Key Engineering Materials Vol. 668

Abstract: When exposed to adverse conditions the concrete must be protected so as to maintain absorption at acceptable levels. This paper presents the assessment of a lightweight expanded clay concrete protected by an acrylic layer exposed to an aggressive environment. The specimens were prepared with 370kg/m³ of cement and the water-binder ratio of 0.50 corresponds to the value established in NBR 6118 types for concrete subjected to highly aggressive environments. The concrete produced presented specific mass of 1,600kg/m³, dry consistency and compressive strength of 25MPa. Visual inspection shows that the protected specimens of lightweight concrete presented a clear reduction of the loss of cohesion of the grout caused by the attack as well as lower water absorption and mass loss. The acrylic layer assessed as a surface protector presented a good adherence level to the substrate and efficiency since it reduced the penetration of the aggressive agent, thus minimizing degradation and increasing durability of the lightweight expanded clay concrete.

Abstract: The concept of sustainable buildings addresses the environmentally efficiency, with respect to energy consumption, by adopting products that offer thermal insulation. Moreover, use of wastes from different materials also contributes to obtain products for this application. The volume of wastes from timber industry and those from tires are an environmental problem. This study aimed to production and characterization of particleboards using wastes from wood and tire rubber with castor-oil polyurethane resin. Panels were produced containing only wood and also with addition of tire rubber. The properties determined were density, modulus of rupture (MOR) and modulus of elasticity (MOE) in bending, according to Brazilian Code NBR 14810-3 (2006), and thermal conductivity. Statistical analysis was conducted in physical and mechanical properties. Panels containing wood were classified as low density (0.55 g/cm³), while those with wood and tire rubber resulted in medium density (0.78 g/cm³). For mechanical properties, the addition of rubber resulted in increased of MOR and reduction for MOE. Superior performance for thermal conductivity was achieved for panels produced only with wood. However, samples with a mixture of wood and tire rubber also showed consistent thermal conductivity with similar products. Considering the results obtained, panels containing wood and tire rubber addition have potential for application as thermal insulation.

Abstract: The southwest region of the state of Goiás stands out for agriculture, especially the production of grain and sugarcane. This high agricultural production has a result of generation of agroindustrial waste and it has a high potential to be exploited for particleboard manufacturing. In this context, the objective of this study was to evaluate the use of sugarcane leaves in the production of particleboards, compared to eucalyptus panels, through the evaluation of their physical properties. Three panels were made with 100% sugarcane leaves, and three with eucalyptus wood were produced. They were produced with a nominal density of 0.60 g/cm3. 12% urea-formaldehyde adhesives were applied based on their resin solid content. The used pressing cycle was: pressure of 4.00 MPa, temperature of 180°C and time of 15 minutes. After production, the same properties were evaluated on their water absorption and thickness swelling after 2 and 24 hours of immersion. A randomized design was used, and the averages were compared by the Scott-Knott test at 5% significance. Based on these results, it can be seen that panels produced with sugarcane leaves exhibited higher values for physical properties than eucalyptus panels.Keywords: Thickness swelling, waste ,water absorption.

Abstract: Gypsum plaster is a material used as internal covering of walls in Brazilian constructions. However, this material has short setting times and generates a great quantity of material loss. The low energy necessary to dehydrate the waste material for utilization becomes recycling methods viable, since the recycled products have the same properties of the commercial material. This paper aims to evaluate the behavior of recycled gypsum plaster calcined at 100 °C, 150 °C and 200 °C. It was also studied the use an admixture (superplasticizer). Physical and mechanical properties were evaluated. The results showed that the dehydration temperature influences in both fresh and hardened gypsum properties. The temperature of 200 °C reported better values of initial and final setting times and compressive strength. Calcination at 150 °C showed higher values of hardness. The admixture utilization modified the initial and final setting times.

Abstract: The concrete material has many advantages as high durability, low permeability, weather resistance and high compressive strength. These qualities have led its application to the rainwater collection since the pipes are usually buried, subject to compressive forces and exposed to the action of water. However, the concrete has some limitations, as, for example, low resistance to tensile stress, high self-weight, ease of cracking and brittle behavior in rupture. Thus, many materials are being studied in order to be used as a new concrete component seeking to minimize its disadvantages. One of them is the tire rubber residue. This residue is a fibrous material that takes a long time to decompose and increases the amount of trash in landfills; but, it may give a greater deformation capacity and also a more effective distribution of stresses to the concrete. Furthermore, the tire rubber residue can provide an increase in energy absorption and a decrease in the propagation of cracks in the hardened state. However several studies mention that the inclusion of the waste rubber into the concrete causes a decrease in mechanical strength to compression, a decrease in the workability of the mixtures and an increased content of entrained air. Therefore, an analysis of the structural behavior of four (4) reinforced concrete pipes was made: two (2) of them was molded without tire rubber residue and the other two (2), with a quantity of residue equal to 20 kg per cubic meter of concrete. All the pipes had a nominal diameter of 600 mm and an effective length of 1500 mm; they were subject to the crushing test standardized by the Brazilian Association of Technical Standards - NBR 8890 (ABNT, 2007) which is similar to the European standard NBN-EM 1616. The diametric displacements at the hub and at the spigot were monitored by the use of two dial gauge indicators. The applied force by a hydraulic jack was measured using a cell load. Finally, tests of water absorption using pieces of the tested pipes were performed, based on the recommendations of the NBR 8890 (ABNT, 2007).

