This research presents a qualitative description of the degradation phenomena that occurred in external walls of the San Carlos Bastion, San Francisco de Campeche, Campeche City, (Mexico), a military structure built with calcareous materials between 16 th and 17 th centuries. Several weathe-investigación / research

Tropical climate create ideal conditions for the development of microbial communities associated with biodegradation of historic buildings made with stony materials. This is the case of Fort San Carlos, a historic colonial building representative of military tendencies during the XVII century in San Francisco de Campeche City. In this study the Polymerase Chain Reaction (PCR), was used to identify microorganisms related with the biodegradation of its masonry structure. Specific primers for amplification of 16S and 18S ribosomal RNA genes were used for organisms identification by PCR. Amplification products were sequenced and after that compared with GENBANK nucleotide database using-BLASTn. Results indicated that microbial communities associated to biodegradation of the Fort San Carlos are bacteria from the Phyla Cyanobacteria, Proteobacteria and Actinobacteria.

The reactive ion etching of polycide films (TiSi2 over polysilicon) is discussed. Experimental conditions which lead to anisotropy and the identification of certain contamination problems as well as their solution are presented.

Abstract-This research evaluates the behaviour of Portland cement-based mortars with additives that act as cementing materials. These additions are silica rich materials used as substitutes for PC (Portland cement type IV ASTM) in the preparation of mortars, as an alternative to reduce the amount of cement, reusing agribusiness waste. The results indicate that the use of some additions in the percentages specified herein is not convenient to mitigate the phenomenon of carbonation, since as the degree of substitution increases, the speed also increases carbonation. On the other hand, if the emission of polluting particles into the environment is mitigated, the amount of cement used in the mortar decreases.

Fue evaluado el efecto de realcalinización electroquímica aplicando las normas UNE-EN-1504, NACE-SP0107 2007 y NMX-C-553-ONNCCE-2018, en muestras de concreto reforzado previamente carbonatadas. Con el seguimiento del grado de realcalinización, mediante mediciones de pH y potencial de media celda a 7, 14, 21 y 28 días, se observa la recuperación del pH en todos los casos, obteniendo valores de potencial de media celda característicos en cada aplicación de corriente, que confirma la polarización del acero modificando la condición termodinámica de la intercara concreto-acero y ocasionando cambios químicos en la pasta de concreto. Con la norma NMX-C-553-ONNCCE-2018 se polarizó el acero sin llegar a la región de sobreprotección, evitando el riesgo de producir hidrógeno y fragilidad en el acero