Rapid Hardening cement Detailed Solution. Rapid Hardening cement has a maximum percentage of C 3 S.

Which cement has high C3S and low C2S?

(A) Rapid Hardening Cement.

What is the work C3S in cement?

Master of Science at University of Trondheim (NTH), Norway – Published Nov 25, 2015 C3S is the main contributor to Strength of cured Concrete in early phases. C3S & C3A are the main contributors to Heat in the early phases. C3A develops approximately 840 Joules/ gram and C3S 500 Joules / gram.

1. Cement used in Concrete contains approximately 5 times as much C3S as C3A.
2. Thus C3S is the main contributor to the Heat Development as well.
3. To Predict Temperature & Strength Development, C3S & C3A content must be stable! But known Regulations does not specify limits! It turns out that C3S content may vary as much as 22% between suppliers and even between batches from the same supplier.

C3A content may vary as much as 16%! (1) HPC-09 v6 has means of Discrepancy Detection that reveals these Concrete Mix variations and provides Safe Maturity Calculations ! HPC-09 v6 combined with the Quality Control Regime of the plant provides the best Quality Control of your end product.

1. Variation in Cement Properties and Its Effect on Quality of Concrete, Thushara PRIYADARSHANA and Ranjith DISSANAYAKE, University of Peradeniya, 20400, Sri Lanka
2. “Integrated Materials and Construction Practices for Concrete Pavement”. A State-of-the-Practice Manual, FHWA Publication No. HIF-07-004, December 2006
3. “Predicting Temperature Rise and Thermal Cracking in Concrete”. Michael Edward Robbins 2007

• What is C3S used in answer?

  Discussion :: Building Materials – Section 3 ( Q.No.2 ) –

  PRITHVI said: (May 30, 2014)
  Early gain of strength is caused due to tricalcium silicate and thus setting time too.

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  Vikas said: (Feb 19, 2016) Tricalcium silicate responsible for early setting of cement.

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  Sonu said: (Jul 29, 2016) Answer is wrong C3S (Tricalcium Silicate) is responsible for initial setting and Di Calcium silicate (c2s) contributes strength after 7 days.

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  Sohan Jangra said: (Sep 29, 2016) Answer is right, When water is mixed with cement to form a paste, reaction starts. In its pure form, the finely ground cement is extremely sensitive to water. Out of the three main compounds, viz. C3A, C3S, and C2S, reacts quickly with water to produce a jelly-like compound which starts solidifying. The action of changing from a fluid state to a solid state is called ‘setting’ and should not be confused with ‘hardening’.

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  Devaraj said: (Dec 31, 2016) Silica indicates strength aluminium indicates settings times.

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  Laxman Prasad said: (Mar 8, 2017) How long time due to tri-calcium aluminate gains the initial setting by cement?

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  Chandrima said: (Apr 22, 2017) I think it is Tri calcium silicate.

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  Amitkumarsachin said: (Jul 1, 2017) C3S is responsible to early strength not early setting time, C3A is responsiblefor early setting time.

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  Ramavtar said: (Dec 13, 2017) C3S is correct.

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  Shekhar Kumar said: (Jan 27, 2018) Properties of cement compounds These compounds contribute to the properties of cement in different ways Tricalcium silicate, C3S:- This compound hydrates and hardens rapidly. It is largely responsible for portland cement’s initial set and early strength gain. Dicalcium silicate, C2S:- C2S hydrates and hardens slowly. It is largely responsible for strength gain after one week. Tricalcium aluminate, C3A:- It liberates a lot of heat during the early stages of hydration, but has little strength contribution. Gypsum slows down the hydration rate of C3A. Cement low in C3A is sulphate resistant. Tetracalcium alumino Ferrite, C4AF:- This is a fluxing agent which reduces the melting temperature of the raw materials in the kiln (from 1650o C to 1450o C). It hydrates rapidly but does not contribute much to the strength of the cement paste. By mixing these compounds appropriately, manufacturers can produce different types of cement to suit several construction environments.

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  Rabindra said: (Apr 10, 2018) The Answer is right because it is asking the for the early setting time of cement which is due to tricalcium aluminate but for the early strength of cement, tricalcium silicate and ultimate strength or final strength is due to dicalcium silicate. So don’t be confused be clear.

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  Basavaraj said: (Aug 21, 2018) C3S for initial setting. C3A for the flash setting. C2s for Ultimate strength.

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  ABHISHEK YADGIRI MUDIRAJ said: (Sep 19, 2018) C3S and C2S for strength and C3A for the early setting of cement.

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  Sunil Kumawat said: (Oct 31, 2018) C3A is responsible for both flash and initial setting time.

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  Muttu said: (Apr 29, 2019) Option A is the correct answer.

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  OPSC AEE said: (Oct 29, 2019) Give ans is right. Here asked about initial setting, not asked speeds the setting. Kindly read the que again.

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  Aditya said: (Jan 30, 2020) The setting and hardenings of cement paste is mainly due to the hydration and hydrolysis.

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  Dharanidharan said: (Feb 21, 2020) Answer C is correct. Be because. C3s strenth property. C3a time &hydration property.

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  Nitesh said: (Mar 9, 2020) Hello guys, the answer is right, because C2S is responsible for early STRENGTH of cement in the INITIAL stage, in this question ask the initial setting time of cement.

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  Joey said: (Jun 15, 2020) C3S – early strength. C2S – ultimate strength. C3A – the initial setting of cement. Heat of hydration C3A > C3S > C4AF > C2S.

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  Sushant Kumar Sahu said: (Jul 29, 2020) When water is added in cement, first tricalcium aluminate is reacted with water and it is responsible for initial setting of cement.

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  Priyanka said: (Apr 2, 2021) Early strength – C3S. Early setting – C3A.

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  Black Lover said: (May 19, 2021) I think option A is correct.

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  Him said: (Aug 7, 2021) I’m agree with you, Thanks @Joey.

  Civil Engineering – Building Materials – Discussion

  What is the percentage of C3A in cement?

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  Tricalcium aluminate (C3A) is one of the main constituents of Portland cement. Even though it represents less than 10% of the total composition, its strong reaction with water can lead to a rapid setting, called flash set. Gypsum is added to regulate this reaction and preserves the workability of the cement paste at early ages.

  1. The understanding of the C3A-gypsum reaction is therefore crucial for the comprehension of the early hydration of cement.
  2. The role of the amount of C3A and the sulfate balance of cement hydration are of major interest since two important routes for the development of new cementitious materials are the increasing rate of substitution materials and the increasing level of aluminate in clinker.

  This thesis aimed to investigate the C3A-gypsum reaction alone and in the presence of alite in order to provide basic knowledge on the C3A-gypsum reactions and study the interactions that occur between the cement phases when hydration occurs in alite-C3A-gypsum systems.

  • Alite and C3A as well as clinkers of controlled composition were synthesized.
  • Model systems composed of C3A with different gypsum additions and alite-C3A-gypsum systems were studied in terms of hydration kinetics, phase assemblage and microstructural development.
  • This work confirmed the findings of previous works on the mechanism that controls C3A-gypsum hydration when sulfate ions are present in solution and gave new results on the reaction when gypsum is depleted.

