Engineering and manufacturing professionals are searching for sustainable solutions and innovative materials. Recycled concrete aggregate (RCA) is becoming prominent because of its environmental potential and performance capabilities.
From waste reduction to water conservation, your team could benefit from this building component. Here are eight things you need to know about RCA.
1. RCA’s Origins
World War II left much structural debris around the globe, leading to initial research on recycled materials. Through the 20th century, builders and manufacturers experimented with sustainable construction practices to find uses for the surplus of wasted concrete.
The supply of worn concrete has increased due to growing infrastructure and populations, so researchers have needed ways to repurpose it.
RCA research significantly progressed and demonstrated positive use cases in the late 1900s and early 2000s. For example, industrial professionals in Switzerland have increased RCA use in new buildings to reduce local urban waste and preserve nature in the community. Since 1994, the country has implemented standards for this recycled material.
2. Source Dependency and Proven Abilities
Vast research and use cases have proven RCA’s ability to support buildings and organizations’ environmental capabilities. However, its performance depends on where you source it.
A 2022 Rutgers University study investigated the potential of RCA systems due to significant changes in the last 80 years. In the report, the researchers wanted more consensus on how to implement recycled concrete.
The researchers numerically generated RCA systems of varying hardened properties, such as flexural strength and elastic modulus.
Then, they implemented a computer algorithm to simulate concrete structures, RCA replacement levels and 200 mechanical loading scenarios. Based on the modeling, you can make more accurate predictions on RCA material variability for modern concrete uses.
3. Environmental Benefits
Increasing sustainability is essential when developing your organization’s environmental goals, such as following LEED principles or ISO 14001 standards. RCA helps these ecological challenges by diverting waste from landfills and limiting the amount of wasted concrete debris.
Therefore, manufacturers and builders can reduce demand for these disposal sites and the burden on waste management systems.
The benefits extend to RCA’s effect on greenhouse gases. Experts say recycling used concrete reduces the carbon footprint typically associated with production. Extracting and incorporating virgin resources can consume a lot of water and energy, leading to higher CO2 and NOx emission rates.
However, modern builders can create RCA slabs and other products to reduce raw material consumption.
4. Saving Money in Each Life Cycle
RCA benefits manufacturing teams throughout project life cycles due to reduced costs. From material procurement to disposal expenses, this recycled material decreases expenditures and helps companies on tight budgets.
Industrial professionals source it from construction and demolition sites, so the by-product is often less expensive than virgin aggregates and other traditional methods.
While RCA benefits the end user, it saves money throughout the supply chain. For instance, you won’t need new quarrying and could get more affordable pricing with local sourcing.
Manufacturing and construction teams can produce RCA at or near the project site, so your employees can reduce fuel and labor costs. If your team uses on-site recycling, you can optimize waste management costs even more.
5. Increased Water Absorption
RCA has demonstrable benefits and proven performance, but there are some drawbacks you must consider. For instance, these aggregates are more porous than standard concrete due to their rougher and more irregular surface.
More surface area increases water absorption and can reduce workability. RCA could also be stiffer and harder to place, thus increasing project time and costs.
RCA’s porous characteristics originate from the hardened cement mortar, which stays attached despite crushing and processing the concrete waste. Engineers must account for the absorption rates by adjusting the water content.
If they don’t, they could reduce compressive strength and risk shrinking. Another way to manage the liquid is to pre-soak the RCA to increase saturation and limit absorption.
6. Reduced Compressive Strength
Another drawback of RCA is its compressive strength, which is the ability to withstand loads and resist compression. Traditional concrete is stronger in this characteristic compared to glass fiber epoxy matrix and other building materials.
Engineers use this material as the standard for compressive strength, though recycled versions don’t always meet expectations, as industry professionals have high target tensile requirements.
Water absorption plays a role by increasing the water-to-cement ratio in RCA mixes, thus lowering compressive strength. Recycled aggregates can contain old mortar pores and weaker cement paste from the original concrete, so there’s more water in the production process.
Microcracks are another compression liability because they introduce weak points in the concrete. While nearly invisible to the naked eye, they can cause shrinkage and thermal changes.
7. Understanding Other Limitations
Besides compression and water absorption, your team should acknowledge all of RCA’s liabilities. For example, this recycled material could include contaminants from the original concrete or the demolition and recycling processes. Sometimes, it can be dangerous to public health if it pollutes local water sources with antimony, chromium or barium.
Another limitation is the alkali-silica reactions that occur in RCA. Cement has sodium and potassium, which can collide with reactive silica in your aggregates.
This chemical reaction can harm RCA mixes by causing cracks and expansions, thus compromising mechanical integrity. From aggregate particles to residual alkalis, RCA can be more susceptible than virgin aggregates.
8. Differing Regulations
While RCA has pros and cons, it’s becoming more prominent in the construction industry due to research and development. Mainstream introduction has meant varying regulations on RCA, depending on the state or country you’re in.
The standards may also vary by industry, so it’s essential to check these guidelines based on the regulatory body and sector-relevant organizations.
For example, the auto industry should adhere to the American Association of State Highway and Transportation Officials’ specifications when using RCA in such infrastructure.
The organization’s standards provide satisfactory installations for RCA base courses, though they may change based on local experience and practices. Other regulatory bodies include the American Concrete Institute, ASTM International and the Federal Highway Administration.
Understanding RCA for Optimized Engineering and Manufacturing
RCA has evolved into a practical and environmentally conscious solution for engineers and manufacturers. From lower costs to reduced carbon footprints, the benefits can be significant for business owners.
However, industry professionals must understand the limitations, challenges and need for quality control. Compressive strength and water absorption can be liabilities, so you should monitor these characteristics for the best results.
Known for his expertise in industry dynamics, Jack Shaw serves as the editor of Modded. Through his insightful analysis and practical advice, Jack seeks to empower readers with the knowledge to thrive in the ever-evolving mechanical landscape, guiding them toward success in their professional endeavors.