Showing papers by "B. V. Venkatarama Reddy published in 2006"

Strength and Elastic Properties of Stabilized Mud Block Masonry Using Cement-Soil Mortars

Abstract: Stabilized mud blocks (SMBs) are manufactured by compacting a wetted mixture of soil, sand, and stabilizer in a machine into a high-density block. Such blocks are used for the construction of load-bearing masonry. Cement soil mortar is commonly used for SMB masonry. This paper presents the results of an experimental investigation in characterizing the properties of SMB masonry using cement-soil mortars. The compressive strength, stress-strain relationships, and elastic properties of SMB masonry using three types of SMBs and cement-soil mortars are discussed. The influence of a cement-soil mortar's composition and strength on masonry characteristics is examined. The results of masonry using cement-soil mortars are compared with those using conventional mortars (cement mortar and cement-lime mortar). Some of the major findings are: (1) SMB masonry strength is sensitive to block strength and increases with increase in block strength; (2) the strength of SMB masonry using cement-soil mortars is more sensitive to the cement content of the mortar than to the clay fraction of the mortar mix; (3) the masonry modulus increases as the block strength increases; and (4) SMB masonry with cement-soil mortars shows higher modulus than the masonry using cement mortar and cement-lime mortar.

Tensile Bond Strength of Soil-Cement Block Masonry Couplets Using Cement-Soil Mortars

Abstract: Soil-cement blocks and cement-soil mortars are used for the load bearing masonry. The paper deals with the scantily explored area of tensile bond strength of soil-cement block masonry using cement-soil mortars. Influence of initial moisture content of the block and block characteristics (strength, cement content, and surface characteristics) as well as composition and workability of cement-soil mortar on direct tensile strength of masonry couplets has been explored. Major findings of this study are (1) initial moisture content of the block at the time of construction affects bond strength and use of partially saturated blocks is better than dry or fully saturated blocks; (2) as the cement content of the block increases, its strength increases, and surface pore size decreases leading to higher bond strength irrespective of the type of mortar; (3) cement-soil mortar gives 15�50% more bond strength when compared to cement mortar and cement-lime mortar; and (4) bond strength of cement-soil mortar decreases with increase in clay content of the mortar. The study clearly demonstrates the superiority of cement-soil mortar over other conventional mortar such as cement mortar. The results of this paper can be conveniently used to select a proportion for cement-soil mortar for soil-cement block masonry structures.

Characterization of Kolar gold field mine tailings for cyanide and acid drainage

Abstract: The gold mining process at Kolar gold field (KGF) mines has generated about 32 million tons of tailings. Gold was extracted from the mined ores using cyanidation technique that involved dissolution of gold in the ore by water soluble alkali metal cyanides (example, sodium cyanide or potassium cyanide). Of the several dumps that received the mine tailings only the Kennedy’s Line dump was active prior to closure of the KGF mines in the year 2000. The Kennedy’s Line dump received sulfide bearing tailings in slurry form that comprised of spent ore and process water bearing soluble alkali metal cyanide. Depending on the pH of the tailing slurry, the free cyanides may exist as aqueous hydrogen cyanide that can escape to the atmosphere as hydrogen cyanide gas or occur as soluble cyanide (CN−) ions that can be leached by infiltrating water to the sub-surface environment. Additionally, the presence of pyrite minerals in the Kennedy’s Line dump makes them susceptible to acid drainage. This study examines the potential of gold tailings of Kennedy’s Line dump to release cyanide ions (CN−) and acid drainage to the sub-surface environment by performing physico-chemical and leaching tests with tailing samples collected from various depths of the dump, sub-surface soil samples beneath the dump and groundwater samples from vicinity of Kennedy’s Line dump. The chemical mechanisms responsible for the ambient cyanide and pH levels of the tailing dump, sub-surface soil samples and groundwater are also inferred from the laboratory results.