Enhancing calcined clay use with inorganic binders

Abstract

The present invention discloses cementitious compositions which contain hydratable cement, limestone, or mixture thereof, having improved strength properties due to the presence of calcined clay and certain higher alkanolamines, wherein the calcined clay has an Fe.sub.2O.sub.3 content of greater than one percent (1%). Also disclosed are exemplary additives and methods for enhancing strength of cement and/or limestone compositions.

Claims

1. A cementitious composition, comprising: a hydratable cement, limestone, or mixture thereof in the amount of 95 to 30% by weight based on the total dry weight of the composition; a calcined clay comprising Fe.sub.2O.sub.3 in an amount of 1% to 15% by weight of the calcined clay, the calcined clay being present in the amount of 5% to 70% based on the total dry weight of the cementitious composition; and at least one tertiary alkanolamine comprising diethanolisopropanolamine (DEIPA) in the amount of 0.002% to 0.2% by weight based on the total dry weight of the cementitious composition.

2. The composition of claim 1 comprising limestone, wherein the ratio of limestone to calcined clay is 2:1 to 1:2 by weight.

3. The composition of claim 1 further comprising an alkanolamine chosen from N,N-bis(2-hydroxypropyl)-N-(hydroxyethyl)amine (EDIPA), triisopropanolamine (TIPA), triethanolamine (TEA), or a mixture thereof.

4. The composition of claim 1 wherein the calcined clay comprises a kaolinite clay in the amount of 30%-100% by total dry weight of the calcined clay.

5. The composition of claim 4 wherein the kaolinite clay is derived from oxisol, ultisol, alfisol, or mixture thereof.

6. The composition of claim 1 wherein the calcined clay contains Fe.sub.2O.sub.3 in an amount of 1.5% to 8% by weight of the calcined clay.

7. The composition of claim 1 wherein the calcined clay contains Fe.sub.2O.sub.3 in an amount of 2.0% to 8% by weight of the calcined clay.

8. The composition of claim 1 further comprising at least one admixture chosen from plasticizers, accelerators, retarders, air entrainers, air detrainers, shrinkage reducing agents, fibers, grinding aids, strength enhancers, or a mixture thereof.

9. The composition of claim 8 wherein the at least one admixture is a plasticizing or superplasticizing polycarboxylate comb polymer comprising a backbone structure and (poly)oxyalkylene groups linked by ether moieties to the backbone structure.

10. An additive composition for increasing strength in cementitious compositions that contain portland cement, limestone, or mixture thereof, the additive composition comprising: calcined clay having Fe.sub.2O.sub.3 in an amount of 1%-15% by weight based on the weight of the calcined clay, the calcined clay being present in the amount of 5% to 95% based on the total dry weight of the additive composition; and at least one tertiary alkanolamine comprising diethanolisopropanolamine (DEIPA), the amount of the at least one tertiary alkanolamine being present in the amount of 0.002% to 0.2% by weight based on the total weight of the additive composition.

11. A method comprising: introducing to cement, limestone, or mixture thereof, the additive composition of claim 10.

12. A method for manufacturing cement, limestone, or mixture thereof, comprising: introducing to cement, limestone, or mixture thereof, during grinding, calcined clay having Fe.sub.2O.sub.3 in the amount of 1% to 15% by weight based on the weight of the calcined clay, the calcined clay being present in the amount of 5% to 70% based on the weight of cement and limestone; at least one tertiary alkanolamine chosen from diethanolisopropanolamine (DEIPA), -N,N-bis(2-hydroxypropyl)-N-(hydroxyethyl)amine (EDIPA), triisopropanolamine, triethanolamine, or mixture thereof, the amount of the at least one tertiary alkanolamine being present in the amount of 0.002% to 0.2% by weight based on the weight of the cement and limestone; and a plasticizing or superplasticizing polycarboxylate comb polymer having a backbone structure and (poly) oxyalkylene groups linked by ether moieties to the backbone structure.

