Properties Of Concrete Research Articles

Testing Mortars for 3D Printing: Correlation with Rheological Behavior

Three-dimensionally printed concrete is a transformative technology that addresses housing shortages due to population growth and enables innovative architectural designs. The objective of this study is to investigate the connection between a conventional test and the rheological properties of 3D-printed concrete. A more precise assessment of material quality based on traditional evaluation techniques is proposed. Standard tests are conducted to evaluate the consistency of 3D-printed concrete materials. Complementarily, a rheometer is employed to accurately measure key rheological properties, thereby establishing a link with empiric testing methodologies. The correlation between the flow table test and rheological coefficients, such as yield stress and viscosity, has been identified as the most effective in basic experiments for evaluating material behavior. This approach allows for a preliminary assessment of printability without the need for additional complex equipment. The study has successfully established a relationship between flow table tests and rheological parameters. However, further research involving a broader range of materials and print-test experiments is essential to enhance the correlation between other conventional testing methods and rheometer results.

The study on bond‐slip constitutive model of recycled concrete under different loading rates

AbstractIf recycled concrete is to be widely, reasonably, and safely applied in practical engineering, the study of bond‐slip performance between steel bars and concrete is crucial. In this paper, the central pull‐out test of recycled concrete under different loading rates was conducted. The characteristics of failure mode and crack directions of the specimens were observed and analyzed. The ultimate bond strength and slip displacement between rebar and concrete were analyzed. The effects of three parameters, namely concrete strength grades, replacement percentage of recycled coarse aggregate, and loading rates on the failure modes and bond‐slip mechanical properties of recycled concrete, were analyzed and summarized. The experimental results showed that there were significant differences in the influence trend and amplitude of the above three parameters on the ultimate bonding strength, slip amount, and slip curve. Based on the above experimental and theoretical analysis, a reasonable bond‐slip constitutive model was established in this paper and was in good agreement with the experimental results.

РАЗРАБОТКА ГЕЛИОУСТРОЙСТВА ДЛЯ ТЕПЛОВОЙ ОБРАБОТКИ ПРИ ПРОИЗВОДСТВЕ БЕТОННЫХ ИЗДЕЛИЙ

The analysis of limestone shell waste from the Mangystau region of Kazakhstan was carried out and it was revealed that limestone shell waste can find its application in building materials, as a concrete filler. The mechanical properties of carbonate concrete have been investigated. In this regard, a technology for the production of concrete using limestone-shell was developed.

EXPERIMENTAL APPROACH FOR DEVELOPMENT OF SUSTAINABLE HYBRID GRADED FIBER REINFORCED CONCRETE BY CONSUMING LATHE WASTE STEEL FIBERS WITH GLASS FIBERS FOR ENHANCED MECHANICAL PROPERTIES

Local workshops generate large quantities of industrial lathe waste steel fibers, which the steel manufacturing industries find difficult to recycle because of their sharp edges. The utilization of lathe waste steel fibers as fiber reinforcement is sustainable in concrete because these fibers have the same properties as steel fibers. Furthermore, using combinations of ductile and elastic fibers improves strain capacity and resistance to pre- and post-cracking. This research employs hybrid fiber reinforcement technology, utilizing industrial lathe waste steel fibers and glass fibers in varying proportions, to bridge the micro and macro cracks in concrete specimens. This research was done to examine the physical (workability) and mechanical properties (compressive and flexural strength) of hybrid fiber-reinforced concrete. In this research different mixtures of hybrid fiber-reinforced concrete were cast and designated as M0, M1, M2, M3, M4, M5, and M6. The mixtures included lathe waste steel fibers at 0%, 0.50%, 1%, 1.5%, 2%, 2.5%, and 3%, and glass fibers at 0%, 0.15%, 0.25%, 0.45%, 0.60%, 0.75%, and 0.90%, respectively. The ASTM-standardised protocols were followed for all laboratory testing. The physical property results showed a decrease in the workability of concrete mixes as the percentage of lathe waste steel and glass fiber increased. This suggests that a higher percentage of lathe waste steel and glass fibers leads to a lower slump value. Consequently, the mechanical property results showed a gradual enhancement in the compressive and flexural strengths of hybrid fiber-reinforced concrete up to 2.5% lathe waste steel fibers and 0.75% (M5). Further incorporation causes a reduction in strength. The physical examination of fractured samples of hybrid fiber-reinforced concrete confirms that the lathe waste steel fibers yield a maximum strain before breaking down in the concrete matrix. Furthermore, lathe waste steel fibers broke rather than being pulled out, indicating a good bond with the concrete. It is recommended that up to 2.5% lathe waste steel fibers and 0.75% of glass fibers by the total weight of the concrete can be used as hybrid fiber reinforcement for optimum strength achievement.

