Study of the Behavior of Secondary Raw Materials in Self- Compacting Cementitious System

Abstract

Self-compacting cementitious system (SCCS) is a modern concept introduced in the construction industry and is being used throughout the world. Self-compacting cementitious Systems have major applications in placements involving heavy and congested reinforcements such as tunnel linings, rafts and pile foundations, bridge piers, high rise buildings, pre-stressed concrete members, transportation structures and aircraft runways etc. SCCS has higher workability, provide uniform compaction throughout the placement area and hence higher durability and strength. These systems contain higher powder content and lower water to cement (w/c) ratio as compared to conventional concrete and thus provide a better packing density, ease of placement in heavily reinforced sections, less heat of hydration, volume stability, higher strength and enhanced durability. Secondary raw materials (SRM’s) are used to replace cement contents to economize the manufacturing of concrete and to make an environment friendly concrete with improved microstructure. This research project was undertaken to assess the feasibility of using various secondary raw materials including Marble Powder (MP), Bagasse Ash (BA), Hemi-hydrate (HH), Fly Ash (FA) and Brick Powder (BP). These materials are industrial by-products and were easily acquired. Various parameters including particle size distribution, chemical analysis using XRF, flow behavior, strength development and micro-structure were studied. Flexural and compressive tests were performed on the paste samples using 10% replacements of all the secondary raw materials. All samples showed high strength development except brick powder. SRM, s were also used in blends, these blends also showed appreciable results. Fineness of SRM, s increases their surface area and thus increasing water demand to some extent. However, due to their smaller size they increase the packing density of the structure by adjusting themselves in the pores and acting as filler materials. Addition of super-plasticizers improved the workability by using their cement dispersion mechanism. They also ameliorated the durability and ease strength development. XRF results of few Secondary raw materials showed their pozzolanic nature because they contained CaO, SiO2 and Fe2O3. Setting times and rate of strength development varied depending upon the type of material used in the sample. Mortar samples containing cement, SRM and sand in the proportion of 1:1:2 respectively were also tested using w/c ratio of 0.4. These mortar systems also exhibited high compressive strength. Therefore, after carrying out careful study and detailed analysis of results it can be concluded that addition of secondary raw materials enhances both fresh and hardened state properties of cement based systems. In addition, use of blends further optimize the properties of self-compacting cementitious systems.