Aggregate Ratio Research Articles

Utilization of Blast Furnace Slag as an Enhancer in Masonry Mortars Made with Thermally Treated Waste Concrete Powder

Every year, a massive amount of natural materials are subjected to high temperatures during cement production, resulting in 5% to 8% of total global carbon dioxide (CO2) emissions. The employment of supplementary cementitious materials (SCMs) for developing construction materials could reduce the use of natural materials and CO2 emissions during cement manufacturing. One option to accomplish this is to examine the possibility of producing masonry mortars using thermally treated waste concrete powder (WCP) and ground granulated blast furnace slag (GGBFS). The main objective of the present study is based on this. The study was conducted in two phases. In Phase I, WCP was thermally treated at various temperatures of 0 °C, 300 °C, 500 °C, and 700 °C and then used to prepare mortars at a binder-to-fine aggregate ratio of 1:3. From the strength results obtained in Phase I, a mortar mixture made with 500 °C WCP was selected for Phase II investigation. Mortars were produced by replacing the 500 °C WCP with GGBFS at 0%, 25%, 40%, 60%, 70%, and 85%. It was found that the performance of the mortars was enhanced when GGBFS was used up to 60%. The mortar mixture containing 60% thermally treated WCP and 40% GGBFS produced the optimal physical and mechanical properties. Also, material characterization was carried out on the binders using X-ray fluorescence, scanning electron microscopy, and thermogravimetric analysis. The results indicate that the thermally treated WCPs and GGBFS contain oxides similar to cement, making them suitable for mortar production. In conclusion, the study has shown the feasibility of producing masonry mortars using thermally treated WCP and GGBFS.

Multi-axial 3D printing of biopolymer-based concrete composites in construction

This paper explores the free-form potential of 3D concrete printing, enabled by a novel concrete-like composite made from 80 %-w/v mammal gelatin solution in water with 35 %-w/w gelatin solution to mineral aggregate ratio. This complete replacement of cementitious binders in 3D printing mortar aims on improving the sustainability and advancing the setting control through the material’s thermoplasticity. The material was extruded with a novel and heated ram extruder, traversed with a KUKA robot arm, and cooled by a box fan under normal ambient temperature and humidity conditions. Printing trials with cylinders of 20 cm diameter and various overhang inclinations were carried out – both vertically and multi-directionally sliced. The overhang was increased until the fresh material could no longer support itself. The multi-directionally sliced objects showed the largest overhang capabilities. The thermoplastic printing mortar was able to print a maximum overhang of 80°. This demonstrated freedom of shape and applicability of the bio-based mortar to a 3D printing process could pave the way for highly optimized building components with a minimum use of material. This can incre the sustainability aspects of concrete structures.

Axial stress strain behavior of FRP-confined rectangular rubber concrete columns with different aspect ratio

At present, the mechanical properties of FRP-confined rectangular rubber concrete columns have not been studied. To fill this gap, thirty-six concrete columns were prepared and tested under axial compression in this study. The effects of the aspect ratio (1, 1.25 and 1.5), rubber volume replacement ratios of fine aggregates (0 %, 40 % and 60 %) and FRP layer number (2 and 3) on the failure state and stress–strain relationship were investigated. The test results showed that with increasing section aspect ratio and rubber volume replacement ratio, the damage zone of the specimen increased, and the compressive strength decreased. As the number of FRP layers increasing, the damage zone and compressive strength of the specimens both showed an upward trend. Based on the test results, the stress–strain model, compressive strength model and ultimate strain model of FRP-confined rubber concrete columns were proposed. The proposed models can accurately predict the stress–strain relationship, compressive strength and ultimate strain of FRP-confined rectangular rubber concrete.

The Multi-Objective Optimization Design and Hydrothermal Performance Evaluation of Anhydrous Calcium Sulfate Whisker and Polyester Fiber Compound Modified Asphalt Mixture in Hot-Humid Areas.

