Understanding Bulking of Sand and its implications in Concrete

Sand in a concrete mix with an ideal proportion allows each particle to insert the pressure and bring uniformity in a lightweight concrete mix. A key phenomenon often observed with sand mixing is bulking that influences the proportion mix along with the concrete properties. At Firstchoice Readymix, we assess, monitor and address any issues regarding bulking while developing our products by using appropriate measures. In this blog, we are going to understand the concept of bulking, causes, implications, testing procedures and remedial measures. Understanding Bulking of Sand and its implications in Concrete.webp

Definition of bulking

Bulking of sand can be defined as a process in which upsurge in volume of sand occurs due to higher moisture content. Additionally ,increasing moisture in the sand forms a thin layer around sand particles that pushes each particle to a significant distance. However, bulking of sand is a phenomenon that is considered as unhealthy for concrete because it leads to inaccurate volume measurement and also affects the homogeneity of lightweight Concrete mix. In a simple word, bulking of sand refers to looseness of soil without compacting. In general, water reduces the sand pores and compacts the sand.

Causes of bulking

Bulking in sand is caused mostly due to the presence of moisture content. For example- When sand is dry, the particles inside it closely packed together, they tend to lose bonding once it gets dry. Once the moisture content increases in the sand, a film of water forms around each sand particle. This film resulted as all the particles pushed each other that increased the overall Sand volume. Apart from that, other factors are influencing bulking of sand starting from particle size, pores in sand to moisture content. For example- Dryer sand tends to have much finer grain that creates more air gap. However, wet sand is commonly used for avoiding air gaps around mineral particles that coarse sand which does not allow it to bulk- up more.

Moisture bulking moisture content

Bulking in sand resulted as maximum when moisture content is identifying in general between 4% to 6%. Once the range goes beyond 6% as more water is added, then the bulking effect diminishes due to water starting to fill the void between sands and makes the bond tighter. Inaccurate maintenance of moisture in the lightweight concrete mix affects the structure for a longer period.

Test procedure to determine bulking

Determining bulking of sand can be done by taking samples of sand inside a container ensuring that they are closely packed. After that, note the exact sand volume in the container and add water gradually to mix the sand uniformly. Once the sand is fully saturated and water has been evenly distributed, then measure the new volume of the sand. Lastly, sand volume in the percentage and also represented it through a bulking curve for precise assessment.

Bulking limit according to IS

Indian standard (IS) is ideal to follow for obtaining accurate results and maintaining permissible limits. As per IS, permissible limits for bulking of sand should be within 20% for concrete structures. In many cases, permissible limits act ideally in between 20%-25% based on requirement. However, permissible limits for concrete within 20% helps to ensure variations in sand volumes, resistance to moisture and ideal concrete mix.

Remedial measures

Avoiding bulking of sand can be done by adjusting the sand volume in terms of moisture content, can perform field tests easily and also keep the sand particles closely packed. In many cases, using dry sand and pre- wetting process so that no air gap can form and sand can achieve consistent moisture level respectively to prevent the bulking effect. As a Ready mix concrete supplier, Firstchoice Readymix suggests regular monitoring of moisture control can be significant in which using covered storage can protect the sand from rain and any other sources.

Conclusion Understanding and managing the bulking of sand is crucial to produce sturdy buildings. At Firstchoice Readymix, our aim is to ensure minimizing the bulking effect of sand by following the right proportion of sand, managing moisture and monitoring to achieve a reliable concrete mix. We do work based on industry standards and also employ best practices so that we can deliver best concrete solutions and meet unfulfilled needs.