Investigation into moisture desorption in concrete constructions

Abstract

The article investigates the moisture desorption of concrete constructions. Three concrete mixtures with different V/C ratio were tested. In one of the mixtures, a plasticizer was used. The test revealed changes in bulk humidity and weight. Specimens were dried in a natural environment after equilibrium moisture in a drying oven was reached. In the beginning of the test, the volume humidity of specimens with D1 composition varied in the range of 2.3 %. At the end of measuring, when constant weight was reached, moisture range decreased up to 0.3 %. When starting the test, the dispersion of the results of bulk humidity of specimens with D2 and D3 composition (Table 1) at an average was 1.3 % and at the end of the test it made 0.2 %. In the specimens of D2 and D3 composition, the results of the measurement of bulk humidity were scattered less. Also, an effect of concrete structure on the desorption process, rating pore and capillary structure in concrete and theirshape has been evaluated. When a constant weight of specimens was reached, the specimen were cut into two parts about 2cm from the plane where moisture had been measured. For subsequent tests, the top cut part was used, because the depthof measuring moisture was about 2 cm. Visual examination displayed that minimum moisture was in the points with large aggregates near the surface. After a comparison of the specimens it can be affirmed that moisture content is less in the points where the structure of concrete is more massive and less capillaries can be seen. Drėgmės desorbcijos tyrimas bentono konstrukcijose Santrauka Nagrinėjama horizontalių betono konstrukcijų (apie 10 cm storio) drėgmės desorbcija. Tirti trys skirtingi betono mišiniai, kurių sudėtys skiriasi V/C santykiu, viename jų klojumui padidinti naudotas plastiklis. Tyrimo metu buvo fiksuojami betono bandinių tūrinio drėgnio ir masės pokyčiai. Betono bandiniai buvo džiovinami natūraliomis sąlygomis po to, kai nusistovėjo pusiausvyros drėgmė – džiovinimo spintoje. Nagrinėjama betono struktūros įtaka desorbcijos procesui, įvertinant tiriamo betono porų ir kapiliarų išsidėstymą bei jų formą. First Published Online: 16 May 2013 Reikšminiai žodžiai: betonas, drėgmė, desorbcija, struktūra, tūrinis drėgnis, poros, kapiliarai

Keywords

• concrete
• desorption
• structure
• volume humidity
• porosity
• capillaries