Properties of concrete incorporating eggshell as partial cement replacement with tire crumb as sand replacement

Rapid urbanization has led to a sharp increase of construction and hence cement usage, a material which contributes greatly to greenhouse gas emission due to high energy consumption. The cement industry is among the largest contributors of greenhouse gas. About 7% of global CO2 emission comes from the industry, with 900 kg CO2 emitted to the atmosphere for producing one ton of cement. Solid waste management is one the leading problems in Malaysia. Rapid development and population growth have prompted researches to improve the recycling and reusing of waste material for sustainable development. Chicken eggshell is discarded in Malaysia as municipal waste, while waste tire is a waste that is difficult to handle and often ends up in the landfill. This paper presents the properties of high performance concrete with eggshell powder and tire rubber crumb as partial replacement of cement and sand. The eggshell was grinded to size passing 150µm sieve while waste tire rubber of 30mesh or 600µm was purchased for the study. Grade 55 high-performance concrete was prepared with up to 15% eggshell as cement replacement and up to 15% tire rubber crumb as sand replacement at an interval of 5% for both materials. The physical properties of concrete specimens were evaluated with various tests such as slump cone test and porosity test. Non-destructive tests, namely rebound hammer and ultrasonic pulse velocity are then conducted on the specimens. Mechanical tests are then conducted to determine the compressive strength, flexural strength and modulus of elasticity of concrete specimens. Design of experiment was used to analyse all collected data and determine the optimum percentage of replacement. Mixed regression and Response Surface Methodology were employed to produce mathematical models of concrete workability and compressive strength. The result shows that both eggshell and tire rubber reduces workability of concrete. However, the optimum specimen with 5% eggshell and tire rubber retained medium workability. Porosity of concrete decreases with eggshell replacement and the optimum specimen has a porosity of 2.71%. Based on non-destructive tests, the rebound number of optimum specimen is 29.50 which indicates satisfactory surface hardness. Meanwhile, both control and optimum concrete specimens achieve high-quality status with UPV value above 4km/s. For mechanical properties, optimum concrete specimen observes a 13.46% increase in compressive strength to achieve 28-days compressive strength of 55.37 MPa. Flexural strength of the optimum specimen recorded 11.245 MPa which is 11.969% higher than the control. In addition, split tensile strength of optimum specimen increases by 8.528% to 35.78MPa. Microstructure analysis of concrete reveals that replacement of cement with eggshell causes a greater hydration rate, denser internal packing, and less internal voids. Mathematical modelling using non-destructive test and replacement proportion shows that eggshell powder replacement has a curvilinear relation with concrete mechanical performance. The models have coefficient of determination above 0.90 while the predicted value from the model has deviation within ±10% from the experimental value. Both regression and RSM model could predict the behaviour of concrete, but Response Surface Methodology model has lower deviation and better accuracy. Hence, eggshell powder and tire rubber concrete is concluded as a feasible option in concrete production for the conservation of natural resources and raw material

Efficiency of waste as cement replacement in foamed concrete—A review

Foamed concrete is a lightweight construction material that has gained popularity due to its excellent thermal and acoustic insulation properties. Foamed concrete production involves using cement as a binding agent, which results in a high carbon footprint. In response to sustainable development goals (SDG), there has been a growing interest in exploring alternative materials that can replace cement to improve energy efficiency, climate change, resource efficiency, and overall improvement of foamed concrete properties. Several tons of waste generated annually from industry, agriculture, and quarries are dumped into landfills and cause environmental impacts. Nevertheless, the efficiency of this waste presents an interesting question and there is limited knowledge of its use in foamed concrete. Hence, a review study is needed to evaluate the efficiency of different waste materials that could be used to replace cement in foamed concrete production. The objective of this research is to summarize the efficiency of industrial waste (IW) as a pozzolan alternative (PA) for cement replacement in foamed concrete (FC) production. This study aims to evaluate the chemical, physical, and pozzolanic reactions of selected IW and compare them to cement and selected pozzolans to determine the effect of efficient IW on the compressive strength and durability of FC. This research evaluated the efficiency of IW in PA by characterizing their chemical, physical, and pozzolanic reactions. The selected IW was studied and compared to cement and selected pozzolans using XRF and XRD analyses. This study also performed the Frattini test to determine the strength activity index (SAI) of efficient IW. The efficiency of IW in PA was evaluated by comparing the SAI of efficient IW to the minimum 75% required by BS3892. The compressive strength and durability of FC with efficient IW were determined by evaluating the microstructure of the hardened paste of FC using capillary void analysis. The study found that efficient IW, which was classified as siliceous pozzolan type F (ASTMC618-SAF > 70%), rich in amorphous silica and a high Blaine specific area, can replace cement in FC production. The XRF and XRD results showed that the m ost crystalline components obtained in the IW are SiO2 , Al2O3, CaCO3, and Fe2O3 . The efficient IW produced more calcium silicate hydrate (CSH) and denser FC, making it stronger, with fewer voids and higher resistance to water absorption. The Frattini test showed that the SAI of efficient IW is greater than the minimum 75% required by BS3892. Incorporating efficient IW as cement replacement in FC produced higher compressive strength and improved the durability of FC. The novelty of this research is in the evaluation of efficient IW as a replacement material for cement in FC production. This study shows that efficient IW can promote the use of waste materials, reduce CO2 emissions, conserve energy and resources, and improve the properties of FC. This study’s findings can be used by construction industry players to support sustainable development goals by reducing the use of cement and promoting the use of waste materials as a replacement material for cement

