تأثير باكتري بر جذب آب و بهبود دوام بتن مسلح به الياف

چكيده انگليسي :

Influence of bacteria on water absorption and durability improvement of concrete reinforced by fibers Nasrin Karimi Ghahfarokhi nasrin karimi1@cv iut ac ir November 21 2018 Department of Civil Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Dr Davood Mostofinejad Prof Email address dmostofi@cc iut ac irAbstractConcrete is one of the world most widely used construction material However concrete has been known thatit is weak in tension since the early 1800 s Weak tensile strength and brittle behavior result in sudden tensilefailure without warning Thus concrete requires some form of tensile reinforcement to compensate its brittlebehavior and improve its tensile strength and strain capacity Historically steel has been used as the materialof choice for tensile reinforcement in concrete Unlike conventional reinforcing bars which are specificallydesigned and placed in the tensile zone of the concrete member fibers are thin short and distributedrandomly throughout the concrete member Fibers are commercially available and manufactured from steel plastic polymeric materials and other materials Fibers improve toughness and tensile properties of concreteand help to control cracking But one of the defects of fiber reinforced concrete is porosity FRC suffers fromhigher porosity compared to normal concrete and the pores are one of the most intensifying weaknessfactores in durability Due to the negative side effects of certain chemical techniques biological methodshave been proposed as an environmental friendly strategy for reducing porosity of fiber reinforced concrete In this regard calcium carbonate precipitation induced by micro organisms has found wide applications inconstruction technology for its effect on improved quality of building materials In this present specimensare divided in two main groups specimens have bacteria and its medium instead of mixing water and bacteriaare used for surface treatment of others For investigation of influence of spores nonactivaty bacteria in fewnumber of concrete specimens are used spores and medium in mixing water Impact of specific bacteria ofbacillus family is called bacillus subtilis with 107 cells mL concentration was investigated by different tests In both cases there are four mix designs with different percentages of polypropylene steel and barchip fibersvolume These four groups are control specimens without fibers specimens containing 0 3 polypropylene fibers specimens containing 0 75 barchip fibers and specimens containing 1 steel fibers Generally 336 specimens were made for compressive strength water absorption electrical resistance flexural strength water impermeability accelerated chloride penetration and carbonation s depth tests The results showed that the produced precipitations by bacteria fill the pores in concrete therefore it leads toreduce some concrete characteristic such as water absorption depth of carbonation water permeability Dueto the effect of peptone in medium of bacteria the compressive strength slightly reduces Furthermore it hasa little increase in modules of rupture in fiber reinforced and normal concrete Pores of FRC increase the freemovement of ions in the concrete consequently it increases chloride ion penetration This phenomenon canreduce by bacteria in mixing water Use of bacteria and spore in concrete increses electrical resistance Theproduced precipitations by spore is lower than the produced precipitations by bacteria This has led toimproved concrete properties In this research curing in calcium source lactate calcium and presence ofbacteria play an important role in performance and durability of concrete Surface treatment generates a layerof calcium carbonate precipitation on the surface and it restricts the permeability KeywordsFiber Bacteria Surface treatment Lactate calcium Calcium carbonate precipitation

كريمي قهفرخي، نسرين

تأثير باكتري بر جذب آب و بهبود دوام بتن مسلح به الياف

الياف , باكتري , ترميم سطحي , رسوب كلسيم كربنات , كلسيم لاكتات