13. The method of claim 12 wherein the calcined clay, the at least one tertiary alkanolamine, and the plasticizing or superplasticizing polycarboxylate comb polymer are introduced as a premixed additive composition.

14. The method of claim 12 further comprising introducing to cement, limestone, or mixture thereof, during grinding, at least one admixture chosen from accelerators, retarders, air entrainers, air detrainers, shrinkage reducing agents, fibers, grinding aids, strength enhancers, or a mixture thereof.

15. A cementitious composition, comprising: a hydratable cement, limestone, or mixture thereof in the amount of 95 to 30% by weight based on the total dry weight of the composition; a calcined clay comprising Fe.sub.2O.sub.3 in an amount of 1% to 15% by weight of the calcined clay, the calcined clay being present in the amount of 5% to 70% based on the total dry weight of the cementitious composition; and at least one tertiary alkanolamine in the amount of 0.002% to 0.2% by weight based on the total dry weight of the cementitious composition, the at least one tertiary alkanolamine comprising diethanolisopropanolamine (DEIPA), -N,N-bis(2-hydroxypropyl)-N-(hydroxyethyl)amine (EDIPA), or mixture of DEIPA and EDIPA.

16. A composition, comprising: limestone in the amount of 95 to 30% by weight based on the total dry weight of the composition; a calcined clay comprising Fe.sub.2O.sub.3 in an amount of 1% to 15% by weight of the calcined clay, the calcined clay being present in the amount of 5% to 70% based on the total dry weight of the composition; and at least one tertiary alkanolamine in the amount of 0.002% to 0.2% by weight based on the total dry weight of the composition; wherein the ratio of limestone to calcined clay is 2:1 to 1:2 by weight.

17. A cementitious composition, comprising: a hydratable cement, limestone, or mixture thereof in the amount of 95 to 30% by weight based on the total dry weight of the composition; a calcined clay comprising Fe.sub.2O.sub.3 in an amount of 1% to 15% by weight of the calcined clay, the calcined clay being present in the amount of 5% to 70% based on the total dry weight of the cementitious composition; at least one tertiary alkanolamine in the amount of 0.002% to 0.2% by weight based on the total dry weight of the cementitious composition; and at least one admixture comprising a plasticizing or superplasticizing polycarboxylate comb polymer having a backbone structure and (poly)oxyalkylene groups linked by ether moieties to the backbone structure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention.

(2) FIGS. 1A, 1B, and 1C are each graphic illustrations of the effect of diethanolisopropaholamine (DEIPA) at 0.02% solids/solids upon the dissolution rates, respectively of alumina, silica and iron for Calcined Clay 3.

(3) FIG. 2 is a graphic showing the effect of different alkanolamines on the pozzolanic activity for Calcined Clay 1 (containing an Fe.sub.2O.sub.3 content >1.0%) based on a R3 pozzolanic test run at 40 C.

(4) FIG. 3 is a graphic illustration of the the effect of DIEPA on the pozzolanic activity for Calcined Clay 2 (containing an Fe.sub.2O.sub.3 content <1.0%) based on a R3 pozzolanic test run at 40 C.

(5) FIG. 4 is a bar plot comparing the compressive strength from 1 to 60 days of portland cement, portland cement with Limestone and Calcined Clay (LCC) and portland cement with LCC and three different alkanolamines at a 0.02% s/s dose.

DETAILED DESCRIPTION OF THE INVENTION

(6) A description of example embodiments of the invention follows.

(7) The content of all components in the compositions described below is indicated relative to the dry weight of the composition, unless indicated otherwise.

