STRENGTH AND DURABILITY CONSIDERATIONS IN DESIGN OF POZZOLANIC MIXES

Abstract

The use of lime4lyaah.aggregate mixture technically termed ae pozzolanic mix Is gemming considerable popui,arity these day$# Satra( ) and VasanC39) have studied the stress deformation characteristics and strength characteristics of pozzolanic pavements, respectively. In ccntnuatai of that study, some further investigations have been made using different proportioning of the mix. The purpose of this investigation :j to design . the optimum proportioning of limes flyash and aggregate mix using varying gradations of aggregates and to determine the structural properties ©f the mix with optimum proportioning. Coarse aggregate at three different maximum sizes viz. 37nnn, 2nn and 19irn and each one, with three different percentages. viz, 3, 40% and 54%' of the total aggregate quantity have been investigated. Thus nine different gradations of aggregate have been studied. For each gradation of aggregate optimum percentage of (lime + flyash) and Lime : lyash has teen. deterxi4ned on the basis of unconfined compressive strength. These mixes have been tested for -dtirabily. by Modified British Tent procedure B.&.3.`,192, 1957. The best mix proportioning of limes flyash and aggregate from considerations off` unconfined compressive strength and durability is obtained as, lime Iflyash t Aggregate ia3:13.31 The aggregates used here have the maximum size of 25mm and have 40 percent as coarse aggregates. The other strength properties viz$ Elastic ro dulu s, p of s sonI s ratio, flexural strength and Fatigue characteristics have been investigated using the optimum proportioning of the mix as determined above. The structural psaperties of the mix clearly indicate that pzzolnic mixes if suitably designed offer adequate resistance to flexing and behave like rigid material. The ultimate load test on model pavement slab laid with the above proportioning gives crack patterns similar to those generally observed concrete pavements.,