ANALYSIS AND CHARACTERISATION OF ADOBE BLOCKS IN JOJUTLA DE JUÁREZ, MÉXICO. SEISMIC VULNERABILITY AND LOSS OF THE EARTHEN ARCHITECTURE AFTER THE 2017 PUEBLA EARTHQUAKE
Keywords: Earthen architecture, Seismic vulnerability, Seismic culture, Sieve analysis, Colorimetry
Abstract. The 2017 Puebla Earthquake on 19 September struck a big part of central Mexico causing the loss of historic buildings in several states, being the state of Morelos one of the most damaged in the whole country. Jojutla de Juarez was the most affected locality of Morelos presenting important structural damages or total collapse in the built heritage, being the traditional earthen buildings, made of adobe bricks, the most vulnerable buildings to seismic efforts. Some of the causes which contributed to the poor behaviour of the buildings were the improper handling of the constructive systems and materials, the insufficient resistance of the structures and the problems with the foundations. The adobe houses of Jojutla presented a mixture between the traditional building techniques and industrial materials like concrete, cement and steel; also with irregular heights and plant layouts and inadequate connections between the walls and foundations and roofs, resulting into a higher seismic vulnerability when the earthquake impacted. Also the adobe bricks presented irregularities in its composition and use of additives which resulted in completely different typologies and the loss of the traditional construction techniques. A study was conducted to determine the properties of the remains of the adobe bricks of the houses in Jojutla, considering that the structures were severely damaged and a whole study of the seismic vulnerability would not be convenient due the loss of the physical traditional buildings. The grain size and composition of the adobe samples of the buildings were determined as well as the natural aggregates like straw, sand, and its proportion. A colorimetric study of the adobes and clays was also conducted, analysing the change of colour on account of the aggregates in the bricks. Also the compressive strength of the pieces was tested with two methods: the compression test and the point-load test, in order to obtain the indicative values which could be compared to other patrimonial and vernacular study cases.