Paul O. Awoyera

Hydration mechanism and strength properties of recycled aggregate concrete made using ceramic blended cement

Abstract A pozzolanic material ordinarily contains high amounts of siliceous or aluminous components, but has no cementitious property until when it reacts with calcium hydroxide, that is available in cement, in the presence of moisture. The present study evaluates the pozzolanicity of ceramic tile powder and its effect on both hydration mechanism and strength property of recycled aggregate concrete. It was seen that ceramic floor and wall tiles sourced from construction and demolition wastes, contain high silica and alumina oxides, which evidently showcased its pozzolanicity. This was further revealed by the microstructural images of ceramic blended cement. Strength properties of recycled aggregate concrete were enhanced with addition of ceramic powder and ceramic coarse fraction, more than the strength developed in the control concrete. The increased strength was an indication that the interfacial transition zone between the aggregate and blended cement paste enhanced the properties of recycled aggregate concrete (RAC). However, the tensile behavior of RAC was irregular, it initially decreased with 20% ceramic powder addition but it increased when 30% ceramic powder was added. Therefore, ceramic power derived from wall and floor tiles can be used as partial replacement for cement in recycled aggregate concrete.

Characterization of ceramic waste aggregate concrete

Abstract There is a growing interest in using waste materials such as ceramics as alternative aggregate materials for construction. While other ceramic product wastes such as sanitary wares and electrical insulators have been extensively investigated, not much findings are available on ceramic wall and floor tiles wastes. Thus, the current study focuses on the mechanical characterization of waste ceramic wall and floor tiles aggregate concrete. Ceramic wastes sourced from construction and demolition wastes were separated from other debris and crushed using a quarry metal hammer. Ceramic tiles were sieved into fine and coarse aggregates in line with standards. Other materials used were gravel, river sand, cement and potable water. Workability of the fresh concrete was checked through slump test, and concrete cubes of 150 mm dimensions and cylinders of 100 mm × 200 mm were cast in the laboratory. After 24 h of casting, the concrete samples were demolded and were cured by immersion in water tank at temperature of 22 °C. The compressive and split-tensile strengths of the hardened concrete samples were determined after curing them for 3, 7, 14 and 28 days. Results showed that both the compressive strength and split tensile strength increased appreciably with the curing age than the conventional concrete.

Predictive models for determination of compressive and split-tensile strengths of steel slag aggregate concrete

Abstract The current study adopts the results of completed laboratory experiments for modelling the strength properties of steel slag aggregate concrete using artificial neural network (ANN) technique. Note worthily, the considered experiments reported that strength properties increased with increasing curing age. The variation of factors for building the network includes: ground granulated blast furnace slag (GGBS) as partial replacement for granite at 20, 40, 60, 80 and 100%; water-cement ratio (w/c) at 0.5, 0.55 and 0.6; curing age at 7, 14 and 28 days. Other factors, such as cement and sand were kept constant. The input data were trained, learned and validated using the feed-forward back propagation algorithm. From the various trial and errors performed, the optimal ANN model which yielded the minimum mean square error and maximum absolute variance was 6-10-2. Therefore, based on the high confidence level of the model predictions, the models are recommended for predicting strength properties of steel slag aggregate concrete that falls within the limit of this study.

Benefits of using ceramic tile waste for making sustainable concrete

Ceramic waste deposit poses a number of environmental challenges, ranging from air, water and soil contaminations. Thus, the present investigation is centred on evaluating the technical viability and environmental benefits of using ceramic floor and wall tile wastes in sustainable concrete mixes. Both geotechnical and microstructural analysis were performed on three phas- es of the ceramics waste preparation: as powder, fine and coarse, and compared with the natu- ral aggregates. Regarding the physical properties, ceramic tile aggregates performed ade- quately well as the natural aggregates, except for the high water absorption observed in ceram- ics. Chemical composition tests conducted on the ceramic tile indicated that it possesses 64.557% silica, which is a pronounced feature of pozzolans. Consequently, ceramic floor and wall tile wastes can be processed for reuse in concrete.

Beneficiated pozzolans as cement replacement in bamboo-reinforced concrete: the intrinsic characteristics

The use of concrete containing supplementary cementitious materials has gained popularity as an eco-efficient and sustainable alternative to a number of concrete applications. In this study, beneficiated pozzolans, ground granulated blast furnace slag (GGBS) and metakaolin (MK), were used as partial replacement of ordinary Portland cement in bamboo-reinforced concrete. In the mixtures, river sand and granite were used as fine and coarse aggregates, respectively. The compressive strength of concrete cubes, split-tensile strength of concrete cylinders, and flexural strength of reinforced concrete beams were determined after stipulated curing regimes. The morphology and mineralogy of bamboo and selected concrete mixtures were obtained using scanning electron microscope and X-ray diffraction, respectively. The concrete samples having blended cement were found to have better compressive and split-tensile strength than those made with conventional binder. Also, the mechanical characteristics of the samples improved up to 40% GGBS substitution. However, steel-reinforced concrete developed better flexural strength than the bamboo-reinforced concrete (BRC). The study recommends pretreatment of bamboo to ensure its adequate bonding with the cement paste, so as to achieve optimum performance of BRC.

Curing, thermal resistance and bending behavior of laterised concrete containing ceramic wastes

Abstract Recent years have witnessed an increase in volumeof construction and demolition wastes generated in some developed and developing countries, which mostly constitute environmental issues. Therefore, it is important to explore the potential of such waste materials, or when used with locally available materials for concrete production. Thus, this research effort aims at determining the effects of curing methods (polythene wrapping and water immersion), and exposure to high temperature, on strength characteristics of laterised concrete samples made with ceramic floor tiles wastes as aggregates. The study also explored the bending behaviour of steel reinforced beam mixes comprising ceramics and laterite. From the obtained results, samples made with ceramic and laterite developed higher strengths when cured with polythene covering than the water cured samples. However, the reference concrete samples developed better strength in normal curing condition (immersion in water). In terms of thermal resistance, the laterised samples had better resistance at elevated temperatures than the reference concrete. Lastly, for the tested beams, the maximum mid span bending strength decreased with increasing laterite content. Overall, it can be considered that ceramic floor tiles wastes with minimal laterite content can be used for concrete production, and by doing so, the negative impact of these wastes on the environment can be controlled.

Using silica mineral waste as aggregate in a green high strength concrete: workability, strength, failure mode, and morphology assessment

ABSTRACT Environmental degradation is a major challenge in the developing countries, which are caused due to unmanaged solid waste, or improper disposal. This study investigates the effect of using silica mineral waste (eco sand) as aggregate in a green high strength concrete, in which properties such as workability, strength, failure mode, and morphology were determined. There was low slump and compacting factor in all the concrete mixtures, however, strength properties were improved with the incorporation of eco sand as a replacement of conventional fine aggregate. Higher strength properties were achieved in the eco sand concrete than the reference mixtures, which occurred at an optimum eco sand content of 25%. The morphology and failure mode of the eco sand concrete showed that there was a significant compactness and constituents parking in the matrix.