Compound modified asphalt and preparation method thereof

The invention discloses compound modified asphalt and a preparation method thereof. The modified asphalt is prepared from the following raw materials in percentage by weight: 1%-3% of butadiene styrene rubber, 0.3%-1% of trans-polyoctylene rubber, 0.3%-1.5% of polyphosphoric acid and the balance of asphalt. In addition, the invention also provides a method for preparing the compound modified asphalt. The method comprises the steps of 1, heating the asphalt, and then adding the butadiene styrene rubber and the trans-polyoctylene rubber to the heated asphalt, and stirring and shearing; and 2, adding the polyphosphoric acid to the sheared asphalt and stirring to obtain the compound modified asphalt. The compound modified asphalt has excellent high and low temperature properties, and the storage stability and the anti-aging property of the compound modified asphalt are improved, and meanwhile, the preparation method is simple in process and advantageous for popularizing the compound modified asphalt.