An Experimental Study into Behaviour of Circular Footing on Reinforced Soil

The experimental investigations are reported on the study of load-deformation behavior of a model circular footing on reinforced soil in respect of two-layered system comprising clay as sub-grade and mine waste as backfill material. The footing was subjected to axial load. Two different types of reinforcing materials such as Kolon Geo-grid (KGR-40) and rubber grids derived out of waste tyres were used in the study. The study revealed appreciable increase in ultimate bearing pressure and decrease in settlement with the provision of a single layer reinforcement. Further, rubber grid performed better than the Geo-grid in respect to BCR and SRF. The study indicates significance of solid waste materials such as mine wastes and discarded tyres as effective civil engineering construction materials

Optimization of cement quantity through the engineering of particle size distribution – a sustainable approach

Cement is the most used building material on the planet and is responsible for 8% of the total CO2 released. In the coming decades, due to increased population and infrastructure needs, a surge in cement demand is expected. To meet the demand without affecting the carbon foot-print the efficiency of cement needs to be enhanced. This paper presents a novel approach to achieve enhanced efficiency through the engineering of particle size distribution. Since raw materials used in cement production vary in quality across the globe, the only feasible method of enhancement is through modification of mechanical parameters such as particle size and distribution. The paper explains the details of an experimental study on cement and concrete using a “Stimulator” produced by grinding commercially available OPC. Stimulator content was varied between 0 and 100% in the interval of 10%. Various tests such as water requirement, setting times, the heat of hydration, chemical shrinkage and compressive strength parameters were conducted, thus determining the optimum dosage of the stimulator. Despite the reduction in the average particle size of cement by 38–47%, water requirement has shown a nominal rise of 10–17% for S40 to S50 cement mixes, respectively. Concrete Samples with the optimum dosage of stimulator depicted 20–25% lesser requirement of cement to achieve strength equivalent to that of concrete containing OPC only. This reduction in the requirement of cement quantity leads to lower cost and lower amount of CO2 released. Implementation of this method of cement production does not require the introduction of new machinery. Unlike pure OPC, the cement & stimulator mix portrayed a double peak PSD arrangement representing the participation of 2 sets of particles in the cement matrix sizes. Durability tests conducted on concrete samples with the optimum dosage of stimulator and OPC have depicted better durability than concrete samples with OPC only

Sodium silicate bonded waste foundry sand - A substitute for fine aggregates in concrete and a potential material for cement phase synthesis

Sodium silicate bonded Waste Foundry Sand (WFS) is being discarded by the foundries after single use. The studies so far are suggestive that the WFS after being discarded cannot be reclaimed by any physico-chemical methods and the silica transformation is within the crystal structure. Hence such sand utilisation in bulk quantity will be one of the options for managing the issue of sodium silicate bonded WFS. Recent research trend in construction materials involve utilization and blending of different industrial byproducts and waste materials to solve the environmental problems. In the present work, sodium silicate bonded WFS was used as a replacement for fine aggregates in concrete in varying percentages of 0%, 10%, 20%, 30%, 40% and 50% by weight. The 30% replacement showed better compressive strength compared to control samples. Further, these samples also passed the durability tests like rapid chloride penetration, water absorption, sorptivity, rebound hammer and ultrasonic pulse velocity. Both the strength and durability results can be attributed to the property of the sand in terms of its size, shape and its reactivity. To prove this hypothesis further fine sodium silicate bonded WFS (less than 45μm) was mixed with calcium carbonate in appropriate molar proportions. The mixture was calcined at 1400°C. This mixture was analyzed using XRD and the results revealed that alite and belite phases were generated during the reaction. This gives new dimension to utilize sodium silicate bonded WFS in concrete or as source of silica in cement industry