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Article

Towards Sustainable Construction: Evaluating Thermal Conductivity in Advanced Foam Concrete Mixtures

by
Alireza Mohtadi
1,2,
Mohammad Ghomeishi
3,* and
Ali Dehghanbanadaki
4,5
1
Department of Architecture, Gheshm Branch, Islamic Azad University, Gheshm 79515-1393, Iran
2
Research and Development, Materials and Technology, Institute of Iran Concrete Clinic, Tehran 14738-63451, Iran
3
Department of Architecture, Damavand Branch, Islamic Azad University, Tehran 39718-78911, Iran
4
Department of Civil Engineering, Damavand Branch, Islamic Azad University, Damavand 39718-78911, Iran
5
Research Center of Concrete and Soil, Damavand Branch, Islamic Azad University, Damavand 39718-78911, Iran
*
Author to whom correspondence should be addressed.
Buildings 2024, 14(11), 3636; https://doi.org/10.3390/buildings14113636
Submission received: 19 October 2024 / Revised: 7 November 2024 / Accepted: 9 November 2024 / Published: 15 November 2024
(This article belongs to the Section Building Energy, Physics, Environment, and Systems)
Browse Figures
Versions Notes

Abstract

Traditional concrete structures are frequently linked to poor energy efficiency and substantial heat loss, which pose significant environmental issues. To enhance thermal insulation and reduce heat loss, the use of precast insulated walls is suggested. This research introduces a new energy-efficient precast concrete panel (PCP). We explored various material combinations, including air bubbles, nano microsilica compound (NMC), nano microsilica powder (NMP), and latex, to determine the most effective formulation. A total of 99 tests were performed to assess the compressive strength of the samples, with 28 tests selected for thermal conductivity evaluations at temperatures of 300 °C and 400 °C based on satisfactory compressive strength results. The results indicated that the optimal mix of 4% air bubbles and 13% NMC achieved the lowest thermal conductivities of 1.31 W/m·K and 1.20 W/m·K at 300 °C and 400 °C, respectively, showing improvement ratios of 7% and 15.5% compared to the baseline tests. Additionally, the tests that included latex did not meet the thermal conductivity standards. The optimal combinations identified in this research can be effectively utilized in PCPs, resulting in significant energy savings. It is expected that stakeholders in the green building sector will recognize these proposed PCPs as a practical energy-efficient solution to advance sustainable and environmentally friendly construction practices.

