1. De harenae copiis cum habeatur explicatum, tum etiam de calce diligentia est adhibenda uti de albo saxo aut silice coquatur. et quae erit ex spisso et duriore, erit utilis in structura, quae autem ex fistuloso, in tectoriis. cum ea erit extincta, tunc materia ita misceatur ut si erit fossicia, tres harenae et una calcis infundantur, si autem fluviatica aut marina duae harenae et una calcis coiciantur. ita enim erit iusta ratio mixtionis temperaturae. etiam in fluviatica aut marina si qui testam tunsam et succretam ex tertia parte adiecerit, efficiet materiae temperaturam ad usum meliorem.
1. After furnishing an account of the supply of sand, we must next be careful about lime, to burn it out of white stone or lava; the lime which shall be out of thick and harder stone will be useful in the main-structure; that which shall be of porous material, in plaster work. When it is slaked, then let it be mingled with the sand in such a way that if it is pit sand, three of sand and one of lime is poured in; but if the sand is from the river or sea, two of sand and one of lime is thrown together. For in this way ther will be the right proportion of the mixture and blending. Also in the case of river or sea sand, if anyone adds crushed and sifted potsherds in the proportion of one to three, he will produce a blending of material which is better for use.
2. Quare autem cum recipita aquam et harenam calx tunc confirmat structuram, haec esse causa videtur quod e principiis uti cetera corpora ita et saxa sunt temperata. et quae plus habent aeris sunt tenera, quae aquae lenta sunt ab umore, quae terrae dura, quae ignis fragiliora. itaque ex his saxa si antequam coquantur, contusa minute mixta harenae in structuram coiciantur, non solidescunt nec eam potuerunt continere. cum vero coniecta in fornacem ignis vehementi fervore correpta amiserint pristinae soliditatis virtutem, tunc exustis atque exhaustis eorum viribus relinquuntur patentibus foraminibus et inanibus. ergo liquor qui est in eius lapidis corpore et aer cum exustus et ereptus fuerit, habueritque in se residuum calorem latentem, intinctus in aqua, priusquam ea ignis vim recipit, umore penetrante in formantium raritates confervescit et ita refrigeratus reicit ex calcis corpore fervorem.
2. And so when lime receives water and sand and then strengthens the structure, the following seems to be the case: just as other bodies, so also stones are blended of the elements. And those which have more air are soft; more water, are pliant from the moisture; more earth, are hard; more fire, are more ffragile. Therefore if stones of this last quality are crushed before they are burnt, and mixed with sand, and thrown into the work, they do not become solid, nor can they hold the building together. But when they are thrown into the kiln, they are seized by the violent heat of the fire and lose the virtue of their former solidity. Their strength is burnt out and exhausted and they are left with open and empty pores.
3. Ideo autem quo pondere saxa coiciuntur in fornacem, cum eximuntur non possunt ad id respondere, sed cum expenduntur, permanente ea magnitudine, excocto liquore circiter tertia parte ponderis inminuta esse inveniuntur. igitur cum patent foramina eorum et raritates, harenae mixtionem in se corripiunt et ita cohaerescunt siccescendoque cum caementis coeunt et efficiunt structurarum soliditatem.
3. Therefore when the moisture which is in the body of that stone, and the air, are burnt out and removed, and the stone retains the remaining latent heat, on being plunged into water (before it recovers power from fire), the moisture penetrates into the open pores, and it seethes and thus, being cooled again, it rejects the heatfrom the substance of the lime. Thus, moreover, whatever weight the stone possesses when it is thrown into the kiln, it cannot answer to that when it is taken out; but when it is weighed, the bulk remaining the same, it is found to lose about one-third of its weight when the moisture is burnt out. Therefore, when the pores and attenuations of the lime are open, it catches up into itself the mixture of the sand; thus it coheres and, as it dries, joins with the rubble and produces solid walling.
Like the previous chapter this chapter also is in the first place based on the technical experience of Vitruvius. He certainly knew how to make lime by burning certain kinds of stones. In the first sentence of this chapter he gives the qualities of harder and softer stones and he certainly knew how to produce a good lime. But when it comes to the explanation of the effect of burning stones we can see that antiquity had no scientific knowledge of this process. They brought it all back to the pre-Socratic and Pythagorean theories about the four elements. So we can see in sentence 2 how the qualities of different stones, and hence of the lime after burning, depend from the supposed prevalent element in these stones.
What Vitruvius doesn't say here is whether he prescribes this mixture of lime and sand (previous chapter) as a binding agent in stone masonry or as the basic material of concrete constructions (opus caementicium). The first words of chapter 4 (In caementiciis autem structuris) make us think that he wants to talk in the first place about concrete and that the effect of binding together masonry comes on the second place.
Concrete as building material seems to have been used from the second century B.C. In the first period it was used in podia and foundations of temples, but we can also find it in the porticus Aemilia which was built in 193 B.C. by the aediles M.Aemilius Lepidus and L.Aemilius Paullus; but it not certain if the concrete remains belong to the first strucures of this portico or are later additions. During the first century the use oc concrete became more widespread and by the time of Augustus the Romans achieved a wonderful new architecture solely based on the use of concrete. To give this concrete structural body the Romans used various kinds of stones: selce (flint), tufa, pumice, broken brick and tile, and stone. Vitruvius refers clearly to this use of material in this chapter.
Les dix livres d'architecture de Vitruve, Corrigés et traduits en 1684 par C. Perrault, Paris, 1684.
Vitruvius, De Architectura libri X, ed. F. Granger, London, 1962.
Ton Peters, Vitruvius, Handboek bouwkunde, Amsterdam, 1999.
A.Boëthius-J.B.Ward-Perkins, Etruscan and Roman Architecture, Harmondsworth, 1970
A.McKay, Vitruvius, Architect and Engineer, London, 1978
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