###### Abstract  
Climate change is already an undeniable reality, and it is a direct consequence of our society's lifestyle and the indiscriminate use of certain materials, such as Portland cement, which causes the emission of gases and waste that contributes to the greenhouse effect. The object of this work is to present the results obtained from research on pyroxenic andesites that have become altered to zeolite and their use as alternative, eco-efficient materials that improve the quality of cement through a standardized partial substitution. In this work, four samples of pyroxenic andesites altered to zeolites (PAAZ) and two samples of unaltered andesites (UPA) were analyzed. The methods used in this study are as follows: petrography of thin section (PTS), chemical analysis of X-ray fluorescence (XRF) and phase determination by X-ray diffraction (XRD). Other tests were carried out to determine the quality of the PAAZ from a technical and practical application point of view, such as chemical analysis of pozzolanicity (CPT) at 8 and 15 days, as well as mechanical compression tests at 2, 7, 28 and 90 days. Petrography and phase analyses show that the original mineral components of the samples such as pyroxene, amphibole, plagioclase and mica were leached and replaced by more than 90% with mordenite and smectic. XRF analyses indicates an anomalous rise in SiO\({}_{2}\), a drastic reduction in alumina Al\({}_{2}\)O\({}_{3}\) and a significant increase in alkaline compounds over alkaline-earth compounds in samples of altered pyroxenic andesites (PAAZ) with respect to samples of unaltered andesites (UPA). The pozzolanicity test establishes that the samples of unaltered andesites do not behave like pozzolanics at 8 or 15 days; however, altered andesites experienced remarkable pozzolanicity in the same periods. The mechanical compression tests carried out on specimens made with PAAZ and Portland cement showed a growing increase in mechanical resistance from 2 days (15.2 MPa) to 90 days (72.1 MPa). These results suggest that pyroxenic andesites altered to zeolite can be an ideal alternative to partially replace Portland cement, which in turn could contribute to the preservation of the environment and a more rational use of traditional resources. altered pyroxenic andesite; zeolite; cement; pozzolanicity; eco-efficient materials; mortars 40.0000-0001-9000-00001-90001-90001-90001-90001-90001-90001-90001-90001-90  
as pozzolans capable of replacing Portland cement by up to 40%, and this substitution is more effective when the rock is heated between 700\({}^{\circ}\) and 900 \({}^{\circ}\)C. [PERSON] et al. [2] highlight the positive effect of andesite as a pozzolan on the mechanical behavior of high-strength concretes, indicating that a substitution of cement by andesite of 10% is the most effective proportion to obtain maximum mechanical resistance. Along the same lines, the works of [PERSON] and [PERSON] [3] as well as those of [PERSON] et al. [4] stand out. Andesites have been used effectively in the manufacture of mortars with mechanical strengths greater than 50 MPa in 48 h of curing [5], and studies have clarified the mechanisms that form microfractures in mortars to predict trends in their growth [6; 7]. The properties of andesites as aggregates have been mentioned for many other uses by several researchers in the following fields: to improve the properties of specific asphalts [8; 9]; to determine the hydrodynamic abrasion resistance of concrete [10]; to improve light concretes [11]; in the use of sewage sludge from wastewater treatment plants generated during the processing of andesitic materials [12] and to pave roads [13; 14]. On the other hand, andesites have traditionally been used in the construction of historic and modern buildings due to their high chemical resistance [15], physical resistance [16], mechanical strength [17], resistance to freeze-thaw cycles [18] and abrasion resistance [19].