Laboratory exercise No. 2 Basic material parameters of porous building materials

Size: px

Start display at page:

Download "Laboratory exercise No. 2 Basic material parameters of porous building materials"

Linda Rose
6 years ago
Views:

Laboratory exerise No. Basi material parameters of porous building materials Materials (building materials) an be lassified aording to the different riteria, e.g. based on their properties, funtion, hemial omposition et.

1 Laboratory exerise No. Basi material parameters of porous building materials Materials (building materials) an be lassified aording to the different riteria, e.g. based on their properties, funtion, hemial omposition et. Using these riteria, we an distinguish between following basi groups of materials: 1) inorgani materials metalli and non-metalli (eramis, glass, inorgani binders and fillers, mono-rystals, surfae oatings) ) organi materials fuel, plastis (polymers), paper 3) omposite materials matrix with reinforement (ombination of two or more materials), glass-eramis, reinfored onrete, glass-ement, arbon fibre based omposites. With respet to the sale of investigation, texture and struture of materials an be distinguished. Texture desribes spatial distribution of partiles and pores on marosopi level (from 0.1 mm). Struture haraterizes type and omposition of partiular phase without relation to spatial distribution. This haraterization is done typially on mirosopi level (<1µm). Fig. 1: Idealized mirostrutures: A) poly-rystalli with grains of different dimension, B) poly-rystalli with grains of similar dimension, C) poly-rystalli with oriented grains (mirotexture), D) mirostruture with small pores, E) mirostruture having pores dimension equal to dimension of grain, F) mirostruture with big pores, G) mirostruture having two phases

2 rystalline and glass (dashed line), H) mirostruture of two phases whereas the rystalline phase has not diret bound Struture of materials is determined by their geometrial harateristis, nominally by volume, porosity, dimension, distribution and shape of pores and by speifi surfae. The shape of pores an be open, open and onneted (onrete, air aerated onrete, briks) and losed (sintered eramis, polystyrene, non-liquid-absorbing materials). Liquid penetration into the open pores of different dimension an be desribed by the following equation r = γ r p osθ Hg 1.7 = r p H O = 0.146, p where p is liquid pressure[pa], Θ wetting angle [ ] (water 0, merury 140 ), γ surfae tension [N.m -1 ] (water N.m -1, merury 0.47 N.m -1 ). Pores of building materials are not simple apillaries. Their shape is omplex and variable. Therefore the porosity of building materials is desribed by the pores distribution urve. It is funtion desribing the dimension and volumetri distribution of pores in materials. For its measurement several different methods were developed, e.g. merury porosimetry, gas adsorption porosimetry, eletron and optial mirosopy et. There is also possible to desribe porosity by aeration method or by nitrogen absorption using BET method. The total porosity of material an be alulated aording to the following equation v P = 100 * (1 ) [%], mat where v is bulk density [kg.m -3 ] and mat matrix density of the studied material [kg.m -3 ]. The simplest way how to aess the basi material parameters represents gravimetri method. From the measured dimensions of the sample and its mass, the bulk density an be alulated. m d = v V [kg.m-3 ]. The value of saturation moisture ontent and the remaining basi material parameters an be measured for example by water vauum saturation method. From the measured dry mass of sample m d, mass of fully water saturated sample m v and from the mass of immersed saturated sample m a (so-alled Arhimedes weight) the sample volume an be alulated

