Study On High Performance Of Basalt Fibers Reinforced Cement- Based Materials

The use of concrete structures is widely-ranged in the world and it is quite known as one of the most useful,effective,and low-cost structures.Along with all the prosperities that can be bargained for concrete elements,several disadvantages have been discovered,such as low tensile strength,low ductility,and low energy absorption.These disadvantages are which researchers are doing their efforts to improve.One of the efficient approaches to improve some of the conventional concrete’s disadvantages have been taken seriously into consideration by researchers is the using of bendable concrete or as it is known by Engineered Cementitious Composite(ECC for short).The University of Michigan has a superior role in investigating in a composite material known as ECC concrete.ECC is developed in the early 1990’s by Prof.Victor C.Li,a Professor of Structural and Materials Engineering at the University of Michigan.The research presented herein describes the testing performed to examine the potential use of ECC materials using basalt chopped fibers in comparison with traditional materials.This study suggests the need for developing a new class of FRCs which has the strain-hardening property,which also called High-Performance Fiber Reinforced Cementitious Composites(HPFRCC).It is demonstrated that such a material can be designed based on micromechanical with strain capacity of about 3 to 5% compared to 0.01% of normal concrete.That extensive Pseudo Strain-Hardening can be achieved by a moderately low fiber volume fraction(<2%).This thesis presents the current situation regarding numerous previous investigations,which have been taking place around the world on study of the behavior of ECC material by basalt chopped fibers.Polyvinyl Alcohol(PVA)and different fibers’ types have been using in studies to improve the strain behavior of Fiber Reinforced Concrete(FRC)under the micromechanical principals and by exploitation numerous mineral admixtures.Basalt fibers have several advantages qualified it to compare with other chopped fibers in ECC concrete’s progress.Basalt fibers are considered as a green product.It has superior properties,such as high strength,higher strain to failure,better stability and thermo-chemical resistance(good chemical resistance,high-temperature resistance,it has significant resistance to low temperatures(freezethaw),besides high resistance to corrosion).Laboratory studies were used to examine the effect of different parameters such as curing days,fibers content,fibers length,and surface treatment on the mechanical properties of Engineered Cementitious Composite reinforced with basalt chopped fiber.Surface treatment with silane coupling agent was applied on basalt fibers and an investigation was carried out to demonstrate its influence on ECC concrete.The compressive,flexural and tensile properties of basalt fibers reinforced cement-based materials are studied under the different parameters.In the study,basalt chopped fibers with different lengths(12 and 24mm),and with different content of 0.50%,1.0%,and 2.0% were used.The enhancement effect of basalt fibers was evaluated comprehensively.It is found that the existence of fibers will reduce the compressive strength of materials.However,it can increase the flexural strength and tensile strength with significant percentages.A total of 130 cubes specimens of(70.7mm × 70.7mm × 70.7mm)dimensions were tested under constant compressive load after two different curing ages for the compressive strength test.104 prisms(40mm wide × 40 mm deep × 160 mm long)were cast to measure the flexural strength(Modulus of Rupture)under three-point loading test.In additional to,groups of 104 specimens were tested to measure the splitting tensile and direct tensile strength.Apart of this thesis,the interface bond strength behavior of bundle dispersion basalt fiber and cement matrix was studied.The objective of this research was to investigate the bond interface strength between bundle dispersion fibers and cement matrix,in order to demonstrate and achieve High-Performance Fiber Reinforced Cementitious Composites(HPFRCC)using basalt fibers.Interface Bond Strength test is considered one of the Mechanical Properties investigation tests to get the desired information about the composites.The interface properties play an important role in the fiber bridging efficiency,which makes interface characterization very important to achieve the bridging behavior of composites.A bundle-dispersion single sided pull-out test was carried out to investigate the interface strength.Water to cement ratio,the embedded length,and adding mineral admixture(Fly Ash)were the main parameters in this investigation.Two different(ratios of water to cement and embedded Length)were studied with and without adding fly ash.The results indicated that adding mineral admixture additives such as fly ash could decrease the bond between fibers and cement matrix.