1. Introduction

Growing global energy and environmental concerns underscore the urgent need for energy efficiency, reduced emissions, and sustainable practices. In this regard, the building sector leads all industries as the top energy consumer and greenhouse gas emitter [1,2]. Residential buildings, as the most prevalent type of structure, demand greater focus to decrease their energy usage. The key to energy conservation in these buildings centers on upgrading the building envelope and heating systems [3]. In 2021, building operations alone were responsible for 30% of global energy consumption and 27% of emissions from the energy sector [4]. Consequently, there is an urgent need to reduce energy consumption in buildings. In this context, enhancing the thermal insulation of building elements such as walls and roofs can be highly effective [5]. Consequently, numerous energy efficiency rating systems and building codes mandate specific thermal resistance levels, especially in colder regions.
To improve the thermal performance of concrete, many researchers have conducted studies on the thermal and mechanical properties of concrete incorporating various additives, both in laboratory settings and at real-world scales [6,7,8,9,10,11,12,13,14]. For example, in the research conducted by Ebru and Atmaca [15], Portland cement (PC) CEM II 42.5R was partially replaced with bentonite clay (BC) in varying proportions, ranging from 0 to 30% by volume. Mechanical and thermal conductivity tests were performed on the concrete samples after 28 days. Samples with 5% bentonite clay showed a substantial 94.7% improvement in compressive strength and a 31.2% decrease in thermal conductivity compared to the control group. However, exceeding 15% bentonite content significantly degraded both mechanical and thermal performance.
Air entrainment consistently proved more effective in lowering concrete’s thermal conductivity than other explored additive modifications in small-scale tests [16,17,18]. For example, Abdellatief et al. [19] explored using eggshell powder (ESP) and sawdust ash (SDA), along with aluminum powder as a foaming agent, to create geopolymer foam concrete (GFC). Partially replacing precursors with up to 20% ESP and SDA, they found that a 10% ESP mix improved compressive strength by 16.54% and a 5% SDA mix by 4.45%, relative to the control mix. In terms of thermal performance, the 10% ESP mixture demonstrated a thermal conductivity of 1.237 W/m.K, which is significantly lower than that of conventional concrete, typically around 1.4–2.5 W/m.K, indicating improved insulation properties.
Beyond small-scale tests on the thermal behavior of concrete, various binders have been shown to positively influence the thermal performance of concrete in full-scale wall applications [20,21,22,23,24]. Moreover, numerical simulations were used to model the thermal behavior of concrete in different building configurations, offering detailed insights into how various factors impact heat transfer and insulation performance in real-world conditions [25,26,27,28]. These studies collectively demonstrate that alternative binders not only enhance thermal insulation properties, but also maintain the structural integrity of concrete, making them viable for practical construction applications. For example, Ding et al. [29] developed prefabricated lightweight self-insulating foamed concrete wall panels using low-density, thermally insulating foamed concrete. While the panels’ impermeability met Chinese standards, their dry shrinkage, though improved, remained suboptimal. Crucially, the 150 mm thick panels exhibited excellent mechanical properties, meeting or exceeding standards for flexural strength, impact resistance, and load-bearing capacity, suggesting their suitability for enhancing building insulation and structural performance.
Two studies explored the enhancement of building insulation using modified foamed concrete. Nguyen-Van et al. [22] incorporated phase-change materials (PCM) into foamed concrete cladding panels, significantly reducing internal wall and air temperatures, although the performance varied with sun exposure. Shi et al. [30] investigated using desert sand (DS) and rice husk ash (RHA) in foamed concrete. While DS improved stability but reduced strength, adding RHA mitigated this by enhancing the matrix structure and thermal performance. The DS/RHA combination improved insulation, lowered environmental impact, and reduced costs. Both studies demonstrate promising approaches to improving building energy efficiency with modified foamed concrete.
Despite significant advancements in building materials and energy efficiency, there remains a critical need to further enhance energy savings in concrete structures. Numerous studies have been published highlighting various approaches to this challenge [8,31,32,33,34,35,36,37,38]; however, innovative solutions are still required to optimize thermal performance. This study aims to contribute to this ongoing effort by focusing on the development of a novel concrete panel specifically designed for interior walls, with the goal of improving energy efficiency in buildings. The primary objective of this study is to develop a new precast concrete panel (PCP) that enhances energy efficiency. To achieve this, the research will evaluate the effects of various combinations of cement dosages, air bubbles, nano microsilica compound (NMC), nano microsilica powder (NMP), and latex on the thermal conductivity of the PCP. The ultimate goal is to reduce the thermal conductivity of the lightweight concrete panel while ensuring that the material maintains an acceptable level of compressive strength.

2. Experimental Design

2.1. Used Materials and Testing Program

A new concrete panel has been developed and proposed for use in buildings situated in cold regions. This study involved the production of samples utilizing various combinations of cement dosages, air bubbles, NMC, NMP, and latex for compressive and thermal testing.
The selection of specific ingredients for developing the concrete mixture was based on their unique properties and potential synergistic effects in achieving both thermal efficiency and structural integrity. The incorporation of NMC and NMP was primarily driven by their nanoscale particle size, which enables them to fill microscopic voids in the cement matrix, creating a denser microstructure. Their high surface area-to-volume ratio enhances reactivity with cement compounds, promoting stronger chemical bonds through pozzolanic reactions that produce additional C-S-H gel. Similarly, air bubbles were introduced through foaming agents to create a cellular structure within the concrete matrix that traps air, naturally reducing thermal conductivity while decreasing the overall density of the concrete panel. This combination of nanomaterials and air voids was designed to optimize thermal resistance while maintaining structural integrity.
The inclusion of latex in certain mix designs was aimed at improving the bond between cement particles and aggregates while enhancing the flexibility and crack resistance of the hardened concrete. This additive also contributes to reduced permeability, which can affect thermal properties, and provides better adhesion properties for potential surface treatments. The systematic selection and combination of these materials directly aligned with our research objectives of developing energy-efficient precast concrete panels while maintaining structural requirements for interior wall applications. Through varying proportions of these materials in different mix designs, we were able to identify the optimal combination that achieves the lowest thermal conductivity while meeting the required compressive strength criteria, making these panels particularly suitable for interior wall applications in buildings situated in cold regions.
Figure 1 illustrates the materials and the proposed concrete panel utilized in this research. The primary investigation focused on evaluating the effects of these materials on the compressive strength of the samples. Both the individual and combined effects of these materials were tested. The concrete mix design is presented in Table 1. The engineering properties of used materials are shown in Table 2. The exact details of these tests, including the specific percentages of each additive, are shown in Table A1 (Appendix A). Based on Table A1, 99 tests (TS-1 to TS-99) were conducted. It should be noted that the effects of these materials were only evaluated using samples cured for 28 days. As expected, the inclusion of air bubbles decreased the compressive strength of the samples. Therefore, thermal conductivity tests were only performed on selected samples that met the minimum required compressive strength. This selection will be discussed in the Results section.

