Fracture behaviors of HVFA-SCC mixed with seawater and sea-sand under three-point bending

This paper aims to study the fracture behaviors of high-volume fly ash-self-compacting concrete (HVFA-SCC) mixed with seawater and sea-sand (SWSS) or freshwater and river sand (FWRS). Three-point bending test were performed on 24 notched beams fabricated with varying in replacement ratio of fly ash (0%, 30%, 50%, and 70%) and the type of water and sand (SWSS and FWRS). The initial and unstable fracture toughness of these test specimens are determined by the double- K fracture model. The effect of fly ash replacement ratio and type of water and sand on the fracture parameters is analyzed and discussed. In addition, the cohesive fracture toughness of all the test specimens is calculated by using Gauss–Chebyshev integral method and the weight function method based on the bilinear tensile softening curve given in CEP-FIP Model Code. A comparison of fracture toughness parameters of determined from the experimental approach and analytical approaches is presented in these SCC specimens. Results show that SCC mixed with SWSS replacing FWRS can improve the unstable fracture toughness and fracture energy, and decrease its brittleness behavior. The cohesive fracture toughness of SWSS-SCC specimens is underestimated by these analytical methods based on the tensile softening curve given in CEP-FIP Model Code.

Investigation of the Performance and Emission Characteristics of Diesel Engine Fueled with Biogas-Diesel Dual Fuel

Due to the popularity of diesel engines, utilization of fossil fuel has increased. However, fossil fuel resources are depleting and their prices are increasing day by day. Additionally, the emissions from the burning of petroleum-derived fuel is harming the global environment. This work covers the performance and emission parameters of a biogas-diesel dual-fuel mode diesel engine and compared them to baseline diesel. The experiment was conducted on a single-cylinder and four-stroke DI diesel engine with a maximum power output of 2.2 kW by varying engine load at a constant speed of 1500 RPM. The diesel was injected as factory setup, whereas biogas mixes with air and then delivered to the combustion chamber through intake manifold at various flow rates of 2, 4, and 6 L/min. At 2 L/min flow rate of biogas, the results were found to have better performance and lower emission, than that of the other flow; with an average reduction in BTE, HC, and NOx by 11.19, 0.52, and 19.91%, respectively, and an average increment in BSFC, CO, and CO2 by 11.81, 1.05, and 12.8%, respectively, as compared to diesel. The diesel replacement ratio was varied from 19.56 to 7.61% at zero engine load and 80% engine load with biogas energy share of 39.6 and 16.59%, respectively.

Enhanced Metakaolin Reactivity in Blended Cement with Additional Calcium Hydroxide

This study aims to increase the pozzolanic reactivity of metakaolin (MK) in Portland cement (PC) blends by adding additional calcium hydroxide (CH_add) to the initial mixture. Cement paste samples were prepared with PC, MK and water with a water-to-binder ratio of 0.6. Cement replacement ratios were chosen from 5 to 40 wt.% MK. For higher replacement ratios, i.e., 20, 30 and 40 wt.% MK, CH_add was included in the mixture. CH_add-to-MK ratios of 0.1, 0.25 and 0.5 were investigated. Thermogravimetric analysis (TGA) was carried out to study the pozzolanic reactivity after 1, 7, 28 and 56 days of hydration. A modified mass balance approach was used to normalize thermogravimetric data and to calculate the calcium hydroxide (CH) consumption of samples with CH_add. Results showed that, without CH_add, a replacement ratio of 30 wt.% or higher results in the complete consumption of CH after 28 days at the latest. In these samples, the pozzolanic reaction of MK turned out to be restricted by the amount of CH available from the cement hydration. The increased amount of CH in the samples with CH_add resulted in an enhanced pozzolanic reaction of MK as confirmed by CH consumption measurements from TGA.

