, Inhomogeneity 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)
12. MOSES J. The practicing Scientist’s Handbook. A Guide for Physical and Terrestrial Scientists and Engineers.
14. 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.
15. 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.
16. LEVITT M. The philosophy of testing concrete. Concrete. December 1985, pp 4-5.
KALMATRON®KF-A FOR HIGH PERFORMANCE CONCRETE
1. Inter crystalline containing liquids of mineral solutios
2. Matrix of cement gel (paste) with pores diameter 15Ǻ
3. Area of primary ettringite formation with pores diameter 30Ǻ
4. Area of alite-belite maturing and micro-capillary system with pores 30Ǻ
5. Ordered crystalline structure with pores 500Ǻ
6. Regular capillaty-porous structure with pores at 500Ǻ to 10,000Ǻ
Figure 4. "SHOTCRETE TECHNOLOGIES" Inc.
did an emergency repair project for the CO D.O.T. on I-70 with KALMATRON® KF-A.
The shotcrete was applied with slump 2.5" or 64 mm, the temperature of concrete mix in the hopper was lower than outside temperature by 8 F or 4.5C.
LIQUID IMPERMEABILIRY OF CONCRETE WITH KALMATRON® KF-A
Pore blockers are very popular and people use this term for concrete impermeability. But the problem with concrete is that it is not a homogeneous material and to add something else into its body means to multiply those problems. Some product applied on or mixed with concrete has the ability to clog pores by growing into them like foreign crystals. Nobody knows about the speed and volume of crystallization of those crystals and what the rheology of these crystals is and how it will work for linear extension under cycling hydro-thermal conditions. The thickness and mass of the concrete structure are crucial factors for a foreign pore blocker.
Impermeability of the Concrete Microstructure
Since the smallest diameter of a pore even in cement paste is 500Ǻ to 10,000 Ǻ and a molecule of water has a diameter of 4 Ǻ only, concrete leaks like a sieve. So, what
kind of pore blocker should be used to fill up pores from at least 500 Ǻ to 4 Ǻ, which is 125 times? Therefore, a pore’s diameter is not a parameter for liquid impermeability but a function of pore gradation and viscosity of inter porous solutions, wherein:
the pore gradation should be as low as possible to reduce hydraulic thresholds and tensile tensions;
the viscosity of inter porous solutions should be high enough for water thickening but not for conductivity.
Impermeability of the Concrete Macrostructure
The liquid impermeability of concrete structures is evaluated by measuring hydraulic pressure applied to a concrete specimen until resistance is lost. After that we can mark water resistance as W2; W4; W6, etc. in accordance with manometer gradation. Therefore, the indication of any improvement relates to a specified level of impermeability. For example, if water resistance of concrete achieves 100% for a specimen with W2, it is not impermeable to a higher hydraulic pressure as opposed to a specimen with W4 resistance. Waterproofing concrete results in its ability to keep constant the mass of water contained under hydraulic pressure with stable indications of density and compressive strength. Obviously, the surface of this concrete will have different capillary suction depth owing to the degree of wetting as described by the Juren formula:
2U• Cos q
h = ; (1)
r •p • g
Wherein: “r” is the radius of capillary, “p” is the density of liquid, “g” is the acceleration of gravity, “Cos q” is degree of wetting, and “U” is a rate of evaporation. Suppose that the radius of the capillary is changed from the depths of the concrete mix to the surface of evaporation:
ri 2U• Cos Q 2U•Cos q ri h = ∫ d r = Ln > or = 0; (2)
ro r •p • g p • g ro
which simply and encouragingly shows that minimizing the difference between the radius of capillaries in the center and at the surface of the concrete structure
(dominantly continuous porosity) increases water impermeability.
Figure 11 shows comparative test result for shrinkage evaluation for concrete with KF-A and Silica Fume. The difference in shrinkage dvelopment was lower for concrete with KF-A by almost two times.
Figure 11. Development of shrinkage for KF-A concrete and concrete with Silica Fume.
Application of KALMATRON® KF-A to concrete structures in chemically complicated environments is an enturely different filed. We found a few technologies to prevent concrete from these solutions. One of them is implanting acids and salts solutions into concrete batch and has been the most successful.
We have measured inter structural tensions, moisture, and temperatures with a combined indicator, shown at right. Most tensions are higher than concrete resistance to rupture.
Slump 2 1/2" or 6.35 cm
Slump 3 1/2" or 8.90 cm
Slump 5" or 12.70 cm
SLUMP IS ZERO
And this batch is workable and pumpable with KF-A.
Figure 5. Comparative testing of concrete electric conductivity. The current in KF-A dosed specimens is higher than in specimens with Silica Fume.
Figure 6. Chloride penetration test specimen after completion of test. The blue colored substance appeared after specimens dried. This is solid film of Tetraculcium Aluminoferrite deposits [2]. p. 20; p. 29.
Figure 7. Waterproofing of water tanks by shotcrete with KALMATRON® KF-A.
Figure 8. Concrete mold made with KALMATRON® KF-A passed a 15- day test under 70 PSI hydraulic pressure, or 5 At.
The effective thickness of tested concrete between injector (plastic pipe) and bottom of concrete mold is 2" or 50 mm.
The most simple and convincing test that was ever done.
Analogue to the Figure 8 where three concrete molds made with KALMATRON® KF-A passed test successfully.
First mold (from left) made with effective thickness 1/2" or 13mm. Second mold made with effective thickness 1" or 25 mm, and third mold with 1 1/2" or 38 mm.
The temperatures on air 88.2 ºF or 31.2 ºC and into concrete batch 77.5 ºF or 25.3 ºC differences at 10.7 ºF or 5.9 ºC. It is proven the bigger volume of concrete mix the more effective heat reduction.
Figure 10. The magnified crystals of Tetracalcium Aluminoferrite deposited into concrete after 3 months. Formed by KF-A, new grows of crystals provides highest protection from chemical corrosions [10].
Figure 12. Acid drip area where the aggregate corroded down under the KF-A concrete cement matrix.
Figure 13. The comparative application of regular concrete with 7.5 Kg/m3 of KALMATRON KF-A next to High Performance Concrete based on High Alumina Cement.
a). Trial and control specimens are after 90 days into 25% of sulfuric acid solutions.
b). Control Quartzite concrete specimen had weight loss of 2.5% after 90 days in sewage tank.
c). Trial Quartzite concrete specimen with premixed 7.5 Kg/m3 KF-A had weight loss of 1.4% after 90 days in sewage tank.
Figure 14. a, b, c.
Unique application of KF-A to repair a clinker kiln foundation: the concrete mix with KF-A admixture was applied in an environment with a temperature of 185ºF (85ºC) with perfect adhesion and without cracks.
2 1/2" slump KALMATRON® KF-A concrete 32 MPa delivered to a 40(m) height. No bleeding of water, no cracks, with 25% higher compressive strength.
Concrete with KALMATRON® KF-A is applied by shotcrete technology for waterproofing underground structures.
KALMATRON® KF-A is applied for waterproofing and durability of concrete pond as a Marin environment for Polar Bear.
KALMATRON® KF-A is applied by shotcrete for waterproofing of vinery caves.
Reduces shrinkage, 200÷300 micro-strains is a typical result. Just no cracks
