Influences of Silica Modulus (SM) and Lime Saturation Factor (LSF) to the Hydraulic Cement Alternative Properties 1- INTRODUCTION The chemical, physical and mineralogical behavior of raw-mix considerably influences its burn ability and reactivity. The characterization of raw-mix is essential for achieving suitable design of the raw-mix and better quality of cements hydraulics alternative. The silica modulus has especially great influence on burning process and on some cement features. The lime saturation factor is the ratio of calcium oxide presented in the clinker to potential possibility of its binding in most basic compounds. The reaction sequence during raw-mix calcinations, with the formation and decomposition of raw materials, in turn, get transformed into intermediate phase. This paper attempts to highlight the burn ability and reactivity of raw-mix and its effects on the behavior of cement hydraulics alternative
2- GENERAL Materials used in this research, such as limestone powders, burnt clay and trass (pozzolanic materials), are obtained from of West Java Province. The mix proportions of cement hydraulics alternative are conducted with three component system methods consisting of limestone, burnt clay and trass that are shown in Table 1. All proportions are kept in percent weight and the burning process temperature is up to 1000°C.
Table 1. Cement hydraulics proportions [1]
3- BURNABILITY AND REACTIVITY [2] The burn ability of raw-mix has been a matter of great importance in cement technology. The burn ability of cement raw-mix conceptually denotes the amount of mass transferred from its constituents with ease or difficulty to the clinker phases. The burnability factor can be calculated as
BF = LSF + 10 SM – 3(MgO + Alkalies)
(1)
The reactivity of raw-mix is defined by the overall rate of chemical reactions among the represented constituents of raw-mix, attained on burning it at a certain temperature for a certain time Rm = f (T,θ). The reactivity of raw-mix can be determined from the chemical composition and sieve analysis of the raw material and sieve analysis of insoluble residue. An empirical equation proposed to determine raw meal reactivity may be written as :
The Lime Saturation Factor used for kiln feed control. When LSF approaches unity, the clinker is difficult to burn and often shows excessive high free lime contents. A clinker showing LSF of 0.97 or higher approaches the threshold of being over limed where in the free lime content could remain at high levels regardless of how much more fuel the kiln operator is feeding to the kiln. The Lime Saturation Factor can be calculated as:
Large variation of Silica Modulus in the clinker can be an indication of poor uniformity in the kiln feed. Changes in coating formation in the burning zone, burn ability of the clinker, and ring formations within the kiln can often be traced to changes of Silica Modulus in the clinker. As a rule, clinker with a high Silica Modulus is more difficult to burn and exhibits poor coating properties. Low Silica Modulus often lead to ring formations in cement. Silica Modulus can be calculated as:
Total alkali content in terms of sodium oxide is calculated from the loss free analysis: Total as Na2O = Na2O + 0.658 K2O
(5)
Factors Affecting Burn ability and Reactivity The following are the important parameters which considerably affect the burn ability and reactivity of raw-mix. Raw-mix mineralogical & chemical composition. Hydraulic cement alternative raw-mix represents a polymineral and polydispersive mixture whose composition can vary within a wide range due to the characteristics of raw materials used. The chemical composition and physical properties of raw material are shown in table 2 and 3.
Raw-mix parameter/characteristics range and effects. Raw-mix constituents consist of four main oxides CaO, Al2O3, SiO2, and Fe2O3, in conjunction with the minor volatiles (K2O, Na2O, SO3) and non volatiles (MgO, Ti, Mn, Sr, Cr). Each component of raw-mix has individual and combined (SM and LSF) effects on its burnability and reactivity, which is illustrated in Table 4. Tabel 4. Raw-mix parameter/characteristics, range and effects [3]
4- KILN TEMPERATURE PROFILE It might be worthwhile to have an idea of specified zones to give a clear picture of the reaction sequence in burning cement raw-mix. The zones are conceptually defined by the temperature ranges and reaction profiles shown in Table 5. Table 5. Zones defines by temperature ranges and reaction profiles [3]
On increasing the holding time, the following changes may be observed 1. C3A content decreases and C4Af content increases. 2. C2S decreases and C3S increases. 3. Higher mechanical strength at later ages and lower at early ages. 4. Heat of hydration at early ages decreases, 5. Unburnt clinker produces high quality cement even in the presence of high CaOf
Minimum burning temperature ˚C = 1300 + 4.51*C3S - 3.74*C3A - 12.64*C4AF
Understanding Clinker Liquid Phase Liquid phase LP = (1.13*C3A)+(1.35*C4AF)+MgO+K2O 23.5 ˂ LP ˂ 28 Clinker liquid phase or clinker melt is the fraction of the kiln feed that melts between the upper transition and the burning zone. The liquid has a critical role in clinker nodulization, as well as clinker minerals development and properties. Without the presence of liquid, the conversion of C2S and free lime to C3S at normal clinkering temperatures would be almost impossible .Plant chemists and kiln operators are usually more concerned with the amount of liquid present rather than with the rheological properties (fluid properties, such as viscosity) of the liquid, although the latter is much more important during the clinkering reactions than the former. Amount of liquid phase If the raw mix consisted of only four oxides-CaO, SiO2, Al2O3, and Fe2O3, it would start melting at 1,338degrees C (2,440degrees F), the so-called eutectic temperature (the lowest melting temperature of a system) for the system C-S-A-F. At the eutectic temperature, the liquid composition is 55% CaO, 6% SiO2, 23% Al2O3, and 16% Fe2O3. Such composition is saturated in lime and unsaturated in silica. Therefore, it is aggressive to refractory products containing silica or silicates in their composition. Industrial raw mixes contain impurities, such as MgO, Na2O, K2O, and SO3. At certain concentrations, these impurities reduce the eutectic temperature of the system to 1,280degrees C (2,336degrees F), thus promoting earlier clinker formation. These oxides act as fluxes (substances that reduce the melting temperature of a system) in the kiln, forming liquid as far up as the calcining zone.
