Use of locally available material to develop a treatment technique to reduce the water absorption capacity of recycled aggregates

Abstract

This study was to find a treatment technique to reduce the water absorption of Recycled Aggregates (RA) which involved preparing a coating to reduce the water penetration. The materials considered for the preparation of coating was Termite Mound Soil (TMS) and ordinary Portland cement. The objective was to find their optimum proportions and the slurry thickness for a coating that gives the lowest absorption. TMS was tested for pozzolanic properties. Chemical composition was tested using Atomic Absorption Spectroscopy and other analytical techniques. Mainly water absorption, particle size distribution, AIV, LAAV of RA was tested to ensure the suitability for construction purposes. Slurry was prepared using cement replacement levels of 0, 20, 40, 60 and 80% of TMS. Three sets of coatings were prepared with water to solid ratios of 1, 1.25 and 1.5. Slurries were prepared in a concrete mixture in which the aggregates were coated for 10 minutes at a speed of 30rpm. After air drying, coated aggregates were tested for the absorption after 14 days. The absorption of treated aggregates was compared with those of natural and untreated recycled aggregates. From the successful aggregate batches three concrete test cubes were prepared from each and tested for the 28 day compressive strength after curing for 28 days. Strength values were compared with those prepared with natural aggregates. Aggregates Coated using 50% cement and 50% TMS showed a significant reduction in the water absorption up to 38.44%. The strength of concrete made from aggregates treated with 50% TMS replacement along with the water solid ratio 1 was 37.15N/mm2 whereas the value obtained from natural aggregates was 37.3N/mm2