Study On Alkali-activated Slag Composite With Engineered Matrix In Coordination With Several Fibers

Engineered cementitious composite(ECC)is well known for its high toughness and ductility.However,it is environmental unfriendly caused by high cement consumption.It has been proved that using alkali-activated cementitious materials to prepare clinker free ECC is an effective way to tackle this problem.Nowadays,clinker free ECC can achieve high tensile strain which is comparable to traditional ECC,while the compressive strength is limited within 63.7 MPa even if use heat curing,which is,to some extent,disadvantageous for its development.To prepare high strength and high ductility clinker free ECC,PVA fibers,PE fibers and steel fibers were used to enhance engineered alkali-activated slag mortar by single and hybrid adding ways.The compressive strength,flexural strength,uniaxial tensile performance,self-healing and drying shrinkage performance were investigated through a series of tests.The fiber-reinforced alkali-activated slag composites with compressive strength of 116.4 MPa,ultimate tensile strength of 6.2 MPa and tensile strain of 0.85% were obtained.Meanwhile,it was comforted that the composites had good self-healing ability at early ages.By analyzing the reinforcing effect of different fibers on alkali-activated slag mortar,it was proposed that the reinforcement of fiber on compressive strength was a kind of static effect.The mechanism causing tensile strain hardening behaviour of PVA and PE fiber-reinforced alkali-activated slag mortar was multiple cracking,while the mechanism causing tensile strain hardening of steel fiber-reinforced alkali-activated slag mortar was single cracking.Hybrid adding way made the reinforcing effect of fibers on alkali-activated slag composites reduced and evenly distributed under uniaxial tension.A method to define the number of cracks in the specimen according to the number of troughs in the strain hardening stage of uniaxial tensile stress-strain curves was proposed and verified in this paper.In addition,through continuous loading of twice compression loads on each group of specimens,it was demonstrated that the fiber-reinforced alkali-activated slag composites could retain more than 80% of the secondary load carrying capacity compared with the first time.