Sustainable inorganic Binders and Their Applications in Building Engineering: A Green Alternative to Ordinary Portland Cement

In the last decades, the building materials and construction industry has been contributing to a great extent to generate a high impact on our environment. As it has been considered one of the key areas in which to operate to significantly reduce our footprint on environment, there has been widespread belief that particular attention now has to be paid and specific measures have to be taken to limit the use of non-renewable resources.The aim of this thesis is therefore to study and evaluate sustainable alternatives to commonly used building materials, mainly based on ordinary Portland Cement, and find a supportable path to reduce CO2 emissions and promote the re-use of waste materials. More specifically, this research explores different solutions for replacing cementitious binders in distinct application fields, particularly where special and more restricting requirements are needed, such as restoration and conservation of architectural heritage. Emphasis was thus placed on aspects and implications more closely related to the concept of non-invasivity and environmental sustainability. A first part of the research was addressed to the study and development of sustainable inorganic matrices, based on lime putty, for the pre-impregnation and on-site binding of continuous carbon fiber fabrics for structural rehabilitation and heritage restoration. Moreover, with the aim to further limit the exploitation of non-renewable resources, the synthesis of chemically activated silico-aluminate materials, as metakaolin, ladle slag or fly ash, was thus successfully achieved. New sustainable binders were hence proposed as novel building materials, suitable to be used as primary component for construction and repair mortars, as bulk materials in high-temperature applications or as matrices for high-toughness fiber reinforced composites.

A Semantic-based Framework for Digital Survey of Architectural Heritage

The research aims at developing a framework for semantic-based digital survey of architectural heritage. Rooted in knowledge-based modeling which extracts mathematical constraints of geometry from architectural treatises, as-built information of architecture obtained from image-based modeling is integrated with the ideal model in BIM platform. The knowledge-based modeling transforms the geometry and parametric relation of architectural components from 2D printings to 3D digital models, and create large amount variations based on shape grammar in real time thanks to parametric modeling. It also provides prior knowledge for semantically segmenting unorganized survey data. The emergence of SfM (Structure from Motion) provides access to reconstruct large complex architectural scenes with high flexibility, low cost and full automation, but low reliability of metric accuracy. We solve this problem by combing photogrammetric approaches which consists of camera configuration, image enhancement, and bundle adjustment, etc. Experiments show the accuracy of image-based modeling following our workflow is comparable to that from range-based modeling. We also demonstrate positive results of our optimized approach in digital reconstruction of portico where low-texture-vault and dramatical transition of illumination bring huge difficulties in the workflow without optimization. Once the as-built model is obtained, it is integrated with the ideal model in BIM platform which allows multiple data enrichment. In spite of its promising prospect in AEC industry, BIM is developed with limited consideration of reverse-engineering from survey data. Besides representing the architectural heritage in parallel ways (ideal model and as-built model) and comparing their difference, we concern how to create as-built model in BIM software which is still an open area to be addressed. The research is supposed to be fundamental for research of architectural history, documentation and conservation of architectural heritage, and renovation of existing buildings.

Solutions for the conservation and restoration of cement-based materials in XX Century architectural heritage

Among the most representative materials of XX Century architectural heritage, this dissertation focuses on the cement-based ones, investigating some different fields where they were exploited. Primarily, concerning the surface preservation of cement-based materials used with aesthetic intent, new self-cleaning treatments based on titania nanoparticles embedded in inorganic matrices were tested. In order to consider the role of porosity, the treatments were applied to different kinds of materials (cement-based mortar, marble and concrete) and several analyses were conducted to investigate the morphology of the coatings, their photocatalytic effectiveness, their durability and the interaction between the coating and the substrate material. The outcomes showed that several parameters influence the treatment’s performances, in particular, the presence and nature of the matrix, the concentration and dispersion of nanoparticles and, in some cases, the amount of substrate material which interacts with the coatings. Secondly, this dissertation deals with the historic “Terranova” render, a colored dry-mix mortar largely widespread in Europe in the first half of XX Century, whose formulation is still basically unknown. Some original samples of supposedly Terranova renders were subjected to several characterization analyses and the results were compared to those of the original “Terranova” render of the Engineering Faculty in Bologna. Despite the recurrence of some features, defining a common formulation seemed to be challenging. Finally, the repair and conservation of structural reinforced concrete in heritage buildings were investigated, adopting the former “Casa del Fascio” in Predappio (FC, Italy) as case study. Three different materials and solutions were tested on a slab of the building, making its repair only from the intrados. Then several analyses were conducted both on site and in laboratory. Aside from the specific features characterizing every product, the results highlighted that the application method played a fundamental role in the effectiveness of the retrofit strategies.