Effects of Recycled Tyre Steel Fibres on the Compressive, Splitting Tensile and Flexural Strengths of Structural Lightweight Concrete Using Palm Kernel Shells as Partial Replacement of Coarse Aggregates

The improper handling and disposal of waste tyres in many African countries is still a serious problem which has caused environmental and health hazards. Like waste tyres, the proper reuse of agricultural wastes, such as palm kernel shells, is also a challenge as the production has increased over the years. In the field of civil engineering, effort have been made to recycle waste tyres and palm kernel shells in concrete production to mitigate some of the environmental problems arising from these wastes. The recycling of such waste for civil engineering applications has been heightened with the development of new technologies. This study was carried out to evaluate and assess the effects of recycled tyre steel fibres and palm kernel shells on the compressive, splitting tensile and flexural strengths of structural lightweight concrete, using recycled tyre steel fibres for reinforcement and palm kernel shells as partial replacement of coarse aggregates. Recycled tyres steel fibres were added in normal-weight concrete at 0.25, 0.50 and 0.75% (Viz., 6, 12 and 18 kg/m3) content and aspect ratio of 20, 40, 60, 80 and 100% to determine the optimal fibres content and aspect ratio. The results show that recycled tyres steel fibres obtained from pyrolysis can improve the compressive and splitting strengths of normal-weight concrete. The optimal fibres content and aspect ratio were used with palm kernel shells at 25, 50, and 75% content to determine the optimal partial replacement of coarse aggregates with palm kernel shells. The maximum compressive and splitting tensile strengths values were obtained at an aspect ratio of 80, palm kernel shell content of 25% and steel content of 0.50%. Normal-weight concrete strength values in flexure were higher than lightweight concrete made with optimal values. Additionally, beams with 25 and 50% content of palm kernel shells with optimal fibre content and aspect ratios qualified as structural lightweight concrete. Keywords: palm kernel shells, recycled tyres steel fibres, waste tyres, lightweight concrete, normal-weight concrete, compressive strength, splitting tensile strength and flexural strength. DOI: 10.7176/CER/11-6-06 Publication date:July 31st 201

Structural behaviour of reinforced concrete beams containing recycled polyethylene terephthalate and sugarcane bagasse ash

Concrete is a widely used construction product. This product is presently concerned with the depleting nature of natural sand. Concrete is also being considered with supplementary materials to enhance its footprints. Hence, this study's goal is to examine the performance of reinforced concrete (RC) beams consisting of sustainable materials. The study seeks to qualify the use of concrete made using Sugarcane Bagasse Ash (SCBA) and Recycled Polyethylene Terephthalate (RPET) as structural elements. Proportionately, 10 % RPET is used to partially substitute sand, and 5 % SCBA is used to partially substitute cement. The innovation of this study is in the dual substitution approach and structural behaviour examination. The research probes how RPET and SCBA affect the RC beams’ flexural and shear capacities. The tests are completed ensuing 28 days of water curing. Three RC beams are made for each of the conventional concrete and SCBA-RPET concrete. A set of beams is made for the shear capacity test, while another set is made to examine flexural capacity. The beam dimensions are 160 × 200 × 1200mm3. The findings inform that the beams made with 5 % SCBA and 10 % RPET have a flexural capacity of 11 % less than the conventional beams'. However, the SCBA-RPET beams revealed a shear capacity that is 17.38 % more than the conventional beams'. The crack patterns during and after the shear and flexural strength tests are similar and comparable for the SCBA-RPET beams and the conventional beams. Thus, a sustainable concrete mix suitable for use as a structural beam is derived

Properties of concrete mixes containing tire rubber and brick powder exposed to sulfuric acid and cured in water: A comparative study

The existing literature shows that rubberised concrete suffers from reduced mechanical properties when it is compared with normal density non-rubberised concrete. This is due to the underlying reduced bonding between tire rubber and other concrete ingredients. The massive sulfuric acid attack in rubberised concrete must have additionally discouraged researchers from attempts to assess the phenomenon of improving performance of rubberised concrete. A research was undertaken to compare the properties of concrete mixes containing tire rubber replacing coarse aggregate and waste clay brick powder (WCBP) replacing cement exposed to sulfuric acid and cured in water. Concrete cubes and cylinders of concrete grades of 20 MPa, 25 MPa and 30 MPa were immersed in 5% sulfuric acid solution up to 90 days following moist curing of 27 days. Other concrete cubes and cylinders were cured in water for comparison. The compressive strength findings indicated that all the specimens exposed to sulfuric acid had lost more than 57% of their compressive strengths after 90 days with reference to the corresponding samples cured in water. In contrast, out of all concrete mixes investigated for all concrete grades, never were the split tensile strength losses of the specimens exposed to sulfuric acid greater than 43.1% compared with those cured in water. In each exposure condition, concrete mixes with 5% WCBP showed slight improvements in compressive and split tensile strengths in contrast with the conventional concrete mixes. Visual inspection of the specimens illustrated depositions of flaky or white substances on the outer layers of specimens exposed to sulfuric acid compared with specimens cured in water. Moreover, the split tensile strengths of specimens were not severely affected with exposure to sulfuric acid in comparison with compressive strengths. Eventually, the research identified the existence of WCBP in rubberised concrete as a promising criterion of minimising strength losses of rubberised concrete