  It was shown that AFm phases do not crystallize only as platelets that fill the space between the C3A grains but also form an “inner” product within the original C3A grain boundaries and that hydrogarnet (for which the presence depends on the gypsum addition) crystallizes as a rim around C3A grains.

  • Moreover the influence of the gypsum addition on the morphology of the AFm platelets and the role of their morphology on the hydration rate were highlighted.
  • In the presence of alite the hydration kinetics of C3A-gypsum systems was subject to change due to the adsorption of sulfate ions on C-S-H and the reduction of the space available for the reaction.

  In addition, with the correlation of calorimetric, XRD and SEM analyses it was possible to observe a second formation of ettringite from C3A and sulfate ions released from C-S-H after the depletion of gypsum. Finally, the rate of alite hydration related to the growth of C-S-H was shown to be modified in the presence of C3A and gypsum.

  Why cement with higher percentage of C3S is better for cold weather concrete construction?

  Is There Hope? – Of course! There are a number of ways to deal with cold weather concrete construction both from production and construction standpoints. These aren’t new or revolutionary ideas—they’ve been known for decades. A very brief review follows, to aid those suffering from temporary amnesia.

  1. Heat the concrete: By using heated mix water, and in some cases heated aggregates, the concrete can be produced at a temperature sufficient to jump start the hydration reaction so that concrete can set and gain enough strength to get through the critical first few hours.
  2. Increase cement content: Heat of hydration in concrete is due to the exothermic (heat producing) nature of the hydration reaction.

  The amount of heat generated is dependent on the quantity of cement: the more cement the more heat. A higher grade of concrete (more cement) can therefore be used to respond to colder conditions. Use high-early-strength (Type III) cement: Type III cements have a higher rate of hydration and therefore a higher rate and amount of heat generated, as well as an increased rate of strength gain.

  Use accelerators: Accelerators increase the rate of hydration, which means that more heat is generated in the early stages and the concrete sets faster. But remember that accelerators do not prevent freezing or frost damage. Retain the concrete’s body temperature: By insulating the forms or covering the concrete with adequate insulation, heat can be retained in the concrete and sustain the hydration reaction so that the concrete can achieve adequate strength.

  Provide an incubator: The temperature of the concrete is related to the temperature of its surroundings. Therefore, we can create an artificial environment for the concrete – as long as the concrete is nice and warm, it doesn’t really care if the outside temperature is 10 below.

  • These are some of the more obvious precautions that can be taken to offset the effects of cold weather on concrete.
  • Concrete mixes and admixtures are under development that will provide new weapons to combat cold weather concrete problems.
  • But the key is that cold weather concreting must be a TEAM effort.

  In cold weather, concrete cannot simply be PLACED, FINISHED, AND FORGOTTEN —it needs continuing warmth and care during its infancy. Be aware that there are potential side effects from some of the methods used to cope with cold weather. For instance, when heating an enclosed area, be sure to use heaters that are vented to the outside.

  • The burning of fossil fuels produces carbon dioxide which can combine with moisture in the air and on the surface of the concrete to produce carbonic acid.
  • The carbonic acid reacts with the calcium hydroxide in the fresh concrete leading to a soft, dusty surface when the concrete hardens.
  • Vented heaters will prevent this problem.

  Calcium chloride is an excellent accelerator but can lead to a dark discoloration of the surface of the flatwork. This is more common on troweled or hard-troweled surfaces and typically appears in a random pattern, almost like the coloring of a pinto pony, hence the term “pinto concrete.” In severe cases, the discoloration can cover the entire slab surface.

  So if you ask, “What’s new in cold weather concreting?” the answer is simple– NOTHING! Cold weather comes, cold weather goes, and eventually cold weather comes again. We’ll face the same problems over and over until we overcome the amnesia and denial that too many people have towards cold weather concreting.

  The next time you encounter a problem with concrete in cold weather, don’t blame the concrete! People decide what mix to use and what level of protection (or lack thereof) to provide for the concrete. Concrete cannot control its own destiny—only people can.

  Which of the following aggregate gives maximum strength in concrete Mcq?

  For maximum strength an angular shape aggregate is suitable because it provides friction and interlocking both.

  What are the hydration products of C3S and C2S?

  Of the two products of C3S and C2S hydration, C-S-H gel and portlandite (Ca(OH)2) ) the importance of the C-S-H gel deserves special mention from the points of view of its engineering properties, elasticity and durability.

  What has the highest compressive strength?

  Hint: Basically, compressive strength refers to the force that is responsible for the deformation of the materials such that the volume of the material reduces. Moreover, it is the stress experienced by a material which leads to a smaller volume. Complete step by step answer: Compressive strength is defined as the maximum compressive stress that is experienced by the material before its breakdown.

  It is generally obtained by dividing the maximum load by the cross- sectional area of the material. High compressive strength leads to the failure of the material due to tension. We can also say that it is the stress on materials that leads to a smaller volume. Now, when the compressive stress is applied to the materials that are brittle, then these materials fracture as there is a sudden release of the stored energy whereas in case of ductile material, they compress and there is no failure.

  The SI unit of compressive stress is Pascal or $N }$, Its mathematical formula is as shown: $\sigma = \dfrac $ Where $\sigma $ is compressive stress F is the compressive force A is the unit area So, among the given options high carbon steel has the highest compressive strength as compared to other options.

  What is C3S compound?

  Tricalcium silicate (Ca3SiO5 or C3S) is the main phase of Portland cement clinker.

  What is the formula of C3S?

  Tricalcium silicate

  PubChem CID	25523
  Molecular Formula	Ca 3 O 5 Si
  Synonyms	TRICALCIUM SILICATE 12168-85-3 Tricalcium silicon pentaoxide dicalcium;oxocalcium;silicate C3S (Cement component) More
  Molecular Weight	228.32
  Component Compounds	CID 14778 (Calcium oxide) CID 14942 (Orthosilicic acid) CID 5460341 (Calcium)

  How is C3S clinker calculated?

  Calculation of the C3A Percentage in High Sulfur Clinker 1 Faculty of Sciences, Saint Joseph University, Campus of Sciences and Technologies, Mar Roukos. Mkallès, P.O. Box.11-514 Riad El Solh, Beirut 11072050, Lebanon 2 Plant- Laboratory Department, Cimenterie Nationale S.A.L., Old Tripoli Road, Chekka, North Lebanon.P.O.

  • Box.11-5101 Riad El Solh, Beirut 11072180, Lebanon Find articles by 1 Faculty of Sciences, Saint Joseph University, Campus of Sciences and Technologies, Mar Roukos.
  • Mkallès, P.O.
  • Box.11-514 Riad El Solh, Beirut 11072050, Lebanon Find articles by 1 Faculty of Sciences, Saint Joseph University, Campus of Sciences and Technologies, Mar Roukos.

  Mkallès, P.O. Box.11-514 Riad El Solh, Beirut 11072050, Lebanon Find articles by 1 Faculty of Sciences, Saint Joseph University, Campus of Sciences and Technologies, Mar Roukos. Mkallès, P.O. Box.11-514 Riad El Solh, Beirut 11072050, Lebanon 2 Plant- Laboratory Department, Cimenterie Nationale S.A.L., Old Tripoli Road, Chekka, North Lebanon.P.O.

