Concrete is a composite building material. Due to its increasing demand in the construction industry, its basic ingredients such as cement, fine aggregate and coarse aggregate have become extremely costly. Studies have been carried out to find better and more economical alternatives to these conventional building materials. One such alternative is fly ash, which can be used to partially replace cement. The main disadvantage of conventional concrete is its brittle failure, which can be avoided by using steel fibers. This study identifies the behavior of concrete with regard to impact resistance and its mechanical properties by adding hooked-end steel fibers at levels of 0, 0.75, 1.15 and 1.55% and partially replacing 40% of the cement with 40% fly ash. In addition to the control concrete, there has been four mixes with respective addition of steel fibers. The behavior of normal and fly ash concrete with steel fibers was compared. The combination of fly ash and steel fibers provided a homogeneous and very rich mix, with a delay in the setting time of the concrete. Of all the mixes, the one containing 40% fly ash and 1.55% steel fibers proved to be the best, with a maximum increase in strength of 17% in compression, 25% in split tension, 30% in flexure and 95% in impact energy at 56 days. A multiple linear regression model was also formulated using SPSS (Statistical Package for Social Sciences) software, through which corresponding equations were developed to predict the strength and energy at 28 and 56 days. The equations were also used to predict the strength of the mixes from other researchers' experimental work. The predicted results corresponded well with the experimental results and the percentage difference was found to be less than 5%.

No abstract

Concrete filled steel tubular columns are preferred due to their excellent static and dynamic resistant properties such as high strength, high ductility and large energy absorption capacity. The comparison of the ultimate strength of CFST with Hollow steel tube, RCC and the bond strength between concrete and the steel was done both experimentally and analytically using ANSYS. A total of 18 specimens were cast, out of which ultimate strength was determined for 13 specimens and bond strength was observed for 5 specimens using push out test. Both experimental and analytical observations using ANSYS were carried on a cylinder of height 460 mm and a diameter of 113 mm. The grade of concrete used for infill is M30. The tests were carried on an Ultimate Testing Machine. The ultimate strength of CFST, RCC and HST were compared and CFST having the advantages of both concrete and steel is found to behave better and average bond strength ranges between 0.7 to 1.1 N/mm 2 .

The California Bearing Ratio (CBR) is a parameter for evaluation of the mechanical strength of sub grade, base course and other layers of a new carriage way. It depends on various factors and nature of soil. The service life of pavement on weaker soil sub grade is quite low due to the high compressibility and plasticity behavior of soils. Some soils possess less strength, CBR value and have high affinity to moisture content. Hence it is important to increase the strength of soil for sustainable performance of Indian roads. To increase the sub grade soil strength, geogrids are used in roads. Geogrids are cost effective polymeric materials used as soil reinforcement. It helps to increase the stability and bearing capacity of soil, enables good drainage and involves less maintenance. Increase in CBR value of the sample with use of geogrids leads to reduction in the thickness of pavement. Two soil samples are collected from the nearby construction sites. Basic tests are to be conducted on the samples to determine its engineering and index properties followed by CBR test under optimum moisture content. This paper deals with the experimental results of CBR tests on different types of sub grade soil by increasing the number of geogrid layers in each trial. This gives the optimum number of geogrid layer to attain the maximum CBR value. This paper also includes the application of CBR value in the design of flexible pavements as per IRC recommendations.

No abstract