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In recent years, there has been great interest in sustainable construction, which has led to an increased interest in 3D printing or additive manufacturing. However, the use of this technique with conventional materials is not enough to reduce the large environmental impact generated by the construction sector. Although most of the research and advances are focused on the 3D printing of Portland concrete, this review has been oriented towards the 3D printing of building materials based on soils and clays, which can provide an affordable (as it is a locally available material in many regions of the planet), environmentally sustainable, and low-cost approach, which is highly beneficial for housing construction. This paper has been oriented towards the search of scientific literature and prototypes that have been elaborated using ancestral materials, such as soil-clay-sand-sand-fibers like straw and water, for the elaboration of constructive pieces such as 3D printed walls or adobes. The objective of this paper is to close the gap on the use of mixtures based on soils, which, although they seem to have been fully studied for several centuries, to date their application in 3D printing is reduced. Readjustments in properties of soil mixtures such as fluidity for pumping or extrusion, buildability and good working time are variables that are reported in this paper. In addition, this review describes the mixtures that have been developed for 3D printing from soils and clays, and the main characteristics that have been found. Finally, the challenges that still remain for the blends to be applied on a massive industrial scale are presented. [ABSTRACT FROM AUTHOR]

The high penetration of distributed renewable resources requires integration strategies that ensure a balance between supply and demand. Transactive energy (TE) comprises a set of mechanisms capable of achieving this objective by using value as an operational parameter. This paper presents a review of the state of the art in TE, aiming to provide the reader with a general overview of concepts and applications. To accomplish this, the document offers a review of market and operational structures, with a particular focus on the role of TE in the composition of local energy markets. Furthermore, an analysis of the value concept in energy is proposed as a linking element between two current topics of academic interest: multi-energy systems and the water-energy-food nexus. Finally, some international and national pilot projects are showcased, allowing for the identification of the practical validity of the concepts described. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the mechanical behavior of buried pipes subjected to thermal load cycles. Firstly, stresses and deformations are measured experimentally on a buried pipe subjected to monotonic and cyclic thermal loads, hence reproducing the typical operating conditions of buried piping systems. Subsequently, a numerical model is developed using the finite element method, which is validated using the results obtained experimentally. Subsequently, this computational model was used to carry out a parametric study of the influence of the mechanical properties of the soil on the stress state of the system. Finally, from the results obtained experimentally and numerically, it is concluded that the most critical situation in terms of stresses takes place when the pipe is firstly placed into operation, i.e. in the first cycle of thermal load and the other variables studied have little impact. [ABSTRACT FROM AUTHOR]