Formulas used to compute the amount of liquid at any given temperature usually take into account these minor oxides. For most commercial clinker, the amount of liquid phase in the burning zone varies between 23% and 29%. Higher values can be damaging to most refractory bricks in the absence of a stable coating. As the brick is infiltrated and saturated with liquid, its elastic modulus (the ratio between stress and strain) increases, as does its tendency to chip off. The tendency toward coating formation or the coat ability of the clinker increases with the amount of liquid. However, more coating does not necessarily mean better coating. Coating refractoriness, texture, and stability are far more important than the amount of coating deposited on the lining. A good example is the thin but stable coating in a white cement kiln, where the silica ratio of the raw mix is more than five and the C4AF is zero. Importance of the liquid phase The most important clinker mineral, C3S (alite), requires the presence of liquid for its formation. In the absence of liquid, alite formation is extremely slow and would render commercial clinkering impossible. This explains why alite is formed essentially in the burning zone, where the amount of liquid is at a maximum. To understand why alite formation requires liquid phase, one must first understand the alite formation sequence. First, C2S and free CaO dissolve in clinker melt. Then, calcium ions migrate toward the C2S through chemical diffusion. Finally, the C3S is formed and crystallized out of the liquid. Without a liquid phase, the diffusion of Ca ions towards C2S would be extremely slow, and that of C2S almost impossible at commercial clinkering temperatures. It is important to mention that Na2O and K2O decrease the mobility of Ca ions, whereas MgO and sulphates increase it considerably. This is why the addition of gypsum to the raw mix promotes alite formation. Similarly, the addition of metallurgical slags to the raw mix promotes clinker formation. Fluxes, such as calcium chloride, feldspars, and slags should not be confused with mineralizers, although both promote clinker formation. Mineralizers are usually transition metals such as copper, lead, or zinc, which reduce the amount of energy required for clinker silicates to form. Properties of the liquid phase Temperature has the most pronounced effect on liquid-phase viscosity. Increasing the burning temperature by 93degrees C (199degrees F), reduces liquid viscosity by 70% for a regular Type 1 clinker. This simple fact explains why hotter-than-normal temperatures are beneficial to clinkering yet potentially harmful to the refractory lining MgO, alkali sulphates, fluorides, and chlorides also reduce liquid-phase viscosity. Extreme caution should be exerted when insufflating calcium chloride into the burning zone as a way to reduce alkali in the clinker. The injection of sodium carbonate into the burning zone also is detrimental to the refractory lining. Free alkali and phosphorus increase liquid-phase viscosity, but this effect is offset by MgO and SO3. Only clinkers with sulphate-alkali ratio lower than 0.83 and low MgO would experience the negative effects of high liquid viscosity. The liquid-phase viscosity increases linearly with the alumina-iron ratio. For a given burning temperature, high C3A clinkers tend to nodulize better than low C3A clinkers. Moreover, the liquid phase is considerably less damaging to the refractory lining when the liquid is viscous. Another important property of the liquid phase is its surface tension, or its ability to "wet" the lining. The surface tension has a direct impact on clinker fineness, coating adherence to the lining and clinker quality. High surface tension values favor nodule formation and liquid penetration through the nodules. The resulting clinker contains less dust (fraction below 32 mesh) and lower free lime content. A liquid phase with high surface tension has less tendency to wet the brick surface, therefore reducing clinker coat ability or adherence to the lining. Alkali, MgO, and SO3 reduce liquid surface tension, as does temperature. Sulphur and potassium have the strongest effects, followed by sodium and magnesium. Therefore, MgO, SO3, and K2O are good coating promoters. Conclusions Although the amount of liquid phase in the burning and transition zones of the kiln is important to clinker formation and brick performance, the rheological properties of the melt are even more important. The rheological properties of the clinker melt control parameters, such as clinker mineral formation, clinker coatability, clinker fineness, cement strength, and refractory depth of infiltration. It is then very important to keep fuel and raw materials properties and flame temperature as steady as possible. Whenever introducing drastic changes in raw material or fuel properties, the refractory lining must be changed accordingly to meet the differences in clinker
coat ability and burn ability. This proves particularly true when adding slags, kiln dust, or solid wastes to the kiln.