DURABILITY CHARACTERISTIC OF COCONUT FIBER AGGREGATE CONCRETE BOND IN LIGHTWEIGHT FOAM CONCRETE

The research paper probes into coconut fibre used as lightweight aggregate in concrete for thermal conditioning, specifically on durability. The durability properties of coconut fibre and coconut fibre lightweight aggregate concrete were examined on the thermal conditioning. The use of coconut fibre aggregate in construction was tested and verified. It ascertained the moisture content and water absorption capacity found to be 4.20% and 24% respectively. These values can be compared to the conventional aggregate used in normal times. The density of coconut fibre was found to be in the range of 550 -650 kg/m3. They are within the specified limits of lightweight aggregate standards. The study conducted a related hydration test on coconut fibre fines with cement. The coconut fibre-cement ratio has been optimized to satisfy the criteria of structural lightweight concrete for insulation and thermal conditioning to ensure durability. The experiments for long-term investigation continued for 365 days on the compressive strength of coconut fibre aggregate concrete for three different curing conditions.

Study on the Influence of Thermoplastic Microcapsules on the Sulfate Resistance and Self-Healing Performance of Limestone Calcined Clay Cement Concrete.

Limestone calcined clay cement (LC3), enhanced through reactions with volcanic ash and the interaction between limestone and clay, significantly improves the performance of cementitious materials. It has the potential to cut CO2 emissions by up to 30% and energy consumption in cement manufacture by 15% to 20%, providing a promising prospect for the large-scale production of low-carbon cement with a lower environmental effect. To effectively manufacture LC3 concrete, this study utilized limestone (15%), calcined clay (30%), and gypsum (5%) as supplementary cementitious materials (SCMs), replacing 50% of ordinary Portland cement (OPC). However, in regions abundant in sulfate, sulfate attack can cause interior cracking of concrete, reducing the longevity of the building. To address this issue, microcapsules containing microcrystalline wax, ceresine wax, and nano-CaCO3 encapsulated in epoxy resin were prepared and successfully incorporated into LC3 concrete. Sulfate resistance tests were conducted through sulfate dry-wet cycles, comparing samples with and without microcapsules. The findings revealed that the initial mechanical and permeability properties of LC3 concrete did not significantly differ from OPC concrete. LC3 concrete with added microcapsules (SP4) exhibited enhanced resistance to sulfate attack, reducing mass loss and compressive strength degradation. SEM images displayed a mesh-like structure of repair products in SP4. After 14 days of self-repair, SP4 exhibited a 44.2% harmful pore ratio, 98.1% compressive strength retention, 88.7% chloride ion diffusion coefficient retention, 91.12 mV maximum amplitude, and 9.14 mV maximum frequency amplitude. The experimental results indicate that the presence of microcapsules enhances the sulfate attack self-healing performance of LC3 concrete.

Influence of alkaline activators on mechanical properties of environmentally friendly geopolymer concrete under different curing regimes.

