Denny Coffetti

Binders alternative to Portland cement and waste management for sustainable construction—part 1:

This review presents “a state of the art” report on sustainability in construction materials. The authors propose different solutions to make the concrete industry more environmentally friendly in order to reduce greenhouse gases emissions and consumption of non-renewable resources. Part 1—the present paper—focuses on the use of binders alternative to Portland cement, including sulfoaluminate cements, alkali-activated materials, and geopolymers. Part 2 will be dedicated to traditional Portland-free binders and waste management and recycling in mortar and concrete production.

Cement-Based Renders Manufactured with Phase-Change Materials: Applications and Feasibility

The paper focuses on the evaluation of the rheological and mechanical performances of cement-based renders manufactured with phase-change materials (PCM) in form of microencapsulated paraffin for innovative and ecofriendly residential buildings. Specifically, cement-based renders were manufactured by incorporating different amount of paraffin microcapsules—ranging from 5% to 20% by weight with respect to binder. Specific mass, entrained or entrapped air, and setting time were evaluated on fresh mortars. Compressive strength was measured over time to evaluate the effect of the PCM addition on the hydration kinetics of cement. Drying shrinkage was also evaluated. Experimental results confirmed that the compressive strength decreases as the amount of PCM increases. Furthermore, the higher the PCM content, the higher the drying shrinkage. The results confirm the possibility of manufacturing cement-based renders containing up to 20% by weight of PCM microcapsules with respect to binder.

The effect of sodium silicate on the behaviour of shotcretes for tunnel lining

Present case study investigates the rheological, mechanical and in-placing performances of fiber reinforced shotcrete manufactured with different fibers (steel, glass and polypropylene) and with sodium silicate based set-accelerating admixture for tunnel linings. The study compares the performances of concretes manufactured and fully compacted with those shotcretes which are manufactured directly on the job-site. The influence of sodium silicate accelerator on mechanical and rheological properties of fiber-reinforced shotcretes with respect to reference concrete were evaluated. It was observed that: The addition of fibers does not influence slump and workability retention with respect to reference concrete, independent of type and dosage of fibers; Spraying and set accelerator dosage determined a decrease about of 10-30% in compressive strength compared to that of concrete placed and vibrated without sodium silicate accelerator; The set accelerating admixture has negative effect on compressive strength of fiber-reinforced shotcrete (15%).

Per uno sviluppo sostenibile delle costruzioni. Dalla cultura del "non più di" a quella del "non meno di"

With the dawn of twenty-first century, the world has entered into an era of sustainable development. The main challenge for concrete industry is to serve the two major needs of human society, the protection of the environment, on one hand, and - on the other hand - meeting the infrastructural requirements of the world growing population as a consequence of increase in both industrialization and urbanization. In the past, concrete industry has satisfied these needs well. However, for a variety of reasons the situation has changed dramatically in the last years. First of all, the concrete industry is the largest consumer of natural resources. Secondly, portland cement, the binder of modern concrete mixtures, is not as environmentally friendly. The worlds cement production, in fact, contributes to the earths atmosphere about 7% of the total CO2 emissions, CO2 being one of the primary greenhouse gases responsible for global warming and climate change. As a consequence, concrete industry in the future has to face two antithetically needs. In other words how the concrete industry can feed the growing population needs being – at the same time - sustainable? Sustainability in construction industry can be achieved through three differents main routes based on reduction in consumption of gross energy for construction materials production, in polluting emissions and in not renewable natural resources.