Thermal Properties Of Concrete Research Articles

Performance analysis of paraffin microcapsules and phase change concrete based on microporous cenospheres

Combining concrete and phase change materials has created a novel method for building energy conservation. However, introducing phase change materials into the concrete will cause various impacts on its performance. This study explores a novel approach to enhance thermal energy storage in building materials by incorporating phase change materials (PCMs) into concrete. Microporous cenospheres were extracted from fly ash through a three-step process and used to produce composite PCM microcapsules containing paraffin as the core material. The produced PCM microcapsules were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and phase change cycle analysis. Phase change concrete was then formulated by substituting 0–25 % sand with these microcapsules. Effects of the addition of the PCM microcapsule on both the mechanical and thermal properties of concrete were experimentally examined. While the incorporation of microcapsules significantly improved concrete's thermal properties, it also led to a reduction in compressive strength (up to 19.65 % at 28 days), though still meeting specifications. The introduction of microcapsules notably enhanced the temperature control capabilities of concrete. In spring, the model room made with the phase change concrete exhibited a 2.2 °C lower indoor peak temperature 2 h 40 min later than the one room with the ordinary concrete. During active heating in winter, the phase change concrete demonstrated significantly lower indoor temperature fluctuations, with a maximum reduction of 45.39 %. Furthermore, the study found that the particle size of microcapsules had varying effects on concrete performance, with larger particles improving thermal properties and smaller particles enhancing mechanical properties. Overall, this research highlights the potential of composite phase change microcapsules and phase change concrete based on microporous cenospheres for effective temperature control and energy conservation in building applications.

Investigating the Mechanical and Thermal Properties of Concrete with Recycled Nanoplastics for Enhanced Sustainability

Investigating the Mechanical and Thermal Properties of Concrete with Recycled Nanoplastics for Enhanced Sustainability

Thermal property evolution and prediction model of early-age low-heat cement concrete under different curing temperatures

The evolution of low-heat concrete thermal properties is controlled by microstructure growth and affects the early-age mass concrete structure cracking under real curing conditions from the perspective of heat transfer. In this paper, experiments were carried out to obtain the evolution of the hydration heat, thermal conductivity, specific heat capacity, and microstructure of different water-binder low-heat mortars under different curing temperatures. The results show that all the thermal property variation rates are sensitive and positive to the curing temperature. The hydration rate increases with increasing water-binder ratio, and the thermal conductivity and specific heat capacity mainly decrease with increasing hydration degree, but the thermal conductivity has a brief and rapid increase stage when the hydration degree is less than approximately 0.38. At the same curing time, the thermal conductivity is higher with a higher water-binder ratio, and the specific heat capacity is inverse. The microstructure results show that the porosity, pore size distribution curve, and threshold pore size decrease with increasing age and curing temperature and increase with increasing water-binder ratio. Meanwhile, the relations between microstructure and thermal property evolutions also show that thermal properties have an exponential positive correlation with porosity, and their variations are controlled by hydration products and pore water due to the variable hydration process. In addition, based on the results and hydration kinetics, a multiscale thermal parameter prediction model of low-heat concrete considering curing temperature and the water-binder ratio was established by the method of theoretical deduction.

An experimental study investigating the effects of bentonite clay on mechanical and thermal properties of concrete

Concrete is one of the most popular building materials used in civil engineering applications. In order to reach the sustainability goals and produce more environmental construction materials, replacing some amount of cement in concrete with natural or industrial mineral additives is of great importance. In this research, from 0 to 30% by volume Portland cement (PC) CEM II 42.5R was replaced with bentonite clay (BC) and standard mortar samples were prepared in five different series, including control samples. Artificial aggregates (AA) with powder mixture of 90% ground granulated blast furnace slag (GGBFS) and 10% PC by weight were pelletized through cold-bonded agglomeration process in samples containing bentonite with different proportions. Mechanical tests and thermal conductivity tests have been performed on concrete samples at the age of 28 days. The results show that the compressive strength of the samples with 5% BC are 94.7% higher and the thermal conductivity of the same samples are 31.2% lower compared to the control sample. However, it is revealed that, increasing the amount of bentonite more than 15% decreases the mechanical and thermal properties considerably. The study revealed that the use of natural materials with low environmental impacts has increased the mechanical and thermal properties of construction materials which will provide significant benefits for sustainable construction.

