522:, tricalcium aluminate occurs as an "interstitial phase", crystallizing from the melt. Its presence in clinker is solely due to the need to obtain liquid at the peak kiln processing temperature (1400–1450 °C), facilitating the formation of the desired silicate phases. Apart from this benefit, its effects on cement properties are mostly undesirable. It forms an impure solid solution phase, with 15-20% of the aluminium atoms replaced by silicon and iron, and with variable amounts of alkali metal atoms replacing calcium, depending upon the availability of alkali oxides in the melt. The impure form has at least four polymorphs:
188:
115:
336:
92:
846:, but if insufficient sulfate ion is present, any surplus alkalis congregate in the aluminate phase. The feed and fuel in the kiln system are preferably controlled chemically to keep the sulfate and alkalis in balance. However, this stoichiometry is only maintained if there is substantial surplus oxygen in the kiln atmosphere: if "reducing conditions" set in, then sulfur is lost as SO
408:
841:
Because they are even more basic, the alkali-loaded polymorphs are correspondingly more reactive. Appreciable amounts (>1%) in cement make set control difficult, and the cement becomes excessively hygroscopic. The cement powder flowability is reduced, and air-set lumps tend to form. They
826:. This reaction is expansive, and can disrupt mature concrete. Where concrete is to be placed in contact with, for example, sulfate-laden ground waters, either a "sulfate-resisting" cement (with low levels of tricalcium aluminate) is used, or
842:
withdraw water from gypsum on storage of the cement, leading to false set. For this reason, their formation is avoided wherever possible. It is more energetically favorable for sodium and potassium to form sulfates and chlorides in the
729:
In keeping with its high basicity, tricalcium aluminate reacts most strongly with water of all the calcium aluminates, and it is also the most reactive of the
Portland clinker phases. Its hydration to phases of the form
344:
316:
487:
above 1300 °C. The crystals are cubic, with unit cell dimension 1.5263 nm and has density 3064 kg·m. It melts with decomposition at 1542 °C. The unit cell contains 8 cyclic Al
386:
837:
formation, where concrete is cured at temperatures above the decomposition temperature of ettringite (about 65 °C). On cooling, expansive ettringite formation takes place.
421:
752:
leads to the phenomenon of "flash set" (instantaneous set), and a large amount of heat is generated. To avoid this, Portland-type cements include a small addition of
815:
heat release, which can cause spontaneous overheating in large masses of concrete. Where necessary, tricalcium aluminate levels are reduced to control this effect.
503:
tetrahedra in an infinite network, with a slightly higher concentration of bridging oxygens than expected from the composition and around 10% unconnected AlO
227:
1060:
903:
827:
927:
850:, and reactive aluminates start to form. This is readily monitored by tracking the clinker sulfate level on an hour-to-hour basis.
202:
1053:
830:
is added to the cement or to the concrete mix. The slag contributes sufficient aluminium to suppress formation of ettringite.
382:
428:
372:
166:
862:, two hydrates form, the hexahydrate abbreviated C3AH6 and a nonadecahydrate abbreviated C4AH19. In the presence of
335:
1925:
1046:
1698:
122:
800:
774:
744:
811:
Tricalcium aluminate is associated with three important effects that can reduce the durability of concrete:
33:
110:
1836:
1330:
1520:
1387:
1371:
1325:
782:
over the surface of the aluminate crystals, passivating them. The aluminate then reacts slowly to form
358:
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1559:
1479:
1347:
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895:
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68:
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sulfate attack, in which sulfate solutions to which the concrete is exposed react with the
756:(typically 4-8%). Sulfate ions in solution lead to the formation of an insoluble layer of
463:
to highlight the proportions of the oxides from which it is made, is the most basic of the
61:
1920:
1674:
1622:
1610:
1598:
1443:
1435:
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1289:
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1221:
1216:
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1083:
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114:
996:
1504:
1167:
1159:
399:
1914:
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1195:
940:
Mondal, P.; Jeffery, J. W. (1975). "The
Crystal Structure of Tricalcium Aluminate, Ca
480:
301:
154:
103:
1022:
866:, a component of typical clinkers, the sulfate (S) forms with the formula C4ASH12.
378:
499:
tetrahedra. The structure of pure liquid tricalcium aluminate contains mostly AlO
858:
Tricalcium aluminate hydrates in the process of forming
Portland cement. Using
843:
1004:
965:
834:
823:
819:
783:
757:
281:
390:
364:
291:
141:
123:
863:
467:. It does not occur in nature, but is an important mineral phase in
1038:
398:
Except where otherwise noted, data are given for materials in their
495:
anions, which can be considered to consist of 6 corner sharing AlO
91:
81:
1042:
808:. These hydrates contribute little to strength development.
