Thematic Articles

Each year, nearly 40 billion tonnes of raw materials extracted from the Earth’s crust feed into the construction industry. The associated material flows dramatically contribute to anthropogenic CO2 emissions. Therefore, more sustainable supply chains must be envisaged based on the use of locally available resources and the principles of circular economy. Drawing inspiration from vernacular architecture, innovative solutions for green construction based on sustainable exploitation of local resources can be posited. This strategy has also inspired the proposed practice of in situ resource utilization on planetary bodies such as the Moon and Mars.

Concrete structures may develop deleterious damage, which significantly reduces service life, structural integrity, and safety, posing serious issues in large or otherwise critical infrastructure. Routine petrographic assessments, including microstructure, texture, and fabric, of concrete and its (gravel and sand) aggregate and binder constituents in thin section using polarization-fluorescence microscopy (PFM) enables the unequivocal identification of features that would otherwise remain hidden in conventional petrography. Rigorous preparation procedures preserve original microstructural details, make preparation artefacts recognizable, and ensure that the fluorescent emission can be quantified. This contribution outlines the preparation of fluorescence-impregnated thin sections and elaborates on the application of PFM to damaged concrete, with further examples from selected rock types commonly used for concrete aggregate.

A background on non-Portland cementitious binders is presented, f ollowed by a review of the key alternative binders that are currently of interest. The mineralogy of these cements is described, along with
phases present in the reacted/hardened materials. The similarities and differ-ences between the setting processes, as controlled by reactions at the solid–liquid interface, provide insight into the ways in which different classes of binders develop their performance and thus offer value to society.

This chapter tells the story of Portland cement, from its invention in the
19th century until its present-day hegemony as the number one manufactured mineral product. The success story of Portland cement is rooted in
the unique combination of the abundance of its raw materials, the reactivity of the high-temperature clinker product toward water, and the properties of the calcium silicate and aluminate hydration products. Further development of Portland cements today mainly addresses the formidable challenge of reducing process CO2 emissions. Options include partial replacement of clinker by low-carbon resources, material-efficient use of cement and concrete products, and end-of-pipe carbon capture and storage or use.

The history of mineral components in cementitious materials begins with clays and bitumen in the most ancient mortars, followed by gypsum- and lime-based plasters, mortars, and concretes. Romans perfected the fabrication of extremely durable mortars that form the basis of audacious architectural monuments in Rome, massive harbor constructions, and water-proofed cisterns in the Mediterranean region. During the industrial revolution, “natural cements” were developed through the burning of impure limestone or Si- and Al-bearing materials blended with pure limestone. Delving into the past of concrete science and the composition, durability, and resilience of historic binders, mortars, and concretes can inspire the development of modern environmentally friendly cementitious materials.

The need to meet the globally increasing demand for construction
materials, while reducing the environmental impact of cement and concrete production, poses a technological and societal dilemma. Detailed knowledge concerning the mineralogical, geochemical, and microstructural features of ancient and modern binders is fundamental for novel, sustainable, cement-based materials to be designed, manufactured, and deployed. This introduction provides several basic concepts related to cement and concrete, as well as a general overview of the role played by these construction materials in ancient civilizations and in today’s society, and of how they are expected to evolve to ensure a sustainable, inclusive, and resilient urban future.