Key Engineering Materials Vol. 634

Abstract: This work aims to contribute to the minimization of solid construction waste at construction sites through the application of sustainability concepts in the construction industry, addressing the recommendations of the LEED certification. The object of study was the works of reform and adaptation of the Maracanã Stadium, venue of the final match of the 2014 FIFA World Cup. The methodology consists of visits to the construction site of the stadium, interviews with responsible people for the jobs and data analysis collected by the Maracanã Consortium Rio 2014 Report. Based on the data collected, it was evaluated the used strategies and tools in the construction to minimize the generation of waste. It was found that the strategies were well executed, contributing to the reduction of waste at the construction site and to the sustainable disposal of the generated waste. The strategies involved environmental, social and economic aspects, giving the construction an international certification for sustainable building.

Abstract: Environmental concerns regarding the high CO₂ emissions related to the production of ordinary Portland cement (OPC) led to research efforts on the development of eco-efficient alternative binders. Geopolymers constitute promising inorganic binders alternative to OPC which are based on aluminosilicates by-products and alkali activators. The geopolymerization technology of aluminosilicates is a complex chemical process evolving dissolution of raw materials, transportation, orientation and polycondensation of the reaction products. Classical two part geopolymers could become more eco-efficient with a lower CO₂ footprint if sodium silicate usage is avoided. Besides current geopolymeric mixes can suffer from efflorescence originated by the fact that alkaline or soluble silicates that are added during processing cannot be totally consumed during geopolymerisation. Therefore, new and improved geopolymer mixes are needed. One-part geopolymers (sodium silicate free) were first proposed in 2007. However, very few papers were published on these materials. This paper presents experimental results on the durability performance of one-part geopolymers concerning water absorption, penetration of chloride, carbonation resistance and resistance to acid attack. Hydration products results assessed by FTIR spectra are also presented.

Abstract: This paper presents the study of the simultaneous use of two residual catalysts (RAl and RNi) with type II Portland cement, in order to avoid environmental impacts and to use of the solidified products as structural sustainable materials. The solidification/stabilization (S/S) was evaluated by thermogravimetric analysis, X ray diffraction, leaching and compressive strength tests. Mortars with water/cement mass ratio equal to 0.5 were prepared, into which, different percentual masses of each waste were added. The main phases formed due to the retarding and accelerating actions of each waste were evaluated by thermogravimetry and X ray diffraction after 28 days of hydration. The leaching tests done with the solidified mortars presented values of Ni and Al contents below maximum accepted limits, indicating that they attend to environmental legislation, as well as eliminate the original environmental impact of the original wastes. Mortars evaluated after 28 days by compressive strength tests, presented acceptable results for their possible use as construction materials.

Abstract: The catalyst discarded from fluidized catalytic cracking (FCC) units of heavy oil fractions presents in its composition typically high concentrations of silica and alumina, which give to it the possibility to be used as a pozzolanic material. The pozzolanic activity of a spent FCC catalyst from a Brazilian refinery oil was evaluated by studying the influence of the substitution in different degrees of a type II cement, by this catalytic residue on the hydration process and on the compressive strength of the formed materials. The influence of different particle size fractions of the residue and of its milling process was studied as well. The pozzolanic activity was evaluated by thermogravimetry (TG), derivative thermogravimetry (DTG) and non-conventional differential-thermal analysis (NCDTA). The results show that the chemical pozzolanic activity is enhanced when the sample presents a higher specific surface, as well as, the milling of the residue it is fundamental in order to be accepted and used as a pozzolanic material on partial substitution to cement.

Abstract: Over the last decades, extensive research has been undertaken to minimize the use of Portland cement by increasing the amount of various supplementary cementing materials since currently global concrete production accounts for more than five percent of anthropogenic carbon dioxide emissions. The granite cutting industry produces large amounts of wastes. Managing large amounts of sludge can be rather problematic for its producers, which must find appropriate places for storage and deposition. The experimental program carried out involved characterization of granite dust from a quarry in the north of Portugal, including chemical analysis, scanning electron microscopy (SEM) and laser particle size analysis. Subsequently, mechanical and durability properties (alkali-silica reaction and resistance to penetration of chloride ions) were evaluated in mortar produced with different dosages of cement replacement, as well as, different levels of fineness of ground granite. It could be concluded that finely ground granite dust can originate a denser cement matrix and improve durability without compromising fresh behavior or strength.

