Do you know what is the second most-consumed substance in the world after water?
It is concrete. Are you surprised to hear that?
The concrete industry is, in fact, a giant one, having a worth of over $137 billion. Most of the structures you see are made of concrete. Being the most widely used construction material globally, concrete provides the foundation for all kinds of infrastructures.
Each year, its production rate is about 10 billion tons because of its versatile and robust usage.
Concrete is a mixture of cement, fine aggregates, coarse aggregates, and water. In the following sections, you will know about some eco-friendly and cheap alternative aggregates for concrete. These alternative aggregates make concrete more sustainable and environment-friendly.
With the significant increase in construction work, the demand for concrete is growing day by day. Peak demands are causing a scarcity of raw materials. Besides, studies show that concrete production involves about 10% of the total greenhouse gas emissions.
Considering the raw materials depletion and environmental degradation, sustainable aggregate alternatives became a dire need.
From the next section till the end of the blog, you will get a step-by-step guide to suitable alternative aggregates for concrete.
Concrete replacement materials can be of many types. You can replace the cement in concrete with recyclable materials to reduce energy consumption. The list of waste materials used in concrete can consist of wood ash, fly ash, blast furnace slag, or silica fume.
Such type of ecological form of concrete is known as Green Concrete.
Another effective strategy to reduce greenhouse gas emissions by concrete is replacing aggregates. Recently, many reusable and recyclable materials are available for this purpose.
Alternative materials for coarse aggregate in concrete can be rubber, glass, expanded fly ash clay, or plastic materials.
On the other hand, agro-wastes, to industrial by-products, alternative materials for fine aggregate in concrete can be of a wide variety.
In the following section, you will get a brief idea on these aggregate alternatives.
Alternative Aggregates for Concrete
Undergraduate students from MIT followed this manufacturing process of plastic concrete. The steps are as follows.
Glass can be used as a replacement to fine aggregates in concrete. It is broken down into a sieve size of #8 and #4. Few studies produced washed glass sand to gain the Fineness Modulus of natural sand.
Cement, coarse aggregates, and glass aggregates are the constituents of this green concrete form.
The process of mixing of all components is similar to the traditional concrete. Yet, steps to produce desired glass aggregates involve a long method.
According to ‘Jared Robert Wright’ (Published in: Examining Concrete Properties Containing Recycled Glass Cullet as a 100% Fine Aggregate Replacement, 2012), one of the significant issues with glasscrete is Alkali-Silica Reaction (ASR). The silica in glass forms silica gel because of chemical reaction with hydroxyl ions in cement. As this gel absorbs water, it develops cracks in the cement.
Besides, the cleaning process is quite expensive. Any organic residue on glasscrete harms the strength of concrete.
Keep in mind; curing will take about a month. You have to keep the stone damp during this process. It will allow full-strength bonding to occur.
EPScrete is 88% lighter than conventional stone-based concrete. Thus, structural support requirements like steel reinforcements and foundation size needs are smaller. Besides, it has good insulation properties.
Polystyrene materials are sensitive materials. The strength is less than traditional concrete and can be used as light decorative bricks only. You cannot use it to make concrete pavers.
Did your vehicle tire reach the end of the usable life? In that case, you can use it as a replacement for coarse aggregates in concrete.
The vehicle tires ground up to 3-10mm size to form crumb rubber.
The addition of rubber to concrete resists the failure and shattering of concrete. But during its mixing, the air is trapped in the mix. It results in low compressive strength of the concrete mix.
Alternative aggregates for concrete are evolving day by day, followed by modern research and technology. Besides the materials mentioned in this blog, you can also use some waste materials to replace concrete aggregates.
The list of waste material used in concrete comprises of;
But concrete made with these agro-wastes lacks in gaining the required strength. This field has a vast scope of research since you need eco-friendly and cost-effective aggregates.
Note: at this place we can start the extra information!!!!
Compressive strength is one of the most critical metrics of concrete that every designer needs to know.
It is a performance measure for concrete. The compressive strength is expressed in Mega Pascals (MPa) in the S.I. Units and pounds per square inch (psi) in the U.S. customary units. The value can vary from 2500 psi to 6000 psi (i.e. 150 kg/cm2 to 400 kg/cm2) according to different requirements.
Before selecting the alternative aggregates for concrete, it is necessary to know about the required concrete compressive strength. If your alternative aggregates do not meet the strength criteria, those will not be suitable for use.
You can read our blog in detail to know how to measure the compressive strength of concrete.
Do you think what the effect of aggregates properties in concrete is?
You cannot overemphasize the necessity of using the best quality and right type of aggregate in concrete.
Here are a few common questions you may want to know about aggregates.
The PCA (Portland Cement Association) manual states that, in general, aggregates occupy 70 to 80% of the total volume of concrete.
Aggregate shape and its texture can affect the properties of freshly mixed and hardened concrete. Besides, its specific gravity, size gradation, moisture content, and bulk unit weight can directly affect the strength, durability, and concrete workability.
For all these reasons, aggregates are vital to determine the optimum strength and workability of concrete.
If you want to know how aggregates play an important role in concrete, read this article.
Aggregates classes consist of two broad types. These are as follows, according to the PCA manual.
Before you select the best alternative aggregates for concrete, go through its pros and cons – select materials depending on the type of structure you want to construct. To solve any of your doubts, leave your message in the “Ask Your Query” section.
Rubaina Rahman – Rubaina Rahman completed her graduation with a major in structural engineering. At present she is doing her masters on the same subject. From her passion to write blogs, she started her career as a part time content writer in civil engineering and construction genre.