Pond ash as a potential material for sustainable geotechnical applications - a review.

Energy-harnessing sources significantly influence a country's infrastructure and economic development. Though nuclear and hydel power sources are used for energy harnessing, thermal sources are still the primary power source in India and contribute to 75% of the demand. Thermal power plants exploit large volumes of coal reserves. The combustion of coal leads to 30%-40% of waste ash residues such as Fly ash and Bottom ash. Though Fly ash finds greater applicability, pond ash poses a severe environmental hazard due to its large occupancy of terrain in ash dykes and lagoons. Many research efforts are underway to utilize pond ash in various structural and geotechnical infrastructure projects; however, there are still limitations and apprehensions about its properties and determination. The present study provides a detailed review of the morphological and chemical properties. Further, the geotechnical attributes of pond ash, including strength characteristics, consolidation parameters, and durability aspects, are critically reviewed for the probable application as fill material for backfill and many other applications. Based on the earlier research on pond ash, it could be comprehended that pond ash has wide property variability and finds compatibility with many other pozzolanic admixtures and, in this way, finds broader applicability in geotechnical projects. The way forwards could be a significant step towards cleaner and greener technology.

Sustainable use of reclaimed asphalt pavement (RAP) in pavement applications-a review.

The purpose of this review is to examine the innovative usage of Reclaimed Asphalt Pavement (RAP) in flexible pavement applications. RAP is elucidated as isolated pavement earthly materials consisting of asphalt and aggregates. When the existing/old asphalt is removed for reconstruction, and resurfacing, these materials are generated. Now, it is highly required to classify the available RAP for further essential use in road construction. RAP addresses the issues regarding the diminishing of Virgin Aggregate (VA) sources, storage of material and disposal of RAP material nearby the site. The utilization of RAP includes social benefits like depletion of manufacturing waste, conservation of non-renewable natural stockpiles and low energy expenditure. The reviewed literature reveals that RAP has been utilized mainly for base and sub-base materials on the roads. To summarize, 100% replacement of VA by RAP possessed lesser strength and little resistance to creep and long-lasting deformations. Hence, RAP can be appended with natural aggregate or blended with cement or other admixtures like Fly ash (FA) or confined with geocell. It also accelerates the strength and stiffness of the base and sub-base of pavement as it degrades the failure like rutting and fatigue cracking of pavement due to dynamic loads.

Sustainable utilization of industrial wastes in controlled low-strength materials: a review.

The construction industry is experiencing an increasing demand for sustainable alternative materials. There is huge scope for converting the industrial wastes as partial or complete substitution of cementitious materials and fine aggregates. This study focuses on exploring the performance of different industrial waste materials as possible substitutes for flowable fill or controlled low-strength materials (CLSM). The most commonly used waste materials are found to be bottom ash, pond ash, steel slag, alum sludge, waste glass powder, red mud, cement kiln dust, copper slag, treated oil sand waste, and waste oyster shells. In order to verify their  suitability compaas potential CLSM, the plastic properties (flowability, hardening time, segregation, bleeding, and density), hardened or in situ properties (unconfined compressive strength, California bearing ratio, and ultrasonic pulse velocity), durability properties (permeability and freezing-thawing effects), and microstructural properties (X-ray diffraction and scanning electron microscopy) are compared. It is observed that the addition of different industrial wastes could satisfy the provision of CLSM as per ACI standards. There is immense scope for improvising the present utilization through functional optimization as well as investigating the potential of many unused waste materials which are locally available in bulk.

A review on the application of industrial waste as reinforced earth fills in mechanically stabilized earth retaining walls.

The infrastructure development of a country is focussed on the development of roadways that includes the construction of many bridges and flyovers with retaining walls. The construction of the mechanically stabilized earth (MSE) retaining wall gained momentum since 1960 owing to the various beneficial aspects in terms of its durability, economy, stability, appearance, sustainability aspects, etc. A typical MSE retaining wall is a composite structure made up of compacted backfill and reinforcement elements, fixed to a wall facing. The increasing rate of urbanization leads to the development of more industries resulting in the production of wastes such as fly ash, waste foundry sand, pond ash, slags, etc. The disposal of these wastes is often a big issue for the industries, and hence, their utilization in the construction industry is studied by researchers to solve the problem of waste dumping. This review article summarizes the studies involving the potential use of industrial waste material as reinforced earth fills in the MSE retaining wall. The researchers used waste materials from industries like thermal power plant, mining, construction, metal smelting units etc. The important fill properties such as particle size, friction angle, and density were compared with the standard codal provisions. The different dimensions of the research experiments involving the MSE backfill using various industrial wastes were presented in this review.