Abstract: This work intends to evaluate the (mechanical and durability) performance of concrete made with coarse recycled concrete aggregates (CRCA) obtained using two crushing processes: primary crushing (PC) and primary plus secondary crushing (PSC). This analysis intends to select the most efficient production process of recycled aggregates (RA). The RA used here resulted from precast products (P), with strength classes of 20 MPa, 45 MPa and 65 MPa, and from laboratory-made concrete (L) with the same compressive strengths. The evaluation of concrete was made with the following tests: compressive strength; splitting tensile strength; modulus of elasticity; carbonation resistance; chloride penetration resistance; capillary water absorption; and water absorption by immersion. These findings contribute to a solid and innovative basis that allows the precasting industry to use without restrictions the waste it generates.

Abstract: The use of agricultural residues for particleboard manufacturing increases their value-add and help meet the growing demand of raw materials for the panel industry. Accordingly, the aim of this study was to assess the quality of particleboards produced only with sugarcane bagasse or along with Pinus and Eucalyptus wood. The experimental design consisted of 5 treatments: T1) Eucalyptus panels, T2) Pinus panels, T3) sugarcane bagasse panels, T4) 50% Eucalyptus and 50% sugarcane bagasse panels, and T5) 50% Pinus and 50% of sugarcane bagasse panels. For each treatment, three panels were produced using 8% urea-formaldehyde adhesive, with 0.65 g/cm3 apparent density, 160°C pressing temperature, 4 MPa pressure, and 8 min of pressing time. The analyses revealed that use of sugarcane bagasse for particleboard manufacturing resulted in improved water absorption and thickness swelling properties after 2 h of immersion in water. In addition, the panels produced with bagasse only showed significant reductions in the mechanical properties. However, the use of sugarcane bagasse along with Pinus or Eucalyptus wood allowed the manufactured panels to meet all the conditions required by the CS 236-66 [1], ANSI A208.1 [2], and EN 312 [3] standards.

Abstract: The eco-efficient, self-compacting concrete (SCC) production, containing low levels of cement in its formulation, shall contribute for the constructions' sustainability due to the decrease in Portland cement use, to the use of industrial residue, for beyond the minimization of the energy needed for its placement and compaction. In this context, the present paper intends to assess the viability of SCC production with low cement levels by determining the fresh and hardened properties of concrete containing high levels of fly ash (FA) and also metakaolin (MK). Hence, 6 different concrete formulations were produced and tested: two reference concretes made with 300 and 500 kg/m³ of cement; the others were produced in order to evaluate the effects of high replacement levels of cement. Cement replacement by FA of 60% and by 50% of FA plus 20% of MK were tested and the addition of hydrated lime in these two types of concrete were also studied. To evaluate the self-compacting ability slump flow test, T₅₀₀, J-ring, V-funnel and L-box were performed. In the hardened state the compressive strength at 3, 7, 14, 21, 28 and 90 days of age was determined. The results showed that it is possible to produce low cement content SCC by replacing high levels of cement by mineral additions, meeting the rheological requirements for self-compacting, with moderate resistances from 25 to 30 MPa after 28 days.

Abstract: The use of waste in the construction industry is an interesting approach to minimize associated environmental impacts. A substantial body of research has proved the potential use of rice husk ash (RHA) as a mineral additive. A considerable portion of RHA presents pozzolanic characteristics, a result of its amorphous chemical structure and high silica contents. However, variations in particle size and chemical composition may affect applicability, limiting the use of RHA. In this scenario, this study presents a methodology to recycle RHA based on particle segregation and discusses how the process affects RHA performance in terms of its pozzolanic activity. Samples and respective segregated fractions were characterized using physical (loss on ignition, specific weight, surface area, grain size distribution), chemical (chemical composition and X-ray diffraction) and microstructural (scanning electron microscopy and energy dispersion) parameters. Pozzolanic activity was determined after milling of samples and segregation of fractions based on specific assays with cement and on electric conductivity. The results show that segregation opens new perspectives to increase the value of RHA in the construction industry.

Abstract: The objective of this research is the production of concrete with recycled aggregates (RA) from various CDW plants around Portugal. The influence of the RA collection location and consequently of their composition on the characteristics of the concrete produced was analysed. In the mixes produced in this research RA from five plants (Valnor, Vimajas, Ambilei, Europontal and Retria) were used: in three of them coarse and fine RA were analysed and in the remaining ones only coarse RA were used. The experimental campaign comprised two tests in fresh concrete (cone of Abrams slump and density) and eight in hardened concrete (compressive strength in cubes and cylinders, splitting tensile strength, modulus of elasticity, water absorption by immersion and capillarity, carbonation and chloride penetration resistance). It was found that the use of RA causes a quality decrease in concrete. However, there was a wide results scatter according to the plant where the RAs were collected, because of the variation in composition of the RA. It was also found that the use of fine RA causes a more significant performance loss of the concrete properties analysed than the use of coarse RA.