Concrete Mixtures Research Articles

Workability, mechanical, durability, and microstructural investigation of sustainable concrete utilizing secondary treated wastewater, fly ash, and sodium nitrite

ABSTRACT This study explored the use of secondary treated wastewater (STW) from three secondary-level wastewater treatment plants, along with fly ash (FA) and sodium nitrite (SN), to produce sustainable concrete, comparing it to concrete made with tap water. Key properties examined included workability (slump cone), strength (compressive, split tensile, and flexural), and durability (rapid chloride permeability and efflorescence). Scanning electron microscopy (SEM) analysis was performed to investigate the concrete's microstructure. The results indicated that FA and SN content had a notable influence on the workability, mechanical strength, and durability of the concrete mixtures. However, the type of water (STW or tap water) used in the concrete preparation showed no significant impact. Durability tests revealed that the penetrability of the mixtures ranged from low to moderate, signifying good quality, and no efflorescence was observed. Ultimately, the study concluded that concrete made with STW, when supplemented with 10% FA and 2% SN, demonstrated comparable performance to that made with tap water across key properties, offering a viable option for sustainable concrete production.

Enhancing Concrete Properties with Banana Stem Juice Additive: A Study on Workability and Compressive Strength

Additives are integral components of modern concrete mixing materials. This study aimed to evaluate the workability and compressive strength of concrete incorporating banana stem juice as a natural additive (BSJA). A laboratory experiment was conducted to assess the impact of BSJA on concrete properties. Concrete mixtures with a ratio of 1:2:4 were prepared both with and without BSJA. A total of 36 cube specimens were created with varying percentages of banana stem juice, and their compressive strengths were measured. The results indicated that the inclusion of banana stem juice affected the concrete properties. On the 21st day, the compressive strength of the concrete without BSJA was 27.67 N/mm², compared to 29.67 N/mm² for 5% BSJA, 16.33 N/mm² for 10% BSJA, and 8.00 N/mm² for 15% BSJA. The slump values recorded were 15 mm for 0% BSJA, 20 mm for 5% BSJA, 45 mm for 10% BSJA, and 65 mm for 15% BSJA. The average compressive strengths of concrete specimens with 5% BSJA at 14 days (23.3 N/mm²) and 21 days (29.2 N/mm²) were higher than those of specimens without BSJA. Over the 14 and 21-day periods, specimens with BSJA consistently showed higher compressive strengths compared to those without. These results suggest that 5% BSJA enhances the compressive strength properties of concrete.

Study of Structural Defects Evolution in Fine-Grained Concrete Using Computed Tomography Methods

Introduction. When studying composite materials for construction purposes, it is needed to consider the mechanisms of formation of the structure and properties of modern concretes in the process of strength development. In studies of modern composite materials based on cement binder, there is no information about the development of structural defects and destruction of the material at the initial stages of strength development. This information can be obtained using X-ray computed tomography, a promising method of nondestructive testing of the state of the material. Therefore, the objective of this work was to study the formation and propagation of cracks in samples of fine-grained concrete with different fractional composition of sand due to natural processes of cement shrinkage, as well as the mechanics of destruction of samples of modified fine-grained concrete when applying a compressive load at the early stages of strength development. Materials and Methods. The study used fine-grained concrete mixtures of three compositions with different sand gradation. The tomography samples were made by placing fresh mixtures in polymer cylindrical containers. Tomography of the samples immediately after manufacture, as well as after 8 and 51 days, was performed in a YXLON Cheetah microfocus X-ray machine. The composition with two-fraction sand was modified by mechanical activation of the components, 20×20×20 mm cube samples were made. Further, compression tests were performed at the Instron installation after 3 and 7.5 hours, and then — tomography of the destroyed samples.Results. It was established that the destruction of contact zones depended on the ratio of the size of the fractions. In the presence of a bulk of coarse sand grains in concrete, the destruction of contact zones was more pronounced and had a main mode. When using fine or polyfraction sand, contact zones were destroyed locally and had a visually smaller area. The images of the destroyed modified sample, tested 3 hours after manufacturing, showed clear cracks and indents on the edges, which indicated the elastic-plastic nature of the destruction. In 7.5 hours, the edges of the sample upon destruction were covered with a network of small cracks; inside the sample there were also numerous cracks and microcracks, which indicated brittle fracture. Based on the obtained images of the deformed structure of modified concrete, the mechanism of transition from elastic-plastic destruction of the material to brittle one was clearly visible.Discussion and Conclusion. The studied dependences of the influence of the size of fine aggregate on the mechanisms of formation and propagation of structural defects contribute to the theory of the processes of destruction of fine-grained concretes. The results obtained prove the prospects of using X-ray computed tomography as a method of nondestructive testing of the internal structure of fine-grained concrete, including at the early stages of strength development.

