Structural Sustainable Recycled Aggregate Concrete Production Under Environmental Conditions

The use of recycled aggregates (RA) in the concrete industry has become increasingly popular due to the reduction in natural aggregate (NA) consumption and the ability to reuse demolition waste. This research focuses on analyzing the performance of recycled aggregate concrete (RAC) cured with sodium sulfate (Na2SO4). Five different mixtures were created, varying from 0% RA without supplementary cementitious material (SCM), to 0%, 15%, 30%, and 45% substitution of NA with RA and SCM. The slump test was performed on all fresh RAC mixtures, which showed a decrease in slump with an increase in RA content. Both 5% Na2SO4 solution curing at 91 days and standard curing at 7, 28, and 91 days resulted in a reduction in compressive strength and ultrasonic pulse velocity (UPV) as the proportion of RA increased. Compared to standard curing, the compressive strength of specimens cured with 5% Na2SO4 solution at 91 days showed a decrease of approximately 5-7%. The UPV of SCM-based mixes showed 14-28% improvement with respect to normal aggregate concrete (NAC) in normal water curing. Furthermore, the SCM-included specimens have produced less deterioration in Na2SO4 immersion as SCM particles resist the severity of the dominant sulfate environment

Structural Sustainable Recycled Aggregate Concrete Production Under Environmental Conditions

The use of recycled aggregates (RA) in the concrete industry has become increasingly popular due to the reduction in natural aggregate (NA) consumption and the ability to reuse demolition waste. This research focuses on analyzing the performance of recycled aggregate concrete (RAC) cured with sodium sulfate (Na2SO4). Five different mixtures were created, varying from 0% RA without supplementary cementitious material (SCM), to 0%, 15%, 30%, and 45% substitution of NA with RA and SCM. The slump test was performed on all fresh RAC mixtures, which showed a decrease in slump with an increase in RA content. Both 5% Na2SO4 solution curing at 91 days and standard curing at 7, 28, and 91 days resulted in a reduction in compressive strength and ultrasonic pulse velocity (UPV) as the proportion of RA increased. Compared to standard curing, the compressive strength of specimens cured with 5% Na2SO4 solution at 91 days showed a decrease of approximately 5-7%. The UPV of SCM-based mixes showed 14-28% improvement with respect to normal aggregate concrete (NAC) in normal water curing. Furthermore, the SCM-included specimens have produced less deterioration in Na2SO4 immersion as SCM particles resist the severity of the dominant sulfate environment

Porosity and Strength of Pozzolan Modified Cement Systems

Porosity is one of the important properties that determine the durability of concrete and mortar. Porosity represents the amount of voids inside the concrete, which is dimensionless quantity, usually expressed as a percentage value. This aim of this study is to determine the effect of pozzolans such as pulverized fly ash (PFA) silica fume (SF) on the porosity and strength of mortars. The mix proportion with and without pulverized fly ash (PFA) and silica fume (SF) are tested with two properties such as strength and porosity in order to understand the effect against performance of the mortar. In addition, curing condition also does affect the strength and porosity of the modified mortar. The results from this study shows that the pozzolan modified mortar which is the sample with pozzolan replacement, has low in durability and higher porosity compared with non-modified mortar when it is cured under air curing, which is the method of curing that usually been applied at the construction site

Properties Of Concrete By Using Bagasse Ash And Recycle Aggregate

Sustainable concrete structures which imply green building technology has been widely considering in modern structures. The objective of this study is to investigate the concrete properties by using recycle aggregate as a replacement of coarse aggregate and bagasse ash as the partial replacement of cement. Experimental investigation has been carried out by performing several tests which included slump test, compacting factor test, compressive strength test, rebound hammer test and concrete density test. A total of nine mix batches of concrete containing 0%, 25%, 50%, 75% and 100% of recycle aggregate and 0%, 10%, 15% and 20% of bagasse ash were tested to determine the increment of mechanical properties of concrete. It can be observed that significant decrease of concrete strength with the addition of recycle aggregate, and effective increment of concrete strength by using optimum percentage of bagasse ash might be possible. Finally, it can be concluded that recycle aggregate and bagasse ash with optimum percentage can be used to make recycle concrete and sustainable structures

Characterization of rice husk carbon produced through simple technology

Textile wastewater contains different colors which are harmful to the environment. Activated carbon can be used for the decolorization of textile wastewater. Most of the textile plants in Bangladesh do not use the activated carbon due to its expensive cost and still it is classified as imported item. Low-cost activated carbon produced from locally available materials can solve this problem. This paper describes the color removal of textile wastewater by adsorption process using activated carbon derived from rice husk in a low-cost method. Thermal activation system was applied for the preparation of carbon. The maximum adsorption of color was found at an optimum temperature of 400C with the retention time of 60 minutes. Thus this study demonstrated encouraging performance of activated carbon produced from rice husk compared to the industrial grade activated carbon for decolorization of textile wastewater in the analysis

Experimental and Analytical Studies of Size Effects on Compressive Ductility Response of Ultra- High-Performance Fiber-Reinforced Concrete