Previous studies highlighted the significance of tailoring alkaline activators (AA) to specific fly ash (FA) sources for optimal properties of geopolymer concrete (GPC). This study examines the influence of various AA's properties on mechanical properties and microstructures of local low-calcium FA-based GPC under varying curing conditions. A comprehensive investigation consists of several factors such as NaOH molarities (10M, 12M, 14M, 16M), ratios (1.5, 2.0, 2.5) and ratios (0.5, 0.6). The results reveal a complex relationship, demonstrating that NaOH molarity positively influences compressive strength up to a threshold of 14M, beyond which an adverse effect was observed while, the flexural strength was increased up to 16M. Moreover, the study highlights the complex relationship between ratios and mechanical strengths. Notably, these properties exhibited an increase as the ratio rose up to 2.0, but a subsequent decrease was observed when the ratio reached 2.5. Moreover, proposed regression equations predict the compressive and flexural strengths of both ambient-cured GPC and heat-cured GPC with marginal statistical errors. The optimal GPC mix exhibited 49% lower embodied emissions than the corresponding OPC concrete. GPC has higher cost, but it exhibited lower cost-to-strength ratio compared to OPC concrete.

Investigating the effect of polypropylene fibres and curing parameters on the workability and mechanical properties of concrete

Polypropylene fibers possess certain characteristics that make them an ideal counterpart to attain explicit advantages when used for building works, more specifically, when added to concrete. In this investigation, polypropylene fibers were added by weight of cement (0.25%, 0.5%, and 0.75%) in M20 grade of concrete and their impact on workability, compressive strength, and flexural strength were assessed and analyzed. The slump test revealed that as the polypropylene fiber loading in the concrete mix was increased, the workability of the mixture continued to decrease; the workability decreased by 11.11%, 19.44%, and 45.83% upon the addition of 0.25 %, 0.5%, and 0.75% fibers respectively in the concrete. The compressive strength, as well as the flexural strength of the concrete, increased monotonously with an increase in the curing time and fiber loading. For instance, in the case of acidic water curing, the compressive strength enhanced from 19.08 MPa to 22.85 MPa upon increasing the fiber content from 0.25% to 0.75%. Adding 0.25% polypropylene fiber resulted in an increase in the flexural strength of conventional concrete mix by 15.78% and 10.29% when cured in normal water for 28 days and 56 days, respectively. Both the compressive and flexural strength of the samples cured in normal water was found to be higher than the samples cured in acidic water and it was observed that the fibre-reinforced concretes were more resistant to acids than the normal unreinforced concrete.

Aggregate blending optimisation in quarries to improve of the mechanical and environmental properties of concrete

ABSTRACT In this study, concrete mix optimisation was carried out with materials provided by Catalca (Ca) and Cendere (Ce) quarries in the region of Istanbul, Turkey which produce concrete aggregate from different rock formations. Accordingly, the properties of six different concrete aggregates produced from these quarries (3 regions in Catalca quarry and 3 regions in Cendere quarry) and the amounts of CO2-e released into the atmosphere by producing these aggregates were determined. Then, these aggregates were used in different proportions in concrete mixtures and the effects of aggregate types on the mechanical properties of concrete were statistically demonstrated by the experimental design method. According to the results, the mechanical properties of concrete were statistically significantly affected by the use of aggregate in different formations. In addition, empirical approaches that can be used in estimating the compressive strength, tensile strength and elasticity modulus of concrete have been found and using these approaches, mixtures that maximise these mechanical properties of concrete have been determined. Accordingly, mechanical properties of concrete were maximised in mixtures where Ca 1st Region 25% - Ca 2nd Region 75%, Ca 1st Region 60% - Ca 3rd Region 40%, Ca 2nd Region 13% - Ca 3rd Region 87%, Ce 1st Region 10% - Ce 3rd Region 90%, Ce 1st Region 63% - Ca 2nd Region 37%, and Ca 1st Region 35% - Ca 2nd Region 5% - Ca 3rd Region 60% were used. The CO2-e values of these mixtures were calculated as 8.405, 8.248, 8.529, 8.630, 8.476, and 8.365 kg/t respectively.

