Key Engineering Materials Vol. 517

Abstract: The low-cyclic loading tests are carried out for three pieces of recycled concrete high shear walls, with 100% replacement ratio of recycled coarse aggregate under different axial-load ratios. The mechanical performances of shear walls, including failure patterns, the bearing capacity, the hysteretic properties and ductility, are analyzed. The test results indicate that the basic behavior of recycled concrete shear walls resembles quite closely that of the ordinary concrete shear walls, the recycled concrete shear wall under bending failure has good ductility and bearing capacity; the hysteresis loop is stable and the degradation of stiffness is not great; the shear-slip phenomenon becomes significant and the ductility decreases under high axial-load ratio. The calculation of flexural strength of recycled concrete shear walls can be adopted directly from computational theories and formula used for ordinary concrete shear walls. It is feasible to apply reasonably designed recycled concrete shear walls to small high-rise buildings.

Abstract: Cold-rolled ribbed steel wires with improved elongation is a new type of cold-rolled steel wires, this paper presents the test results of 6 concrete slabs reinforced by the cold-rolled ribbed steel wires with improved elongation under flexure, the flexural characteristics, bearing capacity, deflection and cracking of these slabs under loading are analyzed, the formulas for calculating the flexural bearing capacity, the deflection and crack width of the slabs are suggested. This may be as a reference for the applications of this new type of cold-rolled steel wires, and for the revision of Chinese Code Technical specification for concrete structures with cold-rolled ribbed steel wiresJGJ95-2011.

Abstract: This paper presents the test results of 12 R.C. columns with recycled aggregates under axially loading and eccentrically loading, the dimensions of the column are width b=150mm, depth h=200mm and height l=1400mm, the recycled aggregate replacement rate of the concrete are 0%, 50% and 70% respectively, the concrete strength is of C40 grade. The compressive performance such as the strain of concrete and longitudinal reinforcement, the failure modes and the compressive bearing capacity of the R.C. columns with recycled aggregates are analyzed, and compared with the R.C. columns made of ordinary concrete. The results show that the compressive performance such as the loading process, the failure modes and the bearing capacity of the R.C. columns with recycled aggregates are almost the same as that of the columns with natural aggregate, the compressive bearing capacity of R.C. columns with recycled aggregates may be calculated by the stipulations of Chinese current design Code (GB50010). This may be as a reference for the application of the concrete with recycled aggregates in engineering.

Abstract: This paper presents the test results of 2 prestressed concrete beams with manufactured sand under cyclic loading, the concrete is made of manufactured sand to replace natural sand with different replacement rates of 50% and 100%. The stress of re-bars and prestressed strands and the strain of manufactured sand concrete are discussed, the rigidity and cracking of the prestressed beams under cyclic loading are analyzed, and the flexural behavior of the beams after 2.5 million times cyclic loading are also discussed and analyzed. The results show that the fatigue behavior of the prestressed concrete beams with manufactured sand to replace the natural sand under cyclic loading is satisfied, the flexural bearing capacity of the prestressed beams after 2.5 million times cyclic loading is still sufficient. The results also show that the crack width and the mid-span deflection of the prestressed beams are in the allowable range at the serviceability limit state. This may be regarded as a reference for the applications of manufactured sand in the prestressed concrete structure .

Abstract: This paper presents the test results of 6 reinforced concrete beams with recycled aggregates of construction waste under flexure, the beams were made of two strength grade concrete of and with different recycled aggregate replacement rate. The results indicate: the ultimate bearing capacity of recycled concrete beams with natural aggregate concrete beams are almost the same, and can meet the requirements of chinese code; The cracking resistance of the reinforced recycled concrete beams is slightly less than that of the beams with natural aggregates, the influence of recycled aggregate replacement rate to cracking resistance is not obvious. Recycled concrete beam crack load the calculated value is greater than the measured value, should carry out the theoretical value adjustment. Reinforced concrete beams is one of concrete structures, its the most common and most important component, Study of flexural property of reinforced concrete for recycled concrete structure component in the popularization and application to have the important significance [. This paper presents the test results of 6 reinforced concrete beams with recycled aggregates of construction waste under flexure, the beams were made of two strength grade concrete of C30 and C40 and with different recycled aggregate replacement rate of 0%, 50% and 70%. These results may be as a reference for the application of the concrete with recycled aggregates of construction waste in engineering [2,3,.

Abstract: Now, the resource of high quality natural sand is lacking. Manufactured sand is broken by rocks or tailings, which could be used in the mixture of cement concrete as fine aggregate instead of natural sand. The use of manufactured sand in concrete structure has become more and more important. It can make construction industry develop with environmentally friendliness and sustainability. In this paper, the elastic modulus strength was compared between manufactured sand concrete and ordinary concrete by testing on concrete specimens using the manufactured sand, the replacement ratios of manufactured sand by mass to the natural sand are 0, 0.30, 0.5, 0.70 and 1.0 respectively. The experimental research showed that the elastic modulus strength of manufactured sand concrete was stronger than that of natural sand and it had an increasing trend with the increasing of replacement rate and age but the elastic modulus of replacement rate of 50% was largest. This showed that the optimum replacement ratio was 50%.The fitting relations between elastic modulus and compressive strength was different with that of ordinary concrete. The relationship equation between elastic modulus strength and compressive strength of manufactured sand concrete was recommended in this paper. This could be used as a reference for the applications of the concrete using the manufactured sand as a fine aggregate in engineering.