The Importance of Cement Raw Mix Homogeneity On the burning process Cement quality is typically assessed by its compressive strength development in mortar and concrete. The basis for this property is well-burned clinker with consistent chemical composition and free lime. There are only two reasons for the clinker free lime to change in a situation with stable kiln operation and fuel ash: variation in the chemical composition of the kiln feed or variations in its fineness. Variations in fineness depend on possible changes in raw materials or in operation of the raw mill. Variation in chemical composition is related to raw mix control and the homogenization process. To ensure a constant quality of the product and maintain a stable and continuous operation of the kiln, attention must be paid to storage and homogenization of raw materials and kiln feed. This article discusses the role of raw mix control and the homogenization process, assuming the raw materials and fuel ash do not vary and the raw mill operation is in full control. Suggestions are made on methods to improve homogenization.
Homogeneity and burn ability Before discussing the effects of homogeneity, let's take a general look at the transformation of raw materials into clinker. The process of clinker formation is described in Figure 1. The transformation :concludes with the primary clinker phases Alite: Impure tricalcium silicate, generally termed C3S Belite: Impure dicalcium silicate, normally termed C2S Aluminate: Tricalcium aluminate, C3A Ferrite: Nominally tetracalcium aluminoferrite, C4AF The amount of the clinker minerals formed is determined by 1) the time and temperature treatment of the mix, and 2) the overall chemical composition of the kiln feed. If the pyroprocessing time is too short or the temperature too low, combination of the raw material components may be less complete .and some free unreacted lime will be present
Conclusion The homogeneity of feed chemical composition and fineness has an important relationship to fuel consumption, kiln operation, and cement performance. Reacting to in homogeneity by burning harder results in increased fuel consumption, possible kiln buildups due to increased alkali and sulfates, clinker with low porosity, large alite, poor nodulization, and variation in alkali sulfate content. And also may result in cement with increased water demand, decreased early strength, and abnormalities in setting behavior. On the other hand, reacting to variations in feed by improving its homogeneity will avoid these difficulties and produce more uniform clinker, and therefore cement with more uniform .performance characteristics :Suggestions to improve homogenization include When stacking raw materials, stack more reclaimed layers to promote blending efficiency. The higher the number of layers, the better the homogenization. •
In large, continuously operating raw meal silos, keep the silos full to maintain effective blending. •
To 700°C Water is lost from clay minerals. Dehydrated clay recrystallizes. Some reactive silica may displace CO2 .from CaCO3
700-900°C As calcination continues, free lime increases. Calcination maintains feed temperature at around 850°C. .Aluminate and ferrite form
900-1,150°C .Reactive silica combines with CaO to begin stages of C2S formation
1,150-1,200°C When calcination is complete, temperature increases rapidly. Small belite crystals form from .combination of silicates and CaO
1,200-1,350°C .Above 1,250°C, liquid phase is formed. Belite and free CaO form alite in the liquid
1,350-1,400°C .Belite crystals decrease in number, increase in size. Alite crystals increase in size and number
Cooling Upon cooling, the C3A and C4AF crystallize from the liquid phase. Lamellar structure appears in belite .crystals (Hills 2000; Hills, Johansen, and Miller 2002 ) [CaO301400 = [0.343(LSF-93) + 2.74(SR-2.3)] + [0.83Q45 + 0.10C125 +0.39R45 :Where CaO301400 = is the free lime after burning for 30 minutes at 1,400°C (LSF = %CaO/(2.8%SiO2 + 1.18%Al2O3 + 0.65%Fe2O3 (SR = %SiO2/(% Al2O3 + % Fe2O3 Q45 = % quartz grains coarser than 45µm C125 = % calcite grains coarser than 125µm
R45 = % other acid-insoluble minerals, (e.g. feldspar) coarser than 45µm BEFORE
Clinker/Kiln Operation :Possible Effects
Cement Performance :Possible Effects
AFTER — burning harder decrease in free lime • low porosity, difficult grindability • large alite • possible poor nodulization • large variations in free • variation in alkali sulfate content • lime kiln on the hot side • poor belite distribution • increase in alkalis and sulfate in kiln internal • cycle, possible surges, potential for buildups low porosity makes it hard to cool • lower clinker reactivity • color differences, brown clinker center • increased water demand • decreased early strength and increased • admixture incompatibility later strength during • possible erratic expansion • periods where alkalis results due to free lime abnormalities in setting behavior are • decreasing (pack set due to static charge (large alites •
The combinability of a raw mix will depend largely on: • The fineness of the raw materials - fine material will evidently react more readily than will coarser material. • Lime Saturation Factor - higher LSF mixes are more difficult to combine than are lower LSF mixes. • Silica Ratio - mixes of higher SR are more difficult to combine because there is less liquid flux present. • Alumina Ratio - mixes of AR approximately equal to 1.4 will be easier to burn than if the AR is higher or lower. This is because at an AR of about 1.4, there is more clinker liquid at a lower temperature. (Minor constituents such as MgO can alter this optimum AR). • The intrinsic reactivity of the raw materials - some types of silica, for example, will react more easily than will others.
