|Title of Invention||
A HYDRAULIC CEMENT COMPOSITION
|Abstract||Abstract The invention relates to a hydraulic cement composition and the process for production of hydraulic cementitious material containing pozzolana, preferably in the form of flyash, lime and gypsum with the major constituent being flyash, the three constituents being included in the composition In predetermined ratios commensurate to destined stoichiometry.|
The present invention relates to a novel cement composition and a process for the manufacture thereof with its major constituent being pozzolanic material, more particularly fly ash. The novel cement composition has been generally referred to hereinafter as FaL-G, which stands for fly ash, lime and gypsum.
Activating any pozzolanic material or fly ash with lime is a well-known practice in the history of building materials.
However, because such lime activated pozzolanic materials render feeble strengths with protracted span of rheological behaviours spanning to several weeks, some of the processes have used curing of lime activated pozzolanic materials under hydro-thermal conditions, predominantly in a system such as autoclave.
In certain cases, gypsum has been added with abundant precaution in moderate doses not exceeding 1-2%, in order to initiate a specific mineralogical phase called ettringite. But keeping in view the hostile behaviours of ettringite, particularly in the presence of invigorated hydro-thermal process parameters, the addition of gypsum was always taken with a note of confinement.
There is precedence of using activated lime pozzolanic blends in association with cement together with gypsum in certain cases, where no rational synthesis of quantitative explanations were given for the constituent percentages. IS:4098-1983 (specification for lime-pozzolanic mixture) and 1S:3466-1988 (specification for masonry cement) are two such specifications for the referred product.
In another approach, blending fly ash with cement is a known practice in the production of Portland Pozzolan Cement (PPC). For this purpose fly ash and
clinker are interground together with gypsum in one approach. In the other fly ash is added to ground clinker and ground gypsum. IS 1489 (Partl)-1991 allows 10-25% of fly ash that was enlarged to 15-35% through an amendment.
With regard to precast components, 1S:12894-1991 for fly ash-lime bricks is another reference. This code was silent and hesitant in upholding the need to add gypsum while it was authored in 1991. However, after understanding the FaL-G chemistry and upon appeal from the inventors, the code has been duly amended incorporating gypsum as the suitable additive.
While civilisation was using lime mortars and lime activated pozzolanic binders as the binding media to get alongwith the constructional needs. Ordinary Portland Cement (OPC) was innovated in 1S24 A.D. OPC is a versatile binder developed and accepted for its early results (strength gain) that increases day after day in the presence of water to render a hard water-impervious mass. This behaviour could be possible because of the association of certain compounds into mineralogical phases and then their dissociation through hydrolytic forces during the process of hydration to subsequently get associated into new order of hydrated mineralogical phases through solid solutions and crystallisation.
The main problem with OPC is free lime availability even at prolonged age of hydration. The chemistry of mineralogical phases during the process of clinkerisation has called for specified quantity of lime but it is the same lime that remains as excess during hydrolysis and, when concrete becomes permeable, triggers off numerous chemical reactions of detrimental nature. This problem has become acute with the development of high early strength cements such as 43 gr. and 53gr. In low early strength OPC the C3S to C2S ratio was about 1:2 which is almost reversed to 2:1 in the anxiety of early strengths. But, in the process, the surplus hydrated lime and heat of hydration are commensurately released prematurely and prove high at early ages, as indicated in Table 1, opening floodgates for deterioration of concrete.
The production of OPC with high C3S calls for high contents of lime in raw meal to facilitate the synthesis of this particular mineralogical phase. Nevertheless, the very same lime after hydration of C3S is left in surplus in the order of 30-40%, thus making the cement concrete vulnerable to different types of chemical attacks.
To counteract the durability issues of OPC on account of heat of hydration and surplus hydrated lime, blended cements were invented upholding the virtues of complementary cement materials (CCM). Fly ash is one of such CCM and S 1489 (Part l)-1989 permitted the blend of fly ash in the range of 10-25%.