2.2. Implementation of Precast Concrete Panels for Interior Wall Systems

The thermally-efficient PCPs developed in this research are particularly suitable for interior wall applications, offering both thermal insulation and space-efficient solutions for building interiors. This section outlines the practical implementation aspects of these panels as interior wall systems. Interior PCPs primarily utilize two types of connections: floor/ceiling connections and panel-to-panel connections. The floor connection system employs L-shaped steel brackets anchored to the floor slab, allowing for vertical adjustment during installation. At the ceiling interface, adjustable top connections accommodate construction tolerances and potential floor deflection. Panel-to-panel connections are achieved through concealed mechanical fasteners or tongue-and-groove systems, ensuring smooth wall surfaces while maintaining thermal properties. This approach to interior PCP implementation combines the thermal efficiency benefits of our research with practical installation considerations, supporting sustainable interior construction practices while maintaining functionality and esthetics.

2.3. Test Standards

The experimental procedures adhered to specific standards for both the preparation and testing of the samples. The ASTM standard C260-86 (1995) [39] was followed for the suggested combinations and proportions of additives used in the concrete mixtures. This standard outlines the requirements for air-entraining admixtures used in concrete, which are chemical additives that introduce and stabilize microscopic air bubbles in the concrete mix. For evaluating the compressive strength of the samples, the BS EN 12390-3 standard (2009) [40] was employed. This standard outlines the methods for making and curing test specimens, as well as the procedures for conducting the compressive strength tests.
The thermal conductivity coefficient of the samples was tested according to the ISO 8301 standard (1991) [41], which specifies the use of the guarded hot plate apparatus for determining the steady-state thermal transmission properties of materials. The apparatus consists of a central heating plate, surrounded by a guard ring, and two cooling plates, ensuring a uniform one-dimensional heat flow through the sample. The test specimens were placed between the hot and cold plates and the heat flux through the material was measured. The thermal conductivity was calculated based on the temperature gradient and the heat flow across the sample. For this study, measurements were carried out at two distinct temperature levels, 300 °C and 400 °C, to evaluate the material’s performance under varying thermal conditions. The apparatus was calibrated and maintained according to the ISO 8301 (1991) [41] guidelines to ensure the accuracy and repeatability of the results. Figure 2a,b illustrate the compressive strength and thermal conductivity tests conducted in this study, respectively.
A petrographic analysis was conducted on hardened concrete samples to assess the air-void system, specifically to characterize the size, distribution, and morphology of the air bubbles within the cement paste. This analysis provided quantitative data on air content and void characteristics, which are crucial factors influencing the freeze–thaw durability and overall performance of the concrete. Thin sections were prepared and examined under a polarized microscope to identify and measure the air voids, allowing for a detailed assessment of the air-entraining admixture’s effectiveness and the resulting air-void system’s characteristics.

