Crushed Aggregates Research Articles

Overview of the Empirical Relations between Different Aggregate Degradation Values and Rock Strength Parameters

The aggregates are essential materials in civil engineering, they are used for railway and road constructions, for hydraulic engineering but they are also the base material of concrete. The crushed stones are exposed to several effects during their lifespan. Therefore, several tests were developed to evaluate their performance. One of the most important aspects is the resistance to degradation. However, degradation tests require special types of equipment and usually take longer than common strength tests which are more likely to be available for rock materials. Therefore, the empirical connections between strength and degradation values can be extremely useful in practice. The paper aimed to collect all available relationships and datasets from the literature that presents the relations between these different parameters – such as Aggregate Impact Value (AIV), Aggregate Crushing Value (ACV), Ten Percent Fines Value (TFV), Los Angeles Abrasion Value (LAAV), and micro-Deval Coefficient (MDE) – and rock strength parameters – such as Uniaxial Compressive Strength (UCS) and Point Load Strength Index (IS(50)) – and to provide the best-fit formula for different rock types. The paper also highlights the difficulties and limitations of the compared relationships.

Sustainable Impact of Coarse Aggregate Crushing Waste (CACW) in Decreasing Carbon Footprint and Enhancing Geotechnical Properties of Silty Sand Soil

People are forced to use all types of soil, especially bad soils, as infrastructure demands grow. Different procedures must be used to ameliorate these poor soils, which are fragile during building. Natural resource depletion and the rising costs of available materials force us to consider alternative supplies. For several years, researchers have investigated the use of by-products from industry and associated approaches to improve the qualities of various soils. Coarse Aggregate Crushing Waste (CACW) is a waste product that results from the primary crushing of aggregates. Massive amounts of CACW are produced in the business, posing serious issues from handling to disposal. As a result, the widespread use of CACW for diverse purposes has been recommended in the civil engineering profession to address these concerns. Because some natural resources, such as gravel, are nonrenewable, it is vital to decrease their consumption and replace them with recycled, cost-effective, and ecologically acceptable alternatives. This research aimed to investigate the possibility of reusing CACW to improve the geotechnical properties of silty sand (SM) soil available in the Najran region. In this research, soil samples were collected from Najran city and subjected to a variety of lab experiments to determine their characterization. Mixes were designed for a parent soil with a range of percentages of CACW with/without 2% cement. The designed mixes were examined through a set of lab tests to obtain the optimum design for use in road construction. The findings of the tests showed that the optimum dosage is 10% CACW with 2% cement, raising the undrained shear strength of silty sand soil by 323%, CBR by 286%, and P-wave by 180%. The durability tests show that soil mixed with 10% CACW and 2% cement fulfills the requirements and stays within the 14% weight loss limit imposed by the Portland Cement Association (PCA). The microscopic investigation results confirmed the outcomes obtained by macro tests. As a result, the carbon footprint values decrease when CAWA is added, making this treatment approach almost carbon neutral. This study clarifies the long-term effects of CACW on improving the geotechnical characteristics of silty sand soil in the Najran Region of the Kingdom of Saudi Arabia and other comparable soils globally.

Effect of clay fraction on the mechanical properties and microstructural characteristics of waste rock fine-based brick

The disposal of waste rock fine (WRF) from the manufacturing process of crushed aggregates is attracting more and more attention due to the thorny issues related to clay particles. This paper investigated the use of WRF as a substitute for fine aggregate that solidified by phosphogypsum (PG), groundgranulated blast-furnace slag (GGBS), and ordinary Portland cement (OPC) system in manufacturing of baking-free brick. Three kinds of WRF with different clay fraction (i.e., natural WRF, silty WRF, and clayey WRF) were prepared via slurry settlement methods. Thereafter, their mechanical behaviors were compared by unconfined compressive strength (UCS), X-ray diffraction (XRD), and mercury intrusion porosimetry (MIP) tests. The results show that natural WRF contains 81.9% silt and 18.1% clay, after settling-based separation process, the strength of solidified silty and clayey WRF samples decreased by 4.1% and 16.5% at 28 days curing period. Micromorphology, compositional, and microstructural analyses indicate that the strength of solidified WRF is governed by both bonding and filling effect, therein, the strength of solidified silty and clayey WRF samples were lower as compared with natural WRF-based modified samples due to the gradation effect. In addition, it was noticed that although clay particles may participate in the secondary pozzolanic reaction to contribute bonding strength, they also possess superior adsorption capability owing to the large specific surface area, which will adsorb on the surface of cementitious materials and thus hinder the hydration reaction. Moreover, water stability, environmental leaching, economic, and greenhouse gas emission results further confirmed the advantage of reusing WRF and industrial by product resources.