Impacts of Conifer Leaves and Pine Ashes on Concrete Thermal Properties

Global energy consumption has substantially increased. Although the thermal properties of conventional concrete have been comprehensively researched thus far, considerable research is left to address the impacts of agricultural waste ashes on the thermal characteristics of ternary binders. Conifer leaves and pines are inexhaustible resources, and the effects of their ashes on concrete properties, especially the thermal conductivity, are seldom investigated. In this study, 153 concrete samples containing 5, 10, 15, and 20% replacement levels of conifer leave and pine ashes were cast, and water absorption, compressive strength, and thermal conductivity of specimens were monitored. In addition, a thermal performance test of concrete exposed to a heating source was carried out to evaluate the impacts of conifer ashes on concrete thermal conductivity. The results revealed that regarding compressive strength, the optimum replacement levels for pine and leaves ashes are 15% and 10%, respectively. Compared to reference samples, replacing 20% pine and leaves ashes resulted in an 11.9% and 9.3% reduction in water absorption, respectively. The application of conifer ashes considerably reduced concrete thermal conductivity, which is essential for erecting low-energy buildings. Conifer ashes were found to considerably drop the thermal conductivity of the specimens (1.565 W/m/K) to a lower amount. Concrete specimens containing 20% pine and leaves ashes reduced thermal conductivity by 24.7% and 26%, respectively. Thus, the application of conifer ash enhanced the concrete thermal performance, leading to a lower energy consumption overall in concrete buildings.

A multi-site study of a new cement composite brick with partial cement substitutes and waste materials

The building industry is a major contributor to climate change since it emits massive amounts of greenhouse gases. As a result of this research, a cement composite brick with partial cement substitutes and waste material was developed. The fresh formula mixture and hardened concrete were tested for physical, mechanical, and thermal properties to ensure that the assumptions were true. In this study the role of zaolite, metakaolinite and micrometakaolinite at different proportions, i.e. 5%, 10%, and 15% as well as recycled fibers (glass, polypropylene and steel) at 0.5%, 1.0% and 1.5% dosage in the production of cement composites was researched. 20 recipes in total have been tested until achieving the final recipe of the mentioned brick. The main purpose of this research was to develop the concrete mixture that will be used to produce cement bricks with increased physical, mechanical and thermal parameters. The compressive strength of the brick developed with the modified formula increased by 22% compared to the reference sample. Also, higher mechanical values were obtained for the splitting strength and flexural strength, which increased by 14% and 32%, respectively, compared to plain concrete. Based on the thermal test results it was developed that zeolite, metakaolinite and micrometakaolinte have no effect on thermal properties of concrete. Only after incorporating fibers into mixture, those properties changed. Also, the SEM images showed an even distribution of the fibers in the composite matrix and a crack-free structure. Moreover, the image analysis results confirmed the failure character consistent with traditional concretes in the case of compression and the lack of split into two independent samples in the case of bending. Therefore, the new composite brick has great potential to be used as a primary replacement for traditional concrete masonry in civil engineering projects.

Thermal Analysis of Concrete Mixtures with Recycled EPS Aggregates

Reusing recycled waste materials in buildings is gaining more and moreattention for what it offers economic, environmental, and energy benefits;and many researchers are nowadays working on producing new sustainableconstruction materials incorporating recycled wastes. In this scope, thiswork uses an experimental approach aiming at understanding the effect ofincorporating Expanded Polystyrene (EPS) beads in concrete and proposingthermally improved concrete mixtures for the production of hollow blocksin Lebanese constructions by substituting fine aggregates with recycledproducts such as EPS in order to promote their insulating properties. Threedifferent diameters of EPS beads (2 mm ~ 3 mm, 3 mm ~ 4 mm and 4 mm ~5 mm) are studied with different volumetric ratios (20%, 40%, 60% and80%) in order to investigate the effect of EPS on the thermal properties ofconcrete. The results showed that the only the percentage of incorporatedEPS beads impacted the thermal performance of the concrete mixtureswhile the EPS diameters have a negligible effect on the thermal propertiesof the concrete samples.