Rapid Assessment of Sulfate Resistance in Mortar and Concrete.

Extensive research has been conducted on the sulfate attack of concrete structures; however, the need to adopt the use of more sustainable materials is driving a need for a quicker test method to assess sulfate resistance. This work presents accelerated methods that can reduce the time required for assessing the sulfate resistance of mixtures by 70%. Class F fly ash has historically been used in concrete mixtures to improve sulfate resistance. However, environmental considerations and the evolving energy industry have decreased its availability, requiring the identification of economically viable and environmentally friendly alternatives to fly ash. Another challenge in addressing sulfate attack durability issues in concrete is that the standard sulfate attack test (ASTM C1012) is time-consuming and designed for only standard mortars (not concrete mixtures). To expedite the testing process, accelerated testing methods for both mortar and concrete mixtures were adopted from previous work to further the development of the accelerated tests and to assess the feasibility of testing the sulfate resistance of mortar and concrete mixtures rapidly. This study also established criteria for interpreting sulfate resistance for each of the test methods used in this work. A total of 14 mortar mixtures and four concrete mixtures using two types of Portland cement (Type I and Type I/II) and various supplementary cementitious materials (SCMs) were evaluated in this study. The accelerated testing methods significantly reduced the evaluation time from 12 months to 21 days for mortar mixtures and from 6 months to 56 days for concrete mixtures. The proposed interpretation method for mortar accelerated test results showed acceptable consistency with the ACI 318-19 interpretations for ASTM C1012 results. The interpretation methods proposed for the two concrete sulfate attack tests demonstrated excellent consistency with the ASTM C1012 results from mortar mixtures with the same cementitious materials combinations. Metakaolin was shown to improve sulfate resistance for both mortar and concrete mixtures, while silica fume and natural pozzolan had a limited impact. Using 15% metakaolin in mortar or concrete mixtures with Type I/II cement provided the best sulfate resistance.

Enhanced Impact Strength of Ultra-High-Performance Concrete Using Steel Fiber and Polyurethane Grout Materials: A Comparative Study

This study examined the impact properties of ultra-high-performance concrete (UHPC) mixtures with steel fiber (SF) and retrofitted with polyurethane (PU) grouting using repeated drop-weight tests. Micro-steel fiber was added to UHPC mixes from 0 to 3% Vf, and PU grouting overlays of 5 mm, 10 mm, and 15 mm were applied. Digital image correlation (DIC) was used to analyze failure modes. The results showed significant impact durability and energy absorption improvements with increased SF content and thicker PU overlays. UHPC-15PU exhibited 363% and 449% higher first crack and failure strengths than UHPC-5PU. DIC analysis confirmed the failure patterns of the U-shaped UHPC specimen under impact load conditions.

Study on the Flexural Performance of Ultrahigh-Performance Concrete-Normal Concrete Composite Slabs.