Confinement Effect and Efficiency of Concentrically Loaded RACFCST Stub Columns

Recycled aggregate concrete-filled steel tubular (RACFST) columns are widely recognized as efficient structural members that can reduce the environmental impact of the building industry and improve the mechanical behavior of recycled aggregate concrete (RAC). The objective of this study is to investigate the behavior of recycled aggregate concrete-filled circular steel tubular (RACFCST) stub columns subjected to the axial loading. Three-dimensional finite element (FE) models were established using a triaxial plastic-damage constitutive model of RAC considering the replacement ratio of recycled aggregates. The FE analytical results revealed that the decreased ultimate bearing capacity of RACFCST stub columns compared with conventional concrete infilled steel tubular (CFST) columns was mainly due to the weakened confinement effect and efficiency. This trend will become more apparent with the larger replacement ratio of recycled aggregates. A practical design formula of the ultimate bearing capacity of RACFCST stub columns subjected to axial load was proposed on the basis of the reasonably simplified cross-sectional stress nephogram at the ultimate state. The derivation process incorporated the equilibrium condition and the superposition theory. The proposed equation was evaluated by comparing its accuracy and accessibility to some well-known design formulae proposed by other researchers and some widely used design codes.

Investigating antioxidant and antibacterial activity of functional cookies enriched with beetroot during storage

Beetroot (Beta vulgaris L.) is one of the plants that contain biologically active compounds that have a function in the prevention and treatment of a wide variety of diseases. The study aims to design new cookies that will support certain groups, such as schoolchildren who may be anaemic. Also, to determine four cookie treatments that were planned to substitute white wheat flour with extraction rate of 72% as follows: T₀ (0%), T₁ (2.5%), T₂ (5.0%), T₃ (7.5%), and T₄ (10%) of beetroot powder to replace 100 g of flour; the cookies were baked at 180 °C for 30–35 min. The chemical composition was assessed, included total phenols, flavonoids, and minerals. Furthermore, during a three-week storage period, antioxidant activity and betalain pigments were evaluated, and sensory evaluation and microbiological assessment were done. Sensory evaluation revealed that the replacement ratio of 10% beetroot was acceptable to the cookies manufactured from white wheat flour with extraction rate of 72%. Compared to the control, a slight decrease was found in the total count of bacteria, fungi, and moulds. We recommend baking beetroot-enriched cookies since it enhances the organoleptic and microbiological characteristics.

Stabilization of Johor Peat Soil using Sugarcane Bagasse Ash (SCBA)

Peat soil have been categorized as a problematic organic soil, because they have a high settlement rate when placed any structure on it. Therefore, the peat soil must first be stabilized using cement before it can be used. However, massive use of cement can lead to environmental pollution. Therefore, this study intends to use sugar cane bagasse ash as a substitute for cement in peat soil stabilization. The mix ratio of 5% to 20% was used to find the optimal mix ratio. Various tests were carried out on samples such as basic properties tests, Unconfined Compressive Strength (UCS) and Scanning Electron Microscope (SEM). After all the tests, the 5% replacement SCBA mix ratio gave the highest unconfined compressive strength if compared to the other mixtures ratio. Therefore, it is selected as the optimum mix ratio. The soil strength achieved by the SCBA 5% replacement ratio was found to be higher than cement stabilization alone due to the presence of secondary pozzolan reactions. The microstructure result from the SEM test had shown that the 5% replacement SCBA mix ratio filled in the hollow left by the peat soil. Hence, able to improve its soil structure and thus increasing its strength.

Low-Carbon and Fundamental Properties of Eco-Efficient Mortar with Recycled Powders

Using recycled powders from solid waste is accepted as an effective strategy to realize the sustainable development of the construction industry. In our study, the cement was substituted by two kinds of recycled powders, i.e., spontaneous combustion gangue powder (SCGP) and recycled concrete powder (RCP), with a certain replacement ratio of 30%. The experimental variables were mainly the type of replacement powder (e.g., SCGP, RCP, and SCGP + RCP) and the grinding time of RCP (e.g., 25 min, 50 min, and 75 min). The fundamental properties, including mechanical properties, long-term properties, and carbon emission, were analyzed for all the mortar mixtures. Experimental results indicate that incorporation of RCP contributes to enhancing the toughness and dry shrinkage resistance of eco-efficient mortar, while SCGP positively affects the compressive strength and chloride resistance. The grinding process improves the activity of RCP to a certain extent, while a long grinding time leads to fusion and aggregation between powders. Investigation on CO2 emission demonstrates that carbon emission from cement production accounts for the largest proportion, 80~95%, in the total emission from mortar production. Combined with the AHP model, eco-efficient mortar containing 15% RCP ground for 50 min and 15% SCGP displays optimal fundamental properties.