  Box.11-5101 Riad El Solh, Beirut 11072180, Lebanon *Sayed Horkoss: Academic Editor: Peter A. Tanner Received 2010 Apr 1; Revised 2010 May 10; Accepted 2010 May 10. © 2010 Sayed Horkoss et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

  The aim of this paper is to clarify the influence of the clinker SO 3 on the amount of C 3 A. The calculation of the cement phases percentages is based on the research work, Calculation of the Compounds in Portland Cement, published by Bogue in 1929,The usage of high sulphur fuels, industrial wastes, and tires changes completely the working condition of Bogue because the assumed phase compositions may change.

  The results prove that increasing the amount of SO 3 in the low alkali clinker decreases the percentages of C 3 A due to the high incorporation of alumina in the clinker phases mainly C 2 S and C 3 S. The correlation is linear till the clinker SO 3 reaches the 2%. Over that the influence of the clinker SO 3 became undetectable.

  A new calculation method for the determination of the C 3 A in the high sulphur and low alkali clinker was proposed. Portland cement is a hydraulic material composed primary of calcium silicates, aluminates, and ferrites. In a rotary kiln, at temperature reaching the 1450°C, clinker nodules are produced from a finely ground, homogenised blend of limestone, shale and iron ore.

  The nodules are subsequently ground with gypsum, which serves to control setting, to a fine powder to produce finished Portland cement. The composition and texture (crystal size, abundance, and distribution) of clinker phases result from complex interactions of raw feed chemical and mineralogical composition, particle size distribution, feed homogenization, and the heating and cooling regime.

  In order to simplify these phenomena, Bogue proposed an approach for the development of the clinker phases. The ferric oxide (Fe 2 O 3 ) reacts with aluminium oxide (Al 2 O 3 ) and lime (CaO) to form the tetracalcium aluminoferrite (C 4 AF or Ca 4 Al 2 Fe 2 O 10 ).

  • The remaining aluminium oxide reacts with lime to form the tricalcium aluminate (C 3 A or Ca 3 Al 2 O 6 ).
  • The lime reacts with the silicate oxide (SiO 2 ) to form two calcium silicates phases, the dicalcium silicate (Belite, C 2 S or Ca 2 SiO 4 ) and tricalcium silicate (Alite, C 3 S or Ca 3 SiO 5 ).

  Based on the above approach, Bogue proposed four formulae for the calculation of the clinker phase concentrations. Increasing the amount of the high sulphur fuels and the level of waste valorisation, in the cement kilns, changes completely the working condition of Bogue.

  1. The negative influence of sulphate on the percentages of silicate phases (alite and belite) was earlier detected by the XRD but that on the tricalcium aluminate (C 3 A) is still unclear due to the conclusion contradiction in the reported literature.
  2. The sulphates reduce the viscosity and surface tension of the clinker liquid phases, shifting the equilibrium of the melt into unstable range which is characterized by low nucleus forming frequency and high growth rate of crystal leading to stabilization of the Belite crystals.

  The incorporation of sulphur in the Belite stabilizes the Belite structure, whereby the uptake of CaO is inhibited and the formation is suppressed, This phenomenon increases the amount of Belite and decreases that of Alite in the clinker, This reported conclusion was assured by many investigations done later,

  The composition of the matrix (aluminates and ferrites) is not altered by the level of SO 3 in the clinker, In particularly the amount of the tricalcium aluminate (Ca 3 Al 2 O 6 ) is not affected by the SO 3 level, This conclusion was not compatible with the observation of Hamou-Tagnit and Sarker, indicating that increasing the SO 3 level increases the amount of Ca 3 Al 2 O 6 in the clinker where the conclusion of Borgholm and Jons showed the opposite,

  These contradictions in the literature were due to the fact that many parameters could affect the development of C 3 A (Ca 3 Al 2 O 6 ) principally the kiln atmosphere and the raw meal chemistry. Locher and others detect that the kiln atmosphere, especially the amount of oxygen, had an influence on the amount of C 3 A.

  1. Reducing kiln atmosphere inhibits partly the oxidation of the bivalent iron (Fe 2+ ), presented in the kiln feed, leading to increase in the amount of C 3 A.
  2. The sulphur introduced into the cement kiln from both sides, the kiln feed and kiln burner, is in chemically reduced form such as S 0, S 1−, and S 2−,

  These sulphur forms are oxidized to S 4+ and S 6+ in the kiln system. This oxidizing process consumes some oxygen quantity leading to a reduction in the amount of oxygen in the kiln system. The presence of sodium oxide in the kiln feed affects the amount of C 3 A,

  • One of the forms of sodium oxide in the clinker is the Na 2 O · 8CaO · 3Al 2 O 3 · At clinkering temperature this compound reacts with sulphur to produce the Na 2 SO 4 and C 3 A,
  • This study will focus only on the influence of the SO 3 on the development of C 3 A (Ca 3 Al 2 O 6 ).
  • The other factors listed above are controlled to avoid any interaction with the results.

  The development of the Tricalcium aluminates Ca 3 Al 2 O 6, in the cement kiln production, is affected by many parameters such as the kiln atmosphere and the amount of sodium oxide in the raw feed, This could be the reason of the large contradiction in the conclusion of the reported investigations.

  In order to avoid any interactions, not only from the chemical compounds but also that related to the kiln operation, the clinker samples were selected in a stable kiln production operation conditions. All samples are commercial clinker, sampled from Cimenterie Nationale SAL. The free lime of the clinker was less than 1% and the percentage of the kiln inlet oxygen was around 3%.

  The samples were analyzed immediately, to avoid any influence from storage and humidity. The variation of the clinker SO 3 was made by changing the fuel type in the main burner as follows:

  1. fuel oil containing 2.0% S,
  2. petroleum coke containing 4.5% S,
  3. petroleum coke containing 6.0% S.

  The chemical and mineralogical analyses were done respectively according to ASTM C114 and ASTM C1365 standards. The calibration of the ARL 9800 was done using NIST standards. The fusion Claisse machine and the Herzog HTP 40 press were used for the sample preparation of the chemical and mineralogical analysis.

  The KOSH (potassium hydroxide and sucrose) method was implemented in order to detect the percentage of SO 3 and Al 2 O 3 in the silicate phases. The results () showed an obvious influence of the SO 3 percentages on the amount of C 3 A in the low alkali clinker. In all samples, the measured percentages of C 3 A were lower than the calculated.

  Influence of the clinker SO 3 on the C 3 A. The correlation between the amount of C 3 A (Ca 3 Al 2 O 6 ) and the total percentages of clinker SO 3 was linear till the clinker SO 3 reached just 2%. Over that the influence of the clinker SO 3 becomes indistinguishable since the standard deviation of the results according to ASTM C1365:06 is 0.47.

