This research was carried out by the Research Group of Materials Modification at PUCP. The authors would like to acknowledge the Pontificia Universidad Católica del Perú PUCP and its funding office DGI-PUCP (project 2013-0061) for providing funds to the project within which this work was developed. The forth author would also like to thank the fellowship funding for postgraduate studies by CONCYTEC, PERU (Contract N° 012-2013-FONDECYT). Finally, the authors thank the Soils Laboratory of the Civil Engineering Department at PUCP for the availability of their installations and equipment, and Manuel Otero, for providing the carrageenan extract for this study.

The study investigates the feasibility of using chitosan biopolymer as an admixture, or as an external coating, for earthen constructions to improve their resistance in two components: water induced degradation and key mechanical properties. The resistance to water induced degradation was evaluated in terms of contact angle and drip erosion tests, while the influence on mechanical properties was measured through compressive, tensile and three-point bending tests. The results indicate that the use of low concentrations of chitosan can improve significantly the performance in the two components and therefore was found to be a promising treatment for new or existing construction.