Study on Mechanical and Shrinkage Properties of High Belite Sulphoaluminate Cement-Based Green Recycled Aggregate Concrete

Green recycled aggregate concrete (RAC) with high strength and low shrinkage is prepared based on recycled coarse aggregate produced by the particle-shaping and aggregate-strengthening method and green low-carbon new cement. This not only effectively alleviates the shortage of natural resources, but also improves the performance of recycled aggregate concrete, which is of great significance for multi-channel resource utilization of construction waste. In this study, three kinds of recycled coarse aggregates (RCA), including simple crushing recycled coarse aggregate (JD-RCA), one-time particle-shaping recycled coarse aggregate (KL-RCA) and two-time particle-shaping recycled coarse aggregate (EKL-RCA), were prepared from the preparation technology of recycled aggregate, and high belite sulphoaluminate cement with excellent performance was used. The effects of aggregate quality, aggregate replacement ratio, and cementitious material content on mechanical properties and shrinkage properties of green recycled aggregate concrete were studied in comparison with ordinary Portland cement-based recycled aggregate concrete. The testing results show that the particle-shaping method can effectively improve the aggregate quality. The compressive strength and dry shrinkage performance of recycled aggregate concrete made of particle-shaped aggregate are only a little different from those of natural aggregate concrete, and even the performance of recycled aggregate is better than that of natural aggregate concrete under the condition of a low replacement ratio of recycled aggregate. In addition, high belite sulphoaluminate cement-based recycled aggregate concrete (HBRAC) not only has early strength and rapid hardening, but also has excellent drying shrinkage resistance, and its shrinkage rate can be reduced to more than 75% compared with ordinary Portland cement-based recycled aggregate concrete (OPRAC).

Sustainable ground improvement method using encapsulated polypropylene (PP) column reinforcement

This study investigates the effectiveness of encapsulated polypropylene (PP) column in enhancing the undrained shear strength of kaolin (soft clay). The usage of PP in treating problematic soil is a more sustainable and cost-effective alternative compared to other materials. The installation of granular column can be done by using vibro-replacement method. Several geotechnical tests to determine the properties of materials were conducted. The shear strength of treated kaolin sample was examined by using Unconfined Compression Test (UCT). There are seven (7) batches of soil sample in total which included a control sample, three (3) batches of 14 mm and three (3) batches of 20 mm diameter PP column. Different diameters of PP column were examined with 60 mm, 80 mm and 100 mm height, respectively with soil sample of 50 mm in diameter and 100 mm in height. The shear strength improvement of kaolin is 33.82%, 46.51%, and 49.88% when implanted with a PP column with a 7.84 area replacement ratio and 0.6, 0.8 and 1.0 penetration ratio. The soft soil treated using 16.00 area replacement ratio with 0.6, 0.8 and 1.0 penetration ratio has a shear strength increment of 25.22%, 33.39% and 37.59% respectively. In short, the shear strength improvement of the kaolin clay depends on the parameter of the PP column used to reinforce the sample.

Study on the Effect of Recycled Coarse Aggregate on the Shrinkage Performance of Green Recycled Concrete

Shrinkage property is a significant indicator of the durability of concrete, and the shrinkage of green recycled concrete is particularly problematic. In this paper, construction waste was crushed and screened to generate simple-crushed recycled coarse aggregate (SCRCA). The SCRCA was then subjected to particle shaping to create primary particle-shaped recycled coarse aggregate (PPRCA). On this basis, the PPRCA was particle-shaped again to obtain the secondary particle-shaped recycled coarse aggregate (SPRCA). Under conditions where the dosage of cementitious material is 300 kg/m3 and the sand rate is 38%, a new high-belite sulphoaluminate cement (HBSAC) with low carbon emission and superior efficiency was used as the basic cementitious material. Taking the quality of recycled coarse aggregate (SCRCA, PPRCA, and SPRCA) and the replacement ratio (25%, 50%, 75%, and 100%) as the influencing factors to prepare the green recycled concrete, the workability and shrinkage property of the prepared concrete were analyzed. The results show that the water consumption of green recycled concrete decreases as the quality of the recycled coarse aggregate (RCA) increases and the replacement ratio decreases, provided that the green recycled concrete achieves the same workability. With the improvement of RCA quality and the decrease of replacement ratio, the shrinkage of recycled concrete decreases. The shrinkage performance of green recycled concrete configured with the SPRCA completely replacing the natural coarse aggregate (NCA) is basically the same as that of the natural aggregate concrete (NAC).