My job is to represent Sika in the validation / design implementation of concrete for some of the UK’s major and independent ready-mix concrete suppliers.
Here in Sika’s concrete technical services department we are proud to provide a national service from our three concrete laboratories – Welwyn Garden City, Leeds and Livingston, and ‘on the road’ from our mobile unit. These facilities help us service the requirements of our clients efficiently and effectively.
What do we do?
Our main objective is to implement our concrete admixtures and additive technologies into our customer’s specifications or current designs, with the aim of achieving the required performance(s) via a value rather than cost proposition.
Concrete, when being designed, must fit certain criteria when it comes to compressive strength assessment. This will depend on the application itself whether that be:
- Non-structural or structural application
- Its external / internal exposures
- Sustainability requirements
- Design life
Taking all things in to consideration we design our concrete to meet those requirements. We then take the brief to the laboratories to apply theoretical instances to explore how the targets can be achieved
The Science of Compressive Strength Testing
The initial phase of testing is mixing concrete to a condensed size mimicking what would be one cubic metre of concrete in real-time production.
Concrete performances are not only measured during its plastic state, in some instances it is deemed more critical to assess the performance post application (curing).
Curing is a vital part of assessment. There are specific guidelines and standards that we and those who manufacture / test concrete must abide to; BS EN 12390 1 -7. This series of standards dictate the curing and testing conditions which concrete is subjected to.
In reality you may achieve the plastic property requirements during the designer production phase but if the BS EN 12390 standards are deviated from it could have costly consequences.
Poor concrete sample manufacturing and poor initial and post-curing conditions may lead to reduced strengths.
Testing 1, 2, 3
Concrete samples (cubes, cylinders or prisms) are typically tested over a 28-day period, however an initial seven-day sample may be tested as an indicator to show the ‘’projected’’ 28-day strength. Concrete manufactures have a monitoring system called CUSUM.
The CUSUM (or cumulative sum control chart) is a sequential analysis technique. It is typically used for monitoring change detection. It was devised as a method to determine changes and proposed a system for deciding when to take corrective action.
For example, if low compressive strengths are regularly being achieved a systematic change may automatically increase the cementitious contents to the affected area. This will in-turn increase the production cost in which the concrete manufacturer is subjected too.
Hopefully with our help and guidance and the inclusion of Sika’s concreting products the customer may see an increase in compressive strength performance leading to a possible cementitious reduction and cost saving.