Cement Production and Use

In general, this study has shown that, throughout precolumbian mesoamerica, lime cement was used in building construction to the exclusion of any other kind of calcareous cement. Notably, hydraulic cements either of the natural (puzzolanic) or artificial (portland) types were unknown. Also, gypsum cement was conspicuously absent.

Limestone was ostensibly the prime (if not the only) source of cement used in America. My discussions with natives in Yucatan points out that cements for some restoration work are open kiln burned in precisely the same manner they were in ancient times. A circular wood pyre is built of logs and topped with layers of limestone, cobble size. The fire is started from a central hollow, and the whole allowed to burn completely. This method is also described and substantiated by Morley (Brainerd Rev. 1968, chap. 12). Very little carbon has been found in the samples which condition attests to the ability of these ancient peoples and the degree of care exercised by them in obtaining as pure a cement as possible.

Sascab, mentioned in chapter 5. (pp. 5-3, 5-4) is regarded by some authors as a lime cement source rather than having been used merely as an aggregate. ". . . The sides" (of a road) "are built of roughly dressed stone and the tops covered with a natural lime cement called sahcab, which hardens under wetting and pressure." (Morley, p. 309). (Also see Littmann, Jan 1960 and Holmes, 1895).

From the petrographic analysis (chapter 5) there can be no doubt that the sascab (sahcab) was used as a an aggregate wherever available. However, I can find no evidence to supports its role as a "natural cement" which could respond as would a cement to the addition of water without prior calcining.

There have been suggestions concerning the probable use of shell in the manufacturing of some of the prehispanic cements. As Comalcalco "The absence of limestone from the vicinity of the site and the high molar ratios of calcium to magnesium would tend to conform the use of shell as a source of lime . . ." (Littmann, Oct. 1957).

This study has not provided data with which to support any shell source of lime cement theory. To the contrary, close examination of the thin sections, particularly of those at Tulum (J series), where shell is plentiful, revealed that it had been utilized, along with other marine deposited grains and particles, only as aggregate. When chemical analysis shows a high molar ratio of calcium to magnesium to a sample consisting of both cement and aggregate, I suggest this result is likely to be caused by shell in the aggregate rather than in the cement. Evidence which has been presented on either side of this question is inconclusive. The whole problem involving the use of shell in the making of cements is a subject deserving of further intensive investigation.

In sum, the only presently verifyable source of cements in Mesoamerica was limestone which was calcined by an open klin burning method. Pre hydraulic cement technology in the "Western World" at the beginning of the Christian Era corresponds roughly with that in America at the same time (samples A-6 and A-8 Teotihuacan). The precoloumbian peoples apparently never attained the capability of manufacturing hydraulic cements of any kind.

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Epilogue

Technology in the manufacturing and use of calcerous cements in Middle America, equal to any on the world at the advent of the Christian era, remained nearly static for the ensuing fifteen centuries. Hydraulic cement which, after its accidental discovery at Puzzoli, rapidly came into common usage throughout the Roman Empire and beyond did not reach the New World until the European invasions.

The exclusive role of lime cement and the absence of such building techniques as concrete wall and vault construction and the true arch is prehispanic America all act to diminish the statistical probability of meaningful contact with the old "Western World" during the time period designated. Probability is further reduced by wide dissimilarities in architectural ornament and sculptural forms. For indications of any cultural transfer then, it seems we must look back beyond the past two millennia.

Cement making and cementitious products (concrete, mortars and stuccoes) were technically well advanced in America in the first century A.D. Their degree of perfection could not have been instantaneously created, but rather would have required a considerable period of development. Were these materials invented by an indigenous unnamed people far predating the occupation of Teotihuacan, or were they introduced by an exotic culture? The answer lies buried in deep antiquity.