3. Results and Discussions

3.1. Compressive Strength Tests

Figure 3a,b illustrate the compressive strength (f’c) results from the conducted tests. The baseline test, which utilized 300 kg/m3 of cement without any additives, achieved an f’c of 35.53 MPa. It is well established that the incorporation of air bubbles generally reduces f’c. For instance, the addition of 4% air (designated as TS-5) to the baseline mixture, without any other additives, resulted in a significant decrease in compressive strength to 15.77 MPa, reflecting a reduction of approximately 55%. Conversely, in the TS-9 test, the incorporation of 8% NMC led to an increase in f’c to 40.33 MPa, demonstrating an improvement of 13%. Additionally, Figure 3a presents the top four tests ranked by f’c. Notably, the highest f’c was observed in the TS-72 test, which utilized a combination of 5% NMC, achieving an f’c of 56.83 MPa.
For better visualization, Figure 3c presents the f’c values in a 3D format. As expected, reducing the air content and increasing the cement quantity generally led to higher f’c values. However, the presence of the NMC and NMP in some test combinations reveals that the addition of air can actually enhance f’c. This unexpected outcome is attributed to the beneficial effects of NMC and NMP. Nevertheless, due to the influence of four distinct parameters, achieving precise visualization and interpretation of the results, even in a 3D format, remains challenging.
To better illustrate the influence of various parameters on f’c, a correlation matrix of the developed dataset was generated and is presented in Figure 4. Given the complex interactions among the influencing parameters, this chart provides an approximate representation of their effects on the f’c of the samples. As expected, the results indicate a positive correlation between cement content and f’c, while latex exhibits a negative impact on f’c. The reduction in f’c associated with latex-modified concrete can be attributed to several factors. First, latex tends to increase the flexibility of the concrete compared to conventional mixes. While this flexibility enhances crack resistance and improves toughness, it may also lead to lower f’c, especially if the mix is primarily designed for flexibility rather than load-bearing capacity. Additionally, the introduction of latex can result in increased air entrapment within the concrete mix, which further contributes to a decrease in f’c.
The correlation matrix indicates positive correlations for both the NMC and NMP with values of 0.12 and 0.20, respectively. These positive correlations suggest that the inclusion of these materials enhances the f’c of the concrete samples. The beneficial effects of NMC and NMP can be attributed to their ability to improve the microstructure of the concrete. Specifically, these nano-sized materials fill the voids within the cement matrix, leading to a denser and more homogeneous structure. This densification reduces the porosity of the concrete, which, in turn, enhances its mechanical properties, including f’c. Additionally, both NMC and NMP contribute to the pozzolanic reaction, which further enhances strength by producing additional calcium silicate hydrates (C-S-H) during hydration. This reaction not only improves the binding properties of the concrete, but also contributes to increased durability and resistance to environmental factors, making these materials valuable additives in the pursuit of higher f’c.
It should be mentioned that NMP outperforms NMC in enhancing the f’c due to its finer particle size, which allows for better void filling and improved packing density within the concrete matrix. NMP exhibits higher pozzolanic reactivity, leading to the greater production of calcium silicate hydrate (C-S-H) during hydration. Additionally, NMP contributes less to air entrapment, resulting in a denser mix. Its superior workability facilitates more uniform material distribution, enhancing the overall concrete performance. These factors collectively make NMP a more effective additive for achieving higher f’c.

3.2. Thermal Conductivity Tests

Figure 5a–c depict the thermal conductivity of the test samples across various conditions. Based on these results, the thermal conductivity and f’c of various PCP mixtures at 300 °C were analyzed in relation to different material compositions. The thermal conductivity (K) values were found to range from 1.20 W/m·K to 2.12 W/m·K, while the f’c varied between 15.77 MPa and 46.57 MPa. These variations are attributed to the influence of cement content, air entrainment, latex, NMP, and NMC.
The effect of air entrainment on the thermal and mechanical properties was particularly evident. Samples containing air (e.g., TS-5, TS-21, TS-29) exhibited lower thermal conductivity values, as air acts as an effective insulator. For instance, TS-5, which contained 4% air, showed a thermal conductivity of 1.28 W/m·K, one of the lowest values recorded. However, this reduction in thermal conductivity was accompanied by a significant decrease in f’c, with TS-5 exhibiting the lowest f’c of 15.77 MPa. This suggests that while air entrainment improves thermal insulation, it has a detrimental effect on the mechanical strength of the concrete.
The inclusion of latex in the mixtures was found to increase thermal conductivity, but it also enhanced compressive strength. For example, TS-66, which contained 5% latex, exhibited a thermal conductivity of 2.02 W/m·K, higher than most other samples. Despite this, the compressive strength of TS-66 remained relatively high at 26.77 MPa. Similarly, TS-99, which also contained 5% latex, displayed the highest thermal conductivity at 2.12 W/m·K, but still maintained a compressive strength of 31.9 MPa. These results indicate that latex improves the mechanical performance of the concrete, albeit at the cost of increased thermal conductivity.
The effects of NMC on both thermal and mechanical properties were also significant. Samples containing NMC (e.g., TS-21, TS-33, TS-54, TS-66, TS-87, TS-99) generally exhibited higher thermal conductivity values. For instance, TS-99, which contained 8% NMC, showed the highest thermal conductivity of 2.12 W/m·K. However, its f’c was also relatively high at 31.9 MPa, suggesting that the use of NMC enhances the mechanical properties of the concrete, albeit with an associated increase in thermal conductivity. This trend was consistent across other samples containing NMC, such as TS-33 and TS-66, both of which exhibited high thermal conductivity but maintained good f’c.
The addition of NMP was found to have a significant impact on reducing thermal conductivity. For example, TS-29, which contained 13% NMP, exhibited the lowest thermal conductivity of 1.20 W/m·K. The f’c of this sample was moderate at 23.83 MPa, indicating that NMP is effective in improving the thermal insulation properties of concrete without severely compromising its mechanical strength. This trend was also observed in TS-62 and TS-95, both of which contained 13% NMP and displayed relatively low thermal conductivity values while maintaining adequate f’c.