Effect of using Fly Ash and Attapulgite Lightweight Aggregates on Some Properties of Concrete

Effect of using Fly Ash and Attapulgite Lightweight Aggregates on Some Properties of Concrete

Performance Assessment of a Novel Green Concrete Using Coffee Grounds Biochar Waste

An actual scientific problem in current concrete science is poor knowledge of the problem of modifying concrete with plant waste. At the same time, plant waste benefits from other types of waste because it is a recycled raw material. A promising technological approach to modifying concrete with plant waste is the introduction of components based on the processing of coffee production waste into concrete. This study aims to investigate the use of biochar additives from spent coffee grounds (biochar spent coffee grounds—BSCG) in the technology of cement composites and to identify rational formulations. A biochar-modifying additive was produced from waste coffee grounds by heat treatment of these wastes and additional mechanical grinding after pyrolysis. The phase composition of the manufactured BSCG additive was determined, which is characterized by the presence of phases such as quartz, cristobalite, and amorphous carbon. The results showed that the use of BSCG increases the water demand for cement pastes and reduces the cone slump of concrete mixtures. Rational dosages of BSCG have been determined to improve the properties of cement pastes and concrete. As a result of the tests, it was determined that the ideal situation is for the BSCG ratio to be at a maximum of 8% in the concrete and not to exceed this rate. For cement pastes, the most effective BSCG content was 3% for concrete (3%–4%). The compressive and flexural strengths of the cement pastes were 6.06% and 6.32%, respectively. Concrete’s compressive strength increased by 5.85%, and water absorption decreased by 6.58%. The obtained results prove the feasibility of using BSCG in cement composite technology to reduce cement consumption and solve the environmental problem of recycling plant waste.

Experimental and finite element studies on the mechanical properties of high-strength concrete using natural zeolite and additives

Addressing high carbon footprints is a critical global problem in cement production. Using environmentally friendly materials has proven to be a solution to environmental challenges. In this study, High-Strength Concrete of M60 is produced with Natural Zeolite and industrial waste materials. The combinations of 5 % zeolite and varying percentages of industrial wastes such as Silica Fume, Metakaolin, and Fly Ash are tested for mechanical properties. The laboratory test data is compared with numerical simulations to assess the accuracy and determine the error percentage for concrete strength predictions. The process involves the development of numerical solutions by ANSYS to predict strength. The developed numerical solution determines the accuracy of identifying the difference between the experimental and numerical data. The present research on the comparison of experimental and numerical data by ANSYS showed the lowest error percentage, which is acceptable for all the strength properties of concrete.

The Effect of Thermo-Mechanical Properties of Concrete on the Temperature Field in Mass Concrete

The Effect of Thermo-Mechanical Properties of Concrete on the Temperature Field in Mass Concrete

Exploring Current Techniques for Improving the Properties of New Concrete

In modern construction, the properties of new concrete are crucial for building quality and structural performance. Recent technological advancements have led to significant progress in enhancing the properties of new concrete. This study employs theoretical and experimental methods to explore the connection among shear stress and shear strain rate under vibration, the impact of aggregate substitution on concrete performance, and the rheological properties of moist shotcrete. The findings suggest that adjusting mix proportions and using additives can significantly improve concrete's strength, durability, and workability. This research provides engineers with a theoretical foundation for optimizing concrete mixtures and construction techniques, thereby improving overall building quality and construction efficiency. The findings suggest that sustainable materials can be used without compromising structural integrity, making the construction process more environmentally friendly while maintaining high performance standards. Furthermore, this study highlights the importance of understanding concrete behavior under various conditions to develop more resilient and long-lasting structures.