Micromechanical behavior of cement-treated base materials incorporating recycled crushed aggregates arising from C&D waste powder based on DEM

A numerical simulation of the uniaxial compression test (UCT) was conducted based on the discrete element method (DEM), to investigate the mechanical properties of CTBM incorporating recycled crushed aggregates (RCAs) arising from construction waste powder. The components of CTBM were generated via the randomization method to obtain a 2D DEM model. Then, the Linearcbond Model and Linearpbond Model were selected, and the effects of the main micro-parameters of contact models on the stress–strain curves of CTBM were clarified. The final micro-parameters were determined through the trial and error method and inversion analysis. Moreover, the micromechanical results presented that the contact forces between particles during the whole loading process increased continuously until damage occurred. And the contacts between particles failed at the middle and later loading stages, especially the tension contacts. The contact number of the Linearcbond Model reduced significantly, while that of the Linearpbond Model only decreased by 2.6%. Furthermore, the upper and lower particles moved to the mid-span of the specimens, and the particles in the middle moved to both sides when loading. The displacement on both sides was larger due to the failure of the specimen in the middle and later loading periods. The presented 2D DEM has the potential to display the mechanical characteristics of CTBM. It also provides theoretical guidance for the wide application of RCAs due to their great economic and environmental benefits.

Strength and durability status of the Fagfog Quarzite from the Lower Nawakot Group, central Nepal Lesser Himalaya

Railways have played vital role in the development of many countries worldwide. Government of Nepal has already planned to establish various national and international railway networks within the nation. A substantial quantity of durable rock ballasts is required for building a sustainable railway network. Quartzites from central Nepal Lesser Himalaya can be a promising source to fulfill this requirement. Therefore, the quartzites from the stratigraphic unit Fagfog Quartzites of the Lower Nawakot Group located in Dhading District along the Kalu Pandey Highway have been assessed to determine physical, strength and durability characteristics of the ballasts. All quartzite ballasts obtained from the bedrocks were of Precambrian, medium-grained, bladed to prolate shaped, white to brownish white, crushed quartzites. Dry density and water absorption were respectively 2336-2641 kg/m3 and 0-2.5%. The bulk density varies from 1204 and 1387 kg/m3. Point load strength index varies from 2.04 to 11.55 MPa (medium strong to extremely strong). Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV) ranges from 14.85 to 22.77% and 15.51 to 22.17% respectively. Some 7% results of AIV and 20% of ACV results exceeded the established limiting value of 22%. The slake durability index (Id5) ranges from 95.19 and 99.11%, whereas Id2 ranged between 96.94 and 100%, which shows that 80% of the samples have very high slake durability whereas remaining 20% exhibit high slake durability. There was no significant change in slake durability index from the second to the fifth cycles. Los Angeles Abrasion Value (LAAV) varies from 12.07 to 31.34% and Sulphate Soundness Value (SSV) varies within a limited range of 0.20 and 4.59%. Conclusively, the comprehensive evaluation suggests that the quartzite ballast from the Fagfog Quartzite source display favourable qualities in terms of point load, crushing and impact strengths and durable against abrasion, slaking and frosting. Thus, the quartzites from Fagfog Quartzite hold significant potential as a suitable rock type for railway track ballasts.

Static Modulus of Deformation of Uncemented Layers of the Railway Substructure—Comparison of Values and Determination of Correlation Dependence According to the Test Procedure of the Slovak Railways and Deutsche Bahn A.G.

