Assessment of Cumulative Damage of Selected Building Envelopes Exposed to Various Environmental Effects

Hygrothermal performance of building envelopes based on three different building materials (solid brick, high performance concrete, aerated autoclaved concrete) is assessed under climatic conditions of Prague and Atlantic City. Main objective of the paper is to evaluate the influence of cumulative damage, which was induced by means of natural weathering in 2012- 2015 period, on the long-term performance. The performance is assessed using various measures, namely time-of-wetness function, number of freeze/thaw cycles, and annual amount of energy transmitted through the envelope. The results show that thermal performance of the envelopes gets mostly better after weathering as the annual amount of energy is decreased by ~3.5% in average. On the other hand, time-of-wetness function and number of freeze/thaw cycles increase by ~24.1% and ~22.0%, respectively. Based on the results summary it can be concluded, that cumulative damage of materials has an indisputable influence on the hygrothermal performance of building envelopes which might be either negative or positive. A detailed computational assessment is therefore necessary, incorporating not only reference, but also weather-affected material properties

Evaluation of parameters influencing the withdrawal strength of oak and beech dowels

The withdrawal strength of plain dowels with nominal diameter of 8 mm was compared with the spiral dowels manufactured from beech (Fagus sylvatica L.) and oak wood (Quercus robur L.). The test specimens were tested after conditioning at relative humidity (RH) 25%, 45%, 65%, and 85% at a constant temperature of 20 oC. Therefore, the influence of relative humidity (respective moisture content), dowel structure, and wood species of the dowels on the withdrawal strength was determined. The structure and low humidity (RH 25%) caused the highest strength (8.6 MPa) of spiral dowels. Compared to plain dowels, the higher withdrawal strength of spiral dowels was statistically significant. Adversely, the lowest withdrawal strength was found for plain beech dowels (3 MPa), which, in addition to higher relative humidity (RH 85%), was also caused by a combination of plain structure and greater diameter of the dowels, thereby decreasing the amount of adhesive in the bonded joint. The influence of the wood species of the dowels was not statistically significant overall.O

EVALUATION OF THE APPLICATION OF A THERMAL INSULATION SYSTEM: INSITU COMPARISSON OF SEASONAL AND DAILY CLIMATIC FLUCTUATIONS

The current outdated state of many institutional and administrative buildings in the EU region poses a significant burden from the energy sustainability point of view. According to the contemporary EU requirements on the energy efficiency of buildings maintenance, an evaluation of performed improvements is essential for the assessment of expended investments. This paper describes the effect of building envelope reconstruction works consisting in the installation of a thermal insulation system. Here, a long-term continuous monitoring is used for the extensive assessment of the seasonal and daily temperature and relative humidity fluctuations. The obtained results include temperature and relative humidity profiles in the wall cross-section as a response to the changing exterior climatic conditions. The analysis of measured data reveals substantial improvements in thermal stability of the analyzed wall during temperature peaks. While the indoor temperatures exceeding 28 °C are recorded during summer before application of the thermal insulation layer, the thermal stability of the indoor environment is distinctly upgraded after performed improvements. Based on the complex long-term monitoring, a relevant experience is gained for the future work on energy sustainability and fulfilment of the EU directives

Hygric Properties of Lime-cement Plasters with the Addition of a Pozzolana

AbstractThere are more than seven billion people currently living on the Earth and the demands of population are rising. Lime and cement are parts of most building materials, so their global consumption grows. Therefore, it is necessary to think both economically and ecologically, and search for a suitable alternatives and replacements. This study is aimed at an investigation of the influence of pozzolana as the third binder component on basic physical characteristics and hygric properties of lime-cement plasters. Results show that with the increasing amount of pozzolana in the mixture the open porosity goes down. This is accompanied by a liquid water absorption decrease. Also diffusion parameters are somehow worsened, as the water vapour diffusion resistance factor increases

Zastosowanie techniki pomiarowej TDR w badaniach terenowych przy wykorzystaniu sond powierzchniowych

The article presents the possibility of in-situ measurements of building barriers moisture using the TDR technique (Time Domain Reflectometry). To minimize the previous disadvantages of the described method – invasive character, several prototypes of the surface probes were manufactured. With such a sensor solution it was possible to conduct the non-invasive measurements using the full TDR method potential – quick measurements and no sensitivity of salinity influence. The measurements were conducted on the brickworks made of red ceramic brick at the old building located on 1st of May Street in Lublin.W artykule przedstawiono możliwość wykonywania pomiarów terenowych wilgotności murów za pomocą techniki TDR (ang. Time Domain Reflectometry). W celu wyeliminowania dotychczasowych wad niniejszej techniki, do których należy zaliczyć przede wszystkim jej inwazyjny charakter i konieczność wykonywania nawierceń w murach, opracowano i wykonano kilka prototypów sondy powierzchniowej. Dzięki zastosowaniu takiego rozwiązania czujnika, możliwe było przeprowadzenie badań na zasadzie dotykowej z pełnym wykorzystaniem potencjału techniki pomiarowej TDR – szybkości odczytu oraz braku wrażliwości na zasolenie badanego ośrodka. Pomiary wykonano w murach z cegły ceramicznej pełnej budynku zlokalizowanego przy ul. Pierwszego Maja 20 w Lublinie

Application of Ceramic Powder as Supplementary Cementitious Material in Lime Plasters