  	Al 2 O 3	Fe 2 O 3	SO 3	Na 2 O	K 2 O	C 3 A (calculated)	C 3 A (measured)	SO 3 (Silicate phases)	Al 2 O 3 (Silicate phases)	Al 2 O 3 /  SO 3
  1	4.62	3.88	0.69	0.10	0.37	5.68	4.38	0.22	0.92	4.18
  2	4.53	3.89	1.08	0.10	0.26	5.42	3.91	0.55	1.24	2.25
  3	4.48	4.06	1.14	0.10	0.28	5.00	2.72	0.51	1.10	2.16
  4	4.63	3.86	1.27	0.10	0.26	5.74	4.11	0.60	1.22	2.03
  5	4.45	3.79	1.28	0.10	0.33	5.38	3.70	0.56	1.25	2.23
  6	4.75	3.91	1.28	0.09	0.21	5.97	4.13	0.67	1.24	1.85
  7	4.84	3.87	1.52	0.09	0.27	6.28	3.90	0.68	1.37	2.01
  8	4.74	3.95	1.63	0.10	0.31	5.88	3.64	0.71	1.48	2.08
  9	4.51	3.82	1.65	0.09	0.34	5.49	3.64	0.66	1.40	2.12
  10	4.73	3.81	1.73	0.09	0.35	6.09	3.30	0.65	1.35	2.08
  11	4.51	3.85	2.23	0.10	0.39	5.44	3.28	0.80	1.29	1.61
  12	4.55	3.70	2.76	0.10	0.33	5.80	3.13	1.05	1.40	1.33

  Bonafous and other noticed that this ratio is 2.  This conclusion was based on their finding that in the presence of sulphur, 3Si 4+, in the silicate phases, is substituted by 2Al 3+ + S 6+,

  • Taylor declared that this ratio is nearly more than 2, even in individual X-ray microanalyses, due to the presence of other substitutions and the accuracy of the results.
  • Our findings and especially the results of the samples 2 to 10 conform to the previous conclusions.
  • The reason of the high ratio in the low sulphur clinker is coming from the fact that at low temperature the Al 3+ incorporates first in the silicate phases.

  The alumina incorporated in the silicate phases is divided into two groups. The first one enters the structure at low temperature and without the influence of sulphur. In the absence of SO 3 there is an excess of nontetrahedral cations and the number of oxygen atoms lie close to the ideal number for stoichiometric Ca 2 SiO 4,

  This suggests interstitial stuffing of large cation as the main mechanism for accommodating Al on the Si site before significant solid solution of S takes place, The second one is incorporated in the silicate phases with the influence of sulphur. This phenomenon is improved when the temperature exceed the 1200°C,

  In the first sample, the ratio Al 3+ /S 6+ is 4.18. In this case, part of the alumina is incorporated into the silicate phases without the influence of sulfate. The amount of SO 3 in the silicate phases is 0.22% and that for Al 2 O 3 is 0.92 (). Based on the findings of Bonafous and other the ratio Al 3+ /S 6+ is 2.

  The calculated amount of alumina entered into the silicate phase crystals with the influence of sulphur in the first sample is 0.22 × 2 = 0.44%. The amount of alumina entered into the silicate phase crystals without the influence of sulphur in the first sample is 0.92 – 0.44 = 0.48%. The entry of alumina into silicate phase reduces the amount available for the C 3 A formation.

  The amount, of the first group, is influenced to an important degree by the changes in the composition of the ferrite compound and it is compensated by the replacement of Al 3+ by other ions in the C 3 A crystal, mainly the Si 4+ and Fe 3+, These phenomena lead to minimize the effect of the first group on the amount of C 3 A.

  The measured amount of the C 3 A becomes less than that calculated by Bogue by an average of only 3%, The amount of sulphur in the silicate phases depend on the percentages of belite. The concentration of sulfate in belite is 4 to 5 time that in alite, Regarding the second group, the incorporation of sulfate in the Alite and Belite, tends to increase the amount of alumina in the silicate phases,

  This phenomenon was shown in the clinker samples 2 to 10. The incorporation of alumina was increased, in correlation with the sulfate, in the silicate phases. The ratio of Al 2 O 3 /SO 3, in the silicate phase, became around 2. Bonafous and other explain the ability of silicate phases, principally the belite, to accept simultaneously Al and S at higher dosage by the existence of synergism between both.

  The presence of AlO 4 5− decreases the negative charge induced by the substitution of SO 4 2− for SiO 4 4−, The calculation of the sulphate phases becomes inaccurate when the percentage of clinker SO 3 exceeds 1%. The reason for that is related to the SO 3 /Alkali ratio. At lower ratio, sulphate preferably combines with alkali to generate the Acranite K 2 SO 4 and Aphtihitalite (K 3 Na (SO 4 ) 2 ),

  Increasing the ratio leads to the development of calcium langbeinite (Ca 2 K 2 (SO 4 ) 3 ), In remarkably high ratios of SO 3 /Alkali and SO 3 content, the anhydrite CaSO 4 has been detected in particular clinkers, The incorporation of alumina in the silicate phases seams to stop (samples 11 and 12) when the clinker SO 3 exceeds the 2%.

  Our result conforms to previous findings. Taylor calculated the maximum probable amount of SO 3 in the silicate phases to be about 0.8%, Miller and Tang found the largest amount of SO 3 present in the silicate phases to be 0.68%, The extra amount of sulphate shown in the over 2% clinker SO 3 (samples 11 and 12) could come from the presence of anhydrite in the solid phase since it is not in correlation with the alumina.

  The first group of alumina was calculated from the first sample with the lower clinker sulphate. The calculation of the second group of alumina in the silicate phase was done by detecting the amount of the first group (0.48) from the total amount of alumina in the silicate phases.

  The correlation between the total clinker SO 3 and the amount of alumina incorporated in the silicate phases, under the influence of sulphur, is acceptable (). The percentages of alumina in the silicate phase, forced by the sulphur, became 0.469 × %SO 3 + 0.15. The first group of alumina incorporated in the silicate phases, without the sulphur influence, is compensated by the substitution of other elements, where as the second one is not ().

  The impurities are one of the main factors of the stabilization of various clinker crystalline forms. The most important consequence of the occurrence of impurities in the lattices of matrix clinker compounds is a disagreement between the calculated and real amount of phases in clinker.

  The amount of C 3 A in high sulphur clinker could be calculated by the following formula: % of C 3 A = 2.65 × (%Al 2 O 3 – (%Al 2 O 3   (Silicate  phases) ) −1.692 × %Fe 2 O 3       C 3 A =    2.65    ×    ( % Al 2 O 3 − ( 0.469    ×    % SO 3    +    0.15 ) )   − 1.692    ×    % Fe 2 O 3, (1) In the proposed formula, the percentage of SO 3 will be equal to 2 when the clinker SO 3 exceeds the 2%, because over this limit the amount of alumina, in the silicate phases, becomes constant regardless the clinker SO 3,

  The calculated C 3 A amount by the new formula is more realistic than that calculated by Bogue formula (). Comparison of the C 3 A results.

  C 3 A calculated by Bogue formula	C 3 A calculated by the new formula	C 3 A measured according to ASTMC1365:06
  5.68	4.42	4.38
  6.09	3.54	3.30
  6.28	3.99	3.90
  5.44	2.55	3.28
  5.00	3.19	2.72
  5.38	3.39	3.70
  5.80	2.91	3.13
  5.42	3.68	3.91
  5.88	3.45	3.64
  5.49	3.04	3.64
  5.74	3.76	4.11
  5.97	3.98	4.13

  Increasing the amount of SO 3 in the low alkali clinker decreases the percentages of C 3 A due to the high incorporation of alumina in the silicate phases. The correlation is linear till the clinker SO 3 reaches the 2%. Over that the SO 3 influence became undetectable.