The paper focuses on the analysis of the values of the static modulus of deformation obtained by the application of the test procedure specified in the methodology for the diagnostics of the sub-ballast layers used for German railways (DIN 18 134) and the Railways of the Slovak Republic (Regulation TS4). The purpose of the study was to determine the correlation between the measured values of the static modulus of deformation according to the above-mentioned methodologies based on a series of experimental measurements on an experimental field built at a scale of 1:1. It also aimed to develop a numerical model characterising the behaviour of the loaded environment during the experimental measurements using the finite element method, which can subsequently be used for the design of the structural composition of the sub-ballast layers. For the purpose of the experimental measurements, a sub-ballast layer of 0/31.5 mm crushed aggregate of different design thicknesses was applied to the sub-ballast layers. A polynomial dependence with a high value of the reliability coefficient can be found between the results of the static modulus of deformation obtained using the mentioned measurement methodologies during the quality inspection of the implemented construction works. This dependence is valid for the specific boundary conditions of the experimental measurements performed (subsoil of clay with gravel admixture and the sub-ballast crushed aggregate layer of 0/31.5 mm dolomitic gravel). In the future, establishing correlation dependencies for other boundary conditions and structural material compositions can be considered.

Laboratory Investigation on Roller Compaction Technique in Concrete Construction

Roller compacted concrete (RCC) is a concrete compacted by roller compaction. The concrete mixture in its unhardened state must support a roller while being compacted. The aim of this research work was to investigate the behavior and properties of roller compacted concrete when constructed in the laboratory using roller compactor manufactured in local market to simulate the field conditions. The roller compaction was conducts in three stages; each stage has different loading and number of passes of the roller. For the first stage, a load of (24) kg and (5) passes in each direction had been employed. For the second stage, a load of (104) kg and (10) passes in each direction were conducted. Finally, at the third stage, a load of (183) kg and (15) passes were adopted. Such procedure was in accordance to previous work conducted by the author. The effects of the type of coarse aggregate (crushed and rounded), fine aggregate (river and natural) and cement type (OPC and SRPC) on the mechanical properties of RCC were investigated. The effect of compaction method on compressive strength and indirect tensile strength was also discussed. A total of (26) roller compacted concrete slab samples of (380×380×100 mm) were prepared in the laboratory, Then, the slab specimens are taken out of the molds and immersed in the curing tank for (28) days. Core and Beam specimens were obtained from the slab samples for the determination of mechanical properties. Such properties include compressive, indirect tensile, flexural strengths using one point loading. It was concluded that the compressive strength of RCC using crushed aggregate is higher than that when using rounded aggregate in a range of (15-66) % for core specimens, while the compressive strength of RCC when using river sand is higher than that when using natural sand in a range of (9-26)% for core specimens. When river sand is implemented, RCC samples show higher indirect tensile strength than those with natural sand, such variation is within (7-8) %

Three-dimension mesoscale model of concrete by random placement algorithm and its failure mechanism analysis

This contribution presents the development and application of a 3D numerical concrete model for investigating the fracture behavior of concrete at the mesoscale. The reconstruction of actual geometric models of pebble and crushed aggregates is carried out using a 3D laser scanner. An aggregate and pore library were then constructed, and a 3D random placement method is developed to generate the realistic mesostructure of concrete. Additionally, the cohesive zone model-based numerical computation approach was employed to simulate the fracture problem in concrete. Then, the numerical concrete model is applied to investigate the mechanical response and fracture behavior of cylindrical concrete specimens under uniaxial compression and concrete beams under three-point bending. Results show that the 3D mesoscale concrete model effectively captures the complex fracture process and nonlinear mechanical behavior. This methodology can be used for investigating the effect of mesostructure on macroscopic behavior of concrete and also has potential applications in studying the behavior of particulate composites under various conditions.

Thermo-mechanical treatment as an upcycling strategy for mixed recycled aggregate

The study investigates thermo-mechanical treatment for mixed recycled aggregates (MRA). Six treated aggregates were prepared by heating MRA between 300 °C and 800 °C, followed by 100 abrasion cycles. The thermo-mechanical treatment causes loss in the adhered mortar and improves aggregate crushing, impact and abrasion value up to 700 °C. Concrete prepared with MRA treated at 700 °C, as compared to natural aggregates, shows higher workability (166.67%) and comparable mechanical strength, i.e., compressive (93.72%), flexural (99.94%) and split tensile (97.87%). The sustainability assessment shows that treating MRA with renewable energy can have lower economic costs (89.36%) and carbon emissions (58.05%) than manufacturing natural aggregates.