In recent years, there have been an increasing number of examples of using ultrahigh-performance concrete (UHPC) as a pavement layer to form an ultrahigh-performance concrete-normal concrete (UHPC-NC) composite structure to improve the bearing capacity of bridges. In order to study the flexural performance of this kind of structure, this research studied the flexural performance of UHPC-NC composite slabs, with UHPC in the compression zone, using experiments, numerical simulation, and theoretical analysis. The results showed the following. Firstly, after the UHPC-NC interface had been chiseled, there was no obvious slip between the two materials during the test, and the composite plate was always subjected to synergistic stress. Secondly, the composite slabs in the compression zone of the UHPC were all subjected to bending failure, and the cooperative working performance of each part under the bending load was good, indicating that the composite slab had a unique failure mode and a high bearing capacity. Thirdly, increasing the thickness of the UHPC significantly improved the flexural capacity of the composite plate, and the maximum increase was about 15%. Increasing the reinforcement ratio of the tensile steel rebars also had an increasing effect, with a maximum increase of about 181%. Finally, the proposed formula for calculating the flexural capacity of composite slabs with UHPC in the compression zone could accurately predict the bearing capacity of said slabs. The calculated results were in good agreement with the experimental values, and the error was small.

Condition assessment of concrete structures using automated crack detection method for different concrete surface types based on image processing

In the inspection and diagnosis of concrete construction, crack detection is highly recommended in the earliest phases to prevent any potential risks later. However, the flaws in concrete surfaces cannot be reliably and effectively identified using traditional crack detection techniques. The suggested algorithm is a supportive tool for agents or authorities to use in crack detection mechanisms to monitor and assess the current condition of buildings or bridges. The researchers aim to establish an intelligent model for automatic crack detection on different concrete surfaces based on image processing technology. Three different concrete surfaces—bridge decks, walls, and concrete cubes—are used to test the model. A subset of the public dataset of bridge decks and walls from SDNET (2018) and 150*150*150 mm of concrete cubes taken from the material laboratory of the faculty of engineering at Ain Shams University are applied to the model. The model F1-score measures are 98.87%, 97.43%, and 74.11% for detecting cracks in bridges, walls, and concrete cubes, respectively. The validation of the applicability of the suggested novel approach is based on a comparison with recent methods for crack recognition. The contribution of this study is that it could be applied to detect cracks efficiently on three different types of concrete surfaces, including uneven concrete surfaces, random noise, voids, dents, colour changes, and stain marks. The proposed method is transparent in its workflow and has a lower computational cost compared with deep learning frameworks. Thus, the outcomes of this model demonstrate its effectiveness in concrete defect field investigation.

Experimental and numerical study on flexural performance of ultra-high performance concrete frame beams reinforced with steel-FRP composite bars

This paper presents the bending tests of four ultra-high performance concrete (UHPC) frame beams and one normal strength concrete (NSC) frame beam, all reinforced with steel-FRP composite bars (SFCBs). A comprehensive analysis was carried out, encompassing evaluation of the failure mode, crack propagation, bearing capacity, deformation, strain response, and plastic rotational capacity of the frame beams. Investigating the effects of concrete type, reinforcement type, and beam-end reinforcement ratio on the flexural performance of the frame beams was a key aspect of this study. A three-dimensional finite element (FE) model of the frame beam was established and rigorously verified. The developed model enabled a detailed parametric analysis involving the steel ratio, the yield strength of the inner core steel bar, the elastic modulus of the FRP, and the ultimate tensile strength of the SFCB. The results indicated a consistent failure mode of all frame beams: crushing of concrete at the beam-end, initiating a sequence of plastic hinge occurrence starting at the beam-end and then progressing to mid-span. The substitution of normal strength concrete with UHPC significantly enhanced various aspects of the frame beams, including the flexural capacity, deformation, ductility, ultimate energy dissipation, and plastic rotational capacity, while inhibiting the generation and expansion of cracks. Notably, the plastic rotation angle of SFCB-UHPC frame beams was 4.9 times greater than those of steel-UHPC frame beams, emphasizing the effectiveness of SFCB in enhancing the beam-end plastic rotational capacity. A decrease in the beam-end reinforcement ratio significantly reduced the flexural capacity, ultimate energy dissipation, and beam-end plastic rotational capacity, while improving ductility. Additionally, the study established a formula for calculating the equivalent plastic hinge length, utilizing the relative compressive zone height and effective section height of the beam-end controlling section as variables, which demonstrated good alignment between predicted and experimental results.