Mechanical properties of reactive powder concrete under compression at ultra-low temperatures

In this paper, the mechanical properties of reactive powder concrete (RPC) at ultra-low temperatures were studied. RPC prisms (300 mm × 100 mm × 100 mm) were tested at ultra-low temperatures (20 °C, 0 °C, −20 °C, −40 °C, −80 °C, −120 °C, −165 °C) and resulting prism compressive strength, compressive stress-strain curve, and toughness were determined. The increase in prismatic compressive strength of RPC at ultra-low temperatures is greater than that of ordinary concrete, with an overall strength of about 2.12 times that of ordinary concrete. Pore water freezing behavior was also studied to assess the effects on the mechanical properties of RPC in ultra-low temperatures. The water-ice phase transition further improved the RPC strength. With the reduction in temperature, The change in elastic modulus of RPC change is small, the peak strain of specimens at different temperatures increases with the decrease in temperature. The peak strain of RPC showed an overall linear increase with decreasing temperatures, and the water-ice phase transition at negative temperature increases the peak strain of RPC, adding steel fibers improves the RPC ductility, limiting the fracture. With the temperature reduction, RPC toughness first increases and then decreases. The toughness is lowest at room temperature, and highest at −120 °C, which is 2.26 times higher than at room temperature. RPC has better toughness than normal concrete at different temperatures, the reduction of temperature relatively improves the toughness of RPC, and the addition of steel fibers plays a vital role in improving the toughness. This study can serve as technical support for using RPC to design liquefied natural gas full-capacity tanks.

Research Progress on Electrical Properties of Self-sensing Concrete

In order to effectively avoid the different degrees of impact and damage to the existing buildings and structures, it is particularly important to strengthen the health detection of such structures and facilities, which is also an important research field in the development of green building discipline. Smart concrete is both structural and functional, and has the potential of self-monitoring of concrete structures. This paper reviews the basic concepts of self-sensing concrete, including the research progress of self-sensing concrete materials, and summarizes the classification of different conductive phase materials and their conductive properties. Secondly, the basic mechanical properties and electrical properties of self-sensing concrete are discussed. The factors affecting the perceptual performance of self-sensing concrete considered by different scholars are summarized. It is concluded that few scholars have studied the mechano-electric interaction evaluation mechanism that takes the electrical parameters into account the stress, strain, crack or damage of concrete, and evaluates mechanical properties and crack propagation length through the change of electrical signals. Finally, the importance of self-sensing performance of intelligent concrete is emphasized, and the prospect of future research is put forward.

Effect of treatment types of recycled concrete aggregates on the properties of concrete

Reusing waste materials such as construction and demolition waste is an environmentally significant task. This article aims to improve the quality of recycled aggregates after the demolition of concrete structures. Two methods, mechanical cleaning and impregnation, were explored to enhance the quality of coarse aggregates. The findings indicate that mechanical cleaning is more effective than soaking in a sodium silicate solution. The compressive strength of concrete made with mechanically cleaned recycled aggregates was 2.3 times greater than that of concrete made with untreated rubble. Concrete with impregnated rubble had a compressive strength 1.1 times greater than that of concrete with untreated aggregates. Infrared spectroscopy was used to study the microstructure, revealing that the type of treatment does not influence the quantity of portlandite and ettringite in hydrated cement. However, the treatment of recycled aggregates alters the interaction in the gel portion of cement hydration products. Concrete with aggregates treated by sodium silicate has more aluminate components. Additionally, there is a shift of the bands assigned to Si-O stretching to higher wave numbers (from 995 cm–1 to 1088 cm–1), which can be attributed to the formation of calcium-silicate-hydrate gel with a lower calcium/silicon ratio.