OBJECTS OF THE INVENTION
It is proved globally that slow setting and low early strength cement, as used till a few decades back, was more sound and durable comparing to high grade OPC, rendering high early strengths. When there was no OPC, multi-component cement systems were used centuries and millennia back those have lived for durability all along.
FaL-G is an innovation to offer such durable hydraulic cementitious systems, bringing the renaissance of durability to constructions. In the process this invention targets to use the abundantly available pozzolanic material, fly ash, which is a byproduct in coal fired boilers and thermal plants.
By facilitating to minimize the use of OPC clinker, FaL-G helps to conserve limestone and coal, thus enlarging span of their availability to more generations to come.
FaL-G cement system facilitates the production of precast building components; brick and block being predominant among them. Thus, by penetrating into clay brick market, it aims to conserve topsoil so much so the energy used in sintering the product.
Avoidance of energy in brick and cement segments helps to abate CO2 emission, bringing down the potential for global warming.
This invention aims to serve Sustainable Development, the global agenda of 21" century, for that matter the agenda of this (third) millennium, by complying with all the indicators through its multifarious contributions.
Therefore, the object of the present invention is to provide a cementitious blend comprising of fly ash, lime, and/or ground clinker/OPC and gypsum in specified ratio(s) suiting to different end use requirements.
The next object of the present invention is to provide a cementitious blend, wherein the said blend comprises of the byproducts in a ratio, which is different from any conventional blends, summoning for formulation of new codal specifications.
The next object of the present invention is to provide a cementitious blend, which is cost effective.
The next object of the present invention is for better utilisation and value addition of the byproducts such as fly ash, gypsum etc., for the preparation of the cementitious blend of the present invention.
The next object of the present invention is to minimize the exploitation of natural sources to achieve sustainable development In the construction industry.
The next object of the present Invention is to provide a cementitious blend, which conserves energy.
The next object of the present invention is to provide a cementitious blend, which develops a low early strength but achieves equal or more strength at later ages wherever the inputs are suitably monitored.
The next object of the present invention is to provide a cementitious blend, which renders enhanced durability or prolonged life to structures in contrast to conventionally used hydraulic cementitious blends.
The next object of the present invention is to provide a cementitious blend, which helps minimising the emission of CO2 in comparison to conventional cements, thus mitigating the global warming.
The next object of the present invention is to provide a cementitious blend, comprising of the ingredients in a predetermined ratio, which is applicable for the manufacture of bricks, whereby the erosion of topsoil is avoided.
The next object of the present invention is to provide specified cementitious blend as above to manufacture fly ash bricks, which do not need sintering in contrast to clay bricks, thus conserving fuel and abating CO2 emission.
SUMMARY OF THE INVENTION
Accordingly the present invention relates to a hydraulic cement composition comprising of pozzolan in the ratio of 55 to 90%; lime in the ratio of 1 to 45% or a source of lime with commensurate change in input or a combination thereof; and gypsum in the ratio of 5 to 15%.
Accordingly the present invention relates to a process for the preparation of a hydraulic cement composition wherein the pozzolan in the ratio of 55 to 90%; lime in the ratio of 1 to 45% or a source of lime with commensurate change in input or a combination thereof; and gypsum in the ratio of 5 to 15% are blended homogeneously in conventional equipments or in a specially designed dry blenders and wet mixers such as pan mixer.
DETAILED DESCRIPTION OF THE INVENTION
This is an invention to manufacture hydraulic cement mixture in contrast to the known prior art with reference to the role of cement or clinker.
The present invention comprehends the chemistry and mineralogical formation of fly ash-lime gypsum reactions altogether in a new perspective by which the role of ettringite is redefined and that is how FaL-G is synthesised. This
understanding and invention is valid to ail pozzolanic materials that include ground calcined clay and Metakaolin. However fly ash is extensively discussed in viev\/ of its mass scale availability over the other forms of pozzolans.