Hydration of individual cement compounds :Objectives • To explain the hydration of individual cement compounds: C3S, C2S, C2A, C4AF Hydration of Cement
and
• Hydration is the collective term describing the chemical and physical process that take place between cement and water • It is assumed, although not completely valid, that the hydration of each of the four cement compounds takes place independently of the others • Hydration of cement is very important as it is responsible for setting and hardening of concrete I. Hydration of C3S :The following chemical reaction takes place when C3S comes in contact with water 2C3S + 6H → C3S2H3 + 3CH Tri-calcium water C-S-H calcium silicate hydroxide • C-S-H (calcium-silicate-hydrate) is the principal hydration product • The formula C3S2H3 for C-S-H is only approximate because the composition of C-S-H is actually variable over a quite a wide range • C-S-H is poorly crystalline material which forms extremely small particles in the size range of colloidal matter (0.5 to 2 µm long and < 0.2 µm across) o Fibrous particles o Flattened particles o Sometimes branching at the ends • CH (calcium hydroxide) is the secondary hydration product • Unlike the C-S-H, CH is a crystalline material with a fixed composition
Stages of hydration of C3S There are five important stages of the C3S hydration, as described by the following calorimetric curve :((i.e. time versus rate of heat evolution curve
• Stage-1 corresponds to a period of rapid evolution of heat, which ceases within about 15 min. • Stage-2 corresponds to a dormant period which lasts for several hours during which the hydration is almost at halt. This is the reason why the concrete remains in plastic state for several hours. • Stage-3 corresponds to acceleration period starting at the end of dormant period and lasting till the rate of heat evolution reaches a maximum value. By this time (4 to 8 h) final set has been passed and early hardening has begun • Stage-4 corresponds to declaration period during which the rate of heat evolution reduces from its maximum value to a very low steady state rate Chemical and Physical Processes Controlling C3S Hydration :Chemical Control The hydrolysis of the C3S (i.e. the chemical reaction between C3S and water) which results into release of calcium ions and hydroxide ions from the surface of the C3S grains, forming C-S-H and CH through crystallization of ions and increasing the pH to over 12 within a few minutes, is called a .chemical control The chemical control (i.e. the hydrolysis of C3S) slows down quickly but continues throughout the .dormant period .During the dormant period, the increase in Ca++ and OH- concentrations continues slowly
:Nucleation control When the Ca++ and OH- concentrations reach a critical value, the hydration products (C-S-H and CH) start to crystallize from solution and the hydrolysis of C3S again proceeds rapidly. This whole process of attenuation of critical concentrations of Ca++ and OHcorresponding to which the nuclei of the C-S-H and CH crystals starts forming giving way to the further hydrolysis of C3S is termed as nucleation control.