In hot and humid climates, asphalt pavements frequently encounter environmental factors such as elevated temperatures and rainfall, leading to rutting deformations and potholes, which can affect pavement performance. The primary objective of this study was to enhance the hydrothermal characteristics of asphalt mixtures through an investigation into the impact of anhydrous calcium sulfate whisker (ACSW) and polyester fiber (PF) on the hydrothermal properties of asphalt mixtures. In this paper, a central composite concatenation design (CCC) was employed to determine the optimal combination of ACSW and PF contents, as well as the asphalt aggregate ratio (AAR). Each influencing factor was assigned three levels for analysis. The evaluation indexes included dynamic stability, retained Marshall stability, and tensile strength ratio. Using the analysis methods of variance and gray correlation degree analysis, the hydrothermal properties of the asphalt mixture were examined in relation to the contents of ACSW, PF, and AAR based on the CCC results. Consequently, the optimal mix design parameters for composite modified asphalt mixture incorporating ACSW and PF were determined. The results indicated that the asphalt mixtures with hydrothermal qualities exhibited optimal performance in terms of 4.1% ARR, 11.84% ACSW, and 0.4% PF. The interaction between AAR and ACSW content had a greater effect on the dynamic stability and tensile strength ratio of the asphalt mixture, whereas the incorporation of ACSW and PF had a greater effect on the retained Marshall stability of the asphalt mixture. Among the three contributing factors, AAR exhibited the strongest relationship with the hydrothermal characteristics of the asphalt mixture, followed by the ACSW content; the correlation of PF content was the lowest. Therefore, to enhance the hydrothermal characteristics of the asphalt mixture, it is important to conduct a full evaluation of the constituents of ACSW and PF, along with the AAR in hot-humid regions.

Shear strength assessment of reinforced recycled aggregate concrete beams without stirrups using soft computing techniques

This paper presents a study to predict the shear strength of reinforced recycled aggregate concrete beams without stirrups using soft computing techniques. The methodology involves the development of a Multi-Objective Genetic Algorithm Evolutionary Polynomial Regression (MOGA-EPR) and Gene Expression Programming (GEP) models. The input variables considered are the longitudinal reinforcement ratio, recycled coarse aggregate ratio, beam cross-section dimensions, and concrete compressive strength. Data collected from the literature were used to train and validate the models. The results showed that the MOGA-EPR and GEP models can accurately predict the shear strength of beams without stirrups. The models also performed better than equations from the codes and literature. This study provides an alternative approach to accurately predict the shear strength of reinforced recycled aggregate concrete beams without stirrups.

Comparisons of Effectiveness and Safety between On-label Dosing, Off-label Underdosing and Off-label Overdosing in Asian and Non-Asian Atrial Fibrillation Patients Treated with Rivaroxaban: A Systematic Review and Meta-analysis of Observational Studies.

Limited real-world data show that rivaroxaban following dosage criteria from either ROCKET AF (20mg/day or 15mg/day if creatinine clearance [CrCl]<50ml/min) or J-ROCKET AF (15mg/day or 10mg/day if CrCl<50ml/min) are associated with comparable risks of thromboembolism and bleeding with each other in patients with non-valvular atrial fibrillation (NVAF). We are aimed to study whether these observations differ between Asian and non-Asian subjects. A systematic review and meta-analysis with random effects was conducted to estimate the aggregate hazard ratio (HR) and 95% confidence interval (CI) using PubMed and MEDLINE databases from September 8, 2011 to December 31, 2022 searched for adjusted observational studies that reported relevant clinical outcomes of NVAF patients receiving rivaroxaban 10mg/day if CrCl>50ml/min, on-label dose rivaroxaban eligible for ROCKET AF or J-ROCKET AF, and rivaroxaban 20mg/day if CrCl<50ml/min. Effectiveness and safety endpoints were compared between ROCKET AF and J-ROCKET AF dosing regimen in Asian and non-Asian subjects, separately. Also, risks of events of rivaroxaban 10mg/day despite of CrCl>50ml/min and rivaroxaban 20mg/day despite of CrCl<50ml/min were compared to that of "ROCKET AF/J-ROCKET AF dosing". Sensitivity analyses were performed by sequential elimination of each study from the pool. The meta-regression analysis was performed to explore the influence of potential factors on the effectiveness and safety outcomes. Eighteen studies involving 67,571 Asian and 54,882 non-Asian patients were included. Rivaroxaban following J-ROCKET AF criteria was associated with comparable risks of thromboembolism in the Asian subgroup, whereas rivaroxaban following J-ROCKET AF criteria was associated with higher risks of all-cause mortality (HR:1.30; 95%CI:1.05-1.60) compared with that of ROCKET AF criteria in the non-Asian population. There were no differences in risks of major bleeding between rivaroxaban following J-ROCKET AF versus ROCKET AF criteria either in the Asian or non-Asian population. Use of rivaroxaban 10mg despite of CrCl>50ml/min was associated with a higher risk of thromboembolism (HR:1.64; 95%CI:1.28-2.11) but lower risk of major bleeding (HR:0.72; 95%CI:0.57-0.90) compared with eligible dosage criteria. Use of rivaroxaban 20mg despite of CrCl<50ml/min was associated with worse clinical outcomes in the risks of thromboembolism (HR:1.32; 95%CI:1.09-1.59), mortality (HR:1.33; 95%CI:1.10-1.59) and major bleeding (HR:1.26; 95%CI:1.03-1.53) compared with eligible dosage criteria. The pooled results were generally in line with the primary effectiveness and safety outcomes by removing a single study at one time. Meta-regression analyses failed to detect the bias in most potential patient characteristics associated with the clinical outcomes. Rivaroxaban dosing regimen following J-ROCKET criteria may serve as an alternative to ROCKET-AF criteria for the Asian population with NVAF, whereas the dosing regimen following ROCKET AF criteria was more favorable for the non-Asian population. Use of rivaroxaban 10mg despite of CrCl>50ml/min was associated with a higher risk of thromboembolism but a lower risk of major bleeding, while use of rivaroxaban 20mg despite of CrCl<50ml/min was associated with worse outcome in most clinical events.

