Reuse of construction and demolished concrete waste by producing affordable high strength concrete block

Abstract

The issue of achieving sustainable environment is highlighted in different national and international strategic documents, such as Rwanda Viosion 2020, EDPRS II and MDGs. Rwanda on its track towards achieving sustainable environment, is still experiencing some challenges like Environmental degradation for the search of aggregates, energy for extraction of natural aggregates and difficulties in finding dumping sites for demolitions and construction wastes. Therefore, all those problems have created the need for developing a new source of construction materials.

The idea of recycling of C&D concrete wastes aims at finding solution to the environment degradation caused by damped demolished wastes as well as producing affordable high strength concrete blocks. This research investigated the availability of C&D concrete wastes and it was discovered that up to 33.33% of C&D waste came from concrete structures while more than 23.75% of people confirmed to have been involved in demolition works more than three times a year.The research was done by collecting sample composed of C&D concrete wastes at construction site of BPR headquarter where they demolished the existed building for construction of a new multistory building in kigali city and the sample was crushed, batched and mixed with a proportion of 1:3 and 1:5 as stated by Rwanda Bureau of Standards and manufactured new concrete blocks. The research performed on series of concrete blocks: 2 series each made of different proportions of cement for recycled concrete blocks, and one serie of reference blocks made of natural aggregates. Compressive strength test gave an average of 5.13N/mm² for recycled concrete block, which fulfills requirement of Rwanda Bureau of standards for hollow concrete blocks and which is 0.87 times the compressive strength of an ordinary block tested under same conditions. Finally, the cost effectiveness showed that the new recycled concrete block will be affordable by reducing at 15.6% of cost for that one made of natural aggregates.

Keywords: Concrete wastes, Recycled concrete block, Mechanical properties, Cost effectiveness and Environmental protection