Mónica López-Alonso

Nowadays construction sector continues to face major environmental challenges, largely due to the consumption of natural resources, energy, and water, as well as the generation of waste and emissions into the environment. In Andalusia (Spain), the olive oil industry plays a central role in the economy, generating large volumes of waste and by-products, including olive stones. Due to their physical characteristics, olive stones represent a potential substitute for conventional aggregates in cement mortars, which are not subjected to restrictive technical standards as concrete. This study evaluates the technical feasibility of cement mortars prepared by replacing 10% and 20% of conventional sand (by volume) with four different types of olive stones. Tests were carried out on setting times, consistency, density, and air content, in fresh state, as well as on capillarity, density, and flexural and compressive strengths, in hardened state, using a conventional mortar as reference, with favorable results. Mortars could be classified according to the harmonized standards for masonry, rendering and plastering, and flooring and screed mortars, and for the applications described in the Spanish Building Code (CTE). This progress in knowledge would further support the integration of the construction sector into the fields of sustainability and circular economy.

A road was studied to evaluate the implementation of large-scale concrete pavement mixes. 5 different types of sections were included: a control section with conventional concrete, another with the application of eco-hybrid additions to the cement, two sections with replacement of aggregates with recycled materials from the processing of mixed CDW - mixed recycled aggregates and processed olive biomass ash - and finally a section replacing both aggregates with MRA and BBA with the use of eco-hybrid additions. Characterisation studies of the different materials and the design of the experimental sections were carried out in the laboratory. At the plant dosages and consistencies were controlled, while externally a study of the mechanical behaviour in the short and medium term was carried out. For the technical study of concrete behaviour, in situ sensors were included, obtaining monitoring results through temperature sensors and dimensional changes. In addition to a study of behaviour and durability, a life cycle assessment was made, assessing both in environmental and monetary parameters the environmental impact of conventional concrete and mixtures with recycled materials. The cement that included alternative supplementary cementitious materials showed strengths comparable to conventional cement. The substitution of aggregate led to a decrease in mechanical properties. The environmental impact was reduced in mixes in which Eco-Hybrid cement was used. The objective of this concrete road was to reach 30MPa in compression (HA-30).

The development of new building elements, such as concrete and mortar with sustainable materials, which produce a lower carbon footprint, is an achievable milestone in the short term. The need to reduce the environmental impact of the production of cement-based materials is of vital importance. This work focuses on the evaluation of the life-cycle assessment, production costs, mechanical performance, and durability of three mortars and three concrete mixtures in which mixed recycled aggregates (MRAs) and biomass bottom ash from olive waste (oBBA) were included to replace cement and aggregates. Powdered MRA and oBBA were also applied as complementary cementitious materials with a reduced environmental footprint. Chemical and physical tests were performed on the materials, and mechanical performance properties, life-cycle assessment, and life-cycle cost analysis were applied to demonstrate the technical and environmental benefits of using these materials in mortar and concrete mixtures. This research showed that the application of MRA and oBBA produced a small reduction in mechanical strength but a significant benefit in terms of life-cycle population and environmental costs. The results demonstrated that finding long-term mechanical strength decreases between 2.7% and 14% for mortar mixes and between 1.7% and 10.4% for concrete mixes. Although there were small reductions in mechanical performance, the savings in environmental and monetary terms make the feasibility of manufacturing these cement-based materials feasible and interesting for both society and the business world. CO₂ emissions are reduced by 25% for mortar mixes and 12% for concrete mixes with recycled materials, and it is possible to reduce the cost per cubic meter of mortar production by 20%, and the savings in the cost of production of a cubic meter of concrete is 13.8%.

In recent years, the use of self-compacting concrete has been a great advantage and garnered undoubted interest in construction. Due to the environmental impact caused by the consumption of natural aggregates in the manufacture of concrete, a more sustainable approach is needed. An approach for more sustainable construction is to use industrial waste such as bottom ash from the combustion of biomass as a replacement for natural aggregates. This research aims to use biomass bottom ash as a replacement for natural sand (10%, 20% and 30% replacement); in addition, by utilizing a crushing process of the bottom ash, the ash has been used as a filler replacement (replacement 20%, 40% and 60%). The fresh and hardened properties have been evaluated according to the standard. The results show the feasibility of using biomass bottom ash in self-compacting concrete, providing a sustainable alternative in order to minimise environmental impacts related to the extraction and depletion of natural resources.

The management of different industrial by-products, such as recycled aggregates from construction and demolition waste and alumina by-products, as well as the reduction of landfill deposits by incorporating these products in a second life cycle, were the focus of this work. The aim of this study was to demonstrate the technical viability of using these waste and by-product as a material for road pavement base layers. For this purpose, a real-scale application was carried out, and the behavior of three types of materials, applied on a section of an experimental road under real vehicle traffic conditions, was studied and compared. Three materials were used in these sections applied in the road sub-bases. First, a control material composed of a type of artificial gravel was used to be compared with the rest of materials; the second material was composed of recycled aggregates, and the third was composed of a mix of recycled aggregates and alumina waste. The results concluded that the effectiveness of the sections built using recycled aggregates and alumina waste was very positive and similar those constructed using natural aggregates.