Studying Thermal and Mechanical Properties of Recycled Concrete by Using Ceramic Aggregate

Ceramic aggregate has the characteristics of light weight, heat insulation, and low cost, and recycled aggregate is a type of green material that realizes the re-crushing of construction waste. This paper studied the impact of replacing natural coarse aggregate with ceramic aggregate and natural sand with recycled fine aggregate, on the physical, mechanical, and thermal properties of concrete. Recycled fine aggregate was used to completely replace natural sand. A total of five concrete mixes (including a reference mix) were prepared with different levels of ceramic aggregate (0%, 30%, 50%, 70%, 100%). Density, compressive strength, thermal conductivity, and thermal inertia index were measured to evaluate the performance of each mixture, and ceramic concrete board and hollow blocks were designed for testing the thermal properties. Results of testing show that density, strength, and thermal performance are interrelated. The smaller the density, the lower the strength, and it indicates that ceramic aggregate has a negative influence on strength in concrete. Meanwhile, the smaller the density, the higher the thermal resistance, and the addition of ceramic aggregate can improve the thermal insulation of concrete. The mechanical and thermal properties are both affected by the ceramic replacement ratio. Ceramic aggregate improves the thermal properties of recycled concrete, and the negative influence of ceramic aggregate on compressive strength can be controlled by the replacement ratio of aggregate in concrete. Based on the overall comparison and analysis, a mix with 50% ceramic aggregate shows relatively better strength and thermal insulation compared to other mixes. The use of ceramic aggregate in combination with recycled fine aggregate can effectively reduce the environmental pollution and make an economical substitute for their natural counterparts.

Evaluation of Thermal Conductivity of Sustainable Concrete Having Supplementary Cementitious Materials (SCMs) and Recycled Aggregate (RCA) Using Needle Probe Test

The evaluation of thermal properties is commonly conducted to characterize non-structural materials, such as lightweight concrete, that are used for thermal insulation. Such materials are designed for thermal resistivity applications. Due to the increased demand to adopt sustainable practices in the construction industry, municipalities in the United Arab Emirates (UAE) emphasize the use of sustainable materials in construction, such as green concrete. The cement in green concrete is partially replaced with supplementary cementitious materials (SCMs); these materials are by-product waste from other industries. The SCMs can contribute to sustainability by reducing the concrete carbon footprint. They can also help in extending concrete durability and service life. However, there is still a lack in the literature regarding the effects of these materials on the thermal properties of concrete. This paper investigates the thermal properties of sustainable concrete mixes incorporating various types of SCMs. The SCMs that are considered in this investigation are fly ash, ground granulated blast-furnace slag (GGBS), and microsilica. Another way to improve the sustainability of the concrete is to partially replace the natural aggregates with recycled aggregates. Thus, a group of the concrete mixes in this investigation were prepared by replacing 40% of natural aggregates with recycled aggregates to investigate the effects of recycled aggregate on the thermal properties of concrete. Further, the thermal properties of three lightweight concrete mixtures commonly used in construction were evaluated. All concrete mixtures were examined for thermal conductivity and resistivity in accordance with ASTM D5334. The results of this investigation showed that SCMs and recycled aggregates have a significant impact on the thermal properties of concrete. The high replacement of ground granulated blast-furnace slag (GGBS) resulted in a remarkable increase in thermal conductivity. This investigation provides significant conclusions and recommendations that are of practical importance to the construction industry in the UAE to promote sustainability. This research aims at formulating recommendations for the effective use of SCMs in the construction industry in the UAE based on their effects on the thermal properties of concrete.

Mechanical Strength and Thermal Properties of Cement Concrete Containing Waste Materials as Substitutes for Fine Aggregate.