Effects of the Changes of Particle Surface Electric Field and Interaction Force on the Reclaimed Soil Aggregate Structural Stability under the Application of Different Soil Conditioners

Aggregate stability is a key factor in the evaluation of soil structure and erosion resistance, which is largely influenced by soil electric field and particle interaction. However, there are few studies on how different organic and inorganic soil conditioners change the surface electric field and interaction force of reclaimed soil to improve the aggregate stability. Therefore, a five-year field experiment was conducted to quantitatively study the effects of FeSO4 (TM), organic fertilizer (TO), fly ash (TF), maturing agent + organic fertilizer (TMO) and fly ash + organic fertilizer (TFO), compared with control (CK) treatment, on the reclaimed soil internal force and the aggregate crushing strength. The results showed that the reclaimed soil surface potential and electric field intensity increased after 5 years of application of organic and inorganic soil conditioners. Under the same electrolyte concentration and electric field conditions, the crushing strength of aggregates (<5 μm) treated with TFO, TMO, TO, TF and TM decreased by 43.70%, 35.51%, 25.97%, 8.28% and 5.49%, respectively, compared with the control treatment, and the combination of organic and inorganic treatment (TFO and TMO) had a better effect on improving the aggregate crushing resistance. With the application of soil conditioners, the reclaimed soil DLVO force and net resultant force gradually decreased, and the order of magnitude was TFO < TMO < TO < TF < TM < CK, indicating that the application of organic and inorganic soil conditioners enhanced the van der Waals attractive force and net attractive force between reclaimed soil particles, and reduced the net repulsive force between particles. The theoretical calculation results of the reclaimed soil internal force well explain the experimental results of aggregate stability against crushing, and the relationship between aggregate crushing strength and net resultant force is exponential (p < 0.01). Generally speaking, the soil conditioners increase the net attractive force between particles, reduce the possibility of violent crushing of aggregates due to the increase of electric field intensity and improve the aggregate structural stability, among which the combined application of organic and inorganic soil conditioners has a better improvement effect. The results of this study will lay a theoretical foundation for clarifying the improvement of different soil conditioners on the reclaimed soil structural stability and erosion resistance.

Comparative analysis on effectiveness of crushed aggregate and scoria gravel as columnar reinforcement material under raft foundation

Scoria gravel is widely used as stabilizer material in road construction and concrete works. However, limited information regarding its performance as columnar stabilizing material has been reported. This study hence explores suitability of scoria gravel as columnar stabilizing material in compressible soils. Besides, comparative analysis to evaluate effectiveness of crushed aggregate columns (CAC) and scoria gravel columns (SGC) in improving deformation characteristics of clay ground was carried out by using finite element based numerical analysis. Compressible massive clay reinforced with CAC and SGC under building load was modeled to simulate the settlement attributes of the foundation material. The conducted numerical model considered both the floating and end bearing gravel columns. Finding of the study revealed that provision of floating SGC performs better than the crushed aggregate stone column in lessening vertical deformation of the clay foundation. However, the floating SGC did not result in significant improvement in lessening lateral deformation in comparison with group of CAC. Hence, application of granular piles as columnar reinforcing material in purely clay soil is not as effective as SGC from settlement reduction view point. Contrarily, the bridging effect of end bearing crushed aggregate pile is more pronounced than that of scoria gravel as the column material directly gets contact with stiff substratum. It can also be inferred from finding of the study that application of granular pile group suits well compressible grounds where stiffer strata is situated immediately at column tip.

