Strength and deformability of mineral wool slabs under short – term cyclic compression

The strength and deformability of mineral wools slabs, as well as thermo-insulating characteristics can be attributed to the most important indices determining the popularity of these products in practice. The mechanical resistance and stability of mineral wool slabs in use (at construction) of buildings, as well as the requirements for energy saving and heat conservation are in most cases related to the essential requirements set for a building. The mechanical characteristics of mineral wool slabs are subject to structure, density of material, percentage of binder in product, as well as production techniques. The deformability of mineral wools slabs is determined by mobility of fibrous structure, which is best observed under compression by short-term loads. The article considers the strength and deformability properties of mineral wool products under compression by short-term cyclic load. The results obtained while investigating the compression of mineral wool slabs can be applied for determination of fields and conditions for use of such products in constructions of buildings (floors, ceilings, roofs), as well as for substantiation of respective technical requirements in the normative documents for design of these constructions. Trumpalaikėmis ciklinėmis apkrovomis gniuždomų akmens vatos gaminių stiprumo ir deformacinės savybės Santrauka Stiprumo ir deformacines akmens vatos gaminių savybes kartu su šilumos izoliacinėmis savybėmis galima priskirti prie svarbiausių rodiklių, lemiančių šių gaminių populiarumą statybos praktikoje. Akmens vatos gaminių, naudojamų pastatų eksploatacijai (statybai), mechaninis atsparumas ir pastovumas bei energijos taupymo ir šilumos išsaugojimo reikalavimai daugeliu atvejų siejami su esminiais statinio reikalavimais. Mineralinės akmens vatos gaminių mechaninės charakteristikos priklauso nuo medžiagos struktūros, tankio, rišiklio kiekio gaminyje ir nuo gamybos technologijos. Akmens vatos plokščių deformatyvumą lemia pluoštinės struktūros paslankumas, kuris geriausia išryškėja gniuždant trumpalaikėmis apkrovomis. Straipsnyje aptariamas ryšys tarp gaminio storio, tankio, struktūros ir stiprumo bei deformacinių rodiklių, pateikiamos šių priklausomybių diagramos. Straipsnyje nagrinėjamos trumpalaikėmis ciklinėmis apkrovomis gniuždomų akmens vatos gaminių stiprumo ir deformacinės savybės. Gautieji akmens vatos plokščių gniuždymo tyrimo rezultatai gali būti pritaikyti nustatant šių gaminių naudojimo pastatų konstrukcijose (grindyse, perdangose, stoguose) sritis ir sąlygas, taip pat pagrindžiant atitinkamus techninius reikalavimus šių konstrukcijų projektavimo normatyviniuose dokumentuose. First Published Online: 16 May 2013 Reikšminiai žodžiai: akmens vatos plokštės, trumpalaikis gniuždymas, deformacija, kritinis įtempis, ciklinės apkrovo

Prediction of creep strain in mineral wool slabs under compression

In order to successfully use stone wool products as a construction material which is affected by long-term compressive loads, it is not enough to be aware of the strength and deformation characteristics determined under shortterm loads. It is important to know the change in time of deformations (creep deformations) of the products underconstant long-term compressive loads, which cause the enlarged deformations of structural elements of the material.The analysis of the change in thickness of stone wool under constant short-term and long-term loads is presented, predicted values of creep deformations are determined and combined using synthesis procedure, impact factors for joint prediction results and weighted mean values of joint prediction results are determined. For the prediction of consistent pattern of creep deformations for the period of 10 years the relative creep deformations at the time t were used. These relative deformations under constant compressive stress were recalculated to single stress. It has been proposed to evaluate predicted creep deformations of stone wool slabs for any of the constant compressive stress, representing the time period up to 10 years, on the basis of values of creep mobility

Development and investigation of thermal insulation from hemp-polylactide fibres

In the last two decades intensive grow of industry of building materials from renewable resources is observed. Such situation is related to some aspects: global warming, environmental pollution, impact on human health, environmental impact of materials at their end-of-life. In current study development of thermal insulation materials from hemp and polylactide fibres are analysed. While main parameter for thermal insulation materials is thermal conductivity, rational density of composite 40 kg/m3 was chosen. For experiments 11 compositions were prepared. One composition was prepared just with hemp and polylactide fibres, five compositions with different amount of hydrophobic agent and 5 compositions with different amount of fire retardant. Experimentally thermal conductivity, sound absorption coefficient, short-term water absorption, fire resistance, water vapour transfer properties and compressive strength were determined. Rational amount of hydrophobic agent and fire retardants was chosen

