Characterization of ancient construction materials (mud walls and adobe) in the churches at Cisneros, Villada and Boada de Campos (Palencia)

The aim of this work is to characterize the ancient building materials (mud wall and adobe) of three churches in the province of Palencia. This is the first part of a study which seeks to evaluate how the mud walls of the tower of the church of Cisneros reacted to restoration treatment which consisted of a structural reinforcement made by injecting a highly fluid grout of cement/lime/sand mortar. This treatment implies the introduction of large quantities of water into the fabric. The mud walls of the tower of Cisneros are compositionally and texturally very similar to each other, which indicates that despite their large dimensions, care was taken in the homogeneity of the materials. These mud walls are also very similar to those of the church of Villada. The original raw material is mud with some additives (rubble, ashes, bones, etc.) and some remains of lime used as a stabiliser. Although there is a very high proportion of clay, no effervescing clay has been detected. Hence it is deduced that once the mud wall was built, there were no important changes in volume due to variation in the humidity of the fabric. The characteristics of the adobe of the tower of Boada are logically different form those of the mud walls, being made of less sandy, more clayey mud with a high proportion of straw that the mud walls do not have, and without the addition of bricks, bones, etc. El objetivo de este trabajo es caracterizar los materiales antiguos de construcción (tapial y adobe) de tres iglesias en la provincia de Falencia. El trabajo es la primera parte de un estudio en el que se pretende evaluar el comportamiento de los tapiales de la torre de la iglesia de Cisneros frente al tratamiento de restauración, consistente en un cosido estructural mediante la realización de perforaciones en las que se introduce una barra de acero y donde, posteriormente, se inyecta una lechada muy fluidificada de mortero de cemento/cal/arena. Este tratamiento implica la introducción en las fábricas de grandes cantidades de agua. Los tapiales de la torre de Cisneros son, composicional y texturalmente, muy similares entre sí, lo que indica que, a pesar de sus grandes dimensiones, se cuidó la homogeneidad de los materiales. Estos tapiales guardan una notable similitud con los de la iglesia de Villada. La materia prima original es barro con algunos aditivos (escombro, cenizas, huesos, etc.) y algunos restos de cal empleada como estabilizante. Aunque la proporción de arcilla es muy elevada no se han detectado arcillas hinchables, de lo que se deduce que una vez construido el tapial no se hab