Fine and coarse aggregate are fundamental requirements for construction. Sand is the superior choice of fine aggregate for the preparation of mortar and concrete and it also plays a vital role in the mix design. In developing countries such as India, there’s a greater demand for sand because of the rapid growth of infrastructure. The grading and maximum size of aggregates are critical parameters in any concrete mix as they affect the relative proportions in mix, workability, economy, porosity, and depreciation of concrete.
Sand is one of the most extracted substances in the world, beating fossil fuels and biomass. It is a key ingredient for concrete, roads, glass, and electronics. Skyrocketing demand is admittedly the major cause for the sand shortage. Numerous evidence strongly hints that sand is becoming increasingly scarce in many regions all over the world. According to a recent survey, Vietnam’s domestic demand for sand exceeds the country’s total resources and supplies. If the situation is continuing in this manner, the country may run out of sand for construction by the end of 2020. Recent floods in Houston, India, Nepal, and Bangladesh will add to the increasing global requirement for sand for construction.
Sand mining harms humans as well as the environment. A rapid removal of sand leads to deepening of the river beds and causes bank slides, loss of vegetation, etc. It even disturbs aquatic life and even upset industries such as agriculture and aquaculture. The heavy-exploitation of river sand for construction purposes is a threat and find a better alternative for sand is always a tricky task.
Alternative materials for river sand
The construction industry is growing in a staggering pattern even in the years with a high economic slowdown of the GDP. With the rising scarcity of river sand, here are some of the alternatives to consider.
Crushed Sand (Manufactured Sand)
Manufactured sand is produced by grinding rock to give particle size and grading at par with river sand, the composition may differ using Vertical Shaft Impactor Machines. When considering economy and design, crushed sand can be used to partially or fully replace river sand from a concrete mix.
Crusher Dust (Quarry Waste)
In crusher dust, the particles (% finer than 150 microns) are commonly high, a major concern limiting its percentage replacement to a minimum with sand in a concrete mix. It can be replaced with the amount of 25%. Since its a byproduct of stone crushers, while making coarse aggregate, its availability is not an issue.
Washed Bottom Ash
Bottom ashes are waste of coal-fired thermal power plant usually disposed of in landfills. Post washing, this can be used for substituting sand to the volume of 35% in a concrete mix. The availability of washed bottom ash is limited because it is restricted to the power plant area.
Granulated Blast Furnace Slag
Granulated blast furnace slag is a waste of steel industry. This material can be used to replace sand to the amount of 70 % in concrete mixes.
Construction Demolition Waste
These are basically wasted mortar and concrete segregated from steel, which when ground and sieved, can displace sand to the amount of 25% in concrete mixes.
Use of plastic waste in sand concrete
In 2016, a study conducted by M. Guendouz, Farid Debieb, O. Boukendakdji, El-Hadj Kadri, Mohamed Bentchikou, and Hamza Soualhi studied the utilization of two types of waste plastic (Polyethylene Terephthalate (PET) and Low-Density Polyethylene (LDPE) as fibers and fine aggregates (powder) in sand concrete.
The results revealed that the use of plastic waste as biased replacement of sand contributes to reduce the bulk density, decrease the air content, causing an increase in compressive and flexural strength. In addition, the reinforcement of the cementing mold with plastic fibers produced a clear improvement of the tensile strength. Sustainability is the key to survival. Adapting environment-friendly ways for every industry is the only chance of survival and existence. This study ensures that reusing waste plastic in sand concrete gives a positive approach to reduce the cost of materials and solve many environmental problems. Such efforts will aid in industry advancement as well as the betterment of the environmental conditions hand in hand.