(8) The conventional cement chemist notation uses the following abbreviations:

(9) CaO=C

(10) SiO.sub.2=S

(11) Al.sub.2O.sub.3=A

(12) Fe.sub.2O.sub.3=F

(13) The terms cement composition or cementitious composition are used herein to designate a binder or an adhesive that includes a material that will solidify upon addition of water (whereby the cementitious material is deemed hydratable), and an optional additive. Most cementitious materials are produced by high-temperature processing of calcined lime and a clay. When mixed with water, hydratable cementitious materials form mortar or, mixed with sand, gravel, and water, make concrete. The terms cementitious material, cementitious powder, and cement may be used herein interchangeably. For purposes of the present invention, Portland cement, limestone, and mixtures thereof, will be considered binder materials.

(14) Cement compositions includes mortar and concrete compositions comprising a hydratable cement. Cement compositions can be mixtures composed of a cementitious material, for example, Portland cement, either alone or in combination with other components such as fly ash, silica fume, blast furnace slag, limestone, natural pozzolans or artificial pozzolans, and water; mortars are pastes additionally including fine aggregate, and concretes are mortars additionally including coarse aggregate. The cement compositions of this invention are formed by mixing certain amounts of required materials, e.g., a hydratable cement, limestone, water, and fine or coarse aggregate, as may be applicable for the particular cement composition being formed.

(15) As used herein, the term clinker refers to a material made by heating limestone (calcium carbonate) with other materials (such as clay) to about 1450 C. in a kiln, in a process known as calcination, whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide, or quicklime, which is then blended with the other materials that have been included in the mix to form calcium silicates and other cementitious compounds.

(16) As used herein, the term Portland cement include all cementitious compositions which meet either the requirements of the ASTM (as designated by ASTM Specification C150), or the established standards of other countries. Portland cement is prepared by sintering a mixture of components including calcium carbonate (as limestone), aluminum silicate (as clay or shale), silicon dioxide (as sand), and miscellaneous iron oxides. During the sintering process, chemical reactions take place wherein hardened nodules, commonly called clinkers, are formed. Portland cement clinker is formed by the reaction of calcium oxide with acidic components to give, primarily tricalcium silicate, dicalcium silicate, tricalcium aluminate, and a ferrite solid solution phase approximating tetracalcium aluminoferrite.

(17) As used herein, the term limestone shall mean and refer to calcium carbonate, and may refer also to non-combustible solids characteristic of sedimentary rocks and composed mainly of calcium carbonate in the form of the mineral calcite. Dolomitic limestone typically refers to limestone containing some impurities, e.g., more than 5% magnesium carbonate. Siliceous limestone typically refers to limestone containing sand or quartz.

(18) As used herein, alkanolamine means an alkyl, typically a C1-C6 alkyl, functionalized with at least one amino group and at least one hydroxyl group. Examples of alkanolamines include triethanolamine or TEA, diethanolisopropanolamine or DEIPA, and tri-isopropanolamine or TIPA (typically used as conventional grinding aids in cement production).

(19) As used herein, clay is a soil material. There are four main groups of clays: kaolinite, montmorrilonite-smectite, illite and chlorite. Kaolinite is known to be the most reactive clay once activated (such as, for example, by calcination).

(20) As used herein, calcined clay means a clay thermally activated by heating at a temperature above 650 C. The calcination induces a structural disorder due to the dihydroxylation phenomena. For instance, kaolinite becomes metakaolin after calcination. The clay will preferably contains Fe.sub.2O.sub.3 and be calcined in a sufficiently oxygenized environment to form Fe.sub.3+.

(21) As used herein, pozzolanic activity refers to the ability of a pozzolan material to react via the reaction of alumino-silicate (AS) and calcium hydroxide (CH) in presence of water to form products with binding properties. The reaction can be schematically in cement chemistry notation: AS+CH+H.fwdarw.CSH+C-A-H with AS corresponding to the pozzolan and CH to calcium hydroxide. The initiation of the pozzolanic reaction is the dissolution of the silica (S) from the pozzolan, which release silica in the pore solution, which then reacts with calcium hydroxide to form CSH.

(22) Various exemplary aspects (embodiments) of the invention are described below.

