Study on Mechanical And Durability Properties of Engineered Cementitious Composites Using Polypropylene Fibers

Abstract

Fiber present in cementitious matrix tends to reinforce the performance of the composite under any mode of loading. The bond between fiber and matrix elevates the performance of that composite material. Ductile nature and tight crack width are two unique feature of Engineered cementitious not seen in Fiber reinforce concrete. This makes ECC superior to normal concrete which possess inherent weakness in terms of brittle nature. Todays construction industry is very cost sensitive. Cost effectiveness, feasibility and beneficiary are the three main requirements when any material is introduced to commer- cial market. Since fibers increases the cost of the composite and due to lack of knowledge about its dosage or optimum proportion its acceptability is affected. Fiber proportion can be optimized provided the ductile nature of ECC is not compromised. ECC mixture consumes higher cement content approximately three to five times than that of normal concrete. The best way to tackle with this problem is to substitute cement by industrial by product well know as GGBS (Ground granulated blast furnace slag) pro- vided the green ECC should show satisfactory performance as compared to ECC. In this investigation performance of ECC and ECC-GGBS mixes for varying polypropy- lene fiber dosage is evaluated. Mechanical properties like compression, exure, split tensile strength, impact energy, abrasion resistance and bond strength are evaluated. Dumbbell shaped specimen are also prepared and tested for ECC and ECC-GGBS mixes in order to observe its performance under direct tension. Test result re ects that gradual increment is observed with increase in fiber dosage for

exural strength,split tensile strength,direct tensile strength of all ECC and ECC-GGBS mixes at age of 28 and 56 days. GGBS also increases the mechanical properties of all ECC-GGBS mixes after 28 days .Abrasion resistance also increases with increase in fiber dosage. ECC-GGBS mixes shows lesser wear resistance as compared to ECC mixes for same fiber dosage at 28 days. Fiber contributes significantly for increasing impact energy of ECC and ECC-GGBS mixes at the age of 28 days.Ductile failure is observed of all ECC and ECC-GGBS mixes while brittle failure is observed for ECC and ECC-GGBS mixes without fibers.Bendable nature of ECC and ECC-GGBS mixes has been observed by conducting plate test and it is also observed that bendability increases with increase in fiber dosage and age. Polypropylene Fibers has a tendency to diminish the crack width furthermore restrains the crack prolif- eration. To study the effect of local environmental condition on ECC and ECC-GGBS mixes. Different durability test like acid attack, chloride attack and sulphate attack are also car- ried out at 30 and 60 days respectively. ECC and ECC-GGBS mixes without fiber losses higher measure of mass and compressive strength when compared with ECC and ECC-GGBS mixes with fibers under sulphuric acid, sodium chloride and sodium sulphate exposure respectively .Resistance against acid attack,chloride attack and sulphate attack increases with increase in fiber dosage. It is observed that ECC-GGBS mixes shows much better performance as compared to ECC mixes against acid attack,chloride attack and sulphate attack for same amount of fiber dosage.Because GGBS reduces the amount of calcium hydroxide in aggregate paste interface resulting in more dense and strong micro structure.