Diffusion control: Thy hydration process is said to be under diffusion control when the coating over the C3S grains, formed by layers of C-S-H, put a barrier through which water must flow to reach the unhydrated C3S for its hydrolysis and through which ions must diffuse to reach the growing crystals. Sequence of C3S Hydration Reaction Stage
Kinetics of Reaction
Chemical Processes
Initial hydrolysis .1
Chemical control; rapid
Dormant period .2
Nucleation control; slow Chemical control; rapid Chemical and diffusion control; slow Diffusion control; slow
Initial hydrolysis dissolution of ions Continued dissolution of ions Initial formation of hydration products Continued formation of hydration products Slow formation of hydration products
Acceleration .3 Declaration .4 Steady state .5
Relevance to Concrete Properties
Determines initial set Determines final set and rate of initial hardening Determines rate of early Strength gain Determines rate of later strength gain
Effect of Temperature on C3S Hydration • The hydration of C3 S is sensitive to temperature (i.e. there is increase in the rate of hydration with increase in temperature) but only when the reaction is chemically controlled (i.e. stage 3) • Once hydration is completely diffusion-controlled in stage 5, it is much less temperaturesensitive, although the diffusion coefficient of the hydrate barrier varies with temperature • Therefore, it may concluded that the significant effect of temperature on the hydration of C3S is only up to first few hours (i.e. 4 to 8 hours), as shown in the following figure: Figure 4.2 Effect of temperature on the hydration of tricalcium silicate. (Adapted from L.E. Copeland and D.L. Kantro, in Proceedings, Fifth International Symposium on the .(Chemistry of Cement, Tokyo, 1968, Vol. 2.pp. 387-419
II. • C2S hydrates in a similar manner as that of C S: 2C2S + 4H → C3S2H3 + CH
Hydration of C2S
dicalcium water C-S-H calcium silicate hydroxide • But the hydration of C2S is much slower than C3S because it is a less reactive compound than C3S. This is the reason why C2S does not contribute to initial strength • Due to very low amount of heat liberated on the hydration of C2S, it is not easy to measure the low heat experimentally and therefore calorimetric curve for C2S hydration is hardly plotted III. Hydration of C3A In Portland cement the hydration of C3A involves reactions mostly with sulfate ions which are supplied by the dissolution of gypsum added during the manufacturing of cement :Reactions involved in the hydration of C3A :The primary initial reaction of C3A, when ample amount of gypsum is present, is as follows .1 _ _ C3A + 3CS H2 + 26H → C6A S 3H32 Tri-calcium Aluminate
gypsum
water
ettringite
• The above reaction is exothermic (produces heat) • Ettringite (i.e. “calcium sulfoaluminate hydrate”) is the name given to a naturally occurring mineral of the same composition • Ettringite is a stable hydration product only while there is an ample supply of sulfate available • The formation of ettringite slows down the hydration of C3A by creating a diffusion barrier around unhydrated C3A particles, analogous to the behavior of C-S-H during the hydration of silicates 2. If the sulfate is all consumed before the C3A has completely hydrated, then ettringite becomes unstable and transforms to another calcium sulfoaluminate hydrate containing less sulfate through following reaction: _ _ C3A + C6A S 3H32 + 4H → 3C4A S H12 _ • The second product 3C4A S H12 is simply called as “monosulfoaluminate” • Monosulfoaluminate may sometimes form before ettringite if C3A reacts more rapidly with the sulfate ions than they can be supplied by the gypsum to the mix water • The diffusion barrier, created by the formation of ettringite, is broken down during the conversation of ettringite into monosulfoaluminate and C3A is allowed to react rapidly again 3. When monosulfoaluminate is brought into contact with a new source of sulfate ,ions (e.g. external source of sulfate ions), then ettringite can be reformed :as follows _ _ _ C4A S H12 + 2C S H2 + 16H → C6A S 3H32 This potential for reforming ettringite is the basis for sulfate attack of Portland cements when exposed to an external supply .of sulfate ions 4. If gypsum is not added in the cement, the hydration of C3A can lead to flash set C3A