(23) In a first exemplary aspect, the present invention provides a cementitious composition, which comprises: a hydratable cement, limestone, or mixture thereof in the amount of 95 to 30% by weight based on the total dry weight of the composition; a calcined clay comprising Fe.sub.2O.sub.3 in an amount of 1% to 15% by weight of the calcined clay, the calcined clay being present in the amount of 5% to 70% based on the total dry weight of the cementitious composition; and at least one tertiary alkanolamine in the amount of 0.002% (and more preferably 0.005%) to 0.2% (and more preferably 0.1%) by weight based on the total dry weight of the cementitious composition.

(24) In a second aspect based on the first aspect described above, the invention provides an exemplary composition comprising hydratable cement, wherein the ratio of hydratable cement to calcined clay is 2:1 to 1:4 by weight.

(25) In a third aspect based on any of the foregoing first through second exemplary aspects described above, the invention provides a composition comprising hydratable cement, wherein the ratio of hydratable cement to calcined clay is 1:1 to 1:4 by weight.

(26) In a fourth aspect based on any of the foregoing first through third exemplary aspects described above, the invention provides a composition comprising limestone, wherein the ratio of limestone to calcined clay is 3:1 to 1:5 by weight.

(27) In a fifth aspect based on any of the foregoing first through fourth exemplary aspects described above, the invention provides a composition comprising limestone, wherein the ratio of limestone to calcined clay is 2:1 to 1:2 by weight.

(28) In a sixth aspect based on any of the foregoing first through fifth exemplary aspects described above, the invention provides a composition wherein the at least one alkanolamine is chosen from diethanolisopropanolamine (DEIPA), N,N-bis(2-hydroxypropyl)-N-(hydroxyethyl)amine (EDIPA), triisopropanolamine (TIPA), and triethanolamine (TEA), or a mixture thereof.

(29) In a seventh aspect based on any of the foregoing first through sixth exemplary aspects described above, the invention provides a composition wherein the at least one alkanolamine is DEIPA.

(30) In an eighth aspect based on any of the foregoing first through seventh exemplary aspects described above, the invention provides a composition wherein the calcined clay comprises a kaolinite clay in the amount of 30%-100% by total dry weight of the calcined clay.

(31) In an ninth aspect based on any of the foregoing first through eighth exemplary aspects described above, the invention provides a composition wherein the calcined clay comprises a kaolinite clay in the amount of 30%-100% by total dry weight of the calcined clay, and the kaolinite clay is derived from oxisol, ultisol, alfisol, or mixture thereof.

(32) In a tenth aspect based on any of the foregoing first through ninth exemplary aspects described above, the invention provides a composition wherein the calcined clay contains Fe.sub.2O.sub.3 in an amount of 1.5% to 8% by weight of the calcined clay.

(33) In an eleventh aspect based on any of the foregoing first through tenth exemplary aspects described above, the invention provides a composition wherein the calcined clay contains Fe.sub.2O.sub.3 in an amount of 2.0% to 8% by weight of the calcined clay.

(34) In a twelfth aspect based on any of the foregoing first through eleventh exemplary aspects described above, the composition of the invention further comprises at least one admixture chosen from plasticizers which are otherwise known as water-reducing admixtures (e.g., lignosulfonates, hydroxylated carboxylic acids, polycarboxylate comb polymers, and others); accelerators (e.g., calcium chloride, sodium thiocyanate, calcium formate, calcium nitrate, calcium nitrite, and others); retarders (e.g., sugars, corn syrups, molasses, and others); air entrainers (e.g., salts of wood resin, salts of sulfonated lignin, and others); air detrainers (e.g., tributyl phosphate, tri-iso-butyl phosphate, dibutyl phthalate, octyl alcohol, water-insoluble esters of carbonic and boric acid, and others); shrinkage reducing agents, fibers, cement grinding aids, strength enhancers, or a mixture thereof. Conventional admixtures are contemplated for use within these categories. Explanations of conventional admixtures and examples are found in the patent literature (See e.g., lists of admixtures in U.S. Pat. No. 5,895,116 of Kreinheder et al., owned by the common assignee hereof).

