Investigating the effect of building rubble as a filler in bituminous paving mixes

Abstract

Bituminous concrete is one of the most expensive types of flexible pavement layers used in surface course. Being of high cost specifications, the bituminous mixes are properly designed to satisfy the design requirements of the stability and durability. The mixture contains dense grading of coarse aggregate, fine aggregate and mineral filler coated with bitumen binder. The filler is the mineral passing through 0.075 mm sieve and it performs some important roles in bituminous mixes. The common filler material used in Uganda is stone which is obtained through blasting rocks. This is not environmentally friendly and does not ensure sustainability of natural resources. Waste concrete filler and brick filler are considered to be cheaper and in abundant supply in Uganda. This study was made to find the effect of types of filler obtained from building rubble on the behavior of bituminous mixes. The properties of bituminous mixes containing filler like waste concrete filler and brick filler was studied and compared with the mixes containing stone filler mixture generally used in Uganda. The Marshall method of mix design was used for the comparison. The coarse aggregate and Fine aggregate fractions were kept constant throughout the study and the binder content of each aggregate mix was optimized using the Marshall mix design method when carrying out indirect tensile strength test. The Marshall stabilities of mix types containing filler of stone filler mixture, waste concrete filler and brick filler and mixture of concrete and stone filler were found to be 15.0 KN, 15.3 KN, 15.4 KN, and 16.5 KN respectively for bitumen grade 60/70 and 15.2 KN, 16.2 KN, 16.1 KN, and 16.2 KN respectively for bitumen grade 80/100 which satisfy the limiting value of 8-18 KN. The tensile strength ratios of mix types containing filler of stone filler mixture, waste concrete filler and brick filler and mixture of concrete and stone filler were found to be 84%, 83%, 78%, and 80% respectively for bitumen grade 60/70 and 83%, 82%, 76%, and 80% respectively for bitumen grade 80/100 and therefore complies with moisture susceptibility requirements. The study indicates the possibility of using building rubble, that is waste concrete filler and brick filler and a mixture of waste concrete and stone filler as filler in bituminous paving mix.