The increasing volume of waste and the requirements of sustainable development are the reasons for the research on new waste management concepts. The research results presented in this paper show the effect of recycled aggregate on the selected properties of cement concrete. The aggregates obtained from three types of wastes are tested: recycled concrete paving, crushed ceramic bricks, and burnt sewage sludges. The recycled aggregates replaced 25% and 50% of the volume of the fine aggregate. The tested aggregates worsen the concrete mixes' consistency and decrease, to some extent, the compressive strength of the concrete. However, the tensile splitting strength of the concrete with recycled aggregates is similar to that of the reference concrete. Using recycled aggregates worsens the tightness of the concrete, which manifests itself by increasing water penetration depth. The thermal properties of concrete are slightly affected by the type and content of the recycled aggregate. Considering the expected improvement in recycled aggregate processing, they can be an alternative to natural aggregates. Using recycled aggregates in cement concrete requires extensive studies to search for ways to increase their possible content without worsening concrete performance.

Loading phase change material in a concrete based wall to enhance concrete thermal properties

In this study, energy analysis was performed to improve the thermal behavior of the concrete-based wall of the building in the presence of phase change material (PCM). PCMs have low conductivity, acceptable specific capacity, and high latent enthalpy, which makes them a superior candidate for building applications. Considering the thermal properties of concrete in the range of 100–200 mm, PCM was added to the concrete. At concrete thickness of 100 mm, the impact of PCM was maximized so that the combination of PCM with concrete significantly reduced heat load (by 71.5%) as well as cold load (by 61%). Annual analysis showed that in the concrete thickness of 100 mm–200 mm, the presence of PCM reduces energy demand. At a thickness of 100 mm, the energy consumption was reduced by 64.1% while at the thickness of 150 and 200 mm, energy demand reduction was 59% and 56.8%. Due to loading PCM into concrete, an annual energy-saving of 231.6 kWh/m2 at the concrete thickness of 100 cm was achieved. This value at 150 cm and 200 cm was 176.5 and 156.3 kWh/m2, respectively.

The Strength and Thermal Properties of Concrete containing Water Absorptive Aggregate from Well-Graded Bottom Ash (BA) as Partial Sand Replacement

Bottom ash (BA) is a hazardous waste material from power plant. The well-graded BA can be a good sand replacement material in concrete. This study presents strength and thermal properties of concrete containing high calcium and water absorptive fine aggregate from well-graded BA as partial sand replacement (control mix (CM) 0%, BM5: 5%, BM10: 10%, BM15: 15%, and BM20: 20%). The workability of fresh concrete mixes was tested via slump test. The strength of the hardened concrete was assessed based on compressive strength, split tensile strength, and flexural strength. The thermal property was evaluated based on thermal conductivity test. The optimization of these model parameters was conducted via I-Optimal design. The workability of concrete mixes was reduced with an increase of well-graded BA due to high water absorption effect. The compressive strengths of all mixes reached more than 50% on 28th curing days with maximum strength by BM15 (49.0 MPa). The split tensile strengths showed one quadratic curve combining all mixes with maximum strength reached by BM10 (2.7 MPa). The flexural strength has slow growth exponential pattern with maximum strength by BM20 (6.0 MPA). The thermal conductivity values were steadily increased up to BM15 (2.44 W/mK) and reduced at BM20 (2.15 W/mK). The well-graded BA proportions (5 to 20%) were not showing any significant effect on the thermal properties. The optimised model of compressive strength has the highest accuracy with percentage errors below 5% compared to other parameters. The optimal well-graded BA as sand replacement material was BM10 giving 47 MPa compressive strength, 2.7 MPa split tensile strength, 5.3 MPa flexural strength, and 2.1152 W/mK thermal conductivity. The highest positive correlation coefficients were obtained between compressive strength and thermal conductivity (R2: 0.921). Thus, the well-graded BA improved the strength properties providing a sustainable supply in concrete technology.

Experimental Investigation on Mechanical and Thermal Properties of Concrete Using Waste Materials as an Aggregate Substitution.

