Frictional behaviour of segmental retaining wall units infilled with recycled concrete aggregate
The use of segmental retaining wall units as the facing column for mechanically stabilized earth (MSE) retaining walls has increased noticeably all over the world. Hollow and solid, both types of modular block units are used in dry-stacked facing columns. Nowadays, Hollow concrete units are being implicated frequently because of its cost-effectiveness and other technical advantages. The cavities of hollow concrete units are filled with natural (fresh) aggregates for better shear resistance. The use of fresh aggregates as in-fillers in retaining wall constructions is expensive and unsustainable (annihilation of natural resources). This study mainly focuses on frictional behavior of newly designed and manufactured precast “I” blocks infilled with fresh and recycled aggregates. A series of tests were performed using a specially designed & fabricated direct shear apparatus to assess the frictional behavior of infilled blocks under different normal loading conditions. The tests were executed based on the exiting ASTM and National Concrete Masonry Association (NCMA) test protocols. Test results were outlined in the form of shear stress-displacement relationship to compare the effect of recycled aggregate against the fresh aggregate. Shear capacity envelopes were also plotted using Mohr-Coulomb failure criteria to find out the angle of friction for each case. Test results revealed that the angle of friction of the blocks infilled with the recycled aggregate is almost equal to those with the fresh aggregate.
An Experimental Behaviour of Composite Circular Columns with Partial Replacement of RAC
In this paper an experimental behaviour of circular composite columns made with recycled aggregate concrete (RAC) where compared with conventional circular column.MS steel pipes, l-angle member and hollow pipe used as a composite materials. Normally steel is a tension member, when it is combined with concrete it act as both tension and compression member .There is no requirement to provide additional reinforcing steel for composite concrete filled tubular sections, except for requirement s of fire resistance where appropriate. The circular composite columns are casted in size of 1m in length, diameter as 110mm and thickness of circular pipe is 2mm.The l-angled member as size of 1m with 2mm thickness and breadth of 50mm. In hollow composite column, the dia of the pipe is 50mm with 1mm thickness. Mat is designed for columns to place under loading frame. Size o f the mat is 300x300x100mm. To study the deflection, load bearing capacity and buckling behaviour of column is tested under loading frame. The values are computed using universal data acquisition and control system by placing LVDT (linear variable d ifferential transducer). The load vs. deflection curve is drawn using load pattern.
Effect of drawing on creep fracture of polypropylene fibers
The ultimate properties of polypropylene fibers, prepared by drawing the same undrawn fibers to different draw ratios, were determined by the creep fracture method at temperatures from 40 to 120°C. The composite curves of the engineering stress at break, the true stress at break, the ultimate extension ratio were constructed as a function of reduced time to break by assuming time–temperature superposition. The temperature dependence of the shift factor aT used in the superposition could be represented by a single equation of the Williams, Landel, and Ferry form. The composite curves of the true stress at break for the samples with different draw ratios were almost the same independently of draw ratio. The composite curves of the ultimate extension ratio for these samples could be reduced to a single curve by assuming that the ultimate extension ratio evaluated with respect to the unit length of the undrawn fibers were constant independently of draw ratio if the time to break and temperature conditions of the measurement were fixed constant. A possible fracture mechanism is discussed on the basis of the fracture mechanisms proposed by Samuels and Peterlin.