Cement Energy and Environment

Artificial Light Weight Aggregates There are some artificial light weight aggregates produced. Some of them are: Artificial cinder, Clinker, Foamed slag, expanded Clay, expanded Shale. Pumice Aggregate Pumice is a natural sponge-like material of volcanic origin composed from molten lava rapidly cooling and trapping millions of tiny air bubbles. Pumice aggregates are abundant at the outskirts of volcanic mountains, particularly in Mediterranean area, Rocky Mountains in US, and most part of Turkey and Indonesia. Pumice is a natural aggregate of abundant resource around the world and it is environmentally friendly. However, pumice is far from being fully utilized in lightweight concrete. Pumice has a chemical composition similar to that of obsidian , or volcanic glass. It has very thin , translucent bubble walls of extrusive igneous rock. Pumice is very lightweight. This is due to the air bubbles in it, created as gasses departed during the formation process. Pumice stones vary in density, according to the thickness of the solid material bHtween the bubbles. Average porosity is 90 percent, which is extremely high for a rock material. Previous work on Concrete Composites Alduaij et al(1) studied light weight concrete using different unit weight aggregate~s including light weight crushed bricks, light weight expanded clay and normal weight gravel without the use of natural fine aggregate. H.Bomhard( 2) had reported that structural light weight aggregate concretes are considered as alternatives to concrete made with dense natural aggregates because of the relatively high strength to unit weight ratio that can be achieved. F.W. Lydon (3) stated that for light weight aggregate concrete , it is more relevant for mix design purpose to relate strength to cement content. Details of the Present Experimental Investigation In the present investigation, studies are conducted on triple blended pumice fibrous light weight concrete. Fly ash and condensed silica fume (CSF) are the mineral admixtures used for triple blending with optimum percentages of 20 and 10 respectively as replacement to OPC in different mixes. Pumice light weight aggregate is used as replacement to conventional granite aggregate in different percentages varying from 0 to 100. Steel fibers with a constant aspect ratio of 50 were used in varying volume percentages of 0, 0.5 and 1.0. In all, 30 different mixes of M25 concrete including the reference mix are tried and the respective unit weighs and strengths were determined. Comparative analysis of the results was made and the conclusions are drawn. Experimental Investigation Materials used Cement (OPC) Locally available ordinary Portland cement of 53 grade of UltraTech brand conforming to lSI standards was procured and used. Fly Ash Fly ash, an artificial pozzolona is the unburnt residue resulting, from combustion of pulverized coal or lignite. It is collected by mechanical or electrostatic separators called hoppers from flue gasses of power plants where powdered coal is used as fuel. It is obtained from Ramagundam Power Plant. Condensed Silica Fume (CSF) It is obtained from the plant of M/s. VB Ferro Alloys near Hyderabad. The addition of condensed silica fume produces concrete with reduced permeability resulting in increased water tightness enhanced chemical resistance and reduced corrosion of reinforcing steel. Silica fume has a bulk density of approximately 610kg/m 3 . Fine Aggregate The locally available natural river sand conforming to grading zone-2 has been used as fine aggregate. Tests have been carried out as per the procedure of IS 383- 1970. Coarse Aggregate Machine crushed granite conforming to IS 383-1970 consisting 20 mm maximum size of aggregate has been obtained from the local quarry. It has been tested for physical properties such as specific gravity, sieve analysis, bulk density, crushing and impact values. Light Weight Aggregate (PUMICE) Pumice (light weight aggregate) which was used for experimental investigation was brought from Bangalore city. It has been tested in the laboratory for its physical properties. It has a nominal size of 20mm. 48