  1. In order to be more realistic, the proposed calculation of the C 3 A percentages takes into consideration the Al 2 O 3 loss.
  2. The outcome shows that the new calculated results match more closely with the measured one, than with those calculated by Bogue formula.1. Bogue RH.
  3. Calculation of the compounds in Portland cement.

  Industrial and Engineering Chemistry,1929; 1 (4):192–197.2. Strunge J, Knöfel D, Dreizler I. Einflusse der alkaline und des Sulfates unter berucksichtigung des silicatmoduls auf die zementeigenschaften. Teil II. Zement-Kalk-Gips,1985; 38 (9):441–450.3.

  Gutt W, Smith MA. Studies of the role of calcium sulfate in the manufacture of Portland cement clinker. Transactions of the British Ceramic Society,1968; 67 (10):487–510.4. Moranville-Regourd M, Boikova AI. Chemistry structure, properties and quality of clinker. In: Proceedings of the 9th International Congress of the Chemistry of Cement, vol.1; 1992; New Delhi, India.

  pp.3–45.5. Odler I, Zhang H. Investigations on high SO 3 Portland cement clinkers. World Cement,1996; 27 (2):73–77.6. Gies A, Knöfel D. Influence of sulfur on the composition of belite-rich clinkers and the technological properties of the resulting cements.

  Cement and Concrete Research,1987; 17 (2):317–328.7. Knöfel D, Spohn E. Der quantitative phasengehalt in portlandzementklinkern. Zement-Kalk-Gips,1969; 22 (10):471–476.8. Hamou-Tagnit A, Sarkar SL. The influence of varying sulphur content on the microstructure of commercial clinkers and the properties of cement.

  World Cement,1990; 21 (9):389–393.9. Borgholm H, Jons E. Production of mineralised clinker, International Cement Seminar, 2001, FLSmidth.10. Locher FW, Richartz W, Sprung S, Sylla HM. Erstarren von zement. Teil III: Einfluß der Klinkerherstellung. Zement-Kalk-Gips,1982; 35 (12):S669–S676.11.

  Newkirk T. Effect of SO 3 on the alkali compounds of Portland cement clinker. Journal of Research of the National Bureau of Standards,1951; 47 (5):349–356.12. Bonafous L, Bessada C, Massiot D, Coutures J, Holland BL, Colombet P.29 Si MAS NMR study of dicalcium silicate: the structural influence of sulfate and alumina stabilizers.

  Journal of the American Ceramic Society,2005; 78 (10):2603–2608.13. Taylor HFW. Distribution of sulfate between phases in Portland cement clinkers. Cement and Concrete Research,1999; 29 (8):1173–1179.14. Herfort D, Soerensen J, Coulthard E. Mineralogy of sulfate rich clinker and the Potential for internal sulfate attack.

  World Cement,1997; 28 (5):77–85.15. Lea FM. The Chemistry of Cement and Concrete,3rd edition. New York, NY, USA: Chemical Publishing; 1971.16. Taylor HFW. Cement Chemistry,2nd edition. London, UK: Tomas Telford Services; 1998.17. Michaud V, Suderman RW. Anhydrite in high sulfur trioxide (SO 3 )/alkali clinkers: dissolution kinetics and influence on concrete durability.

  Cement, Concrete and Aggregates,1999; 21 (2):196–201.18. Gartner EM, Tang FJ. Formation and properties of high sulfur Portland cement clinkers. Cemento,1987; 84 :141–165.19. Twomey C, Brikinshaw C, Breen S. The identification of sulfur containing phases present in cement clinker manufactured using a high sulfur petroleum coke fuel.

  Why is 2/3 gypsum used for the production of cement?

  Why Gypsum is Added to Cement? Published: October 31, 2015 Portland cement is hydraulic cement. This means that it sets and hardens faster due to a chemical reaction with water. As a result, it will also harden under water. Whenever water is mixed with cement, a smooth paste is formed that remains plastic for a short time.

  During this period, the paste can be disturbed and remixed without injury. As the reaction between water and cement continues, the plasticity of the cement paste is lost. This early period in the hardening of cement is known as `Setting of Cement’. Why Gypsum is added to Cement? When cement is mixed with water, it becomes hard over a period of time.

  This is called setting of cement. Gypsum is often added to Portland cement to prevent early hardening or “flash setting”, allowing a longer working time. Gypsum slows down the setting of cement so that cement is adequately hardened.

  How is C3S clinker calculated?

  Calculation of the C3A Percentage in High Sulfur Clinker 1 Faculty of Sciences, Saint Joseph University, Campus of Sciences and Technologies, Mar Roukos. Mkallès, P.O. Box.11-514 Riad El Solh, Beirut 11072050, Lebanon 2 Plant- Laboratory Department, Cimenterie Nationale S.A.L., Old Tripoli Road, Chekka, North Lebanon.P.O.

  Box.11-5101 Riad El Solh, Beirut 11072180, Lebanon Find articles by 1 Faculty of Sciences, Saint Joseph University, Campus of Sciences and Technologies, Mar Roukos. Mkallès, P.O. Box.11-514 Riad El Solh, Beirut 11072050, Lebanon Find articles by 1 Faculty of Sciences, Saint Joseph University, Campus of Sciences and Technologies, Mar Roukos.

  Mkallès, P.O. Box.11-514 Riad El Solh, Beirut 11072050, Lebanon Find articles by 1 Faculty of Sciences, Saint Joseph University, Campus of Sciences and Technologies, Mar Roukos. Mkallès, P.O. Box.11-514 Riad El Solh, Beirut 11072050, Lebanon 2 Plant- Laboratory Department, Cimenterie Nationale S.A.L., Old Tripoli Road, Chekka, North Lebanon.P.O.

  Box.11-5101 Riad El Solh, Beirut 11072180, Lebanon *Sayed Horkoss: Academic Editor: Peter A. Tanner Received 2010 Apr 1; Revised 2010 May 10; Accepted 2010 May 10. © 2010 Sayed Horkoss et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

  The aim of this paper is to clarify the influence of the clinker SO 3 on the amount of C 3 A. The calculation of the cement phases percentages is based on the research work, Calculation of the Compounds in Portland Cement, published by Bogue in 1929,The usage of high sulphur fuels, industrial wastes, and tires changes completely the working condition of Bogue because the assumed phase compositions may change.

  1. The results prove that increasing the amount of SO 3 in the low alkali clinker decreases the percentages of C 3 A due to the high incorporation of alumina in the clinker phases mainly C 2 S and C 3 S.
  2. The correlation is linear till the clinker SO 3 reaches the 2%.
  3. Over that the influence of the clinker SO 3 became undetectable.

  A new calculation method for the determination of the C 3 A in the high sulphur and low alkali clinker was proposed. Portland cement is a hydraulic material composed primary of calcium silicates, aluminates, and ferrites. In a rotary kiln, at temperature reaching the 1450°C, clinker nodules are produced from a finely ground, homogenised blend of limestone, shale and iron ore.

  The nodules are subsequently ground with gypsum, which serves to control setting, to a fine powder to produce finished Portland cement. The composition and texture (crystal size, abundance, and distribution) of clinker phases result from complex interactions of raw feed chemical and mineralogical composition, particle size distribution, feed homogenization, and the heating and cooling regime.

