TECHNOLOGY OF UNCOURSED RUBBLE MASONRY

Abstract

The art of masonry construction is very old. From times immemorial, builders in India and elsewhere have been constructing important structures like temples$ darns, bridges and important buildings in stone masonry. These structures have withstood$ the actions of destructive agents of nature such as rain, wind) sun etc. for over centuries now. Despite very long history of construction however, its technology i.e. the engineering art of the application of the properties of the materials has not yet received the scientific attention it,. deserves. In India, the development activity involving construction of a very large number of masonry dams, big and small, has increased tremendously after independence. But even after 25 years, since then, the selection of materials, their sizes and proportions for masonry in dams is still done in an arbitrary manner which is based on the experience of past constructions. There are many variables on which the properties and qualities of masonry depend. It is desirable to know the effects of all these factors viz. properties of materials, their sizes, proportions, methods of placing and curing etc. on the density, strength, elasticity and permeability of masonry. It is also necessary to evaluate the bond strength of masonry, as masonry is essentially a ' Jointed' construction and strength of masonry depends to a large extent on this property. In this dissertation a critical review of the existing literature available on the subject9 is presented and the properties of the materials and their effects on the various properties of masonry are studied. The importance of the variables and possibilities of effecting economics in the design, warrants an Oxtensive investigation for their determination. Some work has already been done in this respect, on an experimental basis at Hirakud and Koyna where large size cubes and cylinders of masonry have been tested for compressive strengths and other properties. The methods of evaluation of the properties of the masonry and the data available from these studies have been discussed. It is revealed from these studies at Hirakud and Koyna, that the density of masonry depends on the densities of rubble and mortar and not on the sizes of stones used; vibration of joints increases the density of masonry, as well as its compressive strength; compressive strengths of masonry are more than the compressive strengths of corresponding mortars; The strength ratios ( strength of masonry/ strength of mortar) are found to vary between 80 and 150 percent; tensile strength of masonry as tested by split cylinder method is about 7 to 10 percent of its compressive strength and varies between 10 and 20 kg/cm2I much is considered quite adequate even for masonry dams subjected to heavy seismic forces; masonry is found to be quite impermeable to serve as a construction materla7. for dams, permeabilities generally being less than 0.5 litres/minute/m2 at unit heads