Study on Thixotropy of Mastic Asphalt Binder and Asphalt Mastic

In order to analyze the thixotropy of mastic asphalt concrete during the mixing process, the factors affecting the thixotropy of mastic asphalt binder and asphalt mastic are studied, and the measures to shorten the mixing time of mastic asphalt mixture are given. The dynamic viscosity of mastic asphalt binder and asphalt mastic with time and shear rate is obtained via the step frequency method, and the thixotropic constitutive models of mastic asphalt binder and asphalt mastic are constructed by structural dynamics model, exponential equation, and extended exponential equation respectvely. The improved time thixotropy index is used to analyze the effects of asphalt type, asphalt–aggregate ratio, filler type, heating temperature, and shear rate, and the laws of various factors affecting the thixotropy of mastic asphalt binder and asphalt mastic are obtained. The research shows that the extended exponential model can better characterize the thixotropy of mastic asphalt binder and asphalt mastic under different shear rates. When the amount of lake asphalt or cement is increased, the viscosity of the system and the mixing time to reach a steady viscosity increases; that is, the mixing time needs to be increased. Increasing shear temperature does not change the time parameter to reach steady viscosity; that is, it cannot shorten mixing time. When the shear rate is increased, the time for the system to reach the steady viscosity will be shortened; that is, the time for mixing the mixture can be shortened.

Mechanical and shrinkage performance of steel fiber reinforced high strength self-compacting lightweight concrete

This study investigated the effects of mixture proportion on the mechanical and shrinkage behaviors of steel fiber reinforced high strength self-compacting lightweight concrete (SHSLC) mixtures incorporating bottom ash aggregates for internal curing. In this study, different types of fine aggregates, fine aggregate ratios, supplementary materials such as silica fume (SF) and colloidal nano-silica (CNS), and four types of steel fibers were considered to develop SHSLC. The self-compacting characteristics of concrete were evaluated by means of slump flow, J-ring flow, and V-funnel tests. The test results indicate that incorporation of SF and CNS had a positive effect on the mechanical properties, but 4% incorporation of CNS decreased workability and strength due to the agglomeration of mixture. The addition of steel fibers improved compressive strength, and flexural toughness of SHSLC, but reduced the flowability and passing ability with increased fiber contents. Due to the internal curing from coarse bottom ash, significant reduction of autogenous shrinkage up to 33% was observed, whereas 7% for drying shrinkage. The incorporation of fibers reduced the autogenous and drying shrinkage up to 31% and 22% compared with non-fiber reinforced concrete, respectively. Finally, the autogenous shrinkage behavior was simulated with several models in the literature, and a model for high strength self-compacting lightweight concrete with and without fibers considering equivalent age was proposed.