Machine learning models for predicting unconfined compressive strength: A case study for Precambrian basement complex rocks from Ado-Ekiti, Southwestern Nigeria

This study investigates the applicability of four distinct machine learning (ML) models – Random Forest (RF), Relevance Vector Machine (RVM), Support Vector Machine (SVM), and Artificial Neural Network (ANN) - for predicting the unconfined compressive strength (UCS) values of Precambrian basement rocks. The models employ input parameters such as rock aggregate index (Aggregate Crushing Value (ACV), Aggregate Impact Value (AIV), and Los Angeles Aggregate Value (LAAV)) and mechanical test index values (Schmidt Hammer Rebound Number (SHR) and Point Load Strength Index (IS(50)) for prediction purposes. Additionally, a multilinear regression (MLR) model was implemented to compare the predictive performance of the ML models against the traditional linear regression model. The developed models were validated using performance metrics such as Mean Absolute Error (MAE), Root Mean Squared Error (RMSE), and Adjusted R-Squared (Adj.R2). The Friedman statistical test was also employed to investigate the significance of the differences in the performance of the models. The results indicate that all the models performed well and showed better predictive performance compared to the MLR model during both the training and testing phases, except for the ANN model, which exhibited slightly poorer performance than the MLR model in the testing phase. However, the SVM model demonstrated the best predictive accuracy among all the models with MAE, RMSE, and Adj.R2 scores of 0.76 and 1.45; 1.16 and 1.8; 0.98 and 0.90, respectively, for the training and testing phases. The difference in the performance of the predictive models was statistically significant, as revealed by the Friedman statistical test. A feature importance analysis was conducted to verify the significance of each input parameter, revealing that all input features had a positive effect on the output of all the models. However, IS(50) had the most significant impact on the models.

Petrographic and geotechnical evaluation of Ogwashi-Asaba ferruginised sandstone, Niger Delta, as aggregates for construction

The need to reduce the high cost of long-distance haulage of aggregates has necessitated the search for suitable aggregates close to the construction site(s). The petrographic and geotechnical properties of Ogwashi-Asaba ferruginised sandstone were investigated to ascertain their utility potential. The petrographic, physical, and mechanical properties investigated include; the modal composition, texture, packing density, degree of interlocking of grains, specific gravity (SG), water absorption capacity (WAC), aggregate crushing, aggregate impact, and Los Angeles abrasion values. Which were determined according to BS and ASTM standards. The percentage of iron (Fe2O3) was determined by fusion inductively coupled plasma (FUS-ICP). The results show the mean value of quartz as 59.4%, sub-angular to angular shape, medium, medium-coarse, and coarse-grained with sutured, concavo-convex, and long contacts. The mean values for the S.G., WAC, ACU, AIV, and LAAV are 2.68, 4.80%, 53.76%, 41.99%, and 50.12% respectively, and 17.8% for Fe2O3. The medium-grained sandstone is preferred because of its relatively higher quartz percentage, more sutured contacts, and a greater degree of grains interlocking. Fe2O3 in sandstone has a strong negative correlation with AIV and ACV. This implies that Fe2O3 in sandstone will influence strength in sandstone thereby enhancing its utility potential. Though the ferruginised sandstone may be suitable as base course material in high-density traffic roads, it can be utilized as sub-grade and sub-base materials in low-density traffic roads.

ASSESMENT OF THE POSSIBILITY OF FOAM GLASS APPLICATION IN THE SUB-BALLAST LAYERS

The paper investigates whether foam glass could reduce the structural thickness of the protection layer in the construction of the railway track (saving of natural materials – crushed aggregate) and, at the same time, also provide sufficient thermal protection of the frost-susceptible subgrade surface. It also discusses whether the incorporation of foam glass would have a relevant effect on the increase of the deformation resistance of the railway track structure at the level of the sub-ballast upper surface. Following these assumptions, the paper presents the results of experimental measurements of the deformation resistance of the modified structural composition of the sub-ballast layers (with an embedded foam glass layer) and their comparison with the results determined on a structure with a standard composition of the sub-ballast layers (crushed aggregate sub-ballast layer/protective layer). Also, numerical and mathematical analysis of the influence of the built-in thermal insulation foam glass layer on the reduction of the structural thickness of the protective crushed aggregate layer in terms of the effect of climatic factors is conducted in the paper. The mathematical model, developed by the research, provides the possibility of continuous monitoring of the change in the railway track structure freezing depending on climatic characteristics.