Sapropel as a Binding Material for Wood Processing Waste in the Development of Thermal Insulation Biocomposite

When developing new innovative building materials, their performance characteristics as well as their environmental friendliness are important. It is difficult to produce a fully ecological material for building envelopes, because there is a lack of ecological binding materials on the market, good binding materials are very expensive, and cheaper ones have poorer adhesive properties and performance characteristics. In this work, natural organic sapropel was used as an ecological binder. Before use, an organic sapropel was additionally mechanically activated. Its activation efficiency was evaluated on the basis of consistency and tensile strength. Sapropel activation increased its consistency from 112 to 168 mm and its tensile strength from 466 to 958 kPa. Wood processing waste was used as a filler for the thermal insulation biocomposite. Additionally, the wood waste was chopped to regulate the density and main performance properties of the biocomposite. The density of the biocomposite was also regulated using different amounts of sapropel and the degree of compaction of the composite mixture. In this work, the influence of the amount of sapropel, the level of compression of the biocomposite mixture, and the size of the wood waste particles on the thermal conductivity and compressive stress of the biocomposite was analyzed. It was found that the compression level had the greatest influence on both the compressive stress and thermal conductivity, up to 12 times and 43.3%, respectively

Akustinės ir termoizoliacinės medžiagos

Mokomojoje knygoje pateiktos žinios apie garso sklidimą, garsą sugeriančias ir izoliuojančias medžiagas, šilumos laidumą, šiuo-laikines termoizoliacines medžiagas, akustinių ir termoizoliacinių medžiagų bandymų metodus. Išsamiai nagrinėjamos šiuo metu gaminamos ir naudojamos akustinės bei termoizoliacinės medžia-gos. Pagal įvairius kriterijus mokomoji knyga suskirstyta į skyrius. Juose trumpai pateikiamos žinios apie akustiką ir šilumos laidumą bei šiems tikslams naudojamas akustines ir termoizoliacines me-džiagas, jų gaminių kūrimo istorija, šiuolaikinės gamybos techno-logijos, savybės, naudojimo galimybės ir ypatumai. Mokomoji knyga skirta ne tik aukštųjų mokyklų studentams, studijuojantiems statybos ir medžiagų inžinerijos disciplinas, bet ir projektuotojams, akustinių ir termoizoliacinių medžiagų gamintojams bei jų naudotojams. VGTU statybos ir nekilnojamojo turto sričių I pakopos studijų programų atnaujinimas diegiant inovatyvius mokymo(si) metodus. Projekto kodas Nr. VP1-2.2-ŠMM-07-K-01-032

Investigation of water absorbtion by expanded polystyrene slabs

Article gives analysis of experimental results of water absorption by expanded polystyrene slabs. The investigation was carried out applying different test methods. It was established that the most precise results of water absorption by expanded polystyrene are obtained when method of increased pressure is applied. Results obtained applying this method show that the water absorption of expanded polystyrene considerably increases when its density decreases. When the specimen is immersed, the largest amount of water is accumulated between the pores. Due to an even pressure distribution around the walls of the specimen, water does not push out the air, which is between the pores, and, therefore, a part of the specimen does not soak through. Moreover, spaces between expanded polystyrene pores usually interact, and, depending on the density of a product, the diameter of them may be up to few millimetres. When the specimen is withdrawn from water, all of a sudden the greatest amount of water retires from the spaces between the pores

Evaluation of forming mixture composition impact on properties of water blown rigid polyurethane (PUR) foam from rapeseed oil polyol

Rapeseed oil based water blown rigid polyurethane foam was prepared by two shot method. Water was used as a blowing agent on purpose to increase the green nature of the foams. In order to reduce the temperature and shrinkage, acetone and glycerine were added. The influence of these additives on foaming characteristics, density, closed cell content, compressive strength and water absorption was described. It was found that reduction in shrinkage using glycerine leads to greater open cell content and water absorption, lower compressive strength (by almost 72% and 53%), density (by almost 64% and 74%) for moulded and free rise specimens, respectively, and delayed cream time of foaming mixture. The use of acetone reduced foam formation temperature by 15 ◦C, increased moulded and free rise densities by approximately 8%, as well as compressive strength by 22%, and by 10% for moulded and free rise water blown polyurethane specimens.This work has been supported by the Research Council of Lithuania (Project, No. ATE-07/2012)

