The 18th-Century Baraccato of L’Aquila

ABSTRACT

This article attempts to describe a particular form of baraccata house, found in L’Aquila, Italy. The differences between this form of baraccato and the Italian traditional timber-framed (T-F) structures, the baraccato borbonico and the baraccato alla beneventana, are shown. In the upper valley of the Aterno river (Abruzzo, Italy), a few kilometers far from L’Aquila, wonderful 18^th-century examples of T-F masonry structures are present. The use of wood pervades both the poor and noble buildings. In this article, the documentary and functional features of this peculiar anti-seismic timber-based building technique, which is widespread in L’Aquila and the neighboring areas, is described. After a comparative analysis of the technique’s features, the case of three T-F buildings, belonging to three different social classes is reported, the first is the Ricci palace in Mopolino di Montereale, the second is a middle-class building, and the third is a rural one. The 1703 earthquake, which affected the upper valley of the Aterno river and the nearby city of L’Aquila, gave rise to an ante litteram anti-seismic culture. Timber was not seen as an obstacle to durability but a material to be exploited to protect buildings from earthquakes.     

Assessment of material characteristics of ancient concretes,Grande Aula,Markets of Trajan,Rome

The Grande Aula, or Great Hall, of the Markets of Trajan (AD 96 to 115) is an intact example of the domed, concrete architecture of imperial Rome. Petrographic, x-ray diffraction, chemical, and SEM analyses demonstrate that wall mortars contain Pozzolane Rosse volcanic ash aggregate (harenae fossiciae) and strätlingite, a complex calcium aluminate cement hydrate (C₂ ASH₈) that gives modern cements good durability and compressive strength. Specific gravity tests and a new petrographic method for assessing bulk densities indicate unit weights of about 1750 kg/m³ for the wall mortars and 1430–1640 kg/m³ for the pumice bearing, vaulted ceiling mortars. Innovative point load source tests record the tensile strengths (f_t) of the aggregate and interfacial elements of the conglomeratic concrete fabric. These suggest f_t of about 2.7 MPa for brick, 1.2 MPa for Tufo Lionato tuff, and 0.9 MPa for Tufo Giallo della Via Tiberina tuff coarse aggregate (caementa), based on a tentative, approximate correlation with splitting (Brazilian) tests. The pozzolanic mortar and interfacial zones have lower f_t in the range of 0.8 MPa to 0.5 MPa. The relatively low mortar strength and its somewhat tenuous adhesion to the coarse aggregate suggests that the caementa may have arrested the propagation of tensile microcracks that formed in the mortar, thereby increasing the composite tensile strength of the concrete. Roman builders selected the complex aggregate mixes to optimize the performance of the wall and vault concretes.