(35) In a thirteenth aspect based on any of the foregoing first through twelfth exemplary aspects described above, the composition of the invention further comprises at least one admixture which is a plasticizing or superplasticizing polycarboxylate comb polymer comprising a backbone structure and (poly) oxyalkylene groups linked by ether moieties to the backbone structure. A preferred polycarboxylate comb polymer containing ether linkages for milling preparation of cementitious materials was taught by Cheung et al. in U.S. Pat. No. 8,993,656 (2015) (owned by the present assignee hereof); and is particularly suitable for use in exemplary compositions made in accordance with the present invention. Cheung et al. taught that such polycarboxylate comb polymers containing a carbon backbone and pendant polyoxyalkene groups with ether (including vinyl ether) linkage groups provided sustained robustness for withstanding the harshness of the grinding mill operation and for conferring workability and strength-enhancing properties.

(36) In a fourteenth exemplary aspect, the invention provides an exemplary additive composition for increasing strength in cementitious compositions that contain portland cement, limestone, or mixture thereof, the additive composition comprising: calcined clay having Fe.sub.2O.sub.3 in an amount of 1%-15% by weight based on the weight of the calcined clay, the calcined clay being present in the amount of 5% to 95% based on the total dry weight of the additive composition; and at least one tertiary alkanolamine chosen from diethanolisopropanolamine, triisopropanolamine, and triethanolamine, or mixture thereof, the amount of the at least one tertiary alkanolamine being present in the amount of 0.002% (and more preferably 0.005%) to 0.2% (and more preferably 0.1%) by weight based on the total weight of the additive composition.

(37) In a fifteenth exemplary aspect, which can be based on the fourteenth exemplary aspect described above, the invention provides an additive composition wherein the at least one tertiary alkanolamine is diethanolisopropanolamine.

(38) In a sixteenth exemplary aspect, the invention provides a method comprising introducing to cement, limestone, or mixture thereof, the additive composition in accordance with any of the fourteenth through fifteenth exemplary aspects described above.

(39) In a seventeenth exemplary aspect, the invention provides a method for manufacturing cement, limestone, or mixture thereof, comprising: introducing to cement, limestone, or mixture thereof, during grinding, calcined clay having Fe.sub.2O.sub.3 in the amount of 1% to 15% by weight based on the weight of the calcined clay, the calcined clay being present in the amount of 5% to 70% based on the weight of cement and limestone; and at least one tertiary alkanolamine chosen from diethanolisopropanolamine, triisopropanolamine, and triethanolamine, or mixture thereof, the amount of the at least one tertiary alkanolamine being present in the amount of 0.002% (and more preferably 0.005%) to 0.2% (and more preferably 0.1%) by weight based on the weight of the cement and limestone.

(40) In an eighteenth exemplary aspect, based on the seventeenth exemplary aspect described above, the invention provides a method wherein the calcined clay and at least one tertiary alkanolamine are introduced as a premixed additive composition to the cement, limestone, or mixture thereof, during grinding.

(41) In a nineteenth aspect, based on any of the seventeenth through eighteenth exemplary aspects described above, the method further comprising introducing to cement, limestone, or mixture thereof, during grinding, at least one admixture chose from plasticizers (e.g., superplasticizers), accelerators, retarders, air entrainers, air detrainers, shrinkage reducing agents, fibers, grinding aids, strength enhancers, or a mixture thereof.

(42) In a twentieth aspect, based on the a nineteenth exemplary aspect described above, the at least one admixture introduced during grinding to a cement, limestone, or mixture thereof is a plasticizing or superplasticizing polycarboxylate comb polymer comprising a backbone structure and (poly) oxyalkylene groups linked by ether moieties to the backbone structure. Preferably, it is a polycarboxylate ether polymer as previously taught by in Cheung et al. in U.S. Pat. No. 8,993,656 (owned by the common assignee hereof).