The continuous growth of the concrete industry requires an increased quantity of cement and natural aggregates year after year, and it is responsible for a major part of the global CO2 emissions. These aspects led to rigorous research for suitable raw materials. Taking into account that these raw materials must have a sustainable character and also a low impact on environmental pollution, the replacement of the conventional components of concrete by residual waste can lead to these targets. This paper’s aim is to analyze the density, compressive strength and the thermal conductivity of nine concrete compositions with various rates of waste: four mixes with 10%, 20%, 40% and 60% chopped PET bottles aggregates and 10% fly ash as cement partial substitution; a mix with 60% waste polystyrene of 4–8 mm and 10% fly ash; a mix with 20% waste polystyrene of 4–8 mm, 10% waste polystyrene of 0–4 mm and 10% fly ash; a mix with 50% waste polystyrene of 4–8 mm, 20% waste polystyrene of 0–4 mm and 20% fly ash two mixes with 10% fly ash and 10% and 40% waste sawdust, respectively. Using 60% PET aggregates, 60% polystyrene granules of 4–8 mm, or 20% polystyrene of 0–4 mm together with 50% polystyrene of 4–8 mm led to the obtainment of lightweight concrete, with a density lower than 2000 kg/m3. These mixes also registered the best results from a thermal conductivity point of view, after the concrete mix with 40% saw dust. Regarding compressive strength, the mix with 10% PET obtained a result very close to the reference mix, while those with 20% PET, 40% PET, 30% polystyrene, and 10% saw dust, respectively, registered values between 22 MPa and 25 MPa, values appropriate for structural uses.

Uniaxial Stress-Strain Relationship and Thermal Properties of Concrete with Fine Recycled Aggregate Under Elevated Temperatures

Uniaxial Stress-Strain Relationship and Thermal Properties of Concrete with Fine Recycled Aggregate Under Elevated Temperatures

Experimental study of the thermal and mechanical properties of concrete incorporating recycled polyethylene

The widespread use of plastics worldwide generates a large amount of plastic waste that needs to be recycled to minimize its negative impact on the environment. The use of plastic waste as a partial replacement for traditional aggregates remains a solution not only to reduce the amount of plastic waste but also to reduce the overexploitation of natural resources such as quarries. The objective of this paper is to evaluate the mechanical and thermal properties of concrete containing 0%, 5%, 10%, and 15% polyethylene waste (PEW) particles as a partial replacement of coarse aggregates. Several experiments were conducted to evaluate workability, density, compressive strength, and thermophysical properties. The results show that the substitution of recycled PE for coarse aggregate in concrete improves thermal insulation, which leads to the potential use of these concretes as construction materials with many environmental benefits.

Impacts of Conifer Leaf and Pine Ashes on Concrete Thermal Properties

Impacts of Conifer Leaf and Pine Ashes on Concrete Thermal Properties

Alkali-activated and hybrid materials: Alternative to Portland cement as a storage media for solar thermal energy

This study is part of the research line that sees it necessary to develop materials that are alternatives for Portland cement (PC), using industrial by-products such as blast furnace slag and fly ash. This line arises because of the serious environmental consequences suffered by our planet throughout many decades, which have led the cement industry to reduce the amount of CO2 emitted in the production of PC, since it is a highly polluting process. The chemical and physical properties of the materials were studied. In this way, the study of the thermal properties is interesting to test the feasibility of the mortars to use them as solid media to storage thermal energy, since most of the research focus on the thermal properties of concrete is oriented toward fire resistance. Storing solar thermal energy improves the operation of solar power thermal plants. It is being studied that the use of concrete (composed of PC) contributes efficiently to concentrated solar power (CSP) technology. To avoid the use of PC due to environmental concerns, alkaline-activated mortars are manufactured with blast furnace slag using alkaline solutions such as sodium hydroxide (NaOH) and commercial sodium silicate (SiO2/Na2O=0.8), as well as hybrid mortars using 80% fly ash or blast furnace slag and 20% PC. After experimental analysis and a simulation to measure the conduction within the mortars through a commercial Computational Fluid Dynamic software (CFD, ANSYS Fluent), it can be concluded that the mechanical and thermal properties of most of the alternative mortars manufactured in this study are better than the ones obtained in the PC. Most notably, the slag alkaline-activated mortar increases those properties significantly.