Fly ash is the half cooked cement, which gets activated in association with constituents such as lime and gypsum, and in the presence of moisture, rendering hydrated mineralogical phases akin to hydrated phases of OPC, of course, with different orientation of mineralogical and crystallographic constituents.
While lime activates both silica and alumina of fly ash, in addition to other minor constituents, gypsum interacts with lime activated aluminate hydrate phases, ultimately giving a complex composite matrix, which can behave parallel to any hydraulic cement.
This establishes cementitious behaviour as pronounced by crystallo-mineral combination of setting behaviour whereby it is identified that the feeble strength development of a particular crystallography can be made good through conducive initiation of specific mineralogy.
Ettringite is a hydrated mineralogical phase resulted out of chemistry among lime, reactive alumina and gypsum that formulates as per following equation:
Ettringite is a known mineralogical phase that formulates even in OPC as the first order of phase formation. But this ettringite subsequently transforms into monosulphate with progress of hydration. However, though it is permitted at the initial stage of hydration, care is taken to control the formation of this ettringite in OPC to specific levels, on account of which limited gypsum is added to OPC at
its production stage, because, the rheology of OPC and its mineralogical phase formations do not permit or accept the formation of more ettringite.
The input of gypsum is limited to 2% in prior art of practicing fly ash-lime compositions, preferably in autoclave process. In FaL-G, in view of the designed rheological course, the ettringite formation corresponding to reactive alumina content is accommodated. In other words, the invention does not confine the gypsum input to 2% as practiced in prior art, but it is dosed as high as to 15% in accordance to the need, which is pronounced based on the reactive alumina constituent of fly ash that differs from one source to other.
The invention justifies the addition of gypsum by identifying the role of gypsum in bringing down the permeability in concrete, more so when fly ash content is increased in the blend, as indicated by the data on three different fly ashes in Table 2.
However, this range totally depends upon the properties and characteristics of fly ash for optimum performance as studied on varieties of fly ashes. The three constituents are mixed homogenously in conventional equipment such as dry blenders or in specifically designed wet mixers such as pan mixers.
In order to have absolute control on the process synthesis, the inventors have studied various fly ashes and, based on the coal combustion temperatures, classified them in to two categories. Low Temperature (LT) fly ash and High Temperature (HT) fly ash. The LT fly ashes are generated in sintering zone below 1000 °C, preferably in the zone of 800-900 °C, whereas the HT fly ashes are generated at more than 1000 °C. The data in Table 3 gives distinct difference in the strength pattern of LT and HT fly ash, more so with reference to the Impact of gypsum on fly ash + lime mix.
Upon realising the low strengths of HT fly ash at early ages, in order to enhance the scope of the technology with enlarged scope of raw materials availability, FaL-G was developed in cement route also, availing OPC as the source of lime. In this approach, while the chemistry of OPC renders first order of strengths, the
chemistry of FaL-G, availing the surplus hydrated lime of OPC for pozzolanic reactions in a progressive manner, contribute for subsequent strengths as evident from Table 4.
When FaL-G was developed, it was thought that blending FaL-G and OPC is detrimental because the higher dosage of gypsum in FaL-G may affect the stoichiometry of OPC with particular reference to aluminate phases. But, the studies indicate that OPC and FaL-G can be blended, by which there is compatability of mineralogical and crystallographic formations through a healthy hydration, as indicated by reduction in water consistency factor (WCF), and improvement in strengths. This study on a typical fly ash is shown in Table 5.
While developing Portland.FaL-G, it is essential to balance the lime in accordance to the surplus hydrated lime available from OPC system, so that lime leaching could be minimized as well as durability criteria could be upheld. This has lead to the development of concrete systems serving the structural needs as shown in Table 6.
Portland:FaL-G being cheaper by about 30-40% of the cost of OPC, it proves a boon towards cost saving construction practices.
