Effect of Incorporating Processes of Fumed Silica on Marshall Properties of HMA Concrete

Highways play an important role in the economic and social development of societies, therefore, many studies are directed towards modifying pavement properties. In Iraq as well as other countries, pavement surface cracking and rutting are considered as major problems in roads and airports. The main objective of this work is to evaluate the effect of incorporating method of additives on Marshall properties of hot mix asphalt (HMA) concrete (wearing surface layer) using different percentages of additive. OAC of (4.7) % for control mixtures was determined using Marshall mix design. All modified HMA consist of AC of (40-50) penetration grade brought from Al-Duarah refinery, aggregates obtained from AL-Nibaae quarry with NMAS of (12.5) mm, and mineral filler (Portland cement) obtained from Tazloja factory, Additive (Fumed Silica (F. S)) its chemical compositions were tested in the laboratories of General Directorate of Geological survey and Mining. Modified mixtures with (3, 7, 10) % of F. S were prepared based on two methods of incorporating F. S into the HMA concrete are Stirring and Addition methods. They subdivided into the two groups, the first group refers to the addition of F. S as a percentage of the total weight of AC (the weight of modified AC stayed constant), The second group refers to the addition of F. S as a percentage of the total weight of AC (as additional amount) to the weight of AC. Results show that modified specimens prepared based on stirring method and containing (3 % + AC) are the best among all mixtures.