Claudia Fabiani

2.30 Novel Building Materials

The proper choice of building envelope material may optimize building energy efficiency and indoor–outdoor comfort conditions in the built environment, together with its environmental sustainability. Therefore, a deep and multidisciplinary understanding of building envelopes and the new potentialities associated to building materials is needed in order to design green and smart constructions. In this perspective, the present chapter concerns, firstly, basics of building physics about hygro-thermal, acoustics, and lighting performance of the built environment. Then the main building material properties and the key traditional and innovative typologies are assessed with a specific focus on energy efficiency and environmental sustainability targets.

Durability assessment of soft elastomeric capacitor skin for SHM of wind turbine blades

Renewable energy production has become a key research driver during the last decade. Wind energy represents a ready technology for large-scale implementation in locations all around the world. While important research is conducted to optimize wind energy production efficiency, a critical issue consists of monitoring the structural integrity and functionality of these large structures during their operational life cycle. This paper investigates the durability of a soft elastomeric capacitor strain sensing membrane, designed for structural health monitoring of wind turbines, when exposed to aggressive environmental conditions. The sensor is a capacitor made of three thin layers of an SEBS polymer in a sandwich configuration. The inner layer is doped with titania and acts as the dielectric, while the external layers are filled with carbon black and work as the conductive plates. Here, a variety of samples, not limited to the sensor configuration but also including its dielectric layer, were fabricated and tested within an accelerated weathering chamber (QUV) by simulating thermal, humidity, and UV radiation cycles. A variety of other tests were performed in order to characterize their mechanical, thermal, and electrical performance in addition to their solar reflectance. These tests were carried out before and after the QUV exposures of 1, 7, 15, and 30 days. The tests showed that titania inclusions improved the sensor durability against weathering. These findings contribute to better understanding the field behavior of these skin sensors, while future developments will concern the analysis of the sensing properties of the skin after aging.

Effect of PCM on the Hydration Process of Cement-Based Mixtures: A Novel Thermo-Mechanical Investigation

The use of Phase Change Material (PCM) for improving building indoor thermal comfort and energy saving has been largely investigated in the literature in recent years, thus confirming PCM’s capability to reduce indoor thermal fluctuation in both summer and winter conditions, according to their melting temperature and operation boundaries. Further to that, the present paper aims at investigating an innovative use of PCM for absorbing heat released by cement during its curing process, which typically contributes to micro-cracking of massive concrete elements, therefore compromising their mechanical performance during their service life. The experiments carried out in this work showed how PCM, even in small quantities (i.e., up to 1% in weight of cement) plays a non-negligible benefit in reducing differential thermal increases between core and surface and therefore mechanical stresses originating from differential thermal expansion, as demonstrated by thermal monitoring of cement-based cubes. Both PCM types analyzed in the study (with melting temperatures at 18 and 25 ∘C) were properly dispersed in the mix and were shown to be able to reduce the internal temperature of the cement paste by several degrees, i.e., around 5 ∘C. Additionally, such small amount of PCM produced a reduction of the final density of the composite and an increase of the characteristic compressive strength with respect to the plain recipe.

Novel dynamic thermal characterization of multifunctional concretes with microencapsulated phase change materials

Concrete is widely applied in the construction sector for its reliable mechanical performance, its easiness of use and low costs. It also appears promising for enhancing the thermal-energy behavior of buildings thanks to its capability to be doped with multifunctional fillers. In fact, key studies acknowledged the benefits of thermally insulated concretes for applications in ceilings and walls. At the same time, thermal capacity also represents a key property to be optimized, especially for lightweight constructions. In this view, Thermal-Energy Storage (TES) systems have been recently integrated into building envelopes for increasing thermal inertia. More in detail, numerical experimental investigations showed how Phase Change materials (PCMs), as an acknowledged passive TES strategy, can be effectively included in building envelope, with promising results in terms of thermal buffer potentiality. In particular, this work builds upon previous papers aimed at developing the new PCM-filled concretes for structural applications and optimized thermalenergy efficiency, and it is focused on the development of a new experimental method for testing such composite materials in thermal-energy dynamic conditions simulated in laboratory by exposing samples to environmentally controlled microclimate while measuring thermal conductivity and diffusivity by means of transient plane source techniques. The key findings show how the new composites are able to increasingly delay the thermal wave with increasing the PCM concentration and how the thermal conductivity varies during the course of the phase change, in both melting and solidification processes. The new analysis produces useful findings in proposing an effective method for testing composite materials with adaptive thermal performance, much needed by the scientific community willing to study building envelopes dynamics.

Innovative Structural Concretes with Phase Change Materials for Sustainable Constructions: Mechanical and Thermal Characterization

New phase change materials (PCMs) are promising fillers for the realization of multifunctional concretes, combining good mechanical properties with enhanced thermal storage capabilities within building envelope. These materials are currently receiving a growing interest in the scientific literature. Encapsulated PCMs result particularly suitable for applications in concrete. This paper presents a research on concretes doped with different contents of PCMs, up to the 5% of the total weight. Physical, mechanical and thermal experimental tests were carried out, in order to investigate the physical properties, the stress-strain behaviour, the ductility, the compressive strength, as well as the thermal conductivity, the diffusivity and the specific heat capacity of the novel concretes. The results of thermal tests demonstrated the effective enhancement of the thermal inertia of the materials, while mechanical tests showed performances compatible with structural applications. Overall, new multifunctional concretes with PCM inclusions appear promising for achieving sustainable and lightweight concrete structures.