In the ancient times, attempts were appeared to be made to mix OPC with fly ash, lime and gypsum based on empirical judgements. But in the absence of invention of FaL-G with pronounced and optimum ratios of fly ash, lime and gypsum, no specific product blend could be documented nor claimed earlier containing OPC, fly ash, lime and gypsum with pronounced and definite direction of stoichiometry.
The development of FaL-G and its derivative blends has established that there is compatibility of rheology, mineralogy and crystallography between FaL-G and
OPC which was the point of contest for many cement chemists owing to notional apprehensions. But, the Portland:FaL-G claimed by the subject invention provides specific grade strengths of mortar and concrete as achieved by OPC, at different ratios of FaL-G to OPC depending on the application and desired strengths.
The ratio of OPC to FaL-G in the blend of Portland:FaL-G varies from 1:99 to 99:1, as per applicational need and relevant strengths. In the process, though the recipe gets closer to PPC, by containing the fourth cementitious input, the lime, and having enhanced gypsum commensurate to and contributing for FaL-G chemistry, Portland:FaL-G has its innovative edge. Preferably when 60-70% of FaL-G is blended with 40-30% of OPC, it gives proven strength of concrete in prescribed mix designs at specified ages to satisfy the structural needs. The ingredients can be homogenously mixed with conventional equipment such as blending machines or in specifically designed mixers or pan mixers.
Pozzolanic applications have been well established as durable material of construction for the last 2-3 millennia and FaL-G is nothing but an improved version of the pozzolanic chemistry with pronounced and established scientific rationale.
FaL-G cement is categorised as one of the hydraulic cements. Through appropriate mix designs, this cement can render concrete strengths in the order of M10, M15 and M20, independently or in association with OPC, depending on fly ash character.
OPC, which is principally constituted of four mineraloglcal phases invariably needs specific amount of lime to facilitate the mineraloglcal phases during clinkerisation, whereby some amount of lime, of course, proves surplus upon hydration as given in Table 7.
The gypsum thus formed goes into reaction as in equation 2 above. Hence, it is desirable that the surplus lime with progress of hydration, which could not be avoided due to production imperatives, be engaged in order to veto its availability for subsequent chemical reactions. This is where the reactive constituents of fly ash fit in contributing for the following formations to minimise the lime:
For example, in a Portland pozzolan cement blend, 20% fly ash constituted with 60 parts of SiO2 and 20 parts of AI2O3, with a reactive portion of 30%, consumes 7.68% of lime availing from surplus of OPC hydration in the following lines:
3.6 parts of SiO2 need 5.04 parts 1.2 parts of AI2O3 need 2.64 parts
It is keeping in view the above reactions and the subsequent ongoing reactions; the stoichiometry of FaL-G is conceived and optimised.
The association of constituents to formulate into mineralogical phases, in the presence of water through hydration, initiates the crystal development continuously throughout the process of hydrolysis whereby the matrix of these hydrated crystals attain adhesive and, thereon, cohesive forces making a cementitious product strong after hydration. In the case of conventional OPC, when water is added, electro-chemical forces come into action in the presence of heat of hydration by which the constituents of mineralogical phases dissociate leading to formation of super saturated or metastable solutions. When these solutions, upon ongoing hydrolysis, cross their threshold point, crystallisation of mineralogical phases takes place through association of dissociated constituents in new orientation and equation. The ultimate result is attainment of cohesive forces in the crystal matrix and the development of strength.
The following family of mineralogical phases can be highlighted which, one way or the other, constitute the total matrix of hydrate OPC:
Ettringite / Monosulphate Calcium Silicate Hydrates Calcium Aluminate Hydrates Calcium Ferrite Hydrates
FaL-G is a ground blend of fly ash, lime and calcined gypsum which upon hydration yields strengths in the range of 150-450 kg/cm2 by rendering a totally water impervious hard mass.