(43) While the invention is described herein using a limited number of embodiments, these specific embodiments are not intended to limit the scope of the invention as otherwise described and claimed herein. Modifications and variations from the described embodiments exist. More specifically, the following examples are given as a specific illustration of embodiments of the claimed invention. It should be understood that the invention is not limited to the specific details set forth in the examples. All parts and percentages in the examples, as well as in the remainder of the specification, are by percentage dry weight unless otherwise specified (e.g. s/s refers to solids on solids).

EXEMPLIFICATIONS

Example 1: Calcined Clay, Cement and Limestone Characterization

(44) The oxides were measured for each calcined clay, Porland cement and limestone using X-ray fluorescence (XRF). The median particle diameter (Dv,50) was determined using a Malvern Mastersizer 3000 particle size analyzer. In addition, the total alkali equivalent (T-Alk Eq) was calculated. All values are shown in Table 1 below.

(45) TABLE-US-00001 TABLE 1 Calcined Calcined Calcined clay clay clay Portland Oxide 1 2 3 cement Limestone SiO.sub.2 41.1 54.7 55.4 19.3 Al.sub.2O.sub.3 37.1 39.8 39.3 5.70 Fe.sub.2O.sub.3 1.39 0.52 1.63 3.60 CaO 0.10 0.09 <0.01 63.6 55.0 MgO 0.14 0.18 0.19 1.60 0.20 SO.sub.3 0.02 0.01 <0.01 3.20 Na.sub.2O 0.47 0.12 0.07 0.20 K.sub.2O 0.09 2.15 0.22 1.20 TiO.sub.2 4.67 0.38 1.55 0.30 P.sub.2O.sub.5 0.19 0.55 0.14 0.20 Mn.sub.2O.sub.3 0.04 0.004 <0.01 0.10 T-Alk (Na.sub.2O + 0.53 1.53 0.22 0.658 K.sub.2O) Dv, 50 (um) 15 10 12.00 9.0 8.0

Example 2: Effect of 0.02% s/s DEIPA on the Dissolution Rates of Alumina, Silica and Iron from Calcined Clay Dissolution

(46) The dissolution experiment was prepared by filling a plastic container of 250 mL of ultra-pure water created through boiling deionized water to remove any CO.sub.2. NaOH was added to increase the alkalinity of the water to obtain a pH of 13, which represents the pH of a typical cement paste pore solution. Approximately 0.25 grams (g) of sieved calcined clay was introduced to the alkaline water in a graduated cylinder. To obtain each sample from the cylinder, 5 mL of the prepared solution was removed from at a consistent height for each sample. The sample was filtered over a 2 micron filter and analyzed by inductively coupled plasma mass spectrometry (ICP). Fresh alkaline solution was added after each sampling in order to maintain a pH of 13. FIGS. 1A, 1B, and 1C illustrate the solution analysis by ICP which demonstrated that the evolution of, respectively, alumina, silica and iron, as released from the calcined clay dissolution experiment over 30 hours. Higher alumina, silica and iron release rates can be observed in the presence of DEIPA in comparison to the control sample, indicating a faster dissolution of the calcined clay with DEIPA. The pozzolanic activity is driven by the silica release rates from the pozzolans. Therefore, a faster release rate and higher amount of silica released indicates a higher pozzolanic activity for the sample with DEIPA. Moreover, as reported in the literature, alumina is known to prevent the dissolution of silica. Here, in these experiments, the results show that silica released is accelerated despite a higher presence of alumina. Therefore, DEIPA surprisingly allows the increase of pozzolanic activity of calcined clay even though the alumina experienced increased released rates. In blended cements containing limestone, extra supply of alumina is necessary for the limestone reaction.