Effect of lightweight expanded clay aggregate as partial replacement of coarse aggregate on the mechanical properties of fire-exposed concrete

Abstract As aggregate material typically comprises 65–75% of concrete volume and has a significant effect on its mechanical properties, aggregate type considerably affects concrete behavior at high temperatures. In this study, 80 concrete cylinders and 60 cubes were cast to investigate the residual strength of normal concrete that contains lightweight expanded clay aggregate (LECA) with different volumetric replacement ratios (0, 10, 20, and 30%) of the coarse aggregate. After the fire flame exposure effect of steady-state temperatures (300, 400, 500, and 600°C), and a sudden cooling process, the mechanical tests (compressive strength, tensile strength, and modulus of elasticity; Ec), as well as mass loss and thermal conductivity, were carried out on the specimens. The results indicate that increasing the LECA content in the mixture leads to better strength retention after exposure to fire. After exposure to a steady-state temperature of 600°C, the amount of decrease in mass, residual compressive and tensile strengths, and the residual amount of Ec were 7.61, 7.5, 7.16, and 6.24%; 57.1, 66.8, 69.8, and 72.0%; 22.4, 32.7, 41.8, and 48.6%;, and 16.0, 22.3, 23.4, and 24.3%, respectively, for the considered volumetric replacement ratios of 0, 10, 20, and 30%. Also, the values of the thermal conductivity were 1.4889, 1.1667, 1.0912, and 1.0410 W/m K, respectively.

The response of organic carbon fractions in sediment to rainfall characteristics and slope lengths: Based on four-years on-site monitoring data

The effect of soil erosion processes on the properties of sediment and organic carbon fractions is not well understood under complex erosion environments, such as various rainfall characteristics and transport distances, which leads to a gap in knowledge regarding the role of soil erosion in the global carbon cycle. This study investigated the impact of different rainfall characteristics (patterns and parameters) and slope lengths (5 m ∼ 20 m) on the sediment yield, particle size distribution (PSD) and properties of organic carbon fractions on China’s Loess Plateau. The results show that runoff was highest under rainfall pattern A (extreme rainfall), while the sediment concentration peaked under rainfall pattern B (heavy rainfall), with significant correlation with slope length, rainfall intensity, kinetic energy, rainfall erosivity and precipitation (p less than 0.05). Silt- and clay-sized fractions were transported as primary particles and enriched under rainfall patterns B and C with no differences between slope lengths. The enrichment ratio (ER) of sediment, effective and ultimate particles were primarily influenced by rainfall intensity-related parameters. In contrast, the aggregation ratio (AR) tended to be influenced by rainfall kinetic energy. The content and loss of organic carbon fractions correlated to rainfall parameters and slope length, although no significant difference was observed between different rainfall patterns and slope lengths. Lost organic carbon fractions were predominantly Mineral-associated organic carbon (MOC), with great enrichment under rainfall pattern C and rapid depletion as the slope length increased. Structural equation models (SEM) indicated the effect of rainfall characteristics and slope length on organic carbon loss was mainly due to the regulation of soil loss and particle size distribution of sediment in selective transport erosion processes. We highlighted the need to consider the effect of soil erosion and particle size distribution comprehensively on the carbon cycle from the perspective of organic carbon fractions to describe the potential effects of soil erosion on the carbon budget quantitatively, especially in complex environmental conditions with consideration of scale effect.

Experimental and analytical model of CFRP-confined spontaneous combustion coal gangue aggregate concrete

In this study, carbon fiber reinforced polymer (CFRP) confined cylindrical concrete specimens were tested under monotonic axial loading. The effects of the replacement ratio of the spontaneous combustion coal gangue aggregate (SCGA) and stiffness of the CFRP confinement on the mechanical properties of concrete were mainly considered. The results showed that the confinement efficiency of CFRP on the concrete decreases with increasing SCGA content. Despite the increase in the confinement stiffness, the confinement efficiency of the CFRP confinement on high-content SCGA concrete (SCGAC) will also be significantly reduced. Evidently, the influence of aggregate properties on confined concrete cannot be ignored. A CFRP-confined analysis model considering the SCGA replacement ratio was established. Through the verification of existing test data, its accuracy meets the requirements.