Fly ash is dormantly reactive in itself but when added with lime gets activated to attain strength in the order of 20-1S0 kg/cm2, depending on the reactive constituents of silica and alumina and the optimum requirement of lime. The strength gain takes place at a slow pace stretching for several days and weeks. Hence, where precast elements like aerated/cellular concrete are manufactured, rate of strength gain could be augmented through autoclaving the cast element, for high rate of production, but the mechanical strength of the product could not be increased. These weak strengths are attributed to the short crystals of C-S-H, which thus have a less specific area of cohesive bond. To overcome this weak bond, stoichiometric reform has to be brought in to the product and this is where gypsum plays its constructive role to increase the strength of fly ash lime mix to as high as 150-450 kg/cm2 taking advantage of initial formation of the mineralogical phase Ettringite.
Ettringite is one hydrated form of mineralogical phase which is identified with a note of caution in cement parlance for its destructive role, if it exceeds the threshold quanta, because of its crystal growth by about 2.5 times upon hydration, causing dimensional instability to the set product leading to crack the concrete/mortar. Nevertheless, in the case of FaL-G, the sequential formation of ettringite followed by C-S-H contributes for harmonious and cohesive crystal growth whereby the rheology is parallel to that of supersulphate cement and hence FaL-G could prove as another sulphate resistant cement.
The role of ettringite, which can be hostile in post-hardening stage, is availed towards friendly purpose in FaL-G composition. The ettringite which forms in the initial days of hydration brings C-S-H crystals closer, which, in turn, overcome the bond formation deficiency and attain more area of cohesive bonding in spite of the shorter crystal formation. This whole sequence of achieving high crystal
cohesion, without any external hydrothermal treatments through the contributory role of a single and particular mineral phase is identified by the inventors as crystallo-mlneral combination of setting behaviour. Thereby, the theory says "a weak crystal formation in a hydraulic cement can be made good for attaining healthy cohesive bond if compensatory mineral formation is initiated through conducive stoichiometry".
When FaL-G is hydrated, the lime dissolves vigorously to render a supersaturated solution which has a tendency of absorbing silica and alumina through dissolution by which the metastable solid solutions are emerged. Thereby, as happens in OPC, similar hydrated phases formulate in FaL-G but with different quantitative constituents. Gypsum, being faster in reaction, initiates the formation of ettringite, which do formulates in OPC also, and thereon with the additional reactive lime and alumina available in the mix, it gets converted into monosulphate which is nowhere a new mineral phase than in OPC. The only difference in ettringite's role is that the quanta of ettringite in FaL-G is relatively high which induces more cohesiveness to C-S-H crystal formations through its characteristic expansion.
In the case of FaL-G, the mineralogical phase formation is basically through the association of constituents. Heat of hydration or hydro-thermal reactions are hardly available at later ages, either to dissociate the set mineralogies or to initiate new formations. It is because of this comparison that FaL-G is projected as the cement of stoichiometric stability.
FaL-G is developed as a slow setting but long durability cement. In this approach, the sintered and active phases of silica and alumina are tapped of their cementitious character in association with lime. But, the resultant mineralogical phases being modest in their derivative reactions giving rise to feeble and cohesively weak crystal development, in the absence of required heat of hydration, the innovative approach has summoned the role of gypsum. Gypsum, which undergoes chemical reaction with alumina in fly ash in
association with lime, to formulate into a mineralogicai phase called ettringite, right from the second or third minute of hydration, acts as a mineralogicai nuclei to give internal compaction of mass on one hand and to enlarge the bond formation area of C-S-H crystals on the other.
FACTORS OF STOICHIOMETRIC STABILITY IN FAL-G
The stoichiometric stability of FaL-G is a progressive and conclusive phenomena, in the presence of prolonged heat of hydration, just based on basic mineralogicai formation.
The synthesis of OPC invariably asks for the specific quantity of lime, for its anhydrous mineral phases at production stage, which ultimately prove surplus as the hydration progresses. Whereas the synthesis of FaL-G is such that no abnormal quantities of free lime are available.
