Blend of polyblend and bitumen, when used, helps to increase

Blend of polyblend and bitumen, when used, helps to increase road life by a factor of three. What is the reason?

Polyblend is a fine powder of recycled modified plastic. The binding property of plastic makes the road last longer besides giving added strength to withstand more loads. This is because:
(i) plastic increases the melting point of the bitumen which would prevent it from melting in India’s hot and extremely humid climate, where temperature frequently crosses 50°C.
(ii) rainwater will not seep through because of the plastic in the blend.