sustainability Article Sustainable Development of Human Society in Terms of Natural Depleting Resources Preservation Using Natural Renewable Raw Materials in a Novel Ecological Material Production Cătălina Mihaela Grădinaru 1, * , Radu Muntean 2, *, Adrian Alexandru S , erbănoiu 1 , Vasilică Ciocan 1 and Andrei Burlacu 1 1 Faculty of Civil Engineering and Building Services, “Gheorghe Asachi” Technical University of Ias , i, 700050 Ias , i, Romania; serbanoiu.adrian@tuiasi.ro (A.A.S , .); vasilica.ciocan@tuiasi.ro (V.C.); andrei.burlacu@tuiasi.ro (A.B.) 2 Faculty of Civil Engineering, Transilvania University of Bras , ov, 500152 Bras , ov, Romania * Correspondence: radu.m@unitbv.ro (R.M.); catalina.gradinaru@tuiasi.ro (C.M.G.); Tel.: +40745183892 (R.M.) Received: 23 February 2020; Accepted: 25 March 2020; Published: 27 March 2020   Abstract: In the last few years, the building industry experienced a significant development as a response to the demographic growth of human society and to the increasing demand for housing. Their construction involves the traditional use of concrete as a material that provides added strength to the finished building. This is manufactured respecting standard recipes depending on the way of its use. Anyway, all concrete recipes involve the use of mineral aggregates extracted from the riverbed, as is happening in Romania, or rock blocks crushing, as reported in other countries. Under these conditions, the rationalization of the use of natural mineral resources and the identification of new possibilities to reduce their consumption through their replacement with vegetal waste has become an important research issue. In this study, two types of vegetal waste—namely, shredded corn cobs and sunflower stalks—were used to manufacture novel ecological concretes. The vegetal wastes, both in untreated and treated forms (with 20% and 40% of sodium silicate solution), were used to replace 50% of the river (mineral) aggregate volume. The obtained concretes were tested, and the values of some important parameters in the concrete characterization (such as bulk density, water adsorption capacity, compressive strength and splitting tensile strength) were compared with the concrete contains cement CEM II/A-LL 42.5R. The obtained results show that these vegetal wastes have the potential to be used in the manufacturing of new ecological concrete. In addition, this alternative material meets the requirements for the sustainable and healthy development of the environment, offering low-polluting solutions in the context of an increasing demand for constructions. Keywords: vegetal waste; shredded corn cobs; sunflower stalks; green concrete 1. Introduction Besides various benefits, the traditional materials used in the building industry are considered costly and polluting through the process of obtaining them. Concrete, for example, is a widely used material in the constructions industry, with increasing demand due to the global demographic growth. This is because, a concrete building system is considered energy efficient due to its special ability to combine a high thermal mass, very low air infiltration, and a high R-value (thermal resistance) in the exterior walls [1]. In addition, concrete buildings have fewer joints than those made of wood or steel frame, which means a tighter system in which the material itself absorbs and stores heat energy, with a delayed impact of the exterior temperature on the inside environment [2]. Sustainability 2020, 12, 2651; doi:10.3390/su12072651 www.mdpi.com/journal/sustainability