  In order to simplify these phenomena, Bogue proposed an approach for the development of the clinker phases. The ferric oxide (Fe 2 O 3 ) reacts with aluminium oxide (Al 2 O 3 ) and lime (CaO) to form the tetracalcium aluminoferrite (C 4 AF or Ca 4 Al 2 Fe 2 O 10 ).

  • The remaining aluminium oxide reacts with lime to form the tricalcium aluminate (C 3 A or Ca 3 Al 2 O 6 ).
  • The lime reacts with the silicate oxide (SiO 2 ) to form two calcium silicates phases, the dicalcium silicate (Belite, C 2 S or Ca 2 SiO 4 ) and tricalcium silicate (Alite, C 3 S or Ca 3 SiO 5 ).

  Based on the above approach, Bogue proposed four formulae for the calculation of the clinker phase concentrations. Increasing the amount of the high sulphur fuels and the level of waste valorisation, in the cement kilns, changes completely the working condition of Bogue.

  1. The negative influence of sulphate on the percentages of silicate phases (alite and belite) was earlier detected by the XRD but that on the tricalcium aluminate (C 3 A) is still unclear due to the conclusion contradiction in the reported literature.
  2. The sulphates reduce the viscosity and surface tension of the clinker liquid phases, shifting the equilibrium of the melt into unstable range which is characterized by low nucleus forming frequency and high growth rate of crystal leading to stabilization of the Belite crystals.

  The incorporation of sulphur in the Belite stabilizes the Belite structure, whereby the uptake of CaO is inhibited and the formation is suppressed, This phenomenon increases the amount of Belite and decreases that of Alite in the clinker, This reported conclusion was assured by many investigations done later,

  The composition of the matrix (aluminates and ferrites) is not altered by the level of SO 3 in the clinker, In particularly the amount of the tricalcium aluminate (Ca 3 Al 2 O 6 ) is not affected by the SO 3 level, This conclusion was not compatible with the observation of Hamou-Tagnit and Sarker, indicating that increasing the SO 3 level increases the amount of Ca 3 Al 2 O 6 in the clinker where the conclusion of Borgholm and Jons showed the opposite,

  These contradictions in the literature were due to the fact that many parameters could affect the development of C 3 A (Ca 3 Al 2 O 6 ) principally the kiln atmosphere and the raw meal chemistry. Locher and others detect that the kiln atmosphere, especially the amount of oxygen, had an influence on the amount of C 3 A.

  Reducing kiln atmosphere inhibits partly the oxidation of the bivalent iron (Fe 2+ ), presented in the kiln feed, leading to increase in the amount of C 3 A. The sulphur introduced into the cement kiln from both sides, the kiln feed and kiln burner, is in chemically reduced form such as S 0, S 1−, and S 2−,

  These sulphur forms are oxidized to S 4+ and S 6+ in the kiln system. This oxidizing process consumes some oxygen quantity leading to a reduction in the amount of oxygen in the kiln system. The presence of sodium oxide in the kiln feed affects the amount of C 3 A,

  One of the forms of sodium oxide in the clinker is the Na 2 O · 8CaO · 3Al 2 O 3 · At clinkering temperature this compound reacts with sulphur to produce the Na 2 SO 4 and C 3 A, This study will focus only on the influence of the SO 3 on the development of C 3 A (Ca 3 Al 2 O 6 ). The other factors listed above are controlled to avoid any interaction with the results.

  The development of the Tricalcium aluminates Ca 3 Al 2 O 6, in the cement kiln production, is affected by many parameters such as the kiln atmosphere and the amount of sodium oxide in the raw feed, This could be the reason of the large contradiction in the conclusion of the reported investigations.

  In order to avoid any interactions, not only from the chemical compounds but also that related to the kiln operation, the clinker samples were selected in a stable kiln production operation conditions. All samples are commercial clinker, sampled from Cimenterie Nationale SAL. The free lime of the clinker was less than 1% and the percentage of the kiln inlet oxygen was around 3%.

  The samples were analyzed immediately, to avoid any influence from storage and humidity. The variation of the clinker SO 3 was made by changing the fuel type in the main burner as follows:

  1. fuel oil containing 2.0% S,
  2. petroleum coke containing 4.5% S,
  3. petroleum coke containing 6.0% S.

  The chemical and mineralogical analyses were done respectively according to ASTM C114 and ASTM C1365 standards. The calibration of the ARL 9800 was done using NIST standards. The fusion Claisse machine and the Herzog HTP 40 press were used for the sample preparation of the chemical and mineralogical analysis.

  The KOSH (potassium hydroxide and sucrose) method was implemented in order to detect the percentage of SO 3 and Al 2 O 3 in the silicate phases. The results () showed an obvious influence of the SO 3 percentages on the amount of C 3 A in the low alkali clinker. In all samples, the measured percentages of C 3 A were lower than the calculated.

  Influence of the clinker SO 3 on the C 3 A. The correlation between the amount of C 3 A (Ca 3 Al 2 O 6 ) and the total percentages of clinker SO 3 was linear till the clinker SO 3 reached just 2%. Over that the influence of the clinker SO 3 becomes indistinguishable since the standard deviation of the results according to ASTM C1365:06 is 0.47.

  	Al 2 O 3	Fe 2 O 3	SO 3	Na 2 O	K 2 O	C 3 A (calculated)	C 3 A (measured)	SO 3 (Silicate phases)	Al 2 O 3 (Silicate phases)	Al 2 O 3 /  SO 3
  1	4.62	3.88	0.69	0.10	0.37	5.68	4.38	0.22	0.92	4.18
  2	4.53	3.89	1.08	0.10	0.26	5.42	3.91	0.55	1.24	2.25
  3	4.48	4.06	1.14	0.10	0.28	5.00	2.72	0.51	1.10	2.16
  4	4.63	3.86	1.27	0.10	0.26	5.74	4.11	0.60	1.22	2.03
  5	4.45	3.79	1.28	0.10	0.33	5.38	3.70	0.56	1.25	2.23
  6	4.75	3.91	1.28	0.09	0.21	5.97	4.13	0.67	1.24	1.85
  7	4.84	3.87	1.52	0.09	0.27	6.28	3.90	0.68	1.37	2.01
  8	4.74	3.95	1.63	0.10	0.31	5.88	3.64	0.71	1.48	2.08
  9	4.51	3.82	1.65	0.09	0.34	5.49	3.64	0.66	1.40	2.12
  10	4.73	3.81	1.73	0.09	0.35	6.09	3.30	0.65	1.35	2.08
  11	4.51	3.85	2.23	0.10	0.39	5.44	3.28	0.80	1.29	1.61
  12	4.55	3.70	2.76	0.10	0.33	5.80	3.13	1.05	1.40	1.33

  Bonafous and other noticed that this ratio is 2.  This conclusion was based on their finding that in the presence of sulphur, 3Si 4+, in the silicate phases, is substituted by 2Al 3+ + S 6+,

  • Taylor declared that this ratio is nearly more than 2, even in individual X-ray microanalyses, due to the presence of other substitutions and the accuracy of the results.
  • Our findings and especially the results of the samples 2 to 10 conform to the previous conclusions.
  • The reason of the high ratio in the low sulphur clinker is coming from the fact that at low temperature the Al 3+ incorporates first in the silicate phases.

