Journal of Building Materials and Structures

Partial substitution of coal with palm kernel in cement kilns: effects on cement production and quality

Kalamba Harlene Tshibola — 2023-12-31

The production of Portland cement is a complex process involving several chemical reactions and different materials, complex systems, and high temperatures (up to 1500 °C). Traditional fossil fuels such as coal, petroleum coke and natural gas have been used as primary source of energy for the process, though still abundant, their supply is slowly being depleted, and costs associated with obtaining these fuels are increasing with time. Therefore, alternative fuels such as biomass waste (palm kernel, rice, and coffee husks etc.) or processed waste materials (refuse derived fuel, waste tires, waste plastics, used oil etc.) and other types of waste have gained much interest recently in cement industries as they present a potential substitution option. In order to achieve the aim of this study, chemical and physical properties of both coal and PK have been determined and compared. Results show that the PK has an average calorific value ranging from 18-20 MJ/kg which is significantly acceptable and means that the waste can directly be used as fuel in the cement kiln for clinker production. Coal thermal substitution rate was progressively increased depending on the process conditions with the reference case for each kiln run (2% in August 2021, 3% in September 2021 and 5% in January 2022). Impacts on the product quality and process, benefits in terms of emissions and production cost were evaluated and discussed. Technical challenges encountered during the coal and palm kernel milling process and combustion process have been identified and possible solutions have been recommended.

Optimizing Self-Compacting Concrete through the Incorporation of Calcined Mud at 850°C

Rachida Mohamed Krachaï — 2023-12-31

The quantity of mud increases annually at dam sites, thereby reