How does quartz contribute to the strength of structural clay products?

In the context of structural clay products, quartz (silica) functions primarily as a filler material that contributes to the structural integrity of the product in two key ways.12

First, quartz imparts "green" strength to the object before it is fired, which helps the material maintain its desired shape during the manufacturing process. Second, once the product is formed, the quartz serves as a structural filler that provides strength to the final fired object.12

In the production of items like brick and tile, the clay acts as a former to provide shaping ability, while the quartz particles remain largely unaffected by the relatively low firing temperatures (typically 1,050° to 1,100° C). These particles become embedded in a matrix of glass and crystalline mullite, creating a microstructure that allows the finished product to bear heavy loads without fracturing.2