FaL-G does not contain anhydrous mineralogy as that of OPC, either to release profuse heat of hydration at prolonged ages or to induce late-age stoichiometry at such conditions through release of lime. However, FaL-G has its own anhydrous mineralogy.
The absence of free lime and absence of profuse heat of hydration in FaL-G minimise the chances of allowing detrimental reactions towards distress or chemical instability.
The present invention also discloses a process for the manufacture of a novel cement composition of fly ash, lime and gypsum, which comprises of mixing gypsum with fly ash and lime in predetermined ratio to meet or comply the desired stoichiometry. Preferably, fly ash, lime and gypsum can also be blended
FaL-G could be moulded to form into bricks and blocks with simple process steps of mixing, moulding (with or without pressure) and water curing. Aggregates such as sand, crusher dust, cinder (grit) or baby chips can be added to tune the density and strength. Not only the technology is environmental-friendly, but the costs are also comparable with the conventional products.
As against the high investments advocated by conventional technologies for fly ash brick manufacturing, involving heavy-duty presses and costly utilities like steam-curing equipment, FaL-G technology enables the production of bricks, blocks, hollow blocks, interlocking blocks etc., with simple process steps.
FaL-G bricks and blocks can be manufactured at three different density zones; light density at 400-900 kg/cu.m; medium density at 1000-1700 kg/cu.m and high density at 1S00-2400 kg/cu.m.
Cement & Concrete products
FaL-G is a hydraulic cement material. Hence the products such as pipes, poles, pavers, precast columns, slabs and beams, made out of OPC can also be produced with FaL-G through suitable mix design. FaL-G or Portland:FaL-G can be used for cast in-situ concrete in the lines of using OPC.
FaL-G mix is used for producing medium density (1S00-2200 kg/cu.m) aggregate for application in the concrete.
RAW MATERIALS FOR THE COMPOSITION
The three main ingredients in the composition of FaL-G are pozzolan, lime and gypsum. OPC can also be added as source of lime.
The pozzolans such as fly ash, volcanic ash, ground calcined clay, Metakaolin and any sintered material containing reactive silica and alumina.
All pozzolans are not common so much so the fly ashes too. Each one has its characteristic lime absorption coefficient, whereby the resultant lime pozzolanic constituent has its own gypsum absorbent coefficient. In spite of the assimilations among these coefficients, each pozolana tends to render a specific strength with no linear relation to coefficient factors.
Hence, this process of FaL-G identifies a specific process assimilative approach in order to pronounce the characteristic FaL-G behaviour based on each pozzolanic material, so much so the fly ash, notwithstanding the specifications covered by IS: 3812-1981. Upon suitable collection and evaluation. It is possible to use fly ash as procured. The reactivity that varies based on fineness is taken into consideration to develop commensurate FaL-G recipe. A typical chart on fineness (as collected) vs. reactivity is given below:
Fineness Reactivity in terms of
Cm2/gm Pozzolanic Activity Index (PAI) %
2633 70 90
3403 77 92
4325 86 106
Fineness Reactivity in terms of
Cm^/gm Pozzolanic Activity Index (PAI) %
2633 70 90
3403 77 92
4325 86 106
By virtue of this invention, it could be made possible to rope in as many pozzolanic materials as possible which have been neglected or ignored on account of their deficiencies to qualify for rigid codal specifications drafted in relation to conventional process imperatives. Hence this invention summons for altogether new codal specification.
The byproduct lime is available as carbonate or as hydroxide. Where it is in the form of hydroxide, it can be used without any processing. While it is available in the carbonate form such as from paper and fertiliser industry, it has to be duly sintered in order to bring it to the state of CaO which can be used in FaL-G directly and/or after hydration depending upon process requirements.
Hydrated lime is directly available from the acetylene industry as byproduct. But, depending on locational logistics, mineral lime, duly sintered out of limestone, can also be used with or without slaking as the need warrants.
OPC that contains 20-25% of surplus lime can be used as alternate source of lime.