The effect of artificial metakaolin coarse aggregate on the mechanical and durability properties of lightweight geopolymer concrete

<p style="text-align:justify; margin-bottom:11px"><span style="font-size:11pt"><span style="line-height:150%"><span style="font-family:Calibri,"sans-serif""><span lang="PT-BR" style="font-size:12.0pt"><span style="line-height:150%"><span style="font-family:"Times New Roman","serif""><span style="color:#131413">This study presents a unique methodology for investigating the properties of  Metakaolin Coarse Aggregates (MCA). The NaOH ratios were varied as 8M, 10M, 12M, and 14M, while the NaOH to Na<sub>2</sub>SiO<sub>3</sub> ratio was maintained at 0.5 entire study. The liquid-to-binder (L/B) ratios set at 0.3, 0.35, and 0.4. Testing was conducted on the MCA to determine its physical and mechanical properties, comparing them with those of Natural Coarse Aggregate (NCA). Notably, the 8M mix with a 0.4 L/B ratio was found to be economical for producing MCA and was selected for further research. This chosen mix was then employed to prepare geopolymer concrete with 50% MK and 50% PA, with L/B ratios set at 0.4, 0.45, and 0.5. The NaOH ratio and Na<sub>2</sub>SiO<sub>3</sub> to NaOH ratio were maintained at a constant 8M and 2, respectively. Mechanical and durability properties were compared between Geopolymer concrete with NCA and Geopolymer concrete with MCA. The test results demonstrate that MCA in geopolymer concrete can effectively replace NCA in geopolymer concrete, making it a viable option for structural members. Additionally, microstructural characterization was performed on Geopolymer concrete with MCA mixes with varying L/B ratios of 0.4, 0.45, and 0.5, at 28 days. The study specifically focuses on the Interfacial Transition Zone (ITZ) between MCA and geopolymer paste, revealing an improvement in ITZ and microstructure in the GMCA sample with a 0.4 L/B ratio compared to other mixes.</span></span></span></span></span></span></span></p>

Assessing the Impact of Recycled Concrete Aggregates on the Fresh and Hardened Properties of Self-Consolidating Concrete for Structural Precast Applications

This study explores the influence of different concentrations of recycled concrete aggregate (RCA) on the fresh and hardened properties of self-consolidating concrete (SCC) in order to assess the structural suitability of the use of RCA in a precast concrete plant. The study particularly emphasizes the early strength of the produced concrete. The RCA was sourced from crushed concrete used in roadway applications and was sieved to replicate the characteristics of natural aggregate. Five different SCC mixes were produced, with RCA substituting 0%, 10%, 30%, 50%, and 70% of the natural coarse aggregate (NCA) by weight. For each different mix design, the hardened properties tested were the compressive strength and tensile strength. The fresh properties investigated were the passing and filling ability. Additionally, aggregate properties including grain size distribution and absorption of coarse aggregate were studied. The selected mix design follows a typical well-graded self-consolidating concrete mix with 28-day strength of 8000 psi (55.16 MPa). It was found that replacing up to 50% of the NCA with RCA improves the early strength of concrete without a significant impact on the fresh and hardened concrete properties.

Radiation shielding properties of sustainable concrete with novel plastering techniques

In concrete applications. Major/critical applications of such concrete are radiation-shielding facilities. Both steel slag and silica fume are examples of common by-product materials that can be used as a replacer of aggregates and cement. Thus, in this research work, steel slag was utilized as heavy aggregate in concrete production besides silica fume to present sustainable concrete mixtures probably with better radiation-shielding properties. Different cementitious plasters were applied on the conducted sustainable concrete mixture using different powdery materials; hematite, magnetite, barite, bentonite, and steel slag powders in addition to nano-titanium dioxide as full replacers for sand. The proposed plasters were presented to determine the optimum plaster technique in terms of static performance and attenuation capability against gamma and neutron radiations. The results exhibited that utilizing steel slag and silica fume in concrete mixtures enhanced compressive strength by up to 9.09 % compared to conventional concrete, while the addition of nano-titanium to conventional plaster led to superior enhancement in the compressive strength by up to 38.65 % relative to traditional plaster. Conversely, fully replacing conventional silica sand with the abovementioned powdery materials generally reduced the compressive strength of cementitious plasters by up to 30.83 %. However, the radiation shielding properties against Cs-137, and Co-60 energies have been enhanced by up to 20 % and 26 %, respectively.