Ultra-high-performance fiber-reinforced concrete (UHPFRC) has gained a great deal of increasing interest in structural engineering applications, particularly where high ductility, strength, and high impact resistance are of prime concern. This study focuses primarily on the size effects ductility characteristics of UHPFRC with varying fiber concentrations subjected to uniaxial compressive load. It shows how to process the data from compression cylinder tests to extract the size-dependent strain at peak stress to provide a generic size-dependent stress-strain analytical model. Furthermore, a numerical flexural segmental moment-rotation approach is applied to incorporate an analytical model to quantify apparently disparate UHPFRC member strength and ductility. Tests have shown that it is not the enhancement in the material concrete compressive strength but the phenomenal brittle ductility nature, observed as a result of increasing the slenderness of the specimen; in contrast, a substantial increase in ductility was achieved after crushing of concrete due to the addition of fibers. A size-dependent analytical approach has estimated good fit with the experimental and other published results. Finally, numerical simulation using a segmental approach at the ultimate limit state of rotation dealing with flexural ductility is significantly influenced by the increase in slenderness factor of the specimens and fiber concentrations

Machine learning methods to predict and analyse unconfined compressive strength of stabilised soft soil with polypropylene columns

In this study, several machine learning approaches are used for the prediction of the unconfined compressive strength (UCS) of polypropylene-stabilised soft soil. This research work generates new data and applies several machine learning algorithms for the analysis of UCS. Fifty-two samples are in our generated data. In our generated data, five input features are used: Column Reinforcement Type, Column Diameter, Area replacement ratio,Column Penetration Ratio and Max_Deviator Stress. On the other hand, the output consists of three target stress class. Our experimental result shows that Random Forest (RF) provides good prediction result of unconfined compressive test (UCT) and that is satisfied. RF model gets result of mean absolute error of 0.0625, mean square root error of 0.0625, root mean sqrt error of 0.2500, r2 value of 0.8942 and accuracy of 0.9375. In addition, the sequential model got training loss of 0.2535, training accuracy of 0.9024, validation loss of 0.4056 and validation accuracy: 0.9091. The results showed that the suggested RF and sequential model performs excellently in predicting the UCS of stabilised soft soil with polypropylene. Our technique is more practical and time-consuming than arduous laboratory work. In the future, we will do the experiment with various soft soil characteristics to develop high-performing machine and deep learning models

Flow and Strength Characteristics of Ultra-high Performance Fiber Reinforced Concrete: Influence of Fiber Type and Volume-fraction

Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) has emerged all of the concrete in the construction industry because of its high strength, durability, serviceability and excellent ductility recently. Due to its high production cost, UHPFRC restricts its large-scale structural application. The conventional UHPFRC preparation consists of expensive materials such as specially graded sands which require complex mixing and curing process. The aim of this paper is to determine flow and strength properties of UHPFRC with the variation of fiber type and fiber volume-fraction. The UHPFRC composition was selected with four different fiber volume fractions (Vf = 0%, 1%, 2%, and 3%) of three different steel fibers at varying curing ages of 7, 28, 56 and 90 days within an identical mortar matrix. The paper provides an overview on the workability properties of UHPFRC followed by the presentation of compressive strength test results with different fibers and its volume-fraction with varying curing ages. The higher fiber volume-fraction resulted in a lower flow, and consequently an improvement of compressive strength observed up to 3% volume-fraction of fibers at 56 days curing. Finally, test results are compared and discussed with regard to the main variables: fiber volume-fraction, types of fiber; and curing ages of the specimens

Performance of self-compacting concrete incorporating waste glass as coarse aggregate

The purpose of this paper is to develop gather data on the rheological and mechanical properties of self-compacting concrete (SCC) containing varying percentages of waste glass aggregate (WGA). In this current experiment, the coarse aggregate was substituted by adding WGA, with replacement percentages of 0%, 10%, 20%, and 30% by weight being investigated. The rheological properties of SCC were performed to explore the consequence of WGA using various methods, including the J-ring, slump flow, L-box, and V-funnel. In contrast, the compressive, flexural, modulus of elasticity, and stress-strain responses of hardened concrete were assessed in this study. The results of the fresh concrete tests revealed that the substitution of an optimal level of waste glass in SCC provides adequate implementation in flowability, passing ability, and viscosity behaviors. Besides, hardened characteristics were shown to have a steady decrease in strength with increasing WGA content in the concrete mixtures

Eco-friendly self-consolidating concrete production with reinforcing jute fiber.

Self-consolidating concrete (SCC) has many advantages compared to traditional concrete. However, it often suffers from high brittleness that limits its various applications. Reinforcing the SCC by fiber inclusion can be a fruitful way to enhance its performance. This study aims to investigate how the rheological and mechanical characteristics of SCC are affected by the addition of jute fibers for a specific length of 20 mm at various volumetric fractions of 0.1%, 0.25%, 0.50%, 0.75%, and 1%. Slump flow, J-ring flow, V-funnel, L-box, and Sieve stability tests were performed to investigate the rheological properties of jute fiber reinforced self-consolidating concrete (JFRSCC); while, compressive, splitting tensile, and flexural strength tests were conducted to determine mechanical properties at 7 and 28 days. Scanning electron microscopy (SEM) testing was also used to examine the microstructures of JFR-SCC. These rheological and hardened states were then compared with the control SCC. JFR-SCC performed satisfactorily in terms of flowability, viscosity, and segregation resistance. However, adding more than 0.25% jute fiber in SCC mixes significantly affected the passing ability. The maximum improvements in compressive, splitting tensile, and flexural strength were 2%, 21%, and 18%, respectively, over the reference mix at 28 days. The jute fibers can fill the microcracks in concrete and prolong the ultimate failure. Hence, SCC with jute fiber can be adopted as an eco-friendly alternative to SCC with artificial fibers