Gypsum is selected from any compound of calcium sulphate either in the naturally available form or as a byproduct available in dihydrate, hemihydrate or anhydrite state.
In small scale industries, which have constraint on the scope of plant engineering, hemihydrate or anhydrite is preferably recommended. However, the use of dihydrate cannot be precluded. Normally in large scale plants where plant manoeuvring is possible, dihydrate is used for economic considerations.
The ambients of atmosphere summons the appropriation of using suitable grade of gypsum.
FaL-G complies with the criteria for environmentally friendly products and eligible for ECOMARK on account of the following factors:
♦ All the three inputs i.e. fly ash, lime and gypsum can be availed as industrial byproducts and as such contribute towards mineral conservation and thereon to the ecological balance.
♦ FaL-G abates pollution to the extent wherever byproducts are put to use.
♦ The manufacturing process, being devoid of sintering or autoclaving, is totally energy conservative.
1. A hydraulic cement composition comprising of pozzolan in the ratio of 55 to 90%; lime in the ratio of 1 to 45% or a source of lime with commensurate change in input or a combination thereof; and gypsum in the ratio of 5 to 15%.
2. A hydraulic cement composition as claimed in claim 1 wherein pozzolan is selected from fly ash, ground calcined clay, Metakaolin, any sintered material containing silica and alumina or a combination thereof.
3. A hydraulic cement composition as claimed in claim 1 wherein the source of lime replaces the lime partially.
4. A hydraulic cement composition as claimed in claim 1 wherein the source of lime replaces the lime totally.
5. A hydraulic cement composition as claimed in claims 1, 3 and 4 wherein the source of lime is ground clinker or OPC or a combination thereof.
6. A hydraulic cement composition as claimed in claim 1 and 2 wherein the said fly ash is derived from ESP, bag filter or from the ash pond or ash mohd.
7. A hydraulic cement composition as claimed in claims 1, 2 and 6 wherein the fly ash used is generated at a temperature below 1000 °C, preferably in the zone of 800 to 900 °C.
8. A hydraulic cement composition as claimed in claim 1, 2 and 6 wherein the fly ash used is generated at a temperature above 1000 °C.
9. A hydraulic cement composition as claimed in claim 1 wherein the lime is natural lime.
10. A hydraulic cement composition as claimed in claim 1 wherein the lime used is a byproduct.
11. A hydraulic cement composition as claimed in claims 9 and 10, wherein the lime is any calcareous compound preferably in the form of hydroxide.
12. A hydraulic cement composition as claimed in claim 1 wherein the gypsum used is natural gypsum.
13. A hydraulic cement composition as claimed in claim 1 wherein the gypsum used is a byproduct.
14. A hydraulic cement composition as claimed in claims 12 and 13 wherein
the gypsum is in the form of dihydrate or hemihydrate or anhydrite or a
15. A process for the preparation of a hydraulic cement composition of claim
1 wherein the pozzolan in the ratio of 55 to 90%; lime in the ratio of 1 to
45% or a source of lime with commensurate change in input or a
combination thereof; and gypsum in the ratio of 5 to 15% are blended
homogeneously in a conventional equipments such as blending machines
or in a specially designed mixers such as dry blenders and pan mixers.
16. The process as claimed in claim 15 wherein the fly ash is optionally ground to a required fineness before homogeneous blending.
17. A hydraulic cement composition substantially as herein described.
18. A process for the production of hydraulic cement composition
substantially as herein described.
|Indian Patent Application Number||1425/MAS/1996|
|PG Journal Number||08/2007|
|Date of Filing||13-Aug-1996|
|Name of Patentee||SHRI. NATERI KALIDAS|
|Applicant Address||FAL-G MANSION, 32-10-53, SHRI VENKATESWARA COLONY, VISAKHAPATNAM 530 012|
|PCT International Classification Number||C04B7/345|
|PCT International Application Number||N/A|
|PCT International Filing date|