The QESTDesign module is an extension to the QESTMix system. It assists concrete producers in designing new mixes and optimising existing ones. QESTDesign uses sound mix design principles as well as producer's existing mix design, quality control and performance data to analyse existing mix designs and recommend modifications.

Once the raw materials have been defined (cementitious materials, coarse and fine aggregates and admixtures), the QESTDesign module can be used to undertake two very important tasks in the mix design process:

• Combination (blending) of coarse and fine aggregates; and
• Determination of total water and cement content.

The admixtures chosen will have an effect on water demand and yield, and are also considered.

For the first task (combination of aggregates), the automatic blending routine uses target gradings along with a number of optimisation criteria, such as:

• Optimum fit;
• Cheapest (delivered or net) cost;,
  
• Minimisation of driver products;
  
• Maximisation of (cheap or surplus) by-products; and
  
• Combinations of the above.
  

This method is used for several reasons:

• It leads to good and reliable results;
• It is transparent to the designing engineer;
• It helps in the determination of which of several satisfactory designs is optimal;
  
• Standard quality control test results are used, therefore the system can automatically adjust if materials change (see QESTMonitor); and
  
• The system can be easily trained to learn about any particular operation’s specific requirements and material information and adjust the mix designs accordingly.

The system can use a concrete producer's existing mix design, quality control and trial data to determine the producer's individual "rules" for mix designs, and use these in its recommendations. Alternatively, in cases where little specific material information is available, the target gradings supplied with the system (which are derived from various reputable research sources in the public domain) can be used as a starting point. It is also possible to develop target gradings by specifying aggregate ratios together with actual material gradings used.

For the second task, the water demand and air content will be computed considering mix type, design slump and material properties of cements, aggregates, sands and admixtures. Strength versus water cement ratio will be computed from existing test data using simple or complex relationships (depending of the amount of data available). If no actual test data is available standard formulae (from published research) can be used.

The concrete producer's mix design "rules" that are "learnt" by the system can be used to both optimise existing mixes and design new mixes.

For more information on QESTDesign, please contact Spectra QEST sales.