Determination of optimal percent mixing of cardboard waste in production of non-load bearing concrete

Introductionand Most of paper and cardboard industries regardless of the exorbitant costs use incineration and disposal methods for their waste production. Hazardous substances contained in these wastes can contaminate the environment and cause a risk for the human health. Many recent studies show that some of the paper and cardboard industry wastes can be used as raw material in the construction industry. The aim of this study was to determine the optimal percent mixing of cardboard waste in production of non-load bearing concrete. In this study, two kinds of recycled paperboard mill wastes (type 1: waste contains cardboard and sand and type 2: waste containing nylon, cardboard and Yonolit) that have the most volume of the wastes were used. Physical and microbial characteristic of wastes were measured according to ASTM. As well as the chemical composition of the waste consists of various elements were measured by using an electron microscope. After preparation of the samples, the required tests were carried out to determine the optimal mixture of waste in concrete at the ages of 7, 14 and 28 days respectively. Since the pH of fresh concrete containing waste is greater than 12, can be sure that there will not be any microbiological problem. In general, the use of waste in concrete production reduces the compressive strength of the samples. Comparing the compressive strength of concrete containing waste type 1 and concrete samples containing both waste types shows that reducing the amount of waste type 2 in compare with waste type 1 improves concrete strength. The results of dry density test show the density decrease of concrete samples containing waste by increasing the percentage of waste replacing in the sand. Also using of waste type 2 causes lighter concrete samples in compare with using waste type 1. Optimal amounts of waste replacement instead of sand for samples containing waste type 1 and type 2, 70% and 75%, respectively, as well as for samples containing both waste types, 49% of waste type 1 and 21% waste type 2. According to the results, in terms of economic and environmental benefits, the use of waste type 1 in the production of concrete for the lower use of cement is more satisfactory. The use of paperboard mill wastes in the production of concrete due to environmental and economical efficiency (profitability and employment, reducing the cost of transferring waste to landfills, reducing structural weight, using waste instead of buying sand and reduce the environmental pollution caused by incineration and landfilling) is noticable.