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Verification and validation of an advanced guardedhot plate for determination of thermal conductivity
Get PDFThe Guarded hot plate method (GHP) is a widely used technique to measure thermal conductivity of thermal insulation specimens in steady-state conditions. In this paper, an advance of GHP has been developed in the Laboratory for Thermal technique and fire protection in Institute IMS. The innovative GHP has been applied for measuring thermal conductivity using additional heat flux meters. The design of this GHP is similar to the design of the plate for GHP apparatus; however, it has different design: smaller width of thermal barrier, which is filled with insulation glue. Heaters inside hot and guard plates are built from wire for thermocouples, which is a unique type of heater. Geometry of heater has been optimized inside plates to achieve uniform temperature distribution along the specimen surface. Temperature uniformity of guarded hot plate and energy balance were experimentally determined. The verification and validation results of improved GHP have been shown. The test method was validated comparing test results of thermal conductivity with results of the round-robin test. Four national companies participated in the round-robin comparison on thermal conductivity measurement by guarded hot plate method. The measurement was performed on the same specimen of thermal insulation material (expanded polystyrene) according to SRPS EN 12667 at temperatures ranging between 10℃-40℃. The measured thermal conductivity of all participants in the round-robin test was input data for statistical processing according to SRPS ISO 5725-2 and ISO 13528. To evaluate the performance of the participants, the “z” score has been used. Measurements were conducted successively for all participants. Since 2020, the Accreditation Body of Serbia also approved this test method
Static-Dynamic Tests of Bearing Capacity of Wind Turbine Piles
No full textThe paper presents the static load tests (SLT) and dynamic load tests (DLT) of the piles and numerical analyses of piles in interaction with the soil of wind turbines. Pile tests were conducted using the equipment with counterweights for SLT and an autonomous system for the control of DLT of the piles. Numerical DLT analyses were performed by the signal matching method. Tests proved that the design resistance of piles of SLT and mobilized static resistance of DLT are higher than the design forces obtained from the design of the wind turbine foundations. Also, the need to develop a plan for testing the bearing capacity of piles, concerning large and significant buildings was emphasized
Estimation of the drying behaviour for different clay raw materials - drying sensitivity techniques review Epitoanyang 2022
No full textIn order to rate the drying behavior of different clay raw materials it is necessary to establish
the criteria for comparison. Mineralogical composition, clay minerals content, particle size
distribution, packing, porosity, forming procedure, and raw material aging are known as
intrinsic parameters. Due to the fact that these parameters are cross linked and are usually
inter-dependently related to each other, the attempts to set up a criteria for correlation between
intrinsic parameters and drying sensitivity has been limited. That was the reason why the
estimation of the cracking tendency was linked with the easiness of the drying process in each
reported method. The most applied methods for estimation of the drying sensitivity of clays in
the ceramic industry were proposed by Bigot, Ratzenberger, Piltz, Hermansson and Varlamov.
The fact that previously mentioned methods were not compared up till know has defined the
main objective of this study. The only reported comparison was between Bigot and Ratzenberg
drying sensitivity index. The second objective of this review was to present these methods and to
estimate the drying behavior of tree different clay raw material. It was confirmed that Varlamov
method is very simple, accurate and fast. It is correlated with the mineralogical composition of
clay and cannot be used for description of the drying kinetic. The other two models can provide
info about the drying kinetic. Piltz model is the most relevant for describing the drying behavior at
the beginning of the drying. The results have confirmed that the most suitable conclusion about
the drying behavior of the tested clays is obtained when results from Bigot, Piltz and Varlamov
methods are available
Influence of water/cement ratio on the properties of fresh SCC with fly ash addition
No full textSelf-compacting concrete (SCC) exhibits increased flowability in comparison with the conventional vibrated concrete. This is most often achieved through the incorporation of high amounts of extra-fine particles (i.e. mineral fillers) in the composition of self-compacting concrete. The purpose is to limit the share of cement while reaching the required large paste content. The components and their proportions, as well as type and particle size of filler, casting, manufacturing and curing conditions of SCC, significantly influence the concrete’s fresh and hardened properties. Among fillers employed in SCC, fly ash is one of the most frequent due to its availability and the low cost. Fly as is an industrial by-product and a highly efficient mineral additive whose role is reflected in improvements of microstructure packing, strength and durability of non-shaped composite building materials such as self-compacting concrete. A comparative study of performances of SCC with different quantities of fly ash and standard SCC with limestone filler was conducted in this study. The experimental program included the production of reference self-compacting concrete based on Portland cement and limestone filler (P1) and additional three experimental self-compacting concrete mixtures (P2, P3, P4) with different quantities of fly ash addition. Behaviour of self-compacting concrete in the fresh state is primarily influenced by type of mineral additive used. The effect that fly ash addition has on the physical behaviour and mechanical properties of fresh experimental SCC concrete samples was discussed. The properties and technology of self-compacting concretes in their fresh state in regard to the alternations in water/cement (w/c) ratios are monitored and explained in this paper. Concrete mixtures with fly ash had lower density in comparisons with the referent concrete. For the same class of consistency, higher amount of water was needed for preparation of SCC mixture with fly ash. Increasing w/c ratio induced more favourable properties of self-compacting concrete in its fresh state
Poboljšanje svojstava prefabrikovanih betonskih elemenata primenom SIKA AER SOLID
No full textDa bi se obezbedila trajnost betona, potrebno je zaštititi betonske infrastrukturne objekte u zemljama u kojima se smenjuju godišnja doba i različiti vremenski uslovi, jer je njihovo izlaganje ciklusima zamrzavanja i odmrzavanja (eng. FTC – freezing and thawing cycles) u prisustvu soli za odmrzavanje jedan od najagresivnijih mehanizama za propadanje betona. Šteta od mraza, progresivno pogoršanje koje započinje ljuštenjem površinskog maltera i završava potpunim urušavanjem betonskih elemenata, glavna je briga kada se beton koristi u hladnijim regionima. Ponavljanjem ciklusa zamrzavanja i odmrzavanja javljaju se prsline i pukotine, a beton postepeno gubi svoja prvobitno projektovana svojstva. Betoni koji će biti izloženi dejstvu mraza u svom sastavu imaju veće količine cementa, a problem primene veće količine cementa se poslednjih godina posebno naglašava zbog sve većeg zagađenja životne sredine i stvaranja efekta staklene bašte. Betoni koji se izlažu dejstvu mraza i/ili mraza i soli štite se aeriranjem. To često nije garancija da će se postići projektovan sadržaj vazduha u svežem betonu. Zbog toga se htelo doći do rešenja nekim drugim sredstvima zaštite betona izloženih dejstvu mraza. Jedno od rešenja je Sika Aer Solid. Kako bi ovaj materijal mogao da se primenjuje na našem podneblju i sa našim materijalima, obavljena su ispitivanja svojstava betona u svežem i očvrslom stanju, sa posebnom osvrtom na trajnost betona. Primenom Sika Aer Solid kao zamene za aerant, moguće je proizvesti betonske elemente čija svojstva zadovoljavaju zahtevane klase izloženosti koje su definisane prema SRPS EN 206 i SRPS U.M1.206. Dodavanjem Sika Aer Solid u beton postiže se trajnost betonskih prefabrikovanih elemenata kroz postizanje otpornosti na dejstvo mraza, otpornosti na dejstvo mraza u prisustvu soli za odmrzavanje, otpornosti na penetraciju vode pod prisitkom, kao i otpornosti na migraciju hloridnih jona.Institut IMS, Ponuda br. 50/20 od 08.05.2020. (IMS broj 41-4302), verifikovao MNO za Saobraćaj, urbanizam i građevinarstv
Monitoring and analyzing the classical counter current industrial tunnel dryer for masonry clay units
No full textThis paper goal was to increase the quality of the drying ware and to lower the drying scarp rate in one local brick factory. The registration of drying air parameters (temperature, humidity and velocity) along the dryer channels as well as the drying ware linear shrinkage and mass change were monitored for a month. Material and Energy balances were also recorded. Results have revealed that the drying air humidity and temperature profiles were not evenly distributed along the height of the drying tunnels. The ambient air breakthrough into the dryer was experimentally identified and quantified. It was the cause of the product quality deterioration and the reason why the critical and residual moisture in some of the products was larger than the desired one. Based on monitored data and mass and energy balances a solution was proposed for preventing the “false” air breakthrough, upgrade of the existing dryer fans and installation of the novel, measuring equipment. A hypothetical solution for increasing the capacity of the dryer, which uses the registered material and energy balances as well as factory management expectation, that the production of 50.000 masonry units per day will be achieved soon, was given also
Overview of the new rulebook on testing fire resistance, external fire performances and reaction to fire in the Republic of Serbia
Get PDFThe growing expansion of construction and import of new, as well as existing materials from around the world, has led to a large number of tests materials and elements of constructions in the Republic of Serbia. Most of these materials and building constructions have test certificates obtained in foreign laboratories, which mostly refer to European standards. The currently valid Rulebook on mandatory attestation of elements of standard building structures for fire resistance and on working conditions that must be met by organizations of associated labour authorized to attest these products from 1990 requires testing of each product, or structural element, according to the domestic SRPS standards. The condition for accessing the European Union requires the harmonization of regulations related to the testing of construction products. Therefore, the IMS Institute, the Ministry of Interior - Sector for Emergency Situations and the Ministry of Construction of the Republic of Serbia have written a new draft Rulebook on Technical Requirements for construction products for which performance characteristics are important: reaction to fire, fire resistance and external fire performance. The plan is to publish the Rulebook, as valid, at the beginning of 2022, with a transitional period for implementation of two years. The paper presents a overview of the new Rulebook
