With the increase in strength, concrete explodes spontaneously at failure creating a serious safety hazard. Researchers are actively looking for methods to arrest the cracks in concrete and design a higher strength concrete that fails in a more ductile fashion. Fiber-reinforced concrete has emerged as one of the solutions to this problem. This paper presents findings from the experimental investigation conducted to compare the fracture behavior of plain and fiberreinforced high strength concrete of varying compressive strength. Six different concrete mixes were prepared with w/b ratios of 0.47, 0.36, and 0.20 resulting in average compressive strength of 36, 52, and 92 MPa. Each mix consists of two variations, first without fiber and second with 1% of steel fiber by volume. The mixes were tested for their strength and fracture Behavior using various standard codes and recommendations. From the Load-deflection and Load-CMOD (Crack Mouth Opening Displacement) curves obtained from the study, Fracture parameters like Fracture energy, Stress intensity factor, energy release rate, and Characteristic length is evaluated and compared for plain and Steel fiber reinforced concrete. It was found that adding steel fiber significantly improves the fracture properties of the concrete of different compressive strengths. By adding 1% of steel fiber in the high-strength concrete, the average fracture energy increased by 850%, 770%, and 450% respectively for the concrete with compressive strength of 36, 52, and 92 MPa. Other parameters also show a very significant improvement suggesting fiber reinforcement as a suitable choice to prevent brittle failure and increase the fracture performance of high strength concrete.

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The current study is aimed to evaluate and critically analyze the properties of Light Weight Geopolymer Fly Ash Sand (LWGFAS). LWGFAS has been prepared by geopolymerisation of the fly ash. Liquid solution of 4M NaOH, and Na2SiO3/NaOH=2 was used as an activator and post set heat treatment of 1 hour at 100 o C was applied for preparation of LWGFAS. The LWGFAS sample was analyzed for different physical and chemical parameters along with studies on mineralogy and alkali silica reactivity. The molar concentration of activator solution and duration of post set heat treatment plays vital role on the physical and mechanical properties (particularly specific gravity, bulk density and water absorption) of the Geopolymer fly ash sand. The specific gravity and water absorption of LWGFAS were 1.57 and 17.85% respectively. Experimental concrete mixes made with LWGFAS as a replacement of natural sand were evaluated for compressive strength and different durability properties of concrete. The study indicates that LWGFAS can be suitable for a wide range of applications in making concrete ranging from light weight in nature to normal weight concrete based on the physical and chemical characteristics of Geopolymer Fly Ash Sand.

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Hydraulic structures like spillways, glacis, etc. undergoes abrasion-erosion due to impact & cavitation losses due to the flowing water action. To overcome the deterioration of the concrete in such structures, addition of fibers to the concrete can be viable solution as it is known to increase the structural integrity of the concrete. A comparative study of various engineering characteristics using high strength concrete by incorporating steel fibers and micro polypropylene fibers has been carried out. Water/binder ratio of 0.23 has been kept constant for the study. Dosage for steel fibers are kept as 1, 1.25 and 1.5% by volume while for polypropylene fibers were kept as 1, 2 & 3 kg/m3. Engineering properties such compressive strength, flexural strength, toughness, energy absorption, splitting tensile strength, drying shrinkage, abrasion resistance, and water and air permeability of high performance concrete with & without fibers in its fresh & hardened state are investigated in this paper. Based on the study, the steel fibers with 1.5% dosage are found to be more effective in countering the abrasive and repetitive loading which can be more effective in the repairs of spillways and glacis of concrete dams.