+ 21H → C4AH13 + C2AH8 These hydrates (C4AH13 + C2AH8) are not stable and later convert to C3AH6
C4AH13
+
C2AH8
→
2C3AH6
+
9H
When quite a small amounts of gypsum are present, there may still be unhydrated C3A .5 present when all of the ettringite has been converted to monosulfoaluminate In such cases, the monosulfoaluminate reacts with the unhydrated C3A forming _ Monosulfoaluminate solid solution [C3A(CS CH)H12] _ _ C4A S H12 + C3A + CH + 12H → C3A(CS CH)H12 Formation of the hydration products from C3A, depending upon the :ratio, is presented in the following table
sulfate/ C3A
molar
The calorimetric for hydrating C3A, which looks qualitatively much like the curve for C3S, is shown :below
• The first heat peak is completed in 10 to 15 min and then the rate of heat evolution has been reduced to a very lower value due to the formation of the ettringite barrier • The heat of hydration remains at low value till the ettringite barrier is broken by transformation of ettringite to monosulfoaluminate after all the gypsum has been used to form the ettringite • The more gypsum there is in cement, the longer the ettringite will remain stable • In most cements ettringite remains in stable condition for a period of 12 to 36 hours • The rate of heat evolution starts increasing with start of ettringite conversation to monosulfoaluminate and reaches to the second heat peak and then again starts decreasing approaching to a steady-state condition IV. Hydration of C4AF • C4AF forms the same sequence of hydration products as does C3A, with or without gypsum _ _ C4AF + 3CS H2 + 21H → C6(A,F) S 3H32 + (A,F)H3 _ _ C4AF + C6(A,F) S 3H32 + 7H → 3C4(A,F) S H12 + (A,F)H3 • The reactions are slower and involve less heat • C4AF never hydrates rapidly enough to cause flash set, and gypsum retards C4AF hydration even more drastically than it does C3A • With increase in iron content in C4AF, hydration of C4AF becomes slower • Practical experience has shown that cements low in C3A and high in C4AF are resistant to sulfate attack • This means that the formation of ettringite from monosulfoaluminate does not occur in case of C4AF due to presence of iron in it
BOGUE CALCULATION C3S = 4.0710CaO-7.6024SiO2-1.4297Fe2O3-6.7187Al2O3 C2S = 8.6024SiO2+1.0785Fe2O3+5.0683Al2O3-3.0710CaO C3A = 2.6504Al2O3-1.6920Fe2O3 C4AF = 3.0432Fe2O3
Cement 42.5 N Type 1 Chemical Composition (Portland cement 42.5n type 1) Silicon Dioxide (SIO2) 21.00 Aluminum Oxide (A1203) 5.30 Ferric Oxide (FE203) 3.30 Calcium Oxide (CAO) 65.60 Magnesium Oxide (MGO) 1.10 Sulphur Trioxide (SO3) 2.70 Loss of Ignition (LOI) 0.90 Tricalcium Silicate (C3S) 60.00 Dicalcium Silicate (C2S) 15.00 Tricalcium Aluminate (C3A) 8.05 Tricalcium Alumino Ferrice (C4AF) 9.76 Physical and Mechanical Properties Blain CM2/GR 3.250 Autoclave Expansion 0.02 Initial Setting time (VICAT) 105 Minutes Final Setting Time (VIACT) 135 Minutes Compressive Strength @ 03 Days 230 KG/CM2 AND @ 07 DAYS 305 KG/CM2 AND @ 28 Days 439 KG/CM2 Important factors LSF = CaO*100/ (2.8*SiO2+1.18*Al2O3+0.65*Fe2O3 SM = SiO2 / (Fe2O3 + Al2O3)
90 ˂ LSF ˂ 98 2 ˂ SM ˂ 3
SM ˂ 2 → EASY BURNING, excessive liquid phase, attack the bricks, coating washing, balling Hard clinker, kiln unstable, low heat consumption, low cement strength SM ˂ 3 → HARD BURINING, scarce liquid phase, high thermal loads, no coating, dusty clinker High free lime, kiln unstable, high cement strength, slow hardening cement AM = Al2O3 / Fe2O3
1.3 ˂ AR ˂ 2.5
AM ˂ 2.5 → viscous slag, high early strength AM ˂ 1.3 → fluid slag, low early strengths, and low heat of hydration Liquid phase LP = (1.13*C3A) + (1.35*C4AF) +MgO+K2O
23.5 ˂ LP ˂ 28
Coating index C.I = C3A+C4AF+ (0.2*C2S) + (2*Fe2O3) C.I ˂ 20 → scarce coating C.I ˂ 30 → excessive coating but not stable
20 ˂ C.I ˂30
Burn ability factor
B, F = (LSF+ (10*SM))-(3*(MgO+K2O)
110 ˂ B.F ˂ 118
Burn ability index best
B.I = C3S/ (C3A+C4AF)
2.6 ˂ B.I ˂ 4.5 lower =