  The alumina incorporated in the silicate phases is divided into two groups. The first one enters the structure at low temperature and without the influence of sulphur. In the absence of SO 3 there is an excess of nontetrahedral cations and the number of oxygen atoms lie close to the ideal number for stoichiometric Ca 2 SiO 4,

  This suggests interstitial stuffing of large cation as the main mechanism for accommodating Al on the Si site before significant solid solution of S takes place, The second one is incorporated in the silicate phases with the influence of sulphur. This phenomenon is improved when the temperature exceed the 1200°C,

  In the first sample, the ratio Al 3+ /S 6+ is 4.18. In this case, part of the alumina is incorporated into the silicate phases without the influence of sulfate. The amount of SO 3 in the silicate phases is 0.22% and that for Al 2 O 3 is 0.92 (). Based on the findings of Bonafous and other the ratio Al 3+ /S 6+ is 2.

  1. The calculated amount of alumina entered into the silicate phase crystals with the influence of sulphur in the first sample is 0.22 × 2 = 0.44%.
  2. The amount of alumina entered into the silicate phase crystals without the influence of sulphur in the first sample is 0.92 – 0.44 = 0.48%.
  3. The entry of alumina into silicate phase reduces the amount available for the C 3 A formation.

  The amount, of the first group, is influenced to an important degree by the changes in the composition of the ferrite compound and it is compensated by the replacement of Al 3+ by other ions in the C 3 A crystal, mainly the Si 4+ and Fe 3+, These phenomena lead to minimize the effect of the first group on the amount of C 3 A.

  • The measured amount of the C 3 A becomes less than that calculated by Bogue by an average of only 3%,
  • The amount of sulphur in the silicate phases depend on the percentages of belite.
  • The concentration of sulfate in belite is 4 to 5 time that in alite,
  • Regarding the second group, the incorporation of sulfate in the Alite and Belite, tends to increase the amount of alumina in the silicate phases,

  This phenomenon was shown in the clinker samples 2 to 10. The incorporation of alumina was increased, in correlation with the sulfate, in the silicate phases. The ratio of Al 2 O 3 /SO 3, in the silicate phase, became around 2. Bonafous and other explain the ability of silicate phases, principally the belite, to accept simultaneously Al and S at higher dosage by the existence of synergism between both.

  1. The presence of AlO 4 5− decreases the negative charge induced by the substitution of SO 4 2− for SiO 4 4−,
  2. The calculation of the sulphate phases becomes inaccurate when the percentage of clinker SO 3 exceeds 1%.
  3. The reason for that is related to the SO 3 /Alkali ratio.
  4. At lower ratio, sulphate preferably combines with alkali to generate the Acranite K 2 SO 4 and Aphtihitalite (K 3 Na (SO 4 ) 2 ),

  Increasing the ratio leads to the development of calcium langbeinite (Ca 2 K 2 (SO 4 ) 3 ), In remarkably high ratios of SO 3 /Alkali and SO 3 content, the anhydrite CaSO 4 has been detected in particular clinkers, The incorporation of alumina in the silicate phases seams to stop (samples 11 and 12) when the clinker SO 3 exceeds the 2%.

  • Our result conforms to previous findings.
  • Taylor calculated the maximum probable amount of SO 3 in the silicate phases to be about 0.8%,
  • Miller and Tang found the largest amount of SO 3 present in the silicate phases to be 0.68%,
  • The extra amount of sulphate shown in the over 2% clinker SO 3 (samples 11 and 12) could come from the presence of anhydrite in the solid phase since it is not in correlation with the alumina.

  The first group of alumina was calculated from the first sample with the lower clinker sulphate. The calculation of the second group of alumina in the silicate phase was done by detecting the amount of the first group (0.48) from the total amount of alumina in the silicate phases.

  The correlation between the total clinker SO 3 and the amount of alumina incorporated in the silicate phases, under the influence of sulphur, is acceptable (). The percentages of alumina in the silicate phase, forced by the sulphur, became 0.469 × %SO 3 + 0.15. The first group of alumina incorporated in the silicate phases, without the sulphur influence, is compensated by the substitution of other elements, where as the second one is not ().

  The impurities are one of the main factors of the stabilization of various clinker crystalline forms. The most important consequence of the occurrence of impurities in the lattices of matrix clinker compounds is a disagreement between the calculated and real amount of phases in clinker.

  The amount of C 3 A in high sulphur clinker could be calculated by the following formula: % of C 3 A = 2.65 × (%Al 2 O 3 – (%Al 2 O 3   (Silicate  phases) ) −1.692 × %Fe 2 O 3       C 3 A =    2.65    ×    ( % Al 2 O 3 − ( 0.469    ×    % SO 3    +    0.15 ) )   − 1.692    ×    % Fe 2 O 3, (1) In the proposed formula, the percentage of SO 3 will be equal to 2 when the clinker SO 3 exceeds the 2%, because over this limit the amount of alumina, in the silicate phases, becomes constant regardless the clinker SO 3,

  The calculated C 3 A amount by the new formula is more realistic than that calculated by Bogue formula (). Comparison of the C 3 A results.

  C 3 A calculated by Bogue formula	C 3 A calculated by the new formula	C 3 A measured according to ASTMC1365:06
  5.68	4.42	4.38
  6.09	3.54	3.30
  6.28	3.99	3.90
  5.44	2.55	3.28
  5.00	3.19	2.72
  5.38	3.39	3.70
  5.80	2.91	3.13
  5.42	3.68	3.91
  5.88	3.45	3.64
  5.49	3.04	3.64
  5.74	3.76	4.11
  5.97	3.98	4.13

  Increasing the amount of SO 3 in the low alkali clinker decreases the percentages of C 3 A due to the high incorporation of alumina in the silicate phases. The correlation is linear till the clinker SO 3 reaches the 2%. Over that the SO 3 influence became undetectable.

  • In order to be more realistic, the proposed calculation of the C 3 A percentages takes into consideration the Al 2 O 3 loss.
  • The outcome shows that the new calculated results match more closely with the measured one, than with those calculated by Bogue formula.1. Bogue RH.
  • Calculation of the compounds in Portland cement.

  Industrial and Engineering Chemistry,1929; 1 (4):192–197.2. Strunge J, Knöfel D, Dreizler I. Einflusse der alkaline und des Sulfates unter berucksichtigung des silicatmoduls auf die zementeigenschaften. Teil II. Zement-Kalk-Gips,1985; 38 (9):441–450.3.

  Gutt W, Smith MA. Studies of the role of calcium sulfate in the manufacture of Portland cement clinker. Transactions of the British Ceramic Society,1968; 67 (10):487–510.4. Moranville-Regourd M, Boikova AI. Chemistry structure, properties and quality of clinker. In: Proceedings of the 9th International Congress of the Chemistry of Cement, vol.1; 1992; New Delhi, India.

  pp.3–45.5. Odler I, Zhang H. Investigations on high SO 3 Portland cement clinkers. World Cement,1996; 27 (2):73–77.6. Gies A, Knöfel D. Influence of sulfur on the composition of belite-rich clinkers and the technological properties of the resulting cements.

