No abstract

This article presents the influence of granulated foam glass (GFG) on thermal insulation and mechanical properties of lightweight cement mortars. The mortars were additionally modified with addition of ground perlite dust. Ground expanded perlite waste was introduced into the cement matrix in the amounts of 10%, 20%, and 30% of cement mass. The results show that application of this waste increases the strength of the mortars as well as decreases their thermal conductivity coefficient. A series of mortars were prepared with introduction of granulated foam glass with mass per unit filler/cement ratio equal to 0.6, 0.9, and 1.2. The aggregate composition of GFG was combined from different monofractions in the range 0–2 mm so that it filled the mortar volume to the maximum. Additionally, mortars were made, in which 20% of 0–0.25 mm GFG volume was replaced with quartz sand with the same granulation. Each mortar series was modified with addition of ground perlite waste in the amount of 20% of cement mass. The results indicate an improvement of thermal insulation properties along with greater participation of perlite in the mortars. The increase of the thermal conductivity coefficient was observed in the mortars, where the GFG was replaced with quartz sand. Greater amount of GFG results in decrease of compressive strength, but it can be improved by replacing part of the lightweight filler with sand or by introducing the addition of ground expanded perlite to the matrix. This also results in lower water absorption of mortars. Research proved that in most cases, the addition of ground expanded perlite decreased the capillary sorption of mortars, as well as the water absorption coefficient by capillary action, with growing proportion of the lightweight filler.

The following paper presents the results of research on cement composites with expanded graphite as resistance heating elements. Samples of cement mortar were prepared with expanded graphite obtained from intercalated graphite by means of rapid heating at 1000℃. Monotonic and cyclic self-heating tests of cement composites with differing contents of expanded graphite were conducted. In the monotonic self-heating test, the electrical current and the surface temperature of the cement composites with expanded graphite were measured at temperatures 23℃ and –10℃ in order to evaluate their capacity to generate heat. The maximum temperature of composites, the time required to raise the temperature by 10℃, and the power density were determined. Five cycles were applied in the cyclic self-heating test to investigate heat-dependent mechanical properties. The results of the research revealed that cement composites with expanded graphite exhibited promising properties for application as resistance heating elements.

No abstract

No abstract

No abstract

No abstract

The objective of this work was to obtain cement composites with low percolation thresholds, which would reduce the cost of graphite and maintain good mechanical properties. For this purpose, exfoliated graphite was used as a conductive additive, which was obtained by exfoliating the expanded graphite via ultrasonic irradiation in a water bath with surfactant. To obtain evenly distributed graphite particles, the exfoliated graphite was incorporated with the remaining surfactant into the matrix. This study is limited to investigating the influence of exfoliated graphite on the electrical and mechanical properties of cement mortars. The electrical conductivity of the composites was investigated to determine the percolation threshold. The flexural and compressive strength was tested to assess the mechanical properties. In terms of the practical applications of these composites, the piezoresistive, temperature–resistivity, and thermoelectric properties were studied. The results showed that the incorporation of exfoliated graphite with surfactant is an effective way to obtain a composite with a percolation threshold as low as 0.96% (total volume of the composite). In addition, the mechanical properties of the composites are satisfactory for practical application. These composites also have good properties in terms of practical applications. As a result, the exfoliated graphite used can significantly facilitate the practical use of smart composites.