A novel method for measuring and analyzing the characteristics of coarse aggregates in concrete

The characteristic of coarse aggregate is an important factor affecting the building performance of concrete, so it is of great significance to measure and characterize it. In this paper, a method of measuring the characteristics of coarse aggregate in concrete buildings by using borehole camera technology is proposed. For the obtained borehole wall image, the corresponding image processing method is proposed, which can accurately recognize the coarse aggregate structure in the image. On this basis, the characteristics of coarse aggregate in the borehole wall image are calculated and analyzed. The calculation parameters include uniformity, gradation, aspect ratio, inclination angle, shape index, angularity and surface texture. The results show that the coarse aggregate in the borehole wall image used in this paper is not evenly distributed at different depths, the gradation continuity is good, and there are some coarse aggregates with large particle size. The aspect ratio of most coarse aggregates is less than 3 (AR1:97.71%; AR2:96.26%), and the content of needle flake coarse aggregate is less. The inclination angle is mostly distributed in the horizontal direction, accounting for more than 50%. The distribution of shape index and angularity has obvious correlation with the particle size range, and the shape index and angularity in the large particle size range are richer and more uniform. The distribution characteristics of surface texture of coarse aggregate in different particle size range are basically the same, and there is no obvious correlation with particle size. In this paper, a new in-situ measurement and multi characteristic parameter analysis of coarse aggregate in borehole is carried out, which provides a new idea for the evaluation of concrete building performance.

High-performance artificial aggregate prepared with recycled concrete powder and its impact on concrete properties

Given the pollution of waste concrete powder, low utilization rate, sand and stone resources shortage, and poor performance of artificial aggregate, the high-performance artificial aggregate was prepared by high dosage recycled concrete powder (RCP). The effects of curing methods, RCP grinding time, RCP:slag ratio, Na2O dosage, and Na2SiO3 modulus on the properties of the aggregate were studied. The results show that natural curing is the most effective, and the best-performing aggregate was obtained with an RCP grinding time of 40 min. The particle size coefficient of the aggregate was around 1.3, and increasing the proportion of slag increased the content of large particles. The amounts of slag and Na2O had a significant impact on the aggregate. As the amounts of slag and Na2O increased, the amount of C-(A)-S-H gel increased, the microstructure improved, and the macroscopic manifestations increased apparent density and strength and reduced water absorption. The maximum strength of the aggregate reached 8.59 MPa, and water absorption was 12.67% at this point. Concrete was prepared using the aggregate above, and the effects of aggregate curing time, aggregate pre-wetting time, and aggregate material ratios on the properties of the concrete were studied. The results show that the density of RCP artificial aggregate concrete is low, between 2030 kg/m3-2220 kg/m3. The compressive strength and splitting tensile strength of concrete increase with the increase of aggregate curing time, prewetting time, and the dosage of aggregate Slag and Na2O, which reach 59 MPa and 4.5 MPa, respectively. The aggregate strength increased, leading to interfacial failure inside the concrete, while larger aggregate particle size tended to cause aggregate failure inside the concrete.

Pengaruh Rasio Prekursor Agregat Halus Terhadap Karakteristik Mortar Geopolimer Tanah Liat

The basis and main component of any building construction is primarily concrete. With the rapid growth of global construction, the demand for concrete is increasing and consequently the demand for cement as the main component in making concrete is also increasing. This is the single most important factor for using inorganic binders to obtain eco-friendly concrete. Nowadays, inorganic binders such as geopolymers or alumina-silicate polymers are used in many advances of eco-friendly concrete. Geopolymer mortar is one that uses natural components and minerals as binders and has a high concentration of alumina and silica oxide. This study aims to determine how the ratio of precursor (clay) fine aggregate affects the characteristics of geopolymer mortar. The research method used is the Experimental method, alkaline activator with a ratio of 1:1 in NaOH and Na2SiO3 and using 16 M molarity NaOH. Using precursor and fine aggregate in the ratio of 1:0.2; 1:0.4; 1:0.6; 1:0.8; 1:1; 1:1.2; 1:1.4; 1:1.6; 1:1.8 and 1:2. At the age of 3, 14, and 28 days, compressive strength tests were conducted on all specimens. Based on the results of the research, the compressive strength of clay geopolymer mortar has a maximum compressive strength of 8.53 MPa after 28 days of treatment with code M6 at a precursor and fine aggregate ratio of 1: 1.2. The results showed that after passing the maximum compressive strength ratio in code M6 the ratio decreased due to more fine aggregate than the binder (alkali activator).

Comparative Study of M30 and M35 Grades of Concrete Using BIS, ACI, and DOE Methods of Mix Design.