Evaluation of eco-friendly concrete having waste PET as fine aggregates

This study assesses the impacts of recycling waste polyethylene terephthalate (PET) plastic bottles as a partial substitute for fine natural aggregates on the workability, mechanical, microstructural, economic, and thermal properties of concrete. The mix design adopts a concrete mix ratio of 1:2:4 for grade M25, 0.55 water/cement ratio, ordinary Portland cement (OPC) as the binder, varying proportions of heat-processed waste PET and river sand as fine aggregates, and granite as coarse aggregate. Results indicate that workability increased with increasing percentages of waste PET plastics until the 40%PET level, beyond which workability reduces. Compressive and split tensile strength decreased with increasing percentages of waste PET plastics. However, 10% to 40%-PET-modified mixes achieved the recommended strength for M20 concrete. Microstructural analysis on the 30%PET indicates higher quantities of O and Ca, and trivial percentages of Mg, Si, C, Al, and Au. Whereas 100%PET indicates the presence of only C, O, and Au. 100%PET endures three transition stages during heat flow. A glass transition, an exothermic peak below decomposition temperature during cooling at a temperature of 199.88 °C from PET crystallization, and a baseline shift after the endothermic peak at 243.22°C. Thermogravimetry revealed that 100%PET suffers a dual-stage decomposition, an initial stage accounting for an 87.41% reduction in sample mass and a second stage accounting for a further mass loss of 12.79%. Highly significant statistical correlations and regressions developed variations between PET% and the workability and mechanical parameters. The study shows that heat-processed PET-modified concrete is appropriate for structural applications due to its suitable fresh, mechanical, microstructural, and thermal properties. Besides, this practice is eco-friendly and sustainable as it conserves natural resources.

Assessment of Lightweight Concrete Thermal Properties at Elevated Temperatures

Structural lightweight concrete (LWC) has recently acquired research importance because of its good thermal insulation properties. However, there is a lack of knowledge about its thermal properties at elevated temperatures. The thermal properties, such as thermal conductivity and specific heat, of porous LWC vary depending on the aggregates, air voids, and moisture content of the LWC in question. To study these effects, in this paper, we measured the thermal properties of three types of structural LWCs at different temperatures, combining different characterization techniques, namely, differential scanning calorimetry (DSC), laser flash analysis (LFA), and modified transient plane source (MTPS). Bulk density and porosity were also evaluated. Specific heat is analyzed by the DSC technique from 20 to 1000 °C and the MTPS technique from 20 to 160 °C. Thermal conductivity is studied using MTPS and LFA techniques at temperatures ranging from 20 to 160 °C and 100 to 300 °C, respectively. The results indicate that the thermal properties of LWC are highly affected by moisture content, temperature, and porosity. For LWC, the current Eurocodes 2 and 4 assume a constant value of specific heat (840 J/kg°C). This research reveals variability in temperatures near 150, 450, and 850 °C due to endothermic reactions. Furthermore, for low temperatures, the higher the porosity, the higher the thermal conductivity, while, at high temperatures, the higher the porosity, the lower the thermal conductivity. Thus, Eurocodes 2 and 4 should be updated accordingly. This research contributes to a deeper understanding and more accurate prediction of LWC’s effects on thermal properties at elevated temperatures.

Thermal conductivity and shrinkage properties of slag-based cement concretes

The thermal conductivity, specific heat, and total drying shrinkage test of slag blended OPC cement is conducted by using a Hotdisk-2500S thermal conductivity, and non-contact shrinkage deformation measurement apparatus based on ISO 22007-2 and GB/T50082-2009 test standards, respectively. The influence of replacement rates of slag cement (0, 30, 50, and 70%) and high-temperature exposure (21, 200, 400, 600, and 800 °C) on the thermal properties of concrete is analysed. The results show that for all three concretes, the thermal conductivity initially decreases with increasing temperature up to 400 °C, then after it remains almost constant between 400 and 600 °C, and gradually begins to decrease again up to 800 °C. Furthermore, thermal diffusivity of concrete group G-70, shows 21.4, 21.6, and 37.6% increment in 21, 200, and 600 °C temperature exposure respectively compared to concrete group G-0. Though, as the exposure temperature keeps rise to 800 °C, its value starts to decrease. Furthermore, the results indicated that high volume slag cement content in the concrete mix lessen the drying shrinkage of the concrete at later age. Test data is used as a function of temperature and slag replacement to establish high temperature relations for thermal properties. The proposed thermal property relationships can be used as input data for validation in computer programs and to evaluate the response of OPC and slag blended Portland cement concrete structures subjected to fire.