171:
479:
Tricalcium aluminate forms upon heating a 3:1 mixture of
306:
1,542 °C (2,808 °F; 1,815 K) (decomposes)
416:
1591:
1552:
1428:
1262:
1188:
1076:
153:
888:Kirk-Othmer Encyclopedia of Chemical Technology
67:
60:
1054:
8:
896:10.1002/0471238961.0305130508051213.a01.pub3
16:3CaO·Al2O3, a component of Portland clinker
1061:
1047:
1039:
981:"Structure of liquid tricalcium aluminate"
979:Drewitt, James W. E.; et al. (2017).
186:
113:
18:
1014:1983/2dd23037-2924-4b98-a6a1-69c2393cb7f1
1012:
592:
524:
875:
235:0()O()()O()()O()()O()()O()()O0.........
232:
207:
182:
104:
214:Key: HOOWDPSAHIOHCC-UHFFFAOYSA-N
7:
881:
879:
886:Kosmatka, Steven (2012). "Cement".
590:Typical chemical compositions are:
211:InChI=1S/2Al.3Ca.6O/q2*+3;3*+2;6*-2
144:
14:
786:of general composition 3CaO • Al
406:
334:
402:(at 25 °C , 100 kPa).
1:
455:, often formulated as 3CaO·Al
725:Effect on cement properties
286:270.193 g/mol
1947:
1005:10.1103/PhysRevB.95.064203
966:10.1107/S0567740875003639
602:Mass % Orthorhombic
601:
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315:
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223:
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44:
29:
24:
922:, Academic Press, 1990,
530:
373:Precautionary statements
1077:Hydrogen & halogens
20:Tricalcium aluminate
441:Tricalcium aluminate
997:2017PhRvB..95f4203D
518:In Portland cement
21:
599:Mass % Cubic
528:Alkali % m/m
465:calcium aluminates
429:Infobox references
19:
1926:Calcium compounds
1908:
1907:
1429:Group 13 & 14
1070:Calcium compounds
985:Physical Review B
905:978-0-471-48494-3
890:. pp. 1–40.
860:X-ray diffraction
722:
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437:Chemical compound
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359:Hazard statements
167:CompTox Dashboard
93:Interactive image
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296:3.064 g/cm
251:Chemical formula
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754:calcium sulfate
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545:
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507:monomers and Al
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485:aluminium oxide
477:
469:Portland cement
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1002:
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994:
991:(6): 064203.
990:
986:
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928:0-12-683900-X
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573:Orthorhombic
572:
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541:
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481:calcium oxide
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302:Melting point
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184:DTXSID6051223
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105:ECHA InfoCard
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1553:Trans metals
1532:
1026:. Retrieved
988:
984:
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935:
919:
914:
887:
857:
840:
810:
741:
728:
589:
531:Designation
517:
478:
440:
439:
350:
317:
268:, or 3CaO·Al
45:Identifiers
30:Other names
960:: 689-697.
584:Monoclinic
345:Signal word
244:Properties
111:100.031.744
69:161063-05-4
32:aluminate,
1931:Aluminates
1915:Categories
1263:Pnictogens
1189:Chalcogens
1028:2018-07-12
870:References
835:ettringite
824:ettringite
820:AFm phases
784:AFm phases
760:(3CaO • Al
758:ettringite
475:Properties
329:Pictograms
282:Molar mass
80:3D model (
62:12042-78-3
52:CAS Number
854:Hydration
320:labelling
132:234-932-6
124:EC Number
1592:Organics
1023:96446107
833:delayed
822:to form
534:Crystal
515:dimers.
311:Hazards
155:92043201
1108:Ca(ClO)
993:Bibcode
930:, pp 23
768:• 3CaSO
578:4.6-5.7
567:3.7-4.6
553:1.0-2.4
520:clinker
422:what is
420: (
351:Warning
292:Density
276:
142:PubChem
1921:Cement
1611:Ca(HCO
1560:Ca(MnO
1468:Ca(HCO
1444:Ca(CN)
1209:Ca(OH)
1148:Ca(BrO
1128:Ca(ClO
1116:Ca(ClO
1021:
926:
902:
864:gypsum
794:• CaSO
596:Oxide
562:Cubic
548:Cubic
417:verify
414:
228:SMILES
25:Names
1623:Ca(CH
1580:CaTiO
1572:CaCrO
1364:CaHPO
1302:Ca(NO
1290:Ca(NO
1168:Ca(IO
1019:S2CID
799:· 12
773:· 32
663:53.9
634:28.9
539:0–1.0
203:InChI
82:JSmol
1736:Ca(C
1716:Ca(C
1639:Ca(C
1521:CaAl
1485:CaSi
1480:CaSi
1460:CaCO
1452:CaCN
1413:(AsO
1404:CaAs
1372:Ca(H
1254:CaSe
1246:CaSO
1222:CaSO
1180:CaCl
1140:CaBr
1100:CaCl
924:ISBN
900:ISBN
844:kiln
828:slag
738:(OH)
718:0.5
704:4.0
689:0.6
674:1.2
660:56.6
652:6.6
631:31.3
616:4.3
483:and
391:P313
383:P280
379:P264
365:H319
1897:CaO
1877:CaO
1861:CaO
1845:CaO
1829:CaO
1809:CaN
1777:CaC
1764:CaN
1707:CaO
1659:CaC
1599:CaC
1509:(BO
1497:SiO
1436:CaC
1352:(PO
1335:(PO
1326:CaP
1282:CaN
1230:CaH
1217:CaS
1201:CaO
1196:CaO
1160:CaI
1092:CaF
1084:CaH
1009:hdl
1001:doi
962:doi
958:B31
952:".