3.3. Improvement Ratio of the Thermal Conductivity Tests

The analysis of the improvement rates of thermal conductivity for selected tests, as depicted in Figure 6, highlights significant findings. Tests TS-5, TS-29, TS-33, TS-38, and TS-62 showed notable reductions in thermal conductivity compared to the baseline. Among these, TS-29 demonstrated exceptional performance, with the optimal combination of 4% air bubbles and 13% NMP, achieving the lowest thermal conductivities of 1.31 W/m·K at 300 °C and 1.20 W/m·K at 400 °C. These changes resulted in improvement ratios of 7% and 15.5%, respectively, compared to the baseline. The graph illustrates that the selected tests generally achieved better improvement ratios at 400 °C than at 300 °C, indicating enhanced thermal performance at higher temperatures. This trend underscores the effectiveness of the material modifications in maintaining lower thermal conductivity under elevated thermal conditions.
Additionally, it was observed that tests incorporating latex did not meet the desired thermal conductivity requirements, suggesting that latex may not be suitable for applications prioritizing thermal insulation. This insight directs future research towards exploring alternative additives that might better balance thermal and mechanical properties. The findings suggest that the optimal combinations identified, particularly those in TS-29, can be effectively applied in precast concrete panels, offering potential for significant energy savings. The application of these optimized mixtures in construction could lead to improved energy efficiency in buildings, aligning with sustainable development goals. Further research could explore scaling these findings to real-world applications, considering long-term performance and cost-effectiveness.
Figure 7 depicts the microstructure of the concrete samples, specifically highlighting the distribution and characteristics of air bubbles within the matrix. The petrographic analysis of the TS-5 sample, which contains 4% air, reveals the presence and arrangement of air voids throughout the concrete structure. These air bubbles, indicated by red dots in the image, play a crucial role in the thermal performance of the concrete panel. The distribution, size, and frequency of these air voids directly influence the material’s thermal conductivity by creating discontinuities in the solid matrix that impede heat transfer.
The petrographic analysis shown in Figure 7 allows for a detailed examination of the concrete’s internal structure, providing visual evidence of the effectiveness of the air entrainment process. The presence of these air bubbles contributes to the lightweight nature of the concrete and its improved insulating properties. This microscopic view of the concrete sample supports our findings regarding the thermal conductivity improvements observed in the TS-5 mix design, demonstrating the correlation between the intentional introduction of air voids and the enhanced thermal performance of the precast concrete panels. Furthermore, this analysis helps validate the methodology employed in creating energy-efficient concrete mixtures for interior wall applications.