Mathematical analysis on the durability of basalt rebars in acidic environment

Fiber reinforced polymer materials have been used as the alternative to conventional steel reinforcement within the construction industry. While Basalt fiber reinforced polymers (BFRP) have shown improved mechanical properties and durability performance compared to conventional steel, it is not immune to degradation and corrosion when subjected to harsh environments. As such, significant studies have been conducted to simulate the mechanical properties of BFRP bars under degradation when subject to different hostile substances. However, there is no standardized conclusion for the performance of BFRP under an acidic environment and in-depth microstructure evaluation as the degradation of BFRP is influenced by myriad factors. This study aimed to produce a Response Surface Methodology (RSM) model to study the effect of pH, temperature, and immersion time on the tensile strength and elastic modulus. Data from existing literature involving acid emersion of BFRP were collected and modelled using RSM to present an overview of the degradation behavior of BFRP. In addition, a synthesis of the microstructure of BFRP reinforcing bars exposed to the acidic environment was evaluated by referring to SEM and EDX. It was concluded that the tensile strength loss due to corrosion was affected by temperature and immersion time in a linear function. On the other hand, tensile strength drop occurred exponentially as an acid with higher pH was used. Hence, the paper revealed the influence of various factors on the corrosion rate of the BFRP rebar

From Plate to Prevention: A Dietary Nutrient-aided Platform for Health Promotion in Singapore

Singapore has been striving to improve the provision of healthcare services to her people. In this course, the government has taken note of the deficiency in regulating and supervising people's nutrient intake, which is identified as a contributing factor to the development of chronic diseases. Consequently, this issue has garnered significant attention. In this paper, we share our experience in addressing this issue and attaining medical-grade nutrient intake information to benefit Singaporeans in different aspects. To this end, we develop the FoodSG platform to incubate diverse healthcare-oriented applications as a service in Singapore, taking into account their shared requirements. We further identify the profound meaning of localized food datasets and systematically clean and curate a localized Singaporean food dataset FoodSG-233. To overcome the hurdle in recognition performance brought by Singaporean multifarious food dishes, we propose to integrate supervised contrastive learning into our food recognition model FoodSG-SCL for the intrinsic capability to mine hard positive/negative samples and therefore boost the accuracy. Through a comprehensive evaluation, we present performance results of the proposed model and insights on food-related healthcare applications. The FoodSG-233 dataset has been released in https://foodlg.comp.nus.edu.sg/

Synergy study on charge transport dynamics in hybrid organic solar cell: photocurrent mapping and performance analysis under local spectrum

Charge transport dynamics in ZnO based inverted organic solar cell (IOSC) has been characterized with transient photocurrent spectroscopy and localised photocurrent mapping-atomic force microscopy. The value of maximum exciton generation rate was found to vary from 2.6 × 1027 m−3s−1 (Jsat = 79.7 A m−2) to 2.9 × 1027 m−3s−1 (Jsat = 90.8 A m−2) for devices with power conversion efficiency ranging from 2.03 to 2.51%. These results suggest that nanorods served as an excellent electron transporting layer that provides efficient charge transport and enhances IOSC device performance. The photovoltaic performance of OSCs with various growth times of ZnO nanorods have been analysed for a comparison between AM1.5G spectrum and local solar spectrum. The simulated PCE of all devices operating under local spectrum exhibited extensive improvement with the gain of 13.3–13.7% in which the ZnO nanorods grown at 15 min possess the highest PCE under local solar with the value of 2.82%

Compressive strength and durability of foamed concrete incorporating processed spent bleaching earth

Foamed concrete incorporating processed spent bleaching earth (PSBE) produces environmentally friendly foamed concrete. Compressive strength, porosity, and rapid chloride penetration tests were performed to investigate the potential application for building material due to its low density and porous concrete. Laboratory results show that 30% PSBE as cement replacement in foamed concrete produced higher compressive strength. Meanwhile, the porosity of the specimen produced by 30% PSBE was 45% lower than control foamed concrete. The porosity of foamed concrete incorporating PSBE decreases due to the fineness of PSBE that reduces the volume of void space between cement and fine aggregate. It was effectively blocking the pore and enhances the durability. Consistently, the positive effect of incorporating of PSBE has decreased the rapid chloride ion permeability compared to that control foamed concrete. According to ASTM C1202-19 the foamed concrete containing 30% PSBE was considered low moderate permeability based on its charge coulombs value of less than 4000. Besides, the high chloride ion permeability in foamed concrete is because the current quickly passes through the specimen due to its larger air volume. In conclusion, incorporating PSBE in foamed concrete generates an excellent pozzolanic effect, producing more calcium silicate hydrate and denser foamed concrete, making it greater, fewer voids, and higher resistance to chloride penetration