892:doi
734:AlO
715:0.2
709:TiO
701:0.7
686:1.0
671:1.4
668:MgO
657:CaO
649:5.1
613:3.7
607:SiO
318:GHS
172:EPA
145:CID
1917::
1899:24
1891:40
1887:24
1875:70
1871:36
1863:19
1859:32
1855:18
1847:16
1843:26
1839:14
1831:14
1827:22
1823:12
1807:16
1803:10
1793:PO
1783:12
1779:10
1762:11
1758:10
1728:S)
1679:(C
1675:Ca
1627:CO
1537:Al
1533:Ca
1505:Ca
1493:Ca
1409:Ca
1388:Ca
1376:PO
1348:Ca
1331:Ca
1314:Ca
1270:Ca
1017:.
1007:.
999:.
989:95
987:.
983:.
956:.
944:Al
898:.
878:^
740:·
730:Ca
679:Na
639:Fe
621:Al
558:II
493:18
471:.
447:Al
443:Ca
389:,
385:,
381:,
322::
260:Al
256:Ca
1895:2
1893:B
1889:H
1885:C
1879:4
1873:H
1869:C
1857:H
1853:C
1841:H
1837:C
1825:H
1821:C
1815:8
1813:O
1811:2
1805:H
1801:C
1795:4
1791:5
1789:N
1787:4
1785:O
1781:H
1772:P
1770:8
1768:O
1766:4
1760:H
1756:C
1750:2
1748:)
1746:6
1744:O
1742:7
1740:H
1738:6
1730:2
1726:5
1724:O
1722:5
1720:H
1718:6
1711:P
1709:6
1705:7
1703:H
1701:3
1699:C
1693:2
1691:)
1689:7
1687:O
1685:5
1683:H
1681:6
1677:3
1669:4
1667:O
1665:2
1663:H
1661:4
1653:2
1651:)
1649:2
1647:O
1645:5
1643:H
1641:3
1633:2
1631:)
1629:2
1625:3
1617:2
1615:)
1613:2
1605:4
1603:O
1601:2
1582:3
1574:4
1566:2
1564:)
1562:4
1543:6
1541:O
1539:2
1535:3
1527:4
1525:O
1523:2
1515:2
1513:)
1511:3
1507:3
1499:4
1495:2
1487:2
1474:2
1472:)
1470:3
1462:3
1454:2
1446:2
1438:2
1419:2
1417:)
1415:4
1411:3
1398:7
1396:O
1394:2
1392:P
1390:2
1382:2
1380:)
1378:4
1374:2
1366:4
1358:2
1356:)
1354:4
1350:3
1343:O
1341:2
1339:)
1337:4
1333:4
1320:2
1318:P
1316:3
1308:2
1306:)
1304:3
1296:2
1294:)
1292:2
1284:6
1276:2
1274:N
1272:3
1248:4
1240:6
1238:O
1236:2
1234:S
1232:2
1224:3
1211:2
1203:2
1174:2
1172:)
1170:3
1162:2
1154:2
1152:)
1150:3
1142:2
1134:2
1132:)
1130:4
1122:2
1120:)
1118:3
1110:2
1102:2
1094:2
1086:2
1062:e
1055:t
1048:v
1031:.
1011::
1003::
995::
968:.
964::
950:6
948:O
946:2
942:3
908:.
894::
848:2
805:O
803:2
801:H
796:4
792:3
790:O
788:2
779:O
777:2
775:H
770:4
766:3
764:O
762:2
749:O
747:2
745:H
742:n
736:3
732:2
711:2
698:O
696:2
694:K
683:O
681:2
645:3
643:O
641:2
627:3
625:O
623:2
609:2
581:M
570:O
556:C
544:I
542:C
513:7
511:O
509:2
505:4
501:4
497:4
491:O
489:6
461:3
459:O
457:2
453:6
451:O
449:2
445:3
412:N
274:3
272:O
270:2
266:6
264:O
262:2
258:3
174:)
170:(
84:)
38:A
36:3
34:C
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