Analysis of Thermal Insulation from Renewable Resources

Vienas esminių statinio reikalavimų – energijos taupymas ir šilumos išsaugojimas. Apytiksliai 40 % visos Europos Sąjungoje suvartojamos energijos tenka šildomų pastatų eksploatacijai. Didžiąją šių sąnaudų dalį sudaro energija, suvartojama pastatams šildyti šaltuoju metų laikotarpiu ir jiems vėsinti šiltuoju metų laikotarpiu. Kelis kartus mažiau energijos galima suvartoti gaminant termoizoliacines medžiagas iš atsinaujinančiųjų išteklių ir jomis šiltinant pastatus. Tokių medžiagų šilumos laidumo koeficientas yra apytiksliai 0,040 W/(mK). Darbe nagrinėjamos šiaudų naudojimo galimybės termoizoliacinių medžiagų gamybai. Pateikti atliktų įvairaus tankio šiaudų šilumos laidumo tyrimų laboratorinėmis sąlygomis ir vakuumuotoje aplinkoje rezultatai.Abstract in English. One of the essential requirements for buildings is energy saving and heat retention. About 40% of the total energy consumed in the European Union is used for heating of buildings. Most of the energy consumed in buildings is used for heating during the cold period and cooling during the warm period. A significant part of energy can be saved due to suitable insulation of buildings. More efficient energy saving can be ensured by using heat-insulating materials produced from renewable resources. In Lithuania straw is often used for making thermal insulation obtained with a thermal conductivity of 0.040 W/(mK). Straw thermal conductivity under different conditions as well as possibilities to use it for producing heat-insulating materials are analysed in the work

Studies on the thermal conductivity of composite materials based on local renewable resources

Thermal insulation materials produced from local renewable resources are increasingly used for two reasons – they are environmentally friendly and their manufacture requires less amount of energy. The most renewable resources include a wide variety of crop straw – barley, rye, wheat, triticale, etc. the thermal conductivity of which depends on their orientation to the product and structure of the same straw. For specimen composition, the straw stems of bulrush, reeds, bent and triticales were used, producing composites with the mass ratio of 1:1. The paper analyses the results of thermal conductivity tests on different stem composites of herbaceous plants. Thermal conductivity was investigated considering composition specimens such as bulrush-reeds, bulrush-bent, bulrush-straw, reed-straw, reed-bent. The use of composites in all cases reduced thermal conductivity compared with the thermal conductivity of materials used alone. The greatest reduction in thermal conductivity compared with the thermal conductivity of the single straws of herbaceous plants has been observed in bulrush-straw composites. Article in Lithuanian. Kompozicinių termoizoliacinių medžiagų iš vietinių atsinaujinančių išteklių šilumos laidumo tyrimai Santrauka. Termoizoliacinės medžiagos iš vietinių atsinaujinančių išteklių vis plačiau naudojamos dėl dviejų priežasčių – jos yra ekologiškos ir jų gamybai reikalingi maži energijos kiekiai. Iš atsinaujinančių išteklių labiausiai paplitę įvairių kultūrinių augalų šiaudai: miežių, rugių, kviečių, kvietrugių ir kt. Šių medžiagų šilumos laidumas labiausiai priklauso nuo jų orientacijos gaminyje ir pačių stiebelių struktūros. Bandiniams komponuoti buvo naudojama švendrų, nendrių, smilgų ir kvietrugių šiaudų stiebai, iš kurių pagal masės santykį 1:1 buvo komponuojami kompozitai. Atlikta kompozitų, sudarytų iš skirtingų žolinių augalų stiebelių, šilumos laidumo tyrimai. Tirti tokių sudėčių bandinių šilumos laidumai: švendrai + nendrės, švendrai + smilgos, švendrai + šiaudai, nendrės + šiaudai, nendrės + smilgos. Naudojant kompozitus visais atvejais sumažintas šilumos laidumas lyginant su šilumos laidumu, kai naudotos pavienės medžiagos: didžiausias šilumos laidumo sumažėjimas, lyginant su pavienių augalų stiebų šilumos laidumu, gautas švendrų ir šiaudų kompozite. Raktiniai žodžiai: vietiniai atsinaujinantys ištekliai, kompozitinės termoizoliacinės medžiagos, šilumos laidumas, makrostruktūra

Stability of strength and deformation characteristics of expanded polystyrene (EPS) within the time of long-term investigation of creep strain under permanent compressive loading

The results of investigation of strength (σ10 %, σcr) and deformability (E) characteristics of expanded polystyrene specimens are presented. The results are based on the short-term compression in the organization of long-term creep study. For the experiments identical specimens stored 5 years at ambient temperature (23 ±2) °C and relative humidity (50 ±5) % as well specimens after removal long-term loading were used. There were established, that difference between experimental values of stress and initial modulus of tested expanded polystyrene specimens with confidence probability P = 90 % (on-sided test) is negligible (random)