Minimum burning temperature ˚C = 1300 + 4.51*C3S - 3.74*C3A - 12.64*C4AF Activity index A.I = SiO2/Al2O3
2.5 ˂ A.I ˂ 3.5
Alkalis equivalent (A.E) = Na2O + 0.659*K20
A.E ≤ 0.6 %
KH = 100*(CaO-1.65*Al2O3-0.35*Fe2O3-0.7SO3) / 2.8*SiO2 Hydraulic modulus HM = CaO / (SiO2+Al2O3 + Fe2O3)
HM ≈ 2
Complete analysis of cement and Raw material
1- IR 1-1g cement +100 ml distilled water + 10 ml Hcl conc. 2- Filter using filter paper N0 40 3- Wash several times with hot water until all chlorine is finished test it using AgNO3 →no white ppt (or color) 4-add 100 ml of Na2CO3 (sodium carbonate 50 g/l) in a 250 ml beaker, then transfer the filter paper (with the ppt) into the beaker 5-boil for 15-20 minutes, then filter by 40 filter paper, wash with hot water very well 6-add about 15-20 ml of Hcl (1+20) 7-filter, wash, test it using AgNO3 (keep the filtrate for SO3 test) 8- Put the filter papers with the ppt in a weighted crucible, put in the kiln at 950 c (increase temp slowly) for 30 min. 9- Let the platinum crucible cool in a disicator, then weight the residue (wt) IR = wt х 100 (≤ 5 %)
2- SO3 1- Take (200-300 ml) of IR filtrate, adjust PH at (1.0 - 1.5) using (buffer 10) 2- Boil, then add 15 ml Bacl2 (120 g/l) with rapid stirring with glass rod 3- Heat on sand bath, (2-3 hours) 4- Filter by (N0. 42), wash very well by hot water (several times) test it using AgNO3 5- Put the filter paper wit ppt in a weighted platinum crucible in kiln at 950 for 1 hour 6- Cool, weight the ppt (wt) as BaSO4 SO3 % = wt х 34.33 Where, SO3 /BaSO4 = 34.33
3- SiO2 1- take 1 g cement or clinker + 1g ammonium chloride (NH4Cl) + 10 ml conc. HCl + 5 drops conc. HNO3 → mix the sample well with glass rod, put on sand bath, dry 2- After drying, add 5 ml conc. HCl or 10 ml (1+1), mix well with the glass rod, Add 50 ml boiling H2O. 3- filter on( 41) filter paper put 20 ml HCl (1+20) on the filter paper, receive the filtration in 500 ml flask, wash very well by boiling H2O (test with AgNO3). 4- Keep the filtrate for other oxides determination (complete to 500 ml, cool
5- Put in platinum crucible at 1150 c for 30 min. SiO2 % = wt х 100 where wt = weight of ppt
4- CaO 1- Take 50 ml (filterate of SiO2) + 25 ml TEA 2- Adjust PH (12.5 - 13) by KOH (potassium hydroxide) 3- Complete to 200 ml by H2O. 4- Add 0.2 g Calcine indicator. Or (calcon) 5- Titrate by EDTA 0.05 N (color change, green → pale violet) Cao % = 2.804 х V1 х F Where, V1 = volume of EDTA F = factor of EDTA = 1.0081
5- MgO +CaO 1- Take 50 ml filtrate + 25 ml TEA 2- Adjust PH (10.2 - 10.5) by buffer 10 ammonical 3- Complete to 200 ml by H2O 4- Add methyl thymol blue indicator (small amount) 5- Titrate by EDTA 0.05 N (color change, blue → nearly colorless) MgO % = 2.016 х V х F Where, V = V2 - V1 V2 = volume of EDTA for (MgO + CaO) F = factor of EDTA 1.0081
6- Fe2O3 + Al203 1- Take 100 ml filtrate 2- Adjust PH (1.5 ± 0.01) by HCl (1+20) 3- Add sulfu salicylic acid indicator (heat to 40 c) 4- Titrate by EDTA 0.05 N (color change, blood red → yellow lemon) Fe2O3 % =1.996 х V х F Where, V = volume of EDTA F = factor of EDTA
7- Al2O3 1- Take the solution of Fe2o3 determination, adjust PH (3 - 3.05) by ammonium acetate or sodium acetate .OR (acetic acid +drops of buffer 10) 2- Add 0.2 g methyl thymol blue indicator, boil the solution 3- Titrate by EDTA 0.05 N, with covering color change (blue → yellow lemon) Al2o3 % = 1.275 х V х F F = EDTA factor
8- Fcao 1- 1 g sample (in clossed glassy bottle) +40 ml ethylene glycol (shake) 2- Put in water bath for 20 min 3- Filter under suction (Buchner) 4- Put 10 drops of bromo thymol blue indicator 5- Titrate by HCl 0.1 N (blue → yellow) Fcao % = 0.28 х V х F Where, V = volume of HCl F = factor of HCL
9- RAW material Lime stone, Iron ore, clay, sand
1- 1 g sample + 4 g (Na2CO3 + K2CO3) 2- Put in a platinum crucible at 1050 C for 30 min (cover) 3- Cool out side the crucible by distilled water, then transfer the crucible into a beaker 4- Heat 15 ml HCl (1+1) and put inside the crucible 5- Add 0.5 g NH4Cl 6- Cover, dry on sand bath 7- Add 10 ml HCl (1+1), dissolve, then add 50 ml hot H2O 8- Filter on 41 filter paper, wash very well ppt for SiO2 , filtrate (Fe2O3, CaO, MgO, and Al2O3) like before
