Construction has always been considered a major producer of serious environmental problems due to large consumption of resources in terms of materials and energy accompanied by environmental pollution; therefore, the projects aiming to reduce these damaging effects are more than welcome. The objective of sustainable development is difficult to be performed by civil and structural engineers at a global scale. However, some solutions and systems for load bearing and cladding elements that make the buildings or other types of civil engineering applications may contribute, at least partially, to attaining some goals of sustainability. Fiber reinforced polymeric (FRP) composite structures and hybrid systems may become sustainable when they utilise minimum material resources, increase the life span of buildings, have a very low environmental impact and ensure the high quality of civil infrastructures. The main objectives of the paper are related to the use of FRP composites in new construction components as well as rehabilitation of deteriorated civil engineering structures aiming to achieve sustainable solutions in civil and structural engineering. Starting from the concept of FRP composites and hybrid systems the authors describe a number of research and development projects carried out by the Composite in Construction Research Group (CCRG) at the Faculty of Civil Engineering, "Gheorghe Asachi" Technical University of Iasi. After a critical evaluation of FRP composite materials applied in construction, the authors describe and analyse their results which addressed a long term program including: all composite structures, multilayered sandwich construction, concrete elements reinforced with FRP composite bars, and modern solutions for structural rehabilitation of load carrying elements made of traditional building materials aiming to improve the building components performance.

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The versatility of steel, its high resistance in relation to its low mass, as well as the easily accessible technology in the context of using recyclable materials and the low negative impact on the environment represent important arguments in using thin-walled steel profiles to make structures for buildings with a low height regime. This paper presents the results of an experimental program that investigated the behavior of three types of joints in a T-shape form made of thin-walled steel profiles to make shear wall panels or truss beam floors. Due to the small dimensions of the C-profiles of 89 × 41 × 12 × 1 mm, and of the technology of their joining, manufacturers prefer the hinged connections of elements with self-drilling screws. The purpose of the research presented in this paper is to assess the maximum capacity of the joints, the elastic and post-elastic behavior until failure, and also the mechanisms failure. The types of joints analyzed are commonly used in the production of structural systems for houses. The experimental program, which consisted of testing 5 specimens for each type of joint in tension (shear on screws), showed different behavior in terms of load-displacement. The experimental, tested models were analyzed by finite element simulations in an ANSYS nonlinear static structure with 3D solid models. The materials were defined by a bilinear true stress–strain curve obtained after some experimental tensile tests of the steel. The results of the experimental tests showed that the main failure mechanism is a yielding of the holes where the screws were mounted and a shearing of the profile walls. Adding an additional screw on each side increases the capacity of the joints, but not until a yield loss is obtained. In conclusion, it is shown that the solution is suitable for a low level of loading in a static manner; however, additional studies are necessary in order to develop and verify other solutions, thus improving the strength of the connection.

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The paper presents some preliminary results on using a new supplementary Cementitious material based on industrial by-products most of them unrecyclable until recently. The opportunity for using such industrial unrecyclable wastes in construction industry has recently been recognized by researchers as having net benefits for the environment. This strategy has the potential to reduce costs, conserve energy and minimize waste. The concept very much fits into the era of sustainable development. In view of this fact, the effect of curing conditions on the self weight and strength characteristics of an eco-mortar is studied and preliminary encouraging results are presented. The eco-cement, in the form of anhydrous calcium sulphate, is set to replace the ordinary Portland cement in the mix proportion. It is made from industrial wastes and can be entirely recycled after its expiration date. The curing conditions consisted in air curing for 28 days or various time intervals for curing in water until the day of testing. The strength properties at the age of 28 days are investigated in terms of bending tensile strength and compressive strength. The obtained results show that the curing conditions play an important role both on the self weight and on the strength characteristics.