3.4. Energy Saving Estimation

To demonstrate the potential energy savings of the optimized precast concrete panels (PCPs), we present a comparative analysis using a hypothetical building scenario. This example illustrates the energy savings achieved by using our most effective mixture (TS-29) compared to a standard concrete panel.
Example Scenario:
Consider a 10-story office building located in a cold climate region, with each floor having 1000 m2 of floor area. The building has 4000 m2 of interior walls made of precast concrete panels, with a thickness of 0.15 m.
Calculation Method:
  • Heat Transfer Equation: Q = k × A × (ΔT/d)
where:
  • Q = Heat transfer rate (W)
  • k = Thermal conductivity (W/m·K)
  • A = Surface area (m2)
  • ΔT = Temperature difference (K)
  • d = Wall thickness (m)
  • Assumptions:
    • Indoor temperature: 20 °C
    • Average outdoor temperature during heating season: 0 °C
    • Heating season duration: 180 days
  • Comparison:
    (a)
    Standard concrete panel: k = 1.42 W/m·K (baseline value)
    (b)
    Optimized PCP (TS-29): k = 1.20 W/m·K
  • Calculations:
  • Heat transfer rate for standard panel:
  • Q_std = 1.42 × 4000 × (20/0.15) = 756,800 W
  • Heat transfer rate for optimized PCP:
  • Q_opt = 1.20 × 4000 × (20/0.15) = 640,000 W
  • Energy Savings:
  • Daily energy saving: (756,800–640,000) × 24 h = 2,803,200 Wh = 2803.2 kWh
  • Seasonal energy saving: 2803.2 kWh × 180 days = 504,576 kWh
  • Cost Savings:
  • Assuming an electricity cost of USD 0.12 per kWh:
  • Annual cost saving: 504,576 kWh × USD 0.12 = USD 60,549.12
This example demonstrates that using the optimized PCP (TS-29) could potentially save approximately 504,576 kWh of energy per heating season, translating to a cost saving of over USD 60,000 annually for this hypothetical building. This represents a significant reduction in energy consumption and operational costs, highlighting the practical benefits of the developed PCPs in building applications.
It is important to note that the actual savings may vary depending on specific building characteristics, climate conditions, and energy prices. However, this example clearly illustrates the substantial potential for energy and cost savings when implementing the optimized precast concrete panels developed in this study.

4. Conclusions

This study investigated the optimization of concrete mixture designs for enhanced thermal performance in precast concrete panels (PCPs), balancing the need for both low thermal conductivity and adequate compressive strength. A total of 99 initial mixes were tested, with 28 selected for further thermal analysis. The key findings are summarized below.
  • The most effective mixture (TS-29) incorporated 4% air bubbles and 13% nano microsilica powder (NMP), achieving thermal conductivities of 1.31 W/m·K and 1.20 W/m·K at 300 °C and 400 °C, respectively. This represents a 7% and 15.5% improvement compared to the baseline, demonstrating significant potential for energy savings in building applications.
  • While air entrainment effectively reduced thermal conductivity, it also lowered compressive strength. This highlights the importance of carefully balancing air content to achieve optimal performance in both areas.
  • Latex addition, while beneficial for compressive strength, proved detrimental to thermal insulation, increasing conductivity. This suggests latex is unsuitable for PCP applications where thermal performance is a primary concern.
  • Nano microsilica compound (NMC) additions exhibited a complex relationship with both thermal conductivity and compressive strength, generally increasing both. Further investigation is warranted to fully understand the influence of NMC on overall PCP performance.

