Study On The Durability And Toughness Of Reinforced Sand Autoclaved Aerated Concrete

Sand anticlaved aerated concrete(SAAC)is widely used for the interior and exterior walls construction in the industrial and civil buildings,due to its advantages of lightweight,seismic,excellent thermal insulation and easy construction.However,the performances deterioration of SAAC may occur in the course of service because of the effects of carbonation and the erosion of corrosive media.For instance,the mechanical properties decrase of SAAC matrix,the damage and aging of the organic coating on the steel bar.Moreover,for the reason of its high brittleness and low toughness,SAAC is prone to damage,such as "missing edge and corner".Therefore,the performance of SAAC matrix under the carbonation and soluble salt attack,the water-borne inorganic anticorrosive coating for the steel bar in SAAC,and the toughening of SAAC matrix are studied.The main work and conclusions of this paper are listed as follows:(1)Accelerated carbonization test and natural carbonization test of B04,B05 and B06 SAAC were carried out.The effects of carbonization on the porosity,compressive strength,phase composition and micro-morphology of SAAC were evaluated.The carbonation of SAAC was that its main mineral reacted with carbon dioxide and decomposed.Which resulted in that the compressive strength of SAAC gradually decreased along with the increase of carbonation time.Moreover,on the basis of the analysis of various carbonation models,a carbonation prediction model for SAAC based on carbonation depth is builded.The rationality of the model is verified by comparing the experimental results with the calculated values of the model.(2)The effects of soluble salt attack on the mass change ratio,the compressive strength,the relative dynamic modulus of elasticity,the phase composition and the micro-morphology of SAAC were studied by drying-wetting cycle test.The results showed that the damage degree of SAAC caused by common soluble salt erosion was in the order,sodium sulfate > sodium carbonate > magnesium sulfate > ammonium sulfate > sodium nitrate.The main reason was that serious sodium sulfate crystallization expansion occured in SAAC under sodium sulfate erosion.Moreover,the damage degree of SAAC was aggravated with the increase of the concentration of sodium sulfate solution.After 150 drying-wetting cycles,the compressive strength and the relative dynamic elastic modulus of B05 SAAC under 10 wt.% sodium sulfate attack decreased by 48.6% and 55.0% respectively.(3)Waterborne inorganic zinc silicate-potassium silicate coating for the steel bar in SAAC was prepared with the high modulus potassium silicate,silicon-acrylic emulsion,zinc silicate et al.The effects of the modulus of potassium silicate and the content of zinc silicate on the kinematic viscosity,working performance,adhesion,impact strength,adhesion and anticorrosive properties of the coating were studied.The anti-corrosion mechanism of the coatings was discussed on the basis of the characterization of phase composition and micro-morphology of coating.Results revealed that the coating(Z-5.5-50)prepared with 5.5 modulus potassium silicate and 50 wt.% of zinc silicate exhibited the best performance.After immersing in 3.5wt.% Na Cl solution for 7 d,the polarization resistance of sample with Z-5.5-50 coating was 37830 Ω·cm higher than that of the control sample.This was resulted from the excellent physical shielding effect provided by Z-5.5-50 coating and the dense hydrated calcium silicate on the coating-SAAC interface.(4)Waterborne aluminum powder modified zinc oxide-potassium silicate coating the steel bar in SAAC was prepared by using 5.5 modulus potassium silicate,silicon-acrylic emulsion,zinc oxide,aluminium powder and et al.The effects of zinc oxide content and aluminium powder substitution rate on the kinematic viscosity,working performance,adhesion,impact strength,bonding performance and anticorrosive propertes of the coatings were evaluated.Together with the anti-corrosion mechanism of coating revealed with the phase composition and micro-morphology of coating.The results showed that the coatings(Z-A1)prepared with 40 wt.% of zinc oxide and 25% aluminium powder substitution rate had the better performance.The polarization resistance of sample with Z-A1 coating immersed in 3.5wt.% Na Cl solution for 7 d was 39622 Ω·cm higher than that of the control sample,which was attributed to the excellent physical shielding and cathodic protection of Z-A1 coating.(5)To toughen SAAC,different contens of wood fiber was added in.And different contents of rubber powder was added in wood fiber reinforced SAAC to imporved its thermal insulation properties.The effects of wood fiber content and rubber powder content on the fluidity of SAAC slurry,bulk density,pore structure,compressive strength,flexural strength,impact toughness and thermal insulation properties of SAAC were studied.Results showed that wood fiber improved the mechanical properties of SAAC,but caused the increase of thermal conductivity.The pore structure of SAAC was improved by adding rubber powder,which contributed to the improvement of thermal insulation performance of SAAC.The sample with 0.4 wt.% of wod fiber and1.0wt.% of rubber powder has the best performance.Compared with the control sample,its compressive strength,flexural strength and impact toughness are increased by 10.5%,47.5% and 42.9%,respectively,And its thermal conductivity reduced by 2.0%.