A comparative study on the thermal conductivities and mechanical properties of lightweight concretes

The thermal conductivity of concrete is a key factor for efficient energy consumption in concrete buildings because thermal conductivity plays a significant role in heat transfer through concrete walls. This study investigated the effects of replacing fine aggregates with coal bottom ash (CBA) and the influence of curing age on the thermal properties of high-strength concrete with a compressive strength exceeding 60 MPa. The different CBA aggregate contents included 25%, 50%, 75%, and 100%, and different curing ages included 28 and 56 days. For concrete containing CBA fine aggregate, the thermal and mechanical properties, including the unit weight, thermal conductivity, compressive strength, and ultrasonic velocity, were measured. The experimental results reveal that the unit weight and thermal conductivity of the CBA concrete were highly dependent on the CBA content. The unit weight, thermal conductivity, and compressive strength of the concrete decreased as the CBA content increased. Relationships between the thermal conductivity and the unit weight, thermal conductivity and compressive strength of the CBA concrete were proposed in the form of exponential functions. The equations proposed in this study provided predictions that were in good agreement with the test results. In addition, the test results show that there was an approximately linear relationship between the thermal conductivity and ultrasonic velocity of the CBA concrete.

Section: Thermal Conductivitymentioning

confidence: 69%

“…Regarding concrete with low thermal conductivity, some experimental studies have been performed [6][7][8][9][10][11]. Aghdam et al [6] performed an experimental study to estimate the effects of carbon nanotubes on the thermal conductivity of steel fiber-reinforced concrete.…”

Section: Introductionmentioning

confidence: 99%

A Study on the Thermal Properties of High-Strength Concrete Containing CBA Fine Aggregates

Yang

Park

2020

“…However, previous studies focused mainly on wall claddings, board, partitions, and other non-structural elements [11,[22][23][24][25][26]. Thermal conductivity, density, and compressive strength of EPS beads as reported in previous literatures are summarized in Table 1 [23,[27][28][29][30][31][32][33][34][35]. From Table 1, EPS beads improve the thermal insulation of concrete when serving as lightweight aggregates, but reduce its strength as the content increases.…”

Section: Introductionmentioning

confidence: 99%

Structural Applications of Thermal Insulation Alkali Activated Materials with Reduced Graphene Oxide

Long¹,

Lin²,

Tan³

et al. 2020

Development of low thermal conductivity and high strength building materials is an emerging strategy to solve the heavy energy consumption of buildings. This study develops sustainable alkali activated materials (AAMs) for structural members from waste expanded polystyrene (EPS) beads and reduced graphene oxide (rGO) to simultaneously meet the thermal insulation and mechanical requirements of building energy conservation. It was found that the thermal conductivity of AAMs with 80 vol.% EPS and 0.04 wt.% rGO (E8–G4) decreased by 74% compared to the AAMs without EPS and rGO (E0). The 28-day compressive and flexural strengths of E8–G4 increased by 29.8% and 26.5% with the addition of 80 vol.% EPS and 0.04 wt.% rGO, compared to the sample with 80 vol.% EPS without rGO (E8). In terms of compressive strength, thermal conductivity, and cost, the efficiency index of E8–G4 was higher than those of other materials. A building model made from AAMs was designed using building information modeling (BIM) tools to simulate energy consumption, and 31.78% of total energy consumption (including heating and cooling) was saved in the building operation period in Harbin City, China. Hence, AAMs made of waste EPS beads and rGO can realize the structural and functional integrated application in the future.

“…Calcined perlite powder was added into the concrete for a compression test, and it showed that the compressive strength decreased with the increase in perlite replacement ratio. The thermal conductivity and mechanical performance of lightweight concrete showed that the compressive strength decreased with an increase in the amount of lightweight aggregate [2][3][4]. The ultra-lightweight cement composite was exposed to high-temperature and showed that elastic modulus loss was significantly quicker than that of compressive strength.…”

Section: Introductionmentioning

confidence: 99%

A Compressive Peak Strength Model for CFRP-Confined Thermal Insulation Materials under Elevated Temperature

Sio

Tsai

2019

In this paper, a compressive peak strength model for CFRP-confined thermal insulation materials under elevated temperature was proposed. The thermal insulation material was made by Portland cement with different portions of perlite. The compressive strengths of four different perlite ratios in weight, such as 0%, 10%, 20%, and 30% of thermal insulation materials, confined by one-layer, two-layer, and three-layer carbon fiber-reinforced polymer (CFRP) composite materials, were obtained. The test results indicated that the specimen’s compressive strength decreased with an increase in the amount of perlite replacement and increased with an increase in the number of CFRP wrapping layers. Based on the test results, a theoretical compressive peak strength model with some parameters was proposed. In the meantime, the compressive strengths of the above four different perlite ratios of thermal insulation materials under elevated temperature, such as ambient temperature, 100 °C, 150 °C, 200 °C, 250 °C, and 300 °C, were obtained. For compression tests of specimens with a fixed amount of perlite, the test results indicated that the specimen’s compressive strength decreased with an increase in temperature, highlighting a thermal softening phenomenon. Based on the test results, a compressive peak strength model with a thermal softening parameter was proposed to predict the peak strength under elevated temperature. Finally, a compressive peak strength model for thermal insulation material with CFRP confinement under different elevated temperature was derived, and it achieved acceptable results in comparison to the experimental results.