Image Analysis of Surface Porosity Mortar Containing Processed Spent Bleaching Earth

Image analysis techniques are gaining popularity in the studies of civil engineering materials. However, the current established image analysis methods often require advanced machinery and strict image acquisition procedures which may be challenging in actual construction practices. In this study, we develop a simplified image analysis technique that uses images with only a digital camera and does not have a strict image acquisition regime. Mortar with 10%, 20%, 30%, and 40% pozzolanic material as cement replacement are prepared for the study. The properties of mortar are evaluated with flow table test, compressive strength test, water absorption test, and surface porosity based on the proposed image analysis technique. The experimental results show that mortar specimens with 20% processed spent bleaching earth (PSBE) achieve the highest 28-day compressive strength and lowest water absorption. The quantified image analysis results show accurate representation of mortar quality with 20% PSBE mortar having the lowest porosity. The regression analysis found strong correlations between all experimental data and the compressive strength. Hence, the developed technique is verified to be feasible as supplementary mortar properties for the study of mortar with pozzolanic material

Finite element analysis on the effect of hollow section on the strength of foamed concrete beam

Hollow section is introduced on beam to reduce a dead load of the structure, which can ease the usage of IBS and hence minimize construction cost. It can also act as a pathing for mechanical and electrical works. Lightweight concrete produced by replacing 30% cement with PSBE with a density of 1600 kg/m³. Processed Spent Bleaching Earth (PSBE) is a residue from an oil-refining process that can be used to replace cement in the concrete mix. The study is conducted to analyse the best shape and position of the hollow section using ANSYS software. The study will also verify the results of previous experimental studies. Four-point bending test simulated on six beams samples. Beam S1, S2 and S3 have a square opening of size 50mm while beam C1, C2, and C3 have a circular opening of 50mm diameter. Samples Number 1 has opened right on the neutral axis. Samples Number 2 has opening above neutral axis while samples Number 3 have opening below the neutral axis. The size of all six beams is 150mm x 200mm x 1500mm. Finite element analysis performed on the samples with the usage of ANSYS software. The failure load and maximum total deformation are determined. From the result, beams with circular hollow section could withstand higher loading and had smaller deflection compared to its square hollow section counterpart. Also, the best position of the hollow is located above the neutral axis, while beams with hollow below the neutral axis were the weakest. Beam C2 produced the highest load among all sample, which was 4.015kN. The lowest beam was S3, which failed at 3.338kN. For beams with square hollow section, the beam produced a 1% increase in loading when the hollow section was above the neutral axis, but a strength loss of 15.3% observed when the hollow section was below the neutral axis. For beams with circular section, the hollow section above the neutral axis produced a 0.65% increase in loading, while the hollow section below neutral axis caused a strength loss of 3.79%. The resulting pattern agreed with experimental results. Concrete is weak in tension, so in unreinforced beams, the beam loses significant strength when the hollow section is below the neutral axis, which is the tension zone. Shifting the hollow section to above neutral axis strengthened the beams because concrete is good in compression and hollow section at the compression zone has little effect on the performance of the beams. The research aims to provide an understanding of the best shape and position of the hollow for a foamed concrete beam. It also verifies the ability of Finite Element Analysis to predict the performance of the hollow structure in the potential full-scale study

Carbon nanowires fabrications via top down approach

Carbon nanowires are fabricated by the Langmuir Blodgett (LB) method via the top down approach on amorphous carbon. Thick a-C films (500 nm to 1 μm) have been successfully deposited after the treatment on silicon. The anisotropic etching of carbon using reactive ion etching (RIE) has been verified giving near vertical sidewalls. The LB method for depositing monolayer requires a hydrophilic surface. Plasma treatment is being performed on the silicon oxide hard mask to reduce the surface energy thereby making the surface from hydrophobic to hydrophilic. PS balls which are being deposited by LB method have one disadvantage which is the low adhesion of the PS ball to the silicon oxide surface. This adhesion is being improved by subjecting the PS ball to annealing which changes the shape and increase the contact area between the PS balls and the silicon oxide surface. As carbon and PS ball is vulnerable to oxygen plasma, a modified recipe of CF4:Ar was being used to etch the silicon oxide hard mask. There is almost little chemical reaction of the CF4 on carbon and PS ball. Carbon nanowires were successfully fabricated using polystyrene (PS) balls of diameter 450 nm. Through a series of steps, carbon nanowire of 500 nm in length and diameter approximately 250 nm can be produced