Performance Appraisal of Eco-Friendly Mortars and Concretes

Abstract

Cement concrete is the major construction material largely used throughout the world for infrastructures like buildings, pavements, irrigation structures and so on. Concrete is prepared by using locally available materials. One of the important concern facing construction industry today is, the scarcity of virgin materials due to their exponential depletion and continued increase in demand. This is due to rapid growth in construction industry and stringent environmental policies to check and control harmful effects on environment, caused by production or processing methods for construction materials and chemicals. As the natural resources are fast depleting and also the production of cement and aggregates consume energy (energy intensive) which also indirectly produce carbon dioxide posing threat to the environment. Due to the above pressing needs, it is most warranted to search for alternative or promising eco-friendly materials. Huge amount of wastes generated in various fields is not utilized other than for land filling, incineration etc. These wastes can be utilized as ingredients partially or fully by embedding these wastes in either mortars or concretes without being detrimental. Experiments with Broken Mangalore Tiles (BMT) wastes in the form of Secondary Cementitious Material (SCM), Fine Aggregates (FA), and Coarse Aggregates (CA) were planned and executed to replace cement, river sand and granite CA respectively, to study the performance of both BMT based mortars and BMT based concretes. Further experiments have also been conducted to ascertain performance of BMT based mortars and BMT based concretes at elevated temperatures. Usage potential of BMT CA, in pervious concretes is studied. The scope for utilizing Iron Ore Tailings (IOT) and / or Copper Slag (CS) as replacement to River Sand (RS) is also assessed. Further Melt Processed Plastic (MPP) pellets as filler in mortar and concrete is attempted. Use of EPS packaging material as FA (as filler) and CA (as filler) is also undertaken in this investigation. Results show, with BMT waste material as fine aggregate or coarse aggregate to the extent of 100% replacement is possible without compromise on concrete strength,with 90 days of curing. It is interesting to note also that 100% FA and 100% CA could be replaced by 100% BMT FA and 100% BMT CA without loss in concrete strength with 90 days of curing. Even in the case of mortar, there is no loss in strength for mortar with 100% BMT FA, with 90 days curing. 80% addition of BMT powder or 20% replacement of cement by BMT powder with 90 days curing is possible without loss in mortar strength. 100% BMT CA, based concrete has given higher endurance to elevated temperatures as regards to strength. Loss in weight increases with both rise in temperature as well as increase in the BMT CA content. Higher BMT CA increases porosity and assists better elevated temperature endurance. Up to 600°C, the performance of concrete with BMT FA (either half or full replacement) is superior when compared to concrete with 0% BMT FA. Higher BMT FA increases porosity indirectly favouring better elevated temperature endurance up to 600°C. For BMT FA and BMT CA based concrete at elevated temperatures, residual compressive strength remains nearly constant up to 400°C. Further increase in temperature up to 800°C, strength decreases. However, the differences in strengths between various combinations reduce after 400°C. Residual strength of mortar mix BMT FA100, monotonically decreases with increase in temperature. However its performance appears to be better than mortar mix BMT FA50 for temperature levels of 600°C and 800°C. It is observed that mortar with BMT powder as addition to OPC possesses more strength than replacement to OPC at all levels of temperatures. For a given porosity, the density of pervious concrete with BMT CA is always lower than that of granite CA by around 300 kg/cu.m. BMT CA in full replacement to granite CA, performs well in pervious concretes. Compressive strength of concrete reduces by about 26% when sand is replaced from 0 to 100% by IOT. Strength values almost remain constant up to 75% replacement of sand by IOT. Copper slag replacing sand to the extent of 100% does not result in strength reduction of concrete. From mortar strength studies with IOT and CS in place of sand, it is to be noted that for both cases replacement level of 50%, result in no loss in strength with two months of curing period. MPP pellets are added as filler by volume of concrete. It isobserved that the concrete strength drops by 50% for approximately 25% filler. Strength variation of mortars containing river sand, IOT and CS as FA with MPP pellets as filler at different blending dosages is studied. For all the three cases strength drops with increase in filler content, however the rate of drop is lower for mortar containing IOT as FA and higher for CS as FA, when compared to mortar with RS as FA. For concrete, with increase in EPS CA (as filler) content, all the three strengths (compression, split tensile and flexural) decrease by about 70-80% for 100% replacement. For mortar, as EPS FA (as filler) content increase, there is decrease in strength. At 100% replacement, the strength is approximately 15% of the reference mortar strength. This study is a step towards sustainable construction practices and recommends use of these eco-friendly unconventional materials to the extent possible.