Green Circle are one of the leading providers of ready-mix concrete in Cardiff, providing you with high-quality concrete mixes for any size project. Ready Mix Concrete is a highly popular choice for all sorts of construction work, as it is well known for its convenience, durability and versatility. However, just like many other construction materials, it does have restrictions and a shelf life. While ready-mix concrete doesn’t necessarily “expire” in the historical sense, its properties can deteriorate over time, impacting its strength, workability and overall performance. 

Understanding the factors that may affect the shelf-life of ready-mix concrete is crucial for ensuring its efficiency in construction projects, and it can be hard to tell whether your mix is still suitable to use and how appropriate it is to do so once it has passed its sell-by-date. This article explores the duration of the concrete shelf-life, why it expires, the drawbacks of expired concrete, and what to use alternatively.

What Is The Duration of the Concrete Mixes Shelf Life?

The shelf life of ready-mix concrete can vary depending on several factors, including the environmental conditions during storage, specific mix design, and the presence of additives or admixtures. Usually, ready-mix concrete should be used within 90 minutes and 2 hours after batching to ensure unbeaten workability and strength development. After the required hours, the concrete may begin to stiffen and lose its plasticity, making it harder to place and finish a property.

However, the advancements in concrete, such as the use of retarders and admixtures, can extend the working time of concrete mixes, allowing extended time for transportation and placement intervals. Additionally, proper storage practices, such as protecting the concrete from extreme moisture, temperatures, and contamination can help to preserve its properties and extend its shelf life. 

Why Does Concrete Mix Expire?

Concrete mix can be considered to expire when water is added to the cement in the concrete mix. This reaction causes the cement particles to bind together and form a solid material, giving concrete its strength and durability for your construction projects. 

Once the water is added to the concrete mix, the hydration process begins immediately and continues over time. As hydration progresses, the concrete goes under a series of chemical changes that result in the formation of hydration products, contributing to hardening and strengthening the concrete.

However, over time, the hydration process slows down and eventually stops. This means that after a certain period, usually within a few hours after mixing, the concrete reaches its potential strength and workability. After this, hydration becomes minimal, and the concrete begins to lose its plasticity and becomes less workable. 

The Drawbacks of Using Ready Mix Concrete That Has Passed its Expiration Date

Using ready-mix concrete that has passed the expiration date can result in several drawbacks and potential issues in construction projects:

Decreased Strength

As the hydration process slows down, the concrete may not develop its intended strength properties. This can compromise the structural potential and durability of the finished construction, possibly leading to premature deterioration or failure.

Poor Bonding 

Expired concrete may find trouble bonding to adjacent concrete surfaces or reinforced materials. This can result in cracks, weak joints, and delamination from occurring.

Safety Risks 

Compromised concrete properties caused by expiration can pose safety risks to construction workers and occupants of the finished structure. Any weak concrete elements may fail suddenly, causing injuries, accidents, or even fatalities.

What To Use Instead Of Using Expired Concrete Mix

In alternative to using expired ready-mix concrete, there are a few things that construction professionals can consider:

Fresh Concrete Mix

The most straightforward alternative is to order some freshly batched concrete mix that is within its specified working time. Having a fresh concrete mix ensures great workability, performance, and strength development of the concrete in the project.

On-site Mixing 

In some cases, it may be beneficial to mix concrete on-site to allow greater control over the mixing process and make sure that the concrete is used promptly after batching, reducing the risk of expiration.