Concrete produced with recycled concrete aggregate exposed to treatment methods

Some techniques, such as removing the adhered mortar particles and surface modification of recycled aggregates, have been investigated in an attempt to improve their quality. This study intends to evaluate the performance of concrete containing recycled concrete aggregate (RCA) subjected to Portland cement treatment and grinding, as partial replacement of coarse crushed aggregates at 20 % and 50 %. It became evident that using RCA in the mix of new concrete has a negative impact on its properties. However, it was found that the use of treatments such as mechanical grinding and a two-stage mixing approach (TSMA) with 25 % Portland cement in the mix were viable technical alternatives for improving these aggregates. The test results indicated that, due to the efficiency of the grinding treatment (T1), the CRCA50-G mix presented a higher compressive strength than CRCA20-G and, when treatment TSMA (T2) was used, both the CRCA20-G-TS25 and CRCA50-G-TS25 mixes outperformed the conventionally mixed concrete, resulting from a superposition of effects. The splitting tensile strength results were satisfactory when replacing up to 50 % and the use of treatment T2 in concrete with varying RCA did not present a significant effect on this property. The two-stage mixing method applied together with grinding aid in the densification of the porous microstructure, which improved concrete resistance against carbon dioxide diffusion and chloride ingress, beyond improvements in water absorption by capillarity, which enabled greater use of RCA. It was concluded that the use of treatments like these improves the mechanical properties and durability of concrete produced by RCA, mainly when these treatments are used simultaneously. In general, using a properly prepared RCA can be produced concrete with physical and mechanical properties besides performance characteristics.

Influence of Basalt Aggregate Crushing Technology on Its Geometrical Properties-Preliminary Studies.

The use of mineral aggregates is related to the increasing demand in construction, railway and road infrastructures. However, mineral aggregates can appear to be of variable quality, directly affecting their suitability for respective earthwork applications. Since the production of mineral aggregates should ensure the standardized, high-quality requirements of the final product, rock-crushing mechanisms should be investigated in a detailed manner. In this context, the aim of the present study is to evaluate and analyze the geometric parameters of basalt aggregates as a result of several rock comminution processes. Basalt aggregates from two deposits in Poland were used in the study. The samples are differentiated regarding both lithological variances, mineral composition as well as the host rock's tuff content. The rock comminution processes were conducted using two types of crushers, namely the laboratory-scale jaw and cone crushers. The feed for crushing was designed based on the original geometric grain composition and the separated feed in the form of flaky and non-flaky particles. The crushability test results demonstrated that the interparticle compression in the jaw crusher resulted in finer products compared to the one in the cone crusher. It was also observed that the flakiness and shape indexes decreased after crushing, both in the feed with the original geometric composition of the grains and those with flaky and non-flaky particles. Nevertheless, a higher flakiness index was obtained after the crushing of non-flaky particles and a lower one after the crushing of flaky particles. The flakiness index for grains below 16 mm after the crushing process was less than 10%, which indicates a more favorable result compared to the original feed. In addition, it was shown that flaky and non-cubical particles were accumulated in the finest (below 8 mm) and coarsest (above 20 mm) fractions in jaw and cone crushing processes, receiving flakiness and shape indexes ranging up to 80-100%. Finally, it was also observed that the lithological variances of the feed material have a significant impact on the particle size distribution of the product. More profoundly, basalt aggregates with a higher tuff content and weathering degree have a higher degree of crushing. The present study, in this context, provides accurate and satisfying information on understanding the crushing mechanisms of two important crushing equipment as well as their rock-crusher interactions.

Synergic Influence of River Gravels and Crushed Aggregates on the Mechanical Properties of Concrete

Synergic Influence of River Gravels and Crushed Aggregates on the Mechanical Properties of Concrete

Characteristic of Polymeric Lightweight Aggregate with Coal Fly Ash and Epoxy Resin for Manufacturing the Lightweight Concrete