3 m v m V = a [kg.m -3 ], l where l is density of liquid (water). Basi material properties as saturation moisture ontent w sat and material matrix density mat an be determined by the following equation w m m v d sat = Ψ 0 v = [kg.m -3 ], l m = d mat [kg.m -3 ]. V 1 Ψ ) ( 0 where Ψ 0 is total open porosity defined as the ratio of the pores volume to the total volume of material. Experimental proedure: The studied sample is plaed into the vessel for evauation and the vessel is vauumed. Then, the vessel is fulfilled by distilled water and vauumed again. The fully water saturated speimen is then plaed on digital sale and its mass m v and mass under water m a are measured. Experimental assessment of volume of un-shapely building materials samples is very diffiult. On this aount, the indiret pynometri method is used for the matrix density measurement. Pynometer is speial vessel having stopper ontaining apillary for the overflowing liquid. Hene, the pynometer volume is always the same. The matrix density of material an be then alulated using following equation mat = m1 l m ( m m ) [kg.m -3 ], 1 3 where m 1 is mass of dry sample [kg], m mass of losed pynometer with sample and liquid [kg], m 3 mass of pynometer with stopper fulfilled by liquid [kg], l density of used liquid [kg.m -3 ] (for water at 0 C a kg.m -3 ). Not only the total open porosity, but also the dimension and distribution of pores has lear relation to the materials performane within the moisture transport, thermal and mehanial loading. On this aount we will deal also with the theoretial assessment of the apillaries radius, what represents ertain theoretial simplifiation of the real porous struture of building materials.

4 Experimental measurement an be then performed for example by merury or helium pynometry (see above). Using the volumetri water saturation w sat that an be measured by standard laboratory test, the apillary radius r an be theoretially assessed. For demonstration of the pratial assessment of apillary radius we hoose the ube of dimension 1000 mm fully saturated by water. On the basis of fully water saturation value of the partiular material, the volume of apillaries Q, and the weight mass of water in apillaries Q w, an be determined. The volume of apillaries Q an be alulated from equation wsat Q = V, 100 where V [mm 3 ] is ube volume, w sat water saturation of the material related to the perentage of sample volume. Weight mass Q w of the water in apillaries is then given by relation Q =, w Q w where w = kg.m -3. Theoretial length l of the set of apillaries is possible to alulate from equation Q l = w F, where F is shear flow and its value is g.mm -1. On the basis of theoretial assumption of free water transport in apillaries, the number of apillaries an be determined using equation l n =. a Sine we onsider for simpliity the water transport into the ubi sample, the parameter a (parameter of the apillary length) is given for the studied ase of ubi sample by relation 1000 a = = 500 [mm]. The theoretial radius of apillary an be then alulated using formula Q n 1 Q = π r l = r. nπ l

5 Tasks of the laboratory exerise No. : Task 1: On gravimetri priniple determine bulk density of given materials. Using digital length meter are measured the dimensions of speimen whereas every size is measured in different plae three times. For the volume V alulation, the arithmeti average of measured values is used. For the fully dried samples is then measured their weight m d. Determine the bulk density of the studied speimens. Task : On the basis of known value of matrix density and measured bulk density (Task 1) alulate the total open porosity of the investigated materials. Material Matrix density mat [kg.m -3 ] Brik 683 Conrete 60 Expanded Polystyren 1060 Extruded Polystyren 1050 Hemp Wool 1365 Mineral Wool 400 Air-Entrained Conrete (porobeton) 450 Task 3: Determine the matrix density of the tested material using pynometri method. The measurement will be performed on three samples of given material. Task 4: Determine the theoretial radius of apillary of brik masonry and the ompressive stress aused by the apillary elevation Within the laboratory experiment, the saturation moisture ontent of brik masonry was measured. The laboratory measured value of the fully water saturation w sat is equal to 36 vol.%.

6 Laboratory protool: Front page: Protool: Title of experiment Student s name (or the members of study group) Date Short desription of the studied materials Desription of applied experimental methods List of used devies, tools and meters Measured values and used onstants Computational and final results Evaluation and data interpretation, onlusions

Laboratory exercise No. 2 Basic material parameters of porous building materials

Laboratory exercise No. 2 Basic material parameters of porous building materials Laboratory exerise No. 2 Basi ateria paraeters of porous buiding aterias Materias (buiding aterias) an be assified aording to the different riteria, e.g. based on their properties, funtion, heia oposition