Mix design is a critical process in concrete production that determines the optimal combination of materials to produce concrete with desired properties. In this, we will discuss three commonly used methods for mix design: the American Concrete Institute (ACI) method, the Bureau of Indian Standards (BIS), and the Design of Experiments (DOE) method. The cement, water, fine aggregate, and coarse aggregate ratios needed to produce the desired strength and workability are calculated using the commonly used ACI technique. The ACI technique uses experimental data and historical experience to arrive at an appropriate mix design. The BIS technique, which offers recommendations for the selection of materials, proportions, and testing processes to achieve the specified strength and durability of concrete, is comparable to the ACI method. The DOE technique is a statistical strategy that entails developing a design matrix and doing tests to ascertain the impact of various elements on the characteristics of concrete. This approach makes it possible to evaluate the variables that affect mix design in a more systematic and thorough manner, producing a concrete mix that is more effective and optimized. In conclusion, while the DOE method is a more challenging approach that may result in more effective and optimized mix designs, the ACI and BIS approaches are frequently utilized and offer helpful guidance for mix design. In the end, the strategy used will depend on the particular needs of the project and the resources that are available.

Utilization of agricultural wastes as fiber, binder and aggregates of geopolymer mortars: Application of taguchi method for strength and durability optimization

The present study deals with the compressive strength, flexural strength, capillary water absorption, dry shrinkage, resistance to freeze-thaw cycles, and high temperature resistance of geopolymer mixtures based on agricultural wastes. For the construction of geopolymer mixtures, rice husk ash was used as binder, corn stalk was used as aggregates, and wheat straw, barley straw, and sugarcane straw were used as fibers. Since geopolymer mixtures might be influenced by many factors, the present study used the Taguchi method to design experiments, to optimize factors, and to predict properties so as to avoid the relevant full-fledged experimental works. The present study took into account the factors of curing method (heat curing and ambient curing), concentration of sodium hydroxide solution (6, 9, and 12 M), mass ratio of sodium silicate to sodium hydroxide (2, 2.5, and 3), mass ratio of alkaline activator to binder (0.3, 0.4, and 0.5), mass ratio of aggregate to binder (1, 2, and 3), type of fiber (wheat straw, barley straw, and sugarcane straw), and fiber volume (0, 4, and 8% in terms of the binder weight) as inputs for Taguchi analysis. Given the number and levels of considered factors, 18 mix designs were examined on the basis of the L18(63×12) orthogonal array proposed by Taguchi. The results indicated that the optimal levels of the factors of curing method, concentration of sodium hydroxide solution, mass ratio of alkaline activator to binder, and mass ratio of sodium silicate to sodium hydroxide for almost all tests were respectively equal to heat curing, 12, 0.5, and 3, while the optimal levels of other factors were variable depending on the type of test.

Study on the Characteristics of Composite Recycled Aggregate Concrete Based on Box–Behnken Design Response Surface Model

This study investigates the influence of recycled fine aggregates (RFA) and waste concrete powder (WCP) on the compressive strength of concrete. The response surface methodology is employed, considering three factors: the content of WCP, the water–cement ratio, and the replacement ratio of recycled fine aggregates. Compressive tests are conducted at different ages (3 days, 28 days, and 90 days). A statistical approach is used to establish a response surface model for compressive strength and to verify its fitting with experimental results. By combining qualitative and quantitative analyses, including morphological analysis of SEM images, stratified binarization statistics, and fractal dimension calculations, the mechanisms of the effects of singly and doubly mixed RFA and WCP on the compressive strength of concrete are analyzed. The results show that an increase in the content of WCP from 5% to 15% gradually improves the compressive strength of the concrete. The water–cement ratio significantly affects the compressive strength, with an optimal ratio of 0.43. Replacement with less than 33% fine aggregates does not significantly reduce the compressive strength of the concrete. The concrete specimens with singly mixed fine aggregates exhibit the largest pore area after stratified grayscale binarization, while those with doubly mixed aggregates have the largest area of hydrated calcium silicate. Fractal analysis of the binarized images confirms a positive correlation between the fractal dimension of hydrated calcium silicate and compressive strength and a negative correlation between the fractal dimension of pores and compressive strength.

