Effects of the mechanical milling method on transport properties of self-compacting concrete containing perlite powder as a supplementary cementitious material

The purpose of this study is to measure the effects of increasing the specific surface area of perlite natural pozzolan in self-compacting concrete (SCC) by the mechanical milling method. The use of SCC in construction projects allows for a reduction of human resources and equipment, which significantly decreases the labor cost and time of construction. SCC often needs chemical additives to achieve workability requirements. However, the usage of a greater amount of chemical additives as well as cement materials in the mixing designs increases the cost of mixing. Incorporation of inexpensive natural pozzolans as an alternative to cementitious materials can improve the fresh properties and durability of concrete. Moreover, reducing the hydration heat and controlling the shrinkage of SCC mixtures, which mainly contain significant amounts of powdered materials, is another benefit of the natural pozzolans. However, the reactivity of natural pozzolans, specifically in the early ages, is always a concern when using these supplementary materials. In this study, several methods have been proposed to improve the reactivity of these materials. Increasing the specific surface area of pozzolanic materials by mechanical milling is one of the most economical and efficient methods implemented so far. This study measured the performance of various levels of perlite powder, a natural pozzolan, for fresh, mechanical and durability properties. In addition, the effects of increasing the specific surface area of perlite powder on properties of concrete were measured and evaluated. According to the results, an increase in the specific surface of perlite powder improved the compressive strength and durability index as a result of increased reactivity. This was accompanied by a substantial improvement in the properties of SCC mixtures in the workability and stability tests.