Effect of paper sludge ash on properties of cement concrete: A review

Abstract

Urbanisation and Industrialisation lead to high demand for cement, as cement concrete is the main constituent in construction. But the emission of CO2 during the production of cement leads to global warming. Also, the use of natural minerals to manufacture cement causes environmental degradation. Thus, to minimise cement production, an alternative source of cement is to be found. Paper sludge (PS) is a byproduct of the paper and pulp industry. A large mass of the sludge generated daily makes landfills uneconomical, as the sludge from paper mills is bulky. The waste that comes out of the industry acquires more and more space every year. Thus, to minimise environmental degradation, another trend is to be found. Due to the PSA's silica and magnesium concentration, which increases cement concrete's setting time, PSA (paper sludge ash) can be used as a cementitious material. A study reviewed the engineering properties of PSA as a cementitious material, which primarily focuses on how PSA affects the engineering parameters of cement concrete. The feasibility of PSA as a partial replacement for cement has been reported in various reviewed works, as PSA gives superior flexural and tensile strength. According tothe literature assessment, PSA can replace 5 to 10% of cement by weight; cement replacement with 15 to 20 % of PSA shows a decrease in the compressive strength of concrete. From the research paper, it has been found that the PSA is coarser in size, and less variation in the surface area was found at an early age. Due to finesse, PSA absorbs a large amount of water. Also, it has been observed that due to the calcination process, there is a decrease in the chemical properties. Therefore the calcination is done at 700 °C to 850 °C, which does not adversely affect the chemical properties of Paper sludge ash.