Example 3: R3 Pozzolanic Test of Calcined Clay Containing High Amount of Fe2O3

(47) The pozzolanic tests were made according to a method developed and described in the paper from Avet et al. in Development of a new rapid, relevant and reliable (R.sup.3) test method to evaluate the pozzolanic reactivity of calcined kaolinitic clays in Cement and Concrete Research, 2016. Approximately 15.5 g of Calcined Clay 1, 37.5 g of portlandite and 60 g of aqueous solution containing potassium sulfate and potassium hydroxide in the ratio: 0.06 SO.sub.3/Calcined Clay 1 and 0.08 K.sub.2O/Calcined Clay 1 mass ratios in order to ensure high pozzolanic reactivity were heated up to 40 C. in an oven for at least 8 hours. Three samples containing DEIPA, TIPA or TEA were compared to a blank sample. When noted, 0.02% s/s of DEIPA, TIPA or TEA was added to the aqueous solution. Once the materials reached a stable temperature, they were mixed together for 2 minutes at 1600 revolutions per minute (rpm) with an overhead stirrer. About 10 g of the paste was poured into a glass calorimetry vial. The heat release was recorded for 1 day at 40 C. in a calorimeter (TAM-Air).

(48) The heat released by the mix of portlandite and Calcined Clay 1 with the adjusted alkali amount reflects the pozzolanic activity of the calcined clay. FIG. 2 illustrates the cumulative heat evolution of the samples at 40 C. for 24 hours. The curves containing alkanolamines (DEIPA, TEA, TIPA) correspond to greater cumulative heat generated over time, and thus these curves are seen higher compared to the blank curve. This indicates that the reaction between the calcined clay and portlandite is activated by the presence of alkanolamines, and provides extra heat from the calcined clay dissolution. The order of activation ability is DEIPA>TIPA>TEA.

Example 4: R3 Pozzolanic Test of Calcined Clay Containing High Amount of Fe2O3

(49) A similar set of tests as described in Example 3 was performed with Calcined Clay 2. The main difference between Calcined Clay 1 and Calcined Clay 2 is their level of Fe.sub.2O.sub.3. Calcined Clay 2 contains a lower amount of Fe.sub.2O.sub.3 in terms of its composition level (See Example 1). FIG. 3 illustrates that the heat released in this case is not as significantly affected by the presence of DEIPA as in Example 3. This indicates a lower effect of the chemical on calcined clay containing a lower amount of Fe.sub.2O.sub.3. Therefore, the present inventors believe that DEIPA is more efficient in activating the pozzolanic reaction of calcined clay when the calcined clay contains a larger amount of Fe.sub.2O.sub.3. This is of great interest as it can be seen that calcined clays with high levels of Fe.sub.2O.sub.3 are available widely but less reactive than purer calcined clay (i.e., having lower amounts of Fe.sub.2O.sub.3). Therefore, DEIPA, TIPA and TEA can be used to extend significantly one's use of calcined clays to include those which are usually considered less pure containing Fe.sub.2O.sub.3.

Example 4: Compressive Strength Test

(50) The compressive strengths of both plain Portland cement and Limestone Calcined Clay Cements (LC3) were compared to LC3 containing 0.02% s/s of either DEIPA or TIPA or TEA. Mortar prisms were made according to EN-196-1:2016. From FIG. 4, it can be seen that mortar containing one of the alkanolamines have higher strength than the blank LC3 at all ages. LC3 with TEA presented the highest earlier strength until 3 days. At longer ages, TIPA was more efficient on the strength. It can be observed that, after 14 days, the compressive strength of the LC3 blank was not dramatically increased; whereas, with DEIPA and TIPA, the strength increase continued even after 28 days. Overall, in this example, DEIPA provides the better option to overcome limited early strength and stabilized later strength in LC3. Most importantly, it was surprising to note that DEIPA and TIPA were able to increase the strength to be comparable to the plain Portland cement sample at 28 days, thus providing a true cement placement without loss of strength.

(51) While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.