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

Transcription

1 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 et. Using these riteria, we an distinguish between foowing basi groups of aterias: 1) inorgani aterias etai - non-etai (erais, gass, inorgani binders and fiers, onorystas,, surfae oatings) 2) organi aterias fue, pastis (poyers), paper 3) oposite aterias atrix with reinforeent (obination of two or ore aterias); gass-erais, reinfored onrete, gass-eent, arbon fibre based oposites With respet to the sae of investigation, texture and struture of aterias an be distinguished. Texture desribes spatia distribution of parties and pores on arosopi eve (fro 0.1 ). Struture haraterizes type and oposition of partiuar phase without reation to spatia distribution. This haraterization is done typiay on irosopi eve ( 1μ). Fig. 1: Ideaised irostrutures. A) poy-rystai with grains of different diension, B) poy-rystai with grains of siiar diension, C) poy-rystai with oriented grains (irotexture), D) irostruture with sa pores, E) irostruture having pores diension equa

2 to diension of grain, F) irostruture with big pores, G) irostruture having two phases rystaine and gass (dashed ine), H) irostruture of two phases whereas the rystaine phase has not diret bound Struture of aterias is deterined by their geoetria harateristis, noinay by voue, porosity, diension, 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 osed (sintered erais, poystyrene, non-iquid-absorbing aterias). Liquid penetration into the open pores of different diension an be desribed by the foowing equation r = 2γ r posθ Hg 1,227 = r p H O 2 = 0,146, p where p is iquid pressure[pa], Θ wetting ange [ ], water 0, erury 140, γ surfae tension [N -1 ] - water 0,073 N -1, erury 0,47 N -1. Pores of buiding aterias are not sipe apiaries. Their shape is opex and variabe. Therefore the porosity of buiding aterias is desribed by the pores distribution urve. It is funtion desribing the diension and vouetri distribution of pores in aterias. For its easureent severa different ethods were deveoped, e.g. erury porosietry, gas adsorption porosietry, eetron and optia irosopy et. There is aso possibe to desribe porosity by aeration ethod or by nitrogen absorption using BET ethod. The tota porosity of ateria an be auated aording to the foowing equation v P = 100*(1 ) [%], where v is buk density [kg -3 ] and at atrix density of the studied ateria [kg -3 ]. The sipest way how to aess the basi ateria paraeters represents gravietri ethod. Fro the easured diensions of the sape and its ass, the buk density an be auated. V at d v = [kg -3 ].

3 The vaue of saturation oisture ontent and the reaining basi ateria paraeters an be easured for exape by water vauu saturation ethod. Fro the easured dry ass of sape s, ass of fuy water saturated sape v and fro the ass of iersed saturated sape a (so-aed Arhiedes weight) the sape voue an be auated v V = a [kg -3 ], where is density of iquid (water). Basi ateria properties as saturation oisture ontent w sat and ateria atrix density at an be deterined by the foowing equation w V v d sat = ψ 0 v = [kg -3 ], = d at [kg V ( 1 Ψ 0 ) -3 ]. where ψ 0 is tota open porosity defined as the ratio of the pores voue to the tota voue of ateria. Experienta proedure: The studied sape is paed into the vesse for evauation and the vesse is vauued. Then, the vesse is fufied by distied water and vauued again. The fuy water saturated speien is then paed on digita sae and its ass v and ass under water a are easured. Experienta assessent of voue of un-shapey buiding aterias sapes is very diffiut. On this aount, the indiret pynoetri ethod is used for the atrix density easureent. Pynoeter is speia vesse having stopper ontaining apiary for the overfowing iquid. Hene, the pynoeter voue is aways the sae. The atrix density of ateria an be then auated using foowing equation 1 at = 3 ( 2 1) [kg -3 ], where 1 is ass of dry sape [kg], 2 ass of osed pynoeter with sape and iquid [kg], 3 ass of pynoeter with stopper fufied by iquid [kg], density of used iquid [kg -3 ] (for water at 20 C a ). Not ony the tota open porosity, but aso the diension and distribution of pores has ear reation to the aterias perforane within the oisture transport, thera and ehania oading. On this aount we wi dea aso with the theoretia assessent of the

4 apiaries radius, what represents ertain theoretia sipifiation of the rea porous struture of buiding aterias. Experienta easureent an be then perfored for exape by erury or heiu pynoetry (see above). Using the vouetri water saturation w sat that an be easured by standard aboratory test, the apiary radius r an be theoretiay assessed. For deonstration of the pratia assessent of apiary radius we hoose the ube of diension 1000 fuy saturated by water. On the basis of fuy water saturation vaue of the partiuar ateria, the voue of apiaries Q, and the weight ass of water in apiaries Q w, an be deterined. The voue of apiaries Q an be auated fro equation Q wsat = V, 100 where V [ 3 ] is ube voue, w sat water saturation of the ateria reated to the perentage of sape voue. Weight ass Q w of the water in apiaries is then given by reation where w = kg -3 (resp. 0,001 g -3 ). Q. w Q w =, Theoretia ength of the set of apiaries is possibe to auate fro equation Qw =. F On the basis of theoretia assuption of free water transport in apiaries, the nuber of apiaries an be deterined using equation n =. a Sine we onsider for sipiity the water transport into the ubi sape, the paraeter a (paraeter of the apiary ength) is given for the studied ase of ubi sape by reation a = = 500. The theoretia radius of apiary an be then auated using forua Q n = π r => 2.. Q r = n. π. 1/2.

5 Tasks of the aboratory exerise No. 2: Task 1. On gravietri prinipe deterine buk density of given aterias. Using digita ength eter are easured the diensions of speien whereas every size is easured in different pae three ties. For the voue V auation, the aritheti average of easured vaues is used. For the fuy dried sapes is then easured their weight d. Deterine the buk density of the studied speiens. Task 2. On the basis of known vaue of atrix density and easured buk density (Task 1) auate the tota open porosity of the investigated aterias. Materia Matrix density at [kg -3 ] Group 1 Group 2 Group 3 Historia brik Conrete BM FGD Gypsu Task 3. Using pynoetri ethod deterine the atrix density of the tested ateria. The easureent wi be perfored on three sapes of given ateria. Task: 4. Deterine the theoretia radius of apiary of brik asonry and the opressive stress aused by the apiary eevation Within the aboratory experient, the saturation oisture ontent of brik asonry was easured. The aboratory easured vaue of the fuy water saturation w is equa to 36 vo. %. Laboratory protoo: Front page: Protoo: tite of experient Student s nae (or the ebers of study group) date short desription of the studied aterias desription of appied experienta ethods ist of used devies, toos and eters easured vaues and used onstants oputationa and fina resuts evauation and data interpretation, onusions

6 Řešení úohy 4: Obje kapiár Q k činí , ož odpovídá váhovéu nožství vody v kapiáráh Q v = g. Náhradní déka kapiár pode vztahu (4) činí: k = = , 0,00765 tou odpovídá teoretiký počet kapiár n, stanovený ze vztahu: n = = Teoretiký pooěr kapiáry r je odvozen ze vztahu (5) a činí: 1/ r = = 0, π Napětí v taku б ve zdivu vive působení kapiární eevae vody ze vypočítat ze vztahu: 2.0, σ = = 3.01 g. -2, ož odpovídá 0,03 MPa. 0, 00509