  • Cement and Concrete Research,1987; 17 (2):317–328.7.
  • Nöfel D, Spohn E.
  • Der quantitative phasengehalt in portlandzementklinkern.
  • Zement-Kalk-Gips,1969; 22 (10):471–476.8.
  • Hamou-Tagnit A, Sarkar SL.
  • The influence of varying sulphur content on the microstructure of commercial clinkers and the properties of cement.

  World Cement,1990; 21 (9):389–393.9. Borgholm H, Jons E. Production of mineralised clinker, International Cement Seminar, 2001, FLSmidth.10. Locher FW, Richartz W, Sprung S, Sylla HM. Erstarren von zement. Teil III: Einfluß der Klinkerherstellung. Zement-Kalk-Gips,1982; 35 (12):S669–S676.11.

  • Newkirk T.
  • Effect of SO 3 on the alkali compounds of Portland cement clinker.
  • Journal of Research of the National Bureau of Standards,1951; 47 (5):349–356.12.
  • Bonafous L, Bessada C, Massiot D, Coutures J, Holland BL, Colombet P.29 Si MAS NMR study of dicalcium silicate: the structural influence of sulfate and alumina stabilizers.

  Journal of the American Ceramic Society,2005; 78 (10):2603–2608.13. Taylor HFW. Distribution of sulfate between phases in Portland cement clinkers. Cement and Concrete Research,1999; 29 (8):1173–1179.14. Herfort D, Soerensen J, Coulthard E. Mineralogy of sulfate rich clinker and the Potential for internal sulfate attack.

  1. World Cement,1997; 28 (5):77–85.15. Lea FM.
  2. The Chemistry of Cement and Concrete,3rd edition.
  3. New York, NY, USA: Chemical Publishing; 1971.16.
  4. Taylor HFW.
  5. Cement Chemistry,2nd edition.
  6. London, UK: Tomas Telford Services; 1998.17.
  7. Michaud V, Suderman RW.
  8. Anhydrite in high sulfur trioxide (SO 3 )/alkali clinkers: dissolution kinetics and influence on concrete durability.

  Cement, Concrete and Aggregates,1999; 21 (2):196–201.18. Gartner EM, Tang FJ. Formation and properties of high sulfur Portland cement clinkers. Cemento,1987; 84 :141–165.19. Twomey C, Brikinshaw C, Breen S. The identification of sulfur containing phases present in cement clinker manufactured using a high sulfur petroleum coke fuel.

  What is the percentage of C3A in cement?

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  Tricalcium aluminate (C3A) is one of the main constituents of Portland cement. Even though it represents less than 10% of the total composition, its strong reaction with water can lead to a rapid setting, called flash set. Gypsum is added to regulate this reaction and preserves the workability of the cement paste at early ages.

  • The understanding of the C3A-gypsum reaction is therefore crucial for the comprehension of the early hydration of cement.
  • The role of the amount of C3A and the sulfate balance of cement hydration are of major interest since two important routes for the development of new cementitious materials are the increasing rate of substitution materials and the increasing level of aluminate in clinker.

  This thesis aimed to investigate the C3A-gypsum reaction alone and in the presence of alite in order to provide basic knowledge on the C3A-gypsum reactions and study the interactions that occur between the cement phases when hydration occurs in alite-C3A-gypsum systems.

  Alite and C3A as well as clinkers of controlled composition were synthesized. Model systems composed of C3A with different gypsum additions and alite-C3A-gypsum systems were studied in terms of hydration kinetics, phase assemblage and microstructural development. This work confirmed the findings of previous works on the mechanism that controls C3A-gypsum hydration when sulfate ions are present in solution and gave new results on the reaction when gypsum is depleted.

  It was shown that AFm phases do not crystallize only as platelets that fill the space between the C3A grains but also form an “inner” product within the original C3A grain boundaries and that hydrogarnet (for which the presence depends on the gypsum addition) crystallizes as a rim around C3A grains.

  Moreover the influence of the gypsum addition on the morphology of the AFm platelets and the role of their morphology on the hydration rate were highlighted. In the presence of alite the hydration kinetics of C3A-gypsum systems was subject to change due to the adsorption of sulfate ions on C-S-H and the reduction of the space available for the reaction.

  In addition, with the correlation of calorimetric, XRD and SEM analyses it was possible to observe a second formation of ettringite from C3A and sulfate ions released from C-S-H after the depletion of gypsum. Finally, the rate of alite hydration related to the growth of C-S-H was shown to be modified in the presence of C3A and gypsum.

  What is C3S in clinker?

  5.1.1 Chemical stages – Tricalcium silicate (Ca 3 SiO 5 or C 3 S) is the main phase of Portland cement clinker. It is called ‘alite’ in clinker because it is not pure tricalcium silicate and contains a number of impurities substituted in its crystal lattice. Once in contact with water, Ca 3 SiO 5 is hydroxylated and the surface dissolves according to Eq.5.1 ( Barret et al., 1983; Barret and Bertrandie, 1986 ): C a 3 Si O 5 + 3 H 2 O → 3 C a 2 + + 4 O H − + H 2 Si O 4 2 − The solution quickly becomes supersaturated with respect to calcium hydrosilicate (CSH), which is less soluble than tricalcium silicate. When the maximum degree of supersaturation is reached, CSH precipitates according to Eq.5.2 : C / S C a 2 + + 2 C / S − 1 O H − + H 2 Si O 4 2 − → C SH where C/S is the Ca/Si ratio of the CSH formed and C/S < 2. The system never reaches the solubility of tricalcium silicate. Because all the calcium ions are not consumed by the precipitation of CSH, increasing concentrations of calcium and hydroxide ions in solution lead to the maximum supersaturation of the liquid phase with respect to calcium hydroxide (this corresponds to Ca (OH) 2 = 30–36 mmol/l at 25 °C), which then precipitates as Portlandite according to the reaction in Eq.5.3 : C a 2 + + 2 O H − → Ca OH 2 From that moment, the three reactions shown in Eq.5.1 to 5.3 become simultaneous. The concentration of calcium hydroxide is always greater than its solubility (22 mmol/l at 25 °C) and the system is still supersaturated with respect to CSH. The progress of these chemical processes (i.e. hydration) can be described by a sigmoidal evolution with time ( Fig.5.1 ). We observe an initial part where progress remains low, which depends on the number of initial germs of CSH precipitating on the surface of the grain ( Garrault and Nonat, 2001 ). Acceleration is linked to the free growth of CSH on this surface. During this stage, hydration is controlled by the rate of growth of CSH. The covering of anhydrous grains by CSH slows down the reaction, which becomes limited by the diffusion of reactants through the continuous layer of hydrate around the grains. Then there is growth of CSH instead of dissolving tricalcium silicate between the anhydrous grains and first CSH layer and outwardly on the solution–CSH layer interface ( Tennis and Jennings, 2000; Jennings, 2008 ). The reaction becomes very slow and may take several months or years. These chemical reactions start very slowly, allowing for the safe casting of concrete before setting. 5.1, Evolution of the degree of hydration of tricalcium silicate vs. time. Read full chapter URL: https://www.sciencedirect.com/science/article/pii/B9780857090287500054

  

  Nehru Baral