Possibilities of Using Pumice Aggregates into Thermal Insulation Lining of Industrial Chimneys

This paper deals with the possibility of using pumice aggregates into thermal insulation lining of industrial chimneys. It introduces the construction of modern chimneys and mentions possible risks and degradation processes associated with condensate penetration. In the experiment, mixtures with pumice as aggregate were prepared. The thermal insulation properties, compressive strengths and the resistance to sulphates in a 5% sodium sulphate solution were evaluated and compared.

The products of primary magma fragmentation finally revealed by pumice agglomerates

Following rapid decompression in the conduit of a volcano, magma breaks into ash- to block-sized fragments, powering explosive sub-Plinian and Plinian eruptions that may generate destructive pyroclastic falls and flows. It is thus crucial to assess how magma breaks up into fragments. This task is difficult, however, because of the subterranean nature of the entire process and because the original size of pristine fragments is modified by secondary fragmentation and expansion. New textural observations of sub-Plinian and Plinian pumice lapilli reveal that some primary products of magma fragmentation survive by sintering together within seconds of magma break-up. Their size distributions reflect the energetics of fragmentation, consistent with products of rapid decompression experiments. Pumice aggregates thus offer a unique window into the previously inaccessible primary fragmentation process and could be used to determine the potential energy of fragmentation.

Incorporation of Phase Change Materials in Lightweight Aggregate Concrete

An investigation on some methods for the incorporation of phase change materials (PCMs) into concrete and their effect on its properties is presented. PCMs are characterized by high latent fusion heat, which can increase thermal mass of concrete and contribute to the bioclimatic design of buildings. Concrete compositions with different aggregates (limestone, lightweight or their combination), as well as with different PCMs (paraffinic and dodecyl alcohol) were prepared by different incorporation methods (impregnation to lightweight aggregates or immersion of concrete specimens). Properties of fresh and hardened concrete were studied, as well as hydration heat, thermal response and flammability. The results revealed that the selected PCMs do not significantly affect the properties of concrete. Regarding hydration heat, the presence of the PCM in concrete contributes to a decrease of the temperature peak during hydration which also occurs delayed. Thermal response measurements showed that concrete with purely pumice aggregates has a much better thermal behavior than the other two compositions, while the existence of PCM causes large or small increase of concretes heat capacity, in temperature near to each PCM’s melting point. Finally, appropriate application of PCMs is needed in order to moderate the reported effect on concrete’s fire resistance

TRM-to-Masonry Bond under Elevated Temperatures: Lightweight versus Normalweight Matrices

In the last decade, Textile Reinforced Mortar (TRM) systems have increasingly been gaining ground as a means of strengthening damaged or seismically deficient masonry structures, in addition to counterpart reinforced concrete ones. The existing experimental data on the behavior of TRM materials (used as externally bonded reinforcement on masonry – or concrete – substrates) under elevated temperatures still remains scarce. This work aims at enriching the existing data on the influence of elevated temperatures on the TRM-to-masonry bond conditions. The applied TRM systems consisted of a cementitious mortar with normalweight (limestone) or lightweight (pumice) aggregates. Shear bond tests on single-lap/single-prism specimens were conducted after the exposure of the specimens at different temperature levels. All specimens (masonry prisms with ridge-faced fired clay bricks) were unilaterally furnished with a dry AR glass TRM comprising a single textile layer; TRM bond length was kept constant for all specimens tested. Tests were carried out by varying both the type of matrix employed (normalweight vs. lightweight) and the exposing temperature. The experimental results provide an insight on the effect of mortar type (comprising either normalweight or lightweight sand) on the TRM-to-masonry bond capacity as a function of the exposure temperature.

Analysis of shrinkage and creep behaviors in polymer-coated lightweight concretes

The creep and shrinkage properties of polymer-coated lightweight concretes were examined. Five-hundred-dose lightweight concretes were produced by coating pumice aggregates with three different polymers (Sonomeric1: SNMC, KB Pur 214: KBP, and Polipol3455: PLP). The 3-, 7-, and 28-day compressive strength values of the obtained lightweight concrete samples were determined, and the 840-h and 12-month creep and shrinkage deformations were measured. It was found that the ductility of the SNMC- and KBP-coated concrete samples increased, while their shrinkage deformation results decreased when compared with the control samples. In contrast, the ductility of PLP concrete samples decreased and the shrinkage deformation became higher. In conclusion, the use of SNMC- and KBP-coated pumice aggregates had a positive effect on the creep and shrinkage properties of the concrete. Furthermore, it was observed that the compressive strength values of the lightweight concretes made of the coated samples were higher than those of the control sample.

Experimental Study on the Pumice Aggregate Concrete

Pumice is a kind of natural lightweight aggregate with well-developed porosity and moderate-intensity. Amorphous Si-Al oxide is its main mineral composition. This paper focused on the performance and features of the pumice pozzolan and aggregate firstly. Then a kind of pumice concretes was prepared with the ordinary Portland cement, ordinary sand and strengthened coarse pumice aggregates. And its mechanical properties, durability, insulation and absorbing performance were investigated. The result showed that the compressive strength of pumice concrete was 20MPa, anti-freezing durability was more than 100 freeze-thaw cycles, electric flux within 6 hours was 1749C, thermal conductivity coefficient was 0.318W/ mK, and the electromagnetic wave absorption was-5dB ranging from 8 to 18GHz. The results indicated that the pumice concrete could be developed as the green and multi-functional concrete materials in the future.