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2021 | Book

Hygrothermal Behaviour and Building Pathologies


About this book

This book presents recent research in the area of construction pathology, hygrothermal behaviour of buildings, service life and diagnostic techniques, and highlights the latest developments in building physics, hygrothermal behaviour, durability and numerical models applied to building materials analysis. Discussing the state of the art in the field, and covering topics relevant to variety of engineering disciplines, such as civil, materials and mechanical engineering, it will appeal to scientists, students, practitioners, lecturers and other stakeholders.

Table of Contents

Wetting and Drying Patterns in a Wet Moisture Reference Year Identified Using the Weinert’s Index: Station Versus Gridded Data
Hygrothermal simulation of building elements requires consideration of pertinent meteorological parameters which can be accounted by apt identification of a Moisture Reference Year (MRY). There are different indices available for the identification of MRY which depend on the availability of relevant data which are often not available in the desired quality and quantity for the location of interest. This study describes the utility of Weinert’s Index and gridded data for the identification of wet-MRYs across 10 locations in India. Weinert’s Index indicate that the locations pertaining to the cold and hot-dry region of India exhibit the highest and the least severity respectively. The study subsequently compares the wetting and drying pattern exhibited by gridded and station records over the duration of the wet-MRY and its annual wet-spell. A novel wet-spell severity index has been developed to quantify the severity of encompassed wetting and drying patterns. Results reveal that gridded data offer a conservative representation of wet conditions at a location with the severity tending to differ in places bearing complex topography. The values of wet-spell severity index attributes the highest and lowest wetting drying severity to the locations considered in the warm-humid and hot-dry region respectively.
Sneha Das, Kaustav Sarkar
Knee Point Detection in Water Absorption Curves: Hygric Resistance in Multilayer Building Materials
The moisture transfer process in multilayered building components with an interface is very different than the moisture transfer considered when having different materials/layers separately. Quantifying moisture transfer in multi-layered systems through numerical simulations is essential to predict the real behaviour of those building materials in contact with moisture, which depends on the climatic conditions. Unfortunately, the contact phenomenon is neglected in numerical simulations which compromise the feasibility of the results. In this work, the moisture transfer in multi-layered building components is analysed in detail, for perfect contact and hydraulic contact interface. The “knee point” was detected, numerically, in water absorption curves and the moisture-dependent interface resistance was quantified and validated for transient conditions. The methodology proposed to detect the “knee point” can be also used in the future for different multilayer materials with an interface, in order to obtain more correct maximum hygric resistance values, to be used in future numerical simulations.
A. C. Azevedo, J. M. P. Q. Delgado, A. S. Guimarães, I. Ribeiro, R. Sousa
Adhesion of Gypsum Plaster Coatings: Experimental Evaluation
Nearly 95% of the Brazilian production of natural gypsum comes from the state of Pernambuco, from the Araripe Gypsum Center. Of the 95%, that is to say, of the 1.3 million ton/year production, 61% is allotted to the making of blocks and plates, 35% for coverings, 3% for ceramic moulding, and 1% for other uses. The Gypsum Center generates nearly 12,000 jobs directly and approximately 60,000 jobs indirectly, and has an annual invoicing of US$300M per annum. In civil construction, the use of gypsum increases continually, because plaster paste is seen by builders as a low cost, quality alternative material to be applied as coatings to internal walls. The reduced cost results in higher productivity on the part of the craftsperson due to the speed of application as well as providing a good final finish. Paint can be applied without needing to apply putty. Bases commonly used for these types of finishes are ceramic and concrete substrates. These materials are known for their excellent mechanical strength and low thermal conductivity. The superior surface quality on both sides of these materials makes them suitable for any thickness of plaster paste. This study evaluates experimentally the adhesion strength of coatings made with gypsum paste, considering different substrates and application heights. There are four types of blocks (ceramic and concrete, non-structural and structural blocks), two types of slice cutting (superficial and penetrating to the substrate) and three application heights (up to 0.6 m, between 0.6 and 1.2 m and above 1.2 m). The results indicated the strong influence by the base and depth of cut on the adhesion, but there was no influence on adherence attributed to the height of application.
A. C. Azevedo, J. M. P. Q. Delgado, T. H. C. Neves, A. J. Costa e Silva
Model to Estimate Concrete Carbonation Depth and Service Life Prediction
This chapter proposes a mathematical model for estimating the concrete carbonation depth and predicting the service life of concrete structures subject to CO2 action, with easily obtainable input data. The input variables are divided into three groups: concrete properties (concrete compressive strength at 28 days, type of cement used, content and type mineral admixture); exposure conditions (a structure is indoors or outdoors, protected or not from rain) and environmental conditions (relative humidity and CO2 content). The model was obtained by coupling the concrete conduct equations reported in the literature, especially the first Fick’s Law. To adjust the model’s coefficients and parameters, 1298 data obtained through experts’ knowledge were used. The model determination coefficient was 0.9860, and the root-mean-square error (RMSE) was 0.3 mm. The model was validated using 298 data of the natural carbonation available in the literature, representing 87% of tested data. The results indicate that the model has the potential to predict the concrete carbonation depth for the boundary conditions that guided its development. It also presents itself as a potential tool for determining the concrete carbonation depth and service life prediction of new or existing structures.
E. Possan, J. J. O. Andrade, D. C. C. Dal Molin, José Luis Duarte Ribeiro
Artificial Intelligence Applied in the Concrete Durability Study
Interest in artificial intelligence (AI) in engineering research and practice has increased in recent years, especially the use of artificial neural network (ANN). The ANN has similar characteristics to biological neural networks, efficiently recognizing patterns and behaviors, suited to provide an accurate tool to map and understand the concrete degradation. This chapter presents the positive aspects of artificial neural network to model different concrete degradation mechanisms and provides a detailed procedure for ANN design. As example, the concrete carbonation depth is modeled by an ANN and the results show the its ability to map the carbonation phenomenon.
E. F. Felix, E. Possan, R. Carrazedo
Pre-diagnosis Protocol for Large Residential Building Stock. The Case of Barcelona’s Vulnerable Areas
The large-scale evaluation of buildings is an important tool to guarantee that our cities are in good condition. This chapter presents the experience of a pre-diagnosis protocol applied to the most socially vulnerable neighborhoods in Barcelona. The protocol was specifically designed for this purpose and proposes a methodology in several elimination phases, in which attention is gradually focused on buildings that may be damaged and could lead to risk situations. The protocol was used to evaluate buildings in 16 neighborhoods of Barcelona. The original characteristics of the buildings varied widely, but all of them had suffered from a lack of building maintenance over decades. The results provide extensive information about the constructed reality of these neighborhoods and general and specific knowledge about the state of conservation of the buildings and their actual damage.
C. Cornadó, S. Vima-Grau, P. Garcia-Almirall
Hygrothermal Behaviour and Building Pathologies
Prof. J.M.P.Q. Delgado
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