Abstract: Great areas of Brazil present lateritic soils, such as the northeast and the south. Some of these soils have, as main characteristic, instable structures that can present considerable volumetric deformation in the presence of water. This behavior, also named collapse, is responsible for several problems on the building construction such as cracks and fractures that can damage the safety of structures. The aim of this paper is to assess the possibility of improvement of collapsible behavior of a lateritic soil using rice husk ash (RHA). A previous characterization of soil and RHA was performed in order to assess the combined effect of soil/RHA. The results are so promising, showing a new alternative to reduce the collapsible behavior of soils using an environmental friendly technology.

Abstract: The amount of construction waste (CW) at building sites is highly variable, for instance the CW generation index ranges between 50-300 dm3 per square meters of gross floor area. Today there is still a lack of knowledge about variables (building design, construction process, construction technologies, etc.) affecting the CW generation. The objective of this paper is to analyse the influence of multi-storey building design and some construction processes on the CW generation indexes. The CW generation was analysed for two groups of buildings with two different construction processes; one with plumbing and electric services installed inside the masonry element and the other with plumbing and electric services installed onto the masonry element and covered with water-resistant drywall system (reducing the construction waste generation). The gross floor area directly affects the amount of executed construction works in a building site. Since the most important works (concrete, masonry and cladding) for CW generation is related to gross floor area, gross floor of buildings is also directly related to CW generation. For buildings with gross area varying from 20,000 to 80,000 m2, there is a reduction of approximately 18% of construction waste only changing the plumbing and electric services installation system, from embedded in the masonry element to installed onto the masonry element and covered with water-resistant drywall system.

Abstract: Sugar cane production is increasing in Brazil due the demand in manufacturing sugar and alcohol. During production process, several wastes are generated, such as sugar cane straw. After a burning process of this waste material, sugar cane straw ash (SCSA) is obtained, and may be used in the production of alternative binders. The aim of this paper is to assess the possibility of reuse SCSA as supplementary cementitious material in blended Portland cement mortars and as raw material in the production of alkali-activated binders. Blended Portland cement mortars were prepared using 0%, 20% and 30% of SCSA in replacement of Portland cement. For alkali-activated mortars, the activating solution is based on sodium hydroxide (NaOH) solution and different Slag/SCSA proportions in mass were assessed: 100/0, 75/25 and 50/50. Mechanical strength of mortars cured at room temperature was tested for 7 and 28 curing days. The results confirm that enhanced mechanical properties can be obtained for both alternative binders using SCSA on its composition.

Abstract: The gypsum plaster is a material widely used in constructions around the world. It is a material with high versatility that can be applied from wall coverings to decorative ornaments. However, during its application in buildings, large amounts of waste materials are generated. The average values of waste during its application are higher than 45% of the gypsum amount used. A series of tests were conducted to develop a feasible methodology to reuse this waste material. The results collected at this stage indicated that it is possible to obtain a recycled product with low energy consumption. It was noted that after a certain number of procedures in which gypsum was subjected to recycling, there was a loss of workability; however, it did not present relevant changes in mechanical properties. This lack of workability avoids the recycled material maintain its properties in the fresh state as it is subjected to recycling. This work evaluates the calcination time of gypsum plaster waste for the production of a gypsum plaster with binder properties for using as components. The temperature of calcination was kept constant (150 °C), but the residence time in the stationary kiln was modified. The properties in the powder state (bulk density, fineness modulus, specific mass and sieve analysis), fresh state (mini-slump, setting times and kinetics of temperature) and in the hardened state (compressive strength and hardness) were analysed in order to have some answers about the performance of the recycled gypsum. In the fresh state, the recycled material showed good results for precast components. The initial setting times were good for all residence times and the final setting times for the material calcined in periods of 5 and 6 hours. In the hardened state, the best compressive strength results were obtained for all residence times, and hardness for calcination for 3, 4, 5 and 6 hours. All these results were satisfactory when compared to the commercial plaster took as reference. On the other hand, there was a lack of workability in those pastes indicating that an admixture is needed to adjust this property of the recycled material.

Abstract: Homogeneous cement bonded paperboards were made with recycled newsprints and Kraft paper with ordinary Portland cement and curing reagent. Boards were produced at the blending proportions of 100:0, 50:50 and 0:100 respectively and at cement/ paper ratio of 1:1, 2:1 and 3:1 respectively. Dimensional movements were evaluated to investigate the effect of the variables used in board manufacturing before and after exposure to accelerated aging tests procedure. Increase in mixing ratio and blending proportion caused decrease in Thickness Swelling (TS) and Water Absorption (WA) while TS and WA of the untreated boards were lower than the accelerated aging treated boards. The dimensional movement of Kraft paper was higher than that of recycled newsprint before and after accelerated aging treatment. The strongest and most dimensionally stable board was produced at the highest level of cement/ paper ratio. The pre-accelerated ageing test carried out showed that mechanical properties were higher 2:1 and 3:1 paper cement mixing ratios. Kraft paper produced the strongest and most dimensionally stable board than recycled newsprint. From this study Kraft paper and recycled newsprint proved to be suitable for the manufacture of cement bonded paperboard capable of meeting the needs in core and low cost housing construction.