Concrete is an essential element and is widely used in various industrial construction works. However, concrete is weak in its specific gravity range of 2200 – 2500 kg/m³. Using lightweight aggregates is one way to reduce the weight of concrete. In Indonesia, the availability of coal fly-ash (CFA) is easy to obtain and abundant, while the utilization rate is still low. To overcome this problem, CFA mixed with epoxy resin (ER) is used as a binder to manufacture polymer lightweight aggregates (PLA). The manufacturing process uses a simple mixing method using three different compositions. The ratio composition of coal fly-ash and epoxy resin proposed in this study are 90:10 (PLA_90:10), 80:20 (PLA_80:20), and 70:30 (PLA_70:30). From the results of testing the compressive strength and specific gravity of the three aggregate compositions, it was found that PLA_70:30 had a compressive strength of 74.60 MPa and a specific gravity of 1668 kg/m³ at an aggregate age of 28 days. The aggregate microstructure is shown by scanning electron microscope (SEM) photo of each composition. The greater the composition of the epoxy resin on the lightweight polymer aggregate, the better the bond between the aggregate particles. The coal fly-ash is improperly bound and the aggregate becomes more fragile when there is less epoxy resin used. Furthermore, PLA_70:30 aggregate, which has become crushed aggregate, is inserted into a lightweight concrete mixture with a design quality of f'c = 17.5 MPa, following the requirements for lightweight concrete quality. The result is lightweight concrete with a compressive strength of 18.38 at 28 days, and specific gravity that varies between 1918.87 kg/m³ - 1928.93 kg/m³. According to the ASTM, the results of the compressive strength and specific gravity tests show that PLA_70:30 meets the standards specified as lightweight aggregates for lightweight structural concrete.

Effect of aggregate origin on freeze/thaw resistance of self-compacting concrete with and without a de-icing agent

Freezing and thawing cycles, with or without de-icing agents, are the principal causes of concrete structure degradation during the winter. This paper explores the effects of aggregate type on the level of degradation of self-compacting concrete (SCC) due to freeze-thaw (f/t) action. Natural river (NRA) and/or natural crushed (NCA) aggregate, as well as the recycled aggregate of known (RCA-N) and unknown provenance (RCA-A), were employed to produce six different SCC mixtures. The temperature, density, air content, and consistency were determined for fresh concrete, while compressive strength, water absorption by gradual immersion and vacuuming, and frost resistance with and without de-icing salts were tested for hardened concrete. Even though all tested concretes have met the criteria for frost resistance with and without the de-icing salts, it was found that the type of aggregate has a noticeable influence on it. The type of natural aggregate has little effect on SCC frost resistance, but it does influence its behavior when frost and salt are present at the same time. In f/t conditions, RCA-N can be used the same way as natural aggregate, while RCA-A causes the biggest frost resistance reduction. However, both RCAs are not recommended for application in conditions of simultaneous frost and salt impacts.

Comparative Study of Conventional Concrete and Green Concrete Made Of Fly Ash, Recycled Red Bricks and Recycled Crushed Aggregates

Abstract: Because cement is a binding substance, it is commonly utilized in building. Cement production accounts for 8-10% of total world CO2 emissions.. This greenhouse gas is produced when lime stone and clay are smashed and heated to high temps in mills. Concrete contributes significantly to greenhouse gas emissions and complicates waste disposal. Therefore the use of recycled materials in concrete has become necessary. A Danish scientist by the name of Dr. WG made the initial discovery of green concrete in 1998, which has been a groundbreaking idea in the history of concrete. The term "green concrete" refers to a type of concrete that includes recycled components that are environmentally friendly, has greater performance, and have a longer life cycle .By utilizing industrial ecology, green chemistry, as well as the structural behaviour and organisation of cement nano-particles in the mix for higher performance, researchers have made numerous attempts to find alternatives that can significantly reduce high energy consumption and environmental impacts during the fabrication process of cement. It is also Observed that the increase in RHA to 20% i.e (Mix 2) & not changing the other two components, leads to the decrease in the strength, this is because of much replacement of Materials which effects the binding Factor of Cement & Aggregates. The Main Advantage of RHA replacement by 10% shows high strength growth by 33% when compared to conventional Concrete on 28th Day. In this assignment, we'll conduct tests on both freshly laid concrete and hardened concrete, including a compressive strength test. In this project, the typical components of concrete, such as F.A. and C.A., are substituted by powdered clay brick and crushed glass waste, respectively. Cement is also partially replaced with rice husk ash. M20 is the concrete grade that was employed