10- CL 1- 5 g +50 ml H2O + 50 ml HCl (1+2), heat 2- Add 10 ml AgNO3 0.05 N 3- Filter on (40 or 41), wash by HNO3 (1-99) 4- Add 5 ml ammonium ferric sulfate 5- Titrate by ammonium thio cyanate 0.05 N CL = 1.773 (V1F1 -V2F2)
F1 = F AgNO3 F2 = F NH4 SCN # Solutions and reagent preparation
V1 V2
1- Ammonium acetate 60 g ammonium acetate + 560 ml acetic acid, complete to 1 liter by water 2- Methyl red indicator MR 0.1 g MR +100 ml alcohol 3-calcon 1 g calcon + 100 g sodium chloride (NaCL) 4-sodium acetate 30 g sodium acetate + 70 ml H2O 5- Ethanol C2H5OH 6-Ammonium ferric sulfate 80 g amm.ferric sulfate +900 ml H2O +100 ml HNO3 (1+10) 7-Ammonium thio cyanate 0.05 N 3.806 g, complete to 1 liter by H2O (heat) (for standarization of AgNO3) 8- Zn - solution 0.01 N wash Zn with HCl (1+1) then with ethanol , dry, take 0.65 g +30 ml HCl ,,complete to 1 liter by H2O F zn = initial wt in g / 0.6537 9-ammonium thio sulfate (for iron) 80 g + 100 ml HNO3 + complete to 1 L (H2O) 10-sodium tetra borate 0.2012 g + 100 ml H2O (for standardization of HCl 0.1 N) 11-tri ethanol amine TEA indicator 250 ML TEA +750 ml water +8 g hydroxyl ammonium hydrochloride 12-calcine indicator 0.2 g calcine +0.12 thymol phtaline +20 g potassium nitrate KNO3 13-potassium hydroxide KOH 225 g KOH, complete to 1 liter in plastic bottle 14-methyl thymol blue indicator
1 g methyl thymol blue + 100 g NaCl 15-Eriochrome black T EBT (sodium salt indicator) 1 g Eriochrome black + 100 g NaCl. Or, (1g /100 g Na2SO4). 16-NaOH sodium hydroxide 100 g/l 17-bromo thymol blue 1 g bromo thymol blue + 1 liter alcohol +5 drops NaOH (or few crystals) 18- EDTA 0.05 N 14.6129 g, complete to 1 liter by H2O 19-AgNO3 (silver nitrate) O.O5 N 8.494 g +1 L water Note, washing must be very well to insure best results 20-PAN (pyridyle azo naphtol 0.1 g in 100 ml ethanol 21-buffer 10 ammonical 750 ml ammonia + 250 ml water + 50 g ammonium chloride (NH4Cl) 22-copper sulfate solution 1.25 g cupper sulfate in 100 ml 0.02 EDTA 23-ammonium chloride solution (Cl plug) 70 g NH4Cl +570 ml ammoniac solution, complete to 1000 ml by H2O 24-Na2CO3 (sodium carbonate 50 g/l) 25-Bacl2 (120 g/l) 26-conc. Hcl , Hcl (1+20) ammonium chloride NH4Cl-27
EDTA standardization Calculating the factor 1-take 2 g CaCO3 put in the kiln at 1100 c for 2 hours 2- Cool in adesicator 3- take 1 g CaO (obtained by burning) + 10 ml HCl, complete to 1 L by H2O 4- Complete all the steps as CaO % determination Record volume of EDTA 0.05 N consumed V 50 × wt CaO g F EDTA =
50 х 1 =
Mo, wt х N х V
56.079 х 0.05 х V EDTA
Where …
ml of CaO = 50 ml N of EDTA = 0.05 N Mo, wt (cao0 =56.079) V = volume of EDTA 0.05 N consumed Another way by Zn metal Weight 0.65 g Zn + 30 ml HCL (1+1) cover then complete to 1 liter by H2O F zn = 0.65 /eq,wt = 0.65 /0.6537 = 0.9943 Procedure,,, Take 50 ml Zn solution (Ph = 1.2 - 1.5) by buffer 10 ammonical, complete by H2O to 200 ml Indicator, Erochrome black T Titrate by EDTA 0.05 N 50 х Fzn х 100
F EDTA =
0.05 х V EDTA Preparation and standardization HCl 0.1 N 1 liter V = W/D = 36.45 / 1.19 = 30.63 V х N х30.63 Wt = =8.27 ml/l 37 Complete to 1 liter by water 0.1 N HCl Conc. of pure HCl = 37 Standardization (for Fcao) Titrate soln of cao standard 0.065 g cao equivalent to 20 ml HCl 0.1 N indicator calcine F cao = 20 / v v = volume of titration Or, titration of sodium tetra borate, MR indicator F= 20/result Factor of ammonium thio cyanate 20 ml AgNO3 0.05 (3 samples) + 25 ml HNO3 (1+1), ammonium ferric acid indicator to 200 ml H2O Titrate by ammonium thio cyanate (V) F 20 /V Factor of AgNO3 0.05 N NaCl 0.05 N (N eq, wt =wt of NaCl → complete to 1 L) Indicator potassium chromate Titrate 20 ml NaCl using AgNO3 F 20 /V 0.05 х 56.08 х 500 х 100 CaO =
= 2.804 1 х 1000 х 50 N = 0.05
. mo, wt Cao =56.08 Vcao = 50 ml one ca ion = 1 1 liter = 1000 ml
Filtrate = 500 ml
2.804 х FEDTA х V EDTA CaO % = Wt 0.05 х 101.86 х 500 х 100 Al2O3=
= 1.275 2 х 1000 х 100 V Al2O3 = 100 ml
Al 0.05 х 59.813х 500 х 100 Fe2O3=
= 1.996
= 2 ions
2 х 1000 х 100 V =100 ml Fe = 2 ions 0.05 х 40.311х 500 х 100 MgO =
= 1.996 1000 х 100 V = 50 ml Mg = 1 ions
