RESULTS OF EXPERIMENTAL STUDIES OF THERMAL INSULATION PROPERTIES OF CONCRETE WITH THE ADDED VERMICULITE

ABSTRACT

The article investigates the thermal insulation properties of concretes with added vermiculite based on experimental studies. While ordinary concrete has high strength, its thermal conductivity coefficient is relatively high and therefore insufficient to meet energy efficiency requirements. For this reason, samples with 10–75% vermiculite by cement mass were prepared, and their density, thermal conductivity coefficient, and heat capacity were determined. The experiments were conducted on the XND-2-3030C device in accordance with GOST 7076-99 standards. The results showed that as the vermiculite content increased, the density and thermal conductivity coefficient of the concrete decreased significantly. Optimal results were observed when 20–30% vermiculite was added. Vermiculite concrete is environmentally friendly, lightweight, and fire-resistant, making it consistent with “green building” requirements. Its application in construction as energy-efficient wall panels and thermal insulation material has been substantiated.

АННОТАЦИЯ

В статье на основе экспериментальных исследований изучены теплоизоляционные свойства бетонов с добавлением вермикулита. Обычный бетон обладает высокой прочностью, однако его коэффициент теплопроводности велик, что делает его недостаточно эффективным для требований энергосбережения. В связи с этим были приготовлены образцы с добавлением вермикулита в количестве от 10 до 75% от массы цемента, для которых определялись плотность, коэффициент теплопроводности и теплоёмкость. Испытания проводились на установке ХНД-2-3030С в соответствии с требованиями ГОСТ 7076-99. Результаты показали, что с увеличением содержания вермикулита плотность бетона и коэффициент теплопроводности существенно снижаются. Наиболее оптимальные показатели наблюдались при добавлении 20–30% вермикулита. Бетон с вермикулитом является экологически чистым, лёгким и огнестойким материалом, соответствующим требованиям «зелёного строительства». Обоснованы перспективы его применения в строительстве для производства энергосберегающих стеновых панелей и теплоизоляционных материалов.

Keywords: vermiculite concrete, thermal conductivity, density, energy efficiency, thermal insulation, green building.

Ключевые слова: вермикулитобетон, теплопроводность, плотность, энергоэффективность, теплоизоляция, «зелёное строительство».

Introduction. At present, one of the urgent tasks in the construction industry is improving energy efficiency and reducing heat loss. Although conventional concrete has high strength, its thermal conductivity is significant; therefore, it does not fully meet insulation requirements. In this regard, research is being carried out to improve the thermal efficiency of concrete by introducing additives with low thermal conductivity.

Vermiculite is a natural mineral that acquires a porous structure at high temperatures. This significantly reduces its thermal conductivity and makes it possible to use it in construction as an insulating material. In the present study, the thermal properties of concrete with the addition of vermiculite were experimentally investigated.

 Literature Review. The issue of improving the thermal insulation efficiency of concrete by introducing various mineral additives is widely studied in scientific sources. Research conducted in Russia, the USA, India, China, and European countries has shown that the thermal conductivity coefficient of concretes with expanded vermiculite is several times lower than that of traditional concrete.

In particular:

• Studies by Russian and Belarusian scientists established that the thermal conductivity coefficient of concretes with vermiculite is within the range of λ = 0.18–0.30 W/m·K.
• American researchers found that the use of lightweight concrete wall panels based on vermiculite makes it possible to reduce heat loss by 25–30%.
• Chinese and Indian scientists especially emphasized the high fire resistance of vermiculite concrete.
• In experiments by European researchers, it was observed that with the addition of 20–25% vermiculite, thermal efficiency reaches maximum values.

In addition, vermiculite-based concrete is considered an environmentally friendly material that complies with the concept of “green construction.”

Research Methodology.

In this study, special concrete samples were prepared, into which vermiculite was introduced in amounts of 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, and 75% of the cement mass. For each sample, the following parameters were determined:

• Density (kg/m³),
• Thermal conductivity coefficient λ (W/m·K),
• Heat capacity (kJ/kg·K).

The tests were carried out in accordance with GOST 7076-99 “Building materials and products. Method for determining thermal conductivity.”
The thermal conductivity coefficient of the samples was measured using the XND-2-3030C apparatus (Flat Plate Thermal Conductivity Instrument).

Experimental Results

Dependence of the thermal conductivity coefficient on the amount of vermiculite relative to the cement mass

Table 1.

Results

Main Observations:

• With an increase in vermiculite content (from 10% to 75%), the density of the samples (kg/m³) decreases sharply.

For example: at 10% it is about 1345 kg/m³, while at 75% it is about 587 kg/m³.
This indicates the lightweight, porous structure of vermiculite.

• The thermal conductivity coefficient (λ) also decreases: at 10%-0.342 W/(m·K), at 75% — 0.150 W/(m·K). Thus, thermal conductivity was reduced by more than two times.
• In the dry state, both density and thermal conductivity are even lower, which enhances the insulating properties.
• A consistent pattern is observed: as vermiculite content increases, concrete density decreases, and thermal conductivity falls.
• The obtained results are consistent with international studies: the thermal insulation of vermiculite concrete is significantly higher than that of conventional concrete.
• The most favorable results were noted with the addition of 20–30% vermiculite. In this case, the density decreases, but remains acceptable for wall blocks and panels, where high thermal efficiency is particularly important.

Figure 1. XND-2-3030C installation (Flat Plate Thermal Conductivity Instrument) and standard samples

From an environmental perspective, vermiculite is a natural mineral that does not harm human health and is also fire-resistant. Therefore, this material is of great importance as it meets global energy efficiency requirements.

Figure 2. Thermal conductivity graph of 10% and 75% samples

Conclusion

The addition of vermiculite reduces the density of cement-based material and significantly lowers its thermal conductivity. This demonstrates that composite materials with vermiculite become lightweight and possess high thermal insulation properties. In construction, such materials can be highly useful for energy-efficient wall panels and insulation applications.

References:

1. GOST 7076-99. Building materials and products. Method for determining thermal conductivity. Moscow: Standartinform, 2000.
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