Abstract: This research project accomplished a study on the technical feasibility of recycling industrial solid waste generated by the discharge of casting sand agglomeration with clay and blast furnace slag. For this, the plan proposed a methodology that initially establishes a process of solid waste encapsulation, by using solidification/stabilization technique on Portland cement matrices, in which the residuals act as small and large aggregates on the composition of concrete, and later it presents the possibility of using this concrete in the manufacture of concrete pieces (concrete blocks) for paving. The results obtained in this research achieved the objective set with great success, regarding the manufacturing of concrete pieces (blocks) for paving urban roads, whenever there is special vehicle traffic or demands capable of producing accentuated abrasion effects (surpassing the 50 MPa required by the regulation), which probes the technical practicability of using waste from sand casting agglomeration with clay and blast furnace slag used in this study, unlocking usage possibilities for construction.

Abstract: The University Federal of Paraíba has developed various researches to explore the potential for recycling of industrial waste of Paraíba. Among them, the potential of use in the waste generated by processing of kaolin, which is one of the activities of great economic importance to the State of Paraíba and municipalities producers, because it causes a great environmental impact due to lack of an established recycling process. The kaolin processing generates large amounts of waste, one of fractions, a sandy (called in this study of RGC) containing quartz, mica and calcite; and other clay (called in this study of RFC) containing higher amounts of kaolinite. This objective of study is the characterization physical, chemical and mineralogical of waste kaolin (RFC and RGC) in order to evaluate the potential use of these wastes in the alkaline activation using silicates sodium and potassium. The characterizations physics, chemistry and mineralogy were by XRF, XRD, Unit Mass, Specific Mass and Specific Area. With the objective of studying the potential of waste as a material pozzolanic, it was processing through grinding at 10.000, 20.000, 40.000, 60.000 and 80.000 rpm and with the purpose of evaluating the reactivity of materials, these wastes were calcined at 750°C/2h.The wastes RFC and RGC had different properties according to the processing. Thus, the waste RFChas the potential pozzolanic to use in alkaline activation.

Abstract: In the state of Paraíba, one of the activities of great economic importance is that of the kaolin processing industry. This type of processing generates large amounts of waste that are displayed randomly in the environment, which has attracted attention, because the environmental impact caused by it and the lack of established process of recycling. The University Federal o Paraíba has been developing several research to explore the potential for recycling of industrial waste from Paraíba, mainly waste of kaolin. This research have pointed to the feasibility of using waste as aggregate and pozzolan in the development of mortars use multiple. These wastes have different size fractions, depending on the stage of processing: a sandy (termed in this study of RGC) containing mainly quartz, mica and calcite; and other clay (termed in this study of RFC) is thinner, containing higher amounts of kaolinite. This study aims to evaluate the potential of alkaline activation from waste kaolin (RGC and RFC) by comparing the activation using sodium silicate and hidroxide of calcium. With the objective of studying the potential of waste as a material pozzolanic, it was processing through grinding at 80.000, 60.000, 40.000, 20.000 and 10.000 rotations and with the purpose of evaluating the reactivity of materials, these wastes were calcined at 750°C/2h. For the mechanical characterization was using an equipment universal testing of Shimadzu Servopulser, where it was observed that only RFC, when calcined, developed strength in both activations, and the activated with silicate sodium with higher strength. The RGC, both in the state in natura and calcined did not show satisfactory mechanical strength to the test under the conditions of synthesis used in this research. Thus, the waste RFC's studied in this work has the potential to be used as constituent materials for building blocks in terms of its mechanical properties.

Abstract: The degradation of agro-industrial waste-based particle boards reinforced with sugar cane bagasse was evaluated by comparing their physical and mechanical properties. The particle boards were prepared with sugar cane bagasse particles (85% by weight of composite) and mixed with bi-component polyurethane resin based on castor oil (15% by weight). After mixing for 2 to 3 min, the resulting mixtures were pre-pressured. Standard molding conditions were: temperature, 100°C; pressure during heating, 5 MPa; and heating time, 10 min. The dimensions of the particle boards produced in the laboratory were 0.40 m x 0.40 m x 0.01 m. The boards were cut into testing specimens with dimensions 0.25 m × 0.05 m × 0.01 m. The accelerated aging test was carried out based on the ASTM D 1037 standard in order to determine the main factors that cause degradation and to identify their influence. The test consists of cycles of six treatment steps, i.e., immersion in water at 49°C for 1 h, steaming at 93°C for 3 h, freezing at-12°C for 20 h, drying at 99°C for 3 h, steaming at 93°C for 3 h, and drying at 99°C for 18 h. This cycle was applied six times for all specimens. Modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IB), water absorption (WA%) and thickness swelling (TS%) were measured before and after the cycles of accelerated aging. The performance of the particle boards before accelerated aging presented acceptable mechanical performance, MOR: 21.86 ± 2.16 MPa, MOE: 2.77 ± 0.26 GPa, and IB: 1.18 ±0.40. The performance of the particle boards decreased after accelerated aging showed, MOR: 6.25 ± 0.70 MPa, MOE: 0.52 ± 0.10 GPa, and IB: 0.15 ± 0.07. The results were influenced by the temperature, relative humidity and warm water. After the accelerated aging process, the materials showed mechanical behavior similar to Low-Density grade Particleboard (LD1).