ROLLER COMPACTED CONCRETE FOR DAMS

Abstract

A comperhensive and systematic investigation on Roller Compacted Concrete (RCC) to be used for Jamrani dam in India has been carried out using local materials and Harduaganj fly ash. High paste content with fly ash of 0 to 80 per cent by solid volume of cementitious materials have been used along with the conventional concrete for comparative studies. Review of existing literature, testing of materials, design of RCC mixes, fabrica tion of vibro-loaded system for compaction of all RCC specimens in Laboratory, casting and curing of specimens, testing of specimens at the prescribed age upto one year, analysis and interpretation of test results along with mathematical modelling of experi mental results forms a major part of the present work. Preliminary mix proportioning of RCC using local materials was done in accor dance with the procedures outlined in ACI committee 207 Report for high fly ash con tents. The results obtained from specimens prepared according to ACI report were un satisfactory because of poor workability. Avibro-loaded system was fabricated and developed for optimum surcharge load ing ofwet RCC mixes for optimum compaction of all specimens used in the laboratory. The energy of compaction of 2.714 Nmm/mm3 obtained from the vibro-loaded system is equivalent to the energy applied by modified Proctor test which is reported to be satisfactory for compaction ofRCC in the field. For this work more than forty mixes were designed and a large number of RCC specimens were cast and tested in the pre liminary investigations. The relationship developed between optimum moisture content versus optimum density shows that, maximum strength occurs at maximum density, indicating that the established optimum water content is sufficient for compaction as well as hydration of RCC samples. XXIV Based on the optimum moisture content, maximum density and strength, a mix design methodology has been developed. Strength parameters for RCC at the age of 28,91,180 and 365 days for cube and cylinder compressive strengths, split and flexural tensile strengths have been determined for optimumRCC mix with fly ash contents byvolume varying from 0,33,50,60,70 and 80 per cent. Regression analyses of RCC test data give generalised mathematical models between strength parameters, time and percentages of fly ash content in cementitious material. It is a major finding where all the three types of relations i.e. power, hyperbolic and logarithmic relations fit well. However the best fit hyperbolic models require two constants and next best fit power relations give most useful and simple single constant model. The interrelationships between various strength parameters such as cube and cylinder compressive strengths, and split and flexural tensile strengths have been estab lished. The interrelationship results are in agreement with the general trend indicated in the literature. The optimum fly ash content in RCC has been found to be 70 per cent. Similar studies have been carried out for static and dynamic moduli of elasticity and mathematical models and inter relationship similar to strength parameters have been established. The Poissons Ratio for RCC varies between 0.124 to 0.191. Special studies on tensile strain capacity and strength of cold joints using modified split and shear tests have been carried out for the RCC as these are vital. Extensive thermal studies on specific heat by using USCE and USBR methods, thermal diffusivity thermal conductivity by using three methods and finally coefficient of thermal expansion of RCC have been carried out and a comparison with conventional concrete shows the thermal constant values for RCC are slightly lower. Important studies on Permeability ofjointed and parent RCCmaterial, Durability and Shrinkage shows that the internal structure of RCC improves with the reaction of calcium hydroxide and fly ash within the initial pores of RCC and permeability, durabil ity and shrinkage properties improve with the increase of fly ash content. Thus the RCC dams are much superior than dams made out of conventional concrete.