5. Limitations of the Current Study and Recommendations for Future Research

It should be mentioned that, in the present study, the material exploration focused on a specific set of components (air bubbles, NMC, NMP, and latex), potentially overlooking other promising additives. Furthermore, the research was conducted under controlled laboratory conditions, necessitating further investigation into real-world applications and long-term performance. The study primarily evaluated compressive strength, neglecting other important mechanical properties like flexural strength and impact resistance. Finally, a comprehensive cost analysis was not included, limiting the assessment of economic viability.
Building upon the findings of this study, several recommendations for future research emerge. Expanding the material investigation to include a broader range of additives, such as different nanoparticles, fibers, and supplementary cementitious materials, could further enhance PCP performance. Validating the laboratory findings through field studies and pilot projects is crucial for assessing real-world durability and performance. A more comprehensive mechanical testing program, incorporating flexural strength, impact resistance, and other relevant properties, is needed. Finally, life-cycle assessment and cost–benefit analysis are essential for evaluating the environmental and economic impacts of the optimized PCPs, paving the way for their wider adoption in sustainable construction.
While our innovative precast concrete panel design offers significant thermal performance benefits, it is important to acknowledge certain constraints. The incorporation of the nano microsilica compound may result in marginally increased upfront costs. Additionally, the manufacturing process requires the meticulous management of air content to achieve optimal results. Nevertheless, these challenges are outweighed by the considerable enhancements in thermal insulation and long-term energy conservation. The design’s alignment with sustainable building practices and its potential for widespread application in energy-conscious construction make it a valuable contribution to the field. Despite the initial complexities, the design maintains feasibility for practical implementation, striking a balance between advanced performance and real-world applicability in the construction industry.
To build upon the results of this study, we propose implementing extensive energy simulations using sophisticated modeling software like EnergyPlus. Our research primarily concentrated on the experimental creation and evaluation of novel precast concrete panels. However, incorporating comprehensive energy simulations would offer crucial information about the extended performance of these panels in diverse real-world applications. Such simulations would enhance our understanding of the panels’ effectiveness across various building types and climate zones and over extended time periods, thereby providing a more complete picture of their potential impact on energy efficiency in the construction industry.
Further research should also consider optimizing PCP designs for specific climate zones to maximize energy efficiency.

Author Contributions

Methodology, A.M.; Writing—original draft, A.M.; Visualization, A.D.; Supervision, M.G. and A.D. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

Appendix A

Table A1. Details of the compressive strength tests.
Table A1. Details of the compressive strength tests.
TestCement
Dosage		AdditivesAdditive Percentage (%)
TS-1300None0
TS-2300Air bubbles1
TS-3300Air bubbles2
TS-4300Air bubbles3
TS-5300Air bubbles4
TS-6300NMC5
TS-7300NMC6
TS-8300NMC7
TS-9300NMC8
TS-10300Latex2
TS-11300Latex3
TS-12300Latex4
TS-13300Latex5
TS-14300NMP10
TS-15300NMP11
TS-16300NMP12
TS-17300NMP13
TS-18300Air bubbles and NMC1–5
TS-19300Air bubbles and NMC2–6
TS-20300Air bubbles and NMC3–7
TS-21300Air bubbles and NMC3–8
TS-22300Air bubbles and Latex1–2
TS-23300Air bubbles and Latex2–3
TS-24300Air bubbles and Latex3–4
TS-25300Air bubbles and Latex4–5
TS-26300Air bubbles and NMP1–10
TS-27300Air bubbles and NMP2–11
TS-28300Air bubbles and NMP3–12
TS-29300Air bubbles and NMP4–13
TS-30300Air bubbles, NMC, and Latex1–5–2
TS-31300Air bubbles, NMC, and Latex2–6–3
TS-32300Air bubbles, NMC, and Latex3–7–4
TS-33300Air bubbles, NMC, and Latex4–8–5
TS-34350None0
TS-35350Air bubbles1
TS-36350Air bubbles2
TS-37350Air bubbles3
TS-38350Air bubbles4
TS-39350NMC5
TS-40350NMC6
TS-41350NMC7
TS-42350NMC8
TS-43350Latex2
TS-44350Latex3
TS-45350Latex4
TS-46350Latex5
TS-47350NMP10
TS-48350NMP11
TS-49350NMP12
TS-50350NMP13
TS-51350Air bubbles and NMC1–5
TS-52350Air bubbles and NMC2–6
TS-53350Air bubbles and NMC3–7
TS-54350Air bubbles and NMC3–8
TS-55350Air bubbles and Latex1–2
TS-56350Air bubbles and Latex2–3
TS-57350Air bubbles and Latex3–4
TS-58350Air bubbles and Latex4–5
TS-59350Air bubbles and NMP1–10
TS-60350Air bubbles and NMP2–11
TS-61350Air bubbles and NMP3–12
TS-62350Air bubbles and NMP4–13
TS-63350Air bubbles, NMC, and Latex1–5–2
TS-64350Air bubbles, NMC, and Latex2–6–3
TS-65350Air bubbles, NMC, and Latex3–7–4
TS-66350Air bubbles, NMC, and Latex4–8–5
TS-67400None0
TS-68400Air bubbles1
TS-69400Air bubbles2
TS-70400Air bubbles3
TS-71400Air bubbles4
TS-72400NMC5
TS-73400NMC6
TS-74400NMC7
TS-75400NMC8
TS-76400Latex2
TS-77400Latex3
TS-78400Latex4
TS-79400Latex5
TS-80400NMP10
TS-81400NMP11
TS-82400NMP12
TS-83400NMP13
TS-84400Air bubbles and NMC1–5
TS-85400Air bubbles and NMC2–6
TS-86400Air bubbles and NMC3–7
TS-87400Air bubbles and NMC3–8
TS-88400Air bubbles and Latex1–2
TS-89400Air bubbles and Latex2–3
TS-90400Air bubbles and Latex3–4
TS-91400Air bubbles and Latex4–5
TS-92400Air bubbles and NMP1–10
TS-93400Air bubbles and NMP2–11
TS-94400Air bubbles and NMP3–12
TS-95400Air bubbles and NMP4–13
TS-96400Air bubbles, NMC, and Latex1–5–2
TS-97400Air bubbles, NMC, and Latex2–6–3
TS-98400Air bubbles, NMC, and Latex3–7–4
TS-99400Air bubbles, NMC, and Latex4–8–5