In this paper, the properties of plasters based on lime – brick powder binder of varying composition (ceramics content from 0 to 80 %) are studied. The plasters are prepared with a constant water amount. The pore size distribution is thus influenced in a positive way; the total porosity increases with the ceramics content but the volume of capillary pores is reduced. It results in lower water vapor diffusion resistance factor while the apparent moisture diffusivity coefficient increases just moderately. The influence of ceramic on strength of plasters is not found very important. The thermal conductivity of plasters containing ceramics is lower than those with the pure lime what is again in agreement with the pore size distribution. It can be concluded that fine brick powder can be used as pozzolanic admixture in lime based plasters with a positive influence on its functional parameters

Biomass production of Betula pendula stands regenerated in the region of allochthonous Picea abies dieback

The paper deals with production of above-ground biomass of silver birch ( Roth) stands in the Czech Republic. One-year biomass dynamics was studied within chronosequence of birch stands at the age of 4â5, 8â9, 17â18 and 22â23 years. With the exception of the youngest stand, which was established by seeding, all experimental birch stands were regenerated naturally after the allochthonous spruce stands. Above-ground biomass (AB) was calculated from plot inventory data and biomass equations were parameterized from destructive sampling of biomass component of sampled trees. Results reveal that the peak of the mean annual increment (MAI) of birch stands can be expected at the age from 15 to 20 years. Additionally, the stand age, the value of basal area (BA) should be considered as a predictor of stand productivity. If the value of BA varied from 25 to 35 m ha, the MAI of the birch stands reached the range from 5.0 to 6.5 t of dry biomass per ha y at the age ranging between 15 and 25 years. The stem/branch proportion increased with stand age, the stem relative proportion ranging from 75 to 90% of total above-ground biomass. According to the results of this study, birch stand biomass production and utilization is one of the approaches in terms of forest recovery management in large disturbed areas. Although, no silvicultural treatments were occurred in all analysed stands, the pre-commercial thinning method could increase stand productivity and stability as well.Betula pendulaABtotal2â1â

Thermophysical and mechanical properties of fiber‐reinforced composite material subjected to high temperatures

The bulk density, open porosity, matrix density, tensile strength, bending strength, thermal diffusivity, specific heat capacity, thermal conductivity and linear thermal expansion coefficient of high‐density glass fiber reinforced cement composite are determined as functions of temperature up to 1000 °C. The basic physical parameters and mechanical parameters are found to exhibit the most important changes between the reference state and 600 °C pre‐heating where the increase of porosity is as high as 40% and both the tensile strength and bending strength decrease to about one third of their original values. The measured dependences of thermal diffusivity and thermal conductivity on temperature indicate that the heat transfer in the studied material is accelerated once temperature achieves 500–600 °C but the change in heat storage expressed by the specific heat capacity is less important. The linear thermal expansion coefficient is not found to be affected by high temperatures in a negative way; it is either lower or comparable to its low‐temperature values. Santrauka Tiriama, kaip kinta tankiojo stiklo pluoštu armuoto cementinio kompozito tankis, atvirasis poringumas, matricinis tankis, tempiamasis bei lenkiamasis stipris, terminis laidumas, savitasis šilumos imlumas, savitasis šilumos laidumas ir tiesinis terminio pletimosi koeficientas, kai šia medžiaga veikia temperatūra, kylanti iki 1000 °C. Rasta, kad pagrindiniai fiziniai ir mechaniniai parametrai daugiausia keičiasi temperatūrai kylant nuo pradines iki 600 °C. Šioje temperatūros kilimo atkarpoje poringumas išaugo iki 40 %, o tempiamasis ir lenkiamasis stipriai sumažejo maždaug trečdaliu, palyginti su pradinemis reikšmemis. Išmatuotoji terminio laidumo ir savitojo šilumos laidumo priklausomybe nuo temperatūros rodo, kad šilumos perdavimas tiriamoje medžiagoje pagreiteja temperatūrai pasiekus 500–600 °C, tačiau šilumos kaupimas, išreikštas savituoju šilumos imlumu, yra ne toks svarbus. Nenustatyta, kad tiesinis terminio pletimosi koeficientas būtu neigiamai veikiamas aukštos temperatūros. Šio koeficiento reikšmes yra mažesnes arba maždaug lygios reikšmems, išmatuotoms žemoje temperatūroje. First Published Online: 10 Feb 2011 Reikšminiai žodžiai: stiklo pluoštu stiprinti cemento kompozitai, aukšta temperatūra, tempiamasis stipris, lenkiamasis stipris, terminis laidumas, savitasis šilumos imlumas, savitasis šilumos laidumas, tiesinis terminio pletimosi koeficienta

Service Life Assessment of Historical Building Envelopes Constructed Using Different Types of Sandstone: A Computational Analysis Based on Experimental Input Data

Service life assessment of three historical building envelopes constructed using different types of sandstone is presented. At first, experimental measurements of material parameters of sandstones are performed to provide the necessary input data for a subsequent computational analysis. In the second step, the moisture and temperature fields across the studied envelopes are calculated for a representative period of time. The computations are performed using dynamic climatic data as the boundary conditions on the exterior side of building envelope. The climatic data for three characteristic localities are experimentally determined by the Czech Hydrometeorological Institute and contain hourly values of temperature, relative humidity, rainfalls, wind velocity and direction, and sun radiation. Using the measured durability properties of the analyzed sandstones and the calculated numbers of freeze/thaw cycles under different climatic conditions, the service life of the investigated building envelopes is assessed. The obtained results show that the climatic conditions can play a very significant role in the service life assessment of historical buildings, even in the conditions of such a small country as the Czech Republic. In addition, the investigations reveal the importance of the material characteristics of sandstones, in particular the hygric properties, on their service life in a structure