Mechanical and durability properties of standard and high strength geopolymer concrete using particle packing theory

Aggregate packing significantly affects the characteristics of fresh and hardened concrete; aggregates having higher packing density (PD) improve these characteristics. There is a lack of research on how the PD affects the properties of geopolymer concrete (GPC). Hence, the present study includes the effect of the PD on the mechanical and durability properties of the standard and high-strength GPC. The study parameters are the binder content, the concentration of NaOH, and the fly ash to ground granulated blast furnace slag (GGBS) ratio. Six aggregate groups (like 12.5–10 mm, 10–4.75 mm, 4.75–2.36 mm, 2.36-1.18 mm, 1.18–0.6, and 0.6–0.15 mm) were investigated for the particle packing experiment, and the blended coarse:fine aggregate ratio of 55:45 which produced the highest packing density of 0.702, were used in the GPC mixes. A total of 120 cubes of size 100 mm, 30 cylinders of size 100 × 200 mm, and 30 prisms of size 100 × 100 × 500 mm were cast for 10 different mixes in the study. Sorptivity and water absorption are the tests performed for the durability studies. The result shows that GPC mixes with Particle packing theory significantly improved the compressive strength, and durability, and showed better workability. The workability of the GPC reduces by increasing the GGBS and concentration of the NaOH solution. As the GGBS proportion and the concentration of the NaOH solution increases, the concrete compressive, split, and flexural strength increases. As the binder content increases, the strength increases at first, then reduces. Increasing the GGBS content, binder content, and molarity of the NaOH accomplishes a reduction of the sorptivity coefficient and water absorption of the GPC.

Mechanical performance of recycled aggregate concrete in green civil engineering: Review

The use of recycled aggregate concrete can save natural resources and reduce environmental pollution, which has been widely concerned in recent years. The physical and mechanical properties of recycled aggregate concrete (RAC) are studied based on the literature on waste concrete coarse aggregate (RCCA) and waste brick coarse aggregate (RBCA) published around the world in the last 40 years, in order to understand and study the performance of common RAC. The common characteristics (water absorption, density, and crushing value) of two recycled aggregates with the same particle size were compared. The effects of effective water–cement ratio (e–W/C), aggregate cement ratio (A/C), and recycled aggregate content on the compressive properties of recycled concrete are explained, and the microstructure of recycled concrete is explored. The influence of recycled aggregate content on its elastic modulus (Ec) and the correlation between Ec and the compressive strength of recycled concrete are also investigated. Finally, prospects were made for two types of RAC for further research by scholars.

High-performance self-compacting concrete with recycled coarse aggregate: Soft-computing analysis of compressive strength

The growth of cities and industrialization has led to an increase in demand for concrete, resulting in resource depletion and environmental issues. Sustainable alternatives such as using recycled concrete aggregate (RCA) and industrial waste have been proposed to meet construction material demands while adhering to building codes and promoting sustainability. However, compressive strength (CS) is a crucial property of concrete, and the design parameters have different effects on CS for various grades. Recently, researchers have focused on partially replacing natural coarse aggregate (NCA) with RCA in concrete to achieve sustainability goals. This study aims to examine the influence of design parameters (w/c: water-cement ratio, w/b: water-binder ratio, A/c: total aggregate-cement ratio, FA/CA: fine-coarse aggregate ratio, SP: superplasticizer, w/s: water-solid ratio and RCA%) on concrete CS and address controversies in the insights gained from pairwise comparisons using Pearson's correlation coefficient (PCC) analysis. Additionally, five techniques (M5P, RF, SVM, LR, and ANNs) were used to predict the CS of high-performance self-compacting concrete (HP-SCC) with RCA, and the results were compared with an ANNs-based model as was the commonly used one in literature. The approaches were assessed based on their accuracy measured using correlation coefficient (CC), mean absolute error (MAE), Root Mean Square Error (RMSE), Mean absolute percentage error (MAPE), Scatter index (SI), and comprehensive measure (COM) indicators. Accordingly, the analysis indicated that SVM-PUK-based model is the most appropriate and effective technique to predict the CS of HP-SCC for the given datasets, with CC = 0.894, 0.900, MAE = 1.721, 3.813, RMSE = 5.137, 6.306, and MAPE = 4.5%, 7.6% for the training and testing stages, respectively. The uncertainty analysis results were 21%, 20.7%, 19%, 22%, and 19% for M5P, RF, SVM, LR, and ANN-based models, respectively, whereby all of them were under threshold of 35%. Moreover, according to sensitivity analysis, w/c, w/b, and w/s variables influences the most on CS prediction, while the RCA(%) variable has the least impact.