References

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Figure 1. Materials used for the tests. (a) Air bubble, (b) NMC, (c) NMP, (d) latex, (e) PCP.
Figure 1. Materials used for the tests. (a) Air bubble, (b) NMC, (c) NMP, (d) latex, (e) PCP.
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Figure 2. Experimental tests. (a) Compressive strength test; (b) thermal conductivity test.
Figure 2. Experimental tests. (a) Compressive strength test; (b) thermal conductivity test.
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Figure 3. (a) f’c of the tests. (b) Error bar of the f’c; (c) 3D chart for the f’c.
Figure 3. (a) f’c of the tests. (b) Error bar of the f’c; (c) 3D chart for the f’c.
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Figure 4. Correlation between effective parameters for estimating the f’c.
Figure 4. Correlation between effective parameters for estimating the f’c.
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Figure 5. (a) Thermal conductivity of the tests. (b) Compressive vs. thermal conductivity; (c) 3D data.
Figure 5. (a) Thermal conductivity of the tests. (b) Compressive vs. thermal conductivity; (c) 3D data.
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Figure 6. Improvement ratio of the thermal conductivity of the tests.
Figure 6. Improvement ratio of the thermal conductivity of the tests.
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Figure 7. Petrographic analysis of concrete samples, highlighting air bubbles.
Figure 7. Petrographic analysis of concrete samples, highlighting air bubbles.
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Table 1. Concrete mix design.
Table 1. Concrete mix design.
Reference MixtureCement
Dosage (kg/m3)		W/CW (kg)C (kg)G
(Natural Coarse)		S
(Fine Coarse)
I3000.51503001135730
II3500.51753501140745
III4000.52004001160756
Note: W/C = water to cement; C = cement; G = gravel; S = sand.
Table 2. Engineering properties of used materials.
Table 2. Engineering properties of used materials.
PropertiesNMCNMPLatex
Particle Size0.3 µm50 nm100 nm
Density2.2 g/cm32.4 g/cm31.1 g/cm3
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Mohtadi, A.; Ghomeishi, M.; Dehghanbanadaki, A. Towards Sustainable Construction: Evaluating Thermal Conductivity in Advanced Foam Concrete Mixtures. Buildings 2024, 14, 3636. https://doi.org/10.3390/buildings14113636

AMA Style

Mohtadi A, Ghomeishi M, Dehghanbanadaki A. Towards Sustainable Construction: Evaluating Thermal Conductivity in Advanced Foam Concrete Mixtures. Buildings. 2024; 14(11):3636. https://doi.org/10.3390/buildings14113636

Chicago/Turabian Style

Mohtadi, Alireza, Mohammad Ghomeishi, and Ali Dehghanbanadaki. 2024. "Towards Sustainable Construction: Evaluating Thermal Conductivity in Advanced Foam Concrete Mixtures" Buildings 14, no. 11: 3636. https://doi.org/10.3390/buildings14113636

APA Style

Mohtadi, A., Ghomeishi, M., & Dehghanbanadaki, A. (2024). Towards Sustainable Construction: Evaluating Thermal Conductivity in Advanced Foam Concrete Mixtures. Buildings, 14(11), 3636. https://doi.org/10.3390/buildings14113636

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