Effect of rebar ratio, rebar diameter, cover thickness, and fiber shape on flexural and cracking behavior of rebar-reinforced UHPC beams

This study investigated the flexural and cracking behavior of seven ultra-high-performance concrete (UHPC) rectangular beams, reinforced with steel rebars and 2 % hooked-end steel fibers (by volume), under four-point bending. Their failure modes, load-displacement responses, crack spacings, and load-crack width relationships were analyzed and compared with five previously studied UHPC beams reinforced with steel rebars and 2 % straight steel fibers. Key experimental variables included rebar ratio ranging from 1.21 % to 1.99 %, rebar diameters of 16 mm and 20 mm, and concrete cover thicknesses of 20 mm, 30 mm, and 40 mm. The results revealed that all UHPC beams exhibited typical flexural failure, characterized by yielding of the steel reinforcement, multiple cracking, the formation of one localized main crack, and mild crushing of the UHPC. Increasing the rebar ratio significantly enhanced the post-cracking stiffness and load-carrying capacity, while having minimal effect on their cracking load. Rebar diameter, concrete cover thickness, and fiber shape showed negligible influence on flexural performance during the elastic and crack development phases but had varied effects during the yielding phase. Furthermore, a higher rebar ratio, reduced concrete cover thickness, and the use of hooked-end steel fibers improved the beams’ resistance to cracking, while the rebar diameter had a limited impact. A unified average crack spacing model for UHPC beams reinforced with steel rebars and with straight fibers or hook-end fibers was proposed, and analytical models were developed to predict crack width. These predictions aligned well with experimental results from this study and other prior research.

Finite Element Analysis of Pre-Stressed Ultra High-Performance Concrete (UHPC) Girders

Finite Element Analysis of Pre-Stressed Ultra High-Performance Concrete (UHPC) Girders

Shear behavior of RC beams with openings under impact loads: unveiling the effects of HSC and RECC

Incorporating transverse openings in reinforced concrete (RC) beams reduces their load-bearing capacity and stiffness, making them prone to premature failure. This highlights the need for a more nuanced understanding of their behavior to ensure structural integrity, particularly under impact loads. This research delves into a relatively unexplored area, investigating the impact performance of RC beams containing openings through numerical analysis. By comparing different concrete types, the study seeks to identify optimal materials for such applications. The concrete damage plasticity model, accounting for strain rate effects, will be employed to simulate the material behavior of normal-strength concrete (NSC), high-strength concrete (HSC), and a novel eco-friendly alternative: rubberized engineered cementitious composite (RECC). RECC incorporates recycled tire rubber as a partial substitute for traditional concrete aggregates, offering a sustainable solution while mitigating environmental hazards associated with waste tire incineration. The finite element models are validated with experimental results, accurately predicting ultimate capacities, failure modes, and post-cracking response in RC beams (with/without openings) under static/impact loads. A comprehensive parametric analysis investigates the effects of concrete strength, impact energy, impactor mass, drop height, and opening location, providing valuable insights into how these factors influence the impact behavior under drop-weight testing. The results reveal that openings in RC beams under impact loads significantly reduce strength and stiffness, with detrimental effects observed for dual shear-zone openings. Surprisingly, a small mid-span opening can enhance impact response. HSC beams exhibit lower initial displacements but higher residual values, while RECC improves overall behavior in beams with openings, reducing maximum displacement and promoting energy dissipation for improved post-impact recovery.

Effect of concrete strength on the seismic performance of circular reinforced concrete columns confined by basalt and carbon fiber-reinforced polymer

This paper investigated the effect of concrete strength on the seismic performance of circular reinforced concrete (RC) columns confined by basalt and carbon fiber-reinforced polymer (BFRP and CFRP). Eight confined columns and four control columns were tested under a low cyclic lateral load. The variables in the test included concrete compressive strength (i.e., 22.4 MPa, 31.4 MPa, 42.5 MPa and 57.8 MPa) and FRP type (i.e., basalt and carbon fiber). The test results demonstrated that all the columns exhibited flexural failure after confinement. The strength, ductility and energy dissipation capacity of the confined columns were effectively enhanced. With the same confining stress, the peak loads of the BFRP- and CFRP-confined columns were nearly the same. However, the BFRP-confined columns with low and moderate concrete strength showed larger ductility and energy dissipation capacity compared with the CFRP-confined counterparts, and these capacities of the CFRP-confined column with a concrete strength of 57.8 MPa were slightly better than those of the BFRP-confined equivalent. This showed that the FRP jackets with larger modulus had better confinement effect on the columns with higher concrete strength. Finally, formulas for calculating the load carrying and ductility capacities of different FRP-confined circular RC columns were proposed based on the experimental results.

Optimizing foaming agent concentration and recycled fine aggregate content to enhance mechanical and durable properties of foam concrete mixes

This research explores the impact of using recycled fine aggregates from construction and demolition wastes (CD-RFA) through the replacement of natural sand in proportion of 0 %, 10 %, 30 %, 50 %, 70 %, and 100 % for making foam concrete mixes. Protein based foaming agent was diluted with water in ratios of 1:20, 1:40 and 1:60. It was found that with the increase in the proportion of recycled fines, the porosity, sorptivity and water absorption of foam concrete mixes increases significantly. At the same time, a downward trend in the mechanical characteristics was noted. However, the obtained values of compressive strength, flexural strength, and split tensile strength of 22.35, 5.68 and 2.27 MPa were found to be well within the ACI 523 R 2014 recommended ranges of 8–22, 3–6.4 and 1–2.2 MPa, respectively. Hardened density, abrasion resistance, and resistance to sulphates and chlorides attack showed perceptible decline. The present study recommends the replacement of natural sand up to 50 % with CD-RFA. The foam concrete mix prepared using recycled fines will help clearance of a large quantities of CD wastes, thereby benefiting the environment and ecology.

Exploring the synthesis effects of glazed hollow beads and polypropylene fibers on the strength retention of ultra-high performance concrete after fire exposure using X-Ray computed tomography

Ultra-high performance concrete (UHPC) is a cementitious composite characterized by its ultra-high durability attributes and mechanical properties. It is primarily used in large-span and ultra-high-rise structures for control of deflections. However, its mechanical properties decrease significantly after exposure to fire or high temperatures, limiting its applicability. In this paper, the exceptional characteristics of glazed hollow beads (GHBs), including their lightweight, high strength, and thermal insulating properties, were utilized to develop a novel fire-resistant UHPC. UHPC specimens with varying GHB content were prepared, and the corresponding mass loss, thermal performance degradation, and compressive strength after exposure to high temperatures were evaluated. The test results demonstrate that adding GHBs can improve the fire resistance of UHPC. With 40 % (by volume) GHB addition, the resulting UHPC could retain 47 % of its original compressive strength even after exposed to 800°C. The effects of temperature on the UHPC microstructure were analyzed using scanning electron microscopy and X-ray computed tomography. It was found that the combination of polypropylene fibers and GHBs created a release channel for vapor pressure within the concrete, thereby enhancing its high-temperature resistance. This study proposes a practical solution to enhance the high-temperature resistance of UHPC.

Investigation of self-compacting concrete utilizing different supplementary pozzolanic materials for cement replacement

This study enhances self-compacting concrete (SCC) properties by adjusting the mix design, reducing the water-to-cement ratio, and adding permeability-reducing admixtures (GGBS, fly ash, silica fume, bentonite). Different admixture proportions were tested to improve mechanical characteristics. Four SCC mixtures were formulated, varying GGBS and fly ash (0-70%) and silica fume and bentonite (0-20%). Auromix 300 plus (0.6% by weight of cement) was used as a chemical admixture. Strength properties (compressive, flexural, split tensile, elastic modulus) were evaluated on specimens cured normally for 28 days, then in NaCl for 56-112 days. Optimal mixtures were found: GGBS 30% for compressive strength, bentonite 10% for flexural and split tensile strength. Results indicate increased strength and reduced porosity by incorporating these materials.

Self-heating curing and its influence on self-sensing properties of ultra-high performance concrete with hybrid stainless steel wires and steel fibers

This study aims to develop ultra-high performance concrete (UHPC) with self-heating curing and self-sensing properties by incorporating hybrid stainless steel wires (SSWs) and steel fibers (SFs) to advance the safety, function/intelligence, and resilience of infrastructures. 0.2 vol% SSWs with micro diameter can already form overlapped conductive network inside UHPC together with SFs to decrease the electrical resistivity and enhance high-efficiency conversion rate from electric energy to Joule heat. As 20 W input power is applied and sustained, the electrical resistivity of UHPC with hybrid 0.2 vol% SSWs and 1.6 vol% SFs (W02F16) first decreases from 45.1 Ω∙cm to 8.3 Ω∙cm and then to 7.88 Ω∙cm due to the field emission effect and the microscopic thermal expansion of SSWs. The surface temperature of W02F16 specimens reaches 78.6 ℃ for 73 minutes self-heating with an average heating rate of 0.821 ℃/min and a temperature difference lower than 11.6 ℃. Meanwhile, the fractional change in electrical resistivity and sensitivity corresponding to peak flexural stress of W02F16 after 8 h self-heating curing can reach 58.3 % and 3.22 %/MPa, higher 2.1 and 3.6 times than that after 28 d standard curing. Furthermore, self-heating curing UHPC composites at 28 d possesses more stable and sensitive self-sensing performance especially within pre-peak flexural stress period, resulting from the coarsening effect of direct current on SSWs’ interface to regulate and control of conductive pathway in concrete. This is the innovative demonstration that self-heating curing process can endow hybrid SSWs and SFs reinforced UHPC with stable/high self-sensing sensitivity to rapidly fabricate multifunctional/smart infrastructures with the abilities of structural health monitoring, snow and ice self-melting, and indoor heating.

Improving flexural response of rubberized RC beams with multi-dimensional sustainable approaches

This research presents a sustainable solution to waste tire disposal and raw material depletion by incorporating recycled rubber into concrete mixtures. To mitigate the reduction in mechanical properties, a novel slag pretreatment of rubber particles with controlled temperature is proposed. The study also investigates the effects of pouring concrete in layers with rubberized concrete (RuC) in tension side and normal concrete in compression side, as well as evaluating the use of GFRP compared to conventional steel, thereby introducing multiple innovative dimensions to enhance structural performance. The experimental study included a total of 27 specimens, consisting of normal concrete, untreated rubberized concrete, and treated rubberized concrete mixtures with 15 % rubber content. The study investigated both compression and tension mechanical properties of the concrete mixtures and assessed the flexural response of reinforced concrete (RC) beams. Parameters explored included rubber treatment, utilization of steel and GFRP as tensile reinforcement, and layered concrete pouring. Subsequently, a numerical study was conducted to address the impact of reinforcement ratio and layer depth on the behavior of slag-treated rubberized RC beams. The findings reveal a significant recovery of concrete compressive strength by 23 %, along with a 28 % enhancement in toughness and a 17 % increase in splitting tensile strength attributed to the application of slag treatment to rubberized concrete. The effect of rubber treatment was more pronounced in GFRP RC beams, as they showed similar load capacity as normal concrete. Furthermore, utilizing layered concrete beams with a 67 % depth of slag-treated RuC showed a comparable load capacity to normal RC beams, demonstrating only a 1 % reduction for steel-reinforced beams and a 2.4 % improvement for GFRP-reinforced beams. Notably, the numerical model emphasized this outcome and suggested that increasing the layer depth to 72 % of slag-treated depth displayed better performance.

A study on fresh, mechanical, and thermal properties of limestone calcined clay cement (LC3) blended with cementitious materials

In light of environmental concerns about cement manufacture, limestone and thermally activated kaolinitic clays are being explored as supplementary cementitious materials with the potential to reduce CO2 emissions and energy usage. The use of calcined clay and limestone for clinker replacement to create a tertiary blend called limestone calcined clay cement (LC3) is one of the most promising emerging technologies for meeting environmental requirements. This paper reports on the evaluation of the fresh-state and hardened properties of cementitious pastes and self-compacting concretes (SCC) prepared using the concrete equivalent mortar method made with LC3 systems containing 30%, 35%, and 40% metakaolin (LC-30MK, LC-35MK, and LC-40MK) in comparison with ordinary Portland cement (OPC). Paste and concrete equivalent mortar specimens were prepared to investigate water demand, setting time, and workability (mini-slump flow test). Also, the compressive strength and drying shrinkage after 7 and 28 days, as well as thermal conductivity after one year of curing, were examined. The obtained results showed that the incorporation of metakaolin resulted in increased water demand to reach normal consistency. The setting time of LC3 mixtures also increased, while the same workability behavior was observed for all mixtures. LC-30MK can provide compressive strength that is comparable to OPC, especially after the first few days of curing. However, the compressive strengths of LC-35MK and LC-40MK are lower than those of OPC. Nevertheless, they demonstrate noteworthy strength characteristics. All LC3 mixtures exhibited relatively low drying shrinkage and reduced thermal conductivity compared to the OPC mixture.

AN EXPERIMENTAL INVESTIGATION ON EFFECT OF CONCRETE BY USING PARTIAL REPLACEMENT OF EGG SHELL POWDER IN CEMENT ALONG WITH E-WASTE AS COARSE AGGREGATE

The imagination of a world without concrete isimpossible. It is a soul of infrastructures. Concrete is necessary to gain strength in structures. Conventional concrete, which is the mixture of cement, fine aggregate, coarse aggregate and water, needs curing to achieve strength. Concrete is a counterfeit material in which the totals both fine and coarse are reinforced together by the bond when blended with water. The solid has turned out to be so prominent and essential in view of its natural, concrete acquired an upheaval uses of cement. Concrete has boundless open doors for creative applications, plan and development methods. Its extraordinary adaptability and relative economy in filling extensive variety of necessities has made it is exceptionally focused building material. This project focuses on concrete, keeping importance to this, an attempt has been made to develop strength in concrete incorporating recycling waste. As part of the project cement partially replaced with egg shall powder and e- waste as coarse aggregate Comparative studies were carried out for compressive strength, tensile strength and flexural test for conventional and material concrete mixture introducing new recycling materials

Multi-method characterization of 50-year-old mass concrete from the nuclear power plant Unterweser in Germany: A forensic approach

Concrete core samples extracted from the base of the 50-year-old reactor building at the Unterweser nuclear power plant in Germany were analyzed using contemporary and complementary experimental techniques. The analysis focused on qualitative and quantitative assessments of the mineralogical composition of ingredients, mixture composition, aggregate size distribution, presence of cracks, porosity, and compressive strength. Optical microscopy revealed insignificant micro-cracking in the concrete matrix, while the presence of blast furnace slag was clearly visible. Petrographic analysis of polished and thin sections has enabled the estimation of the concrete mixture composition and the grain size characteristics of the aggregates. The aggregates consist of quartz, silt, and volcanic rock with minor amounts of fossil-bearing grains. Pore size distribution obtained from mercury intrusion porosimetry (MIP) reveals that the concrete has a relatively refined pore structure. Hydration products in the matrix, i.e., hardened paste, were analyzed using powder X-ray diffraction (p-XRD) and thermogravimetry (TGA). Furthermore, backscattered electron (BSE SEM) image analysis was conducted to quantify the original mixture composition, including cement and slag contents, and water/binder ratio. This study emphasizes strategic and practical aspects of conducting in-depth analysis on hardened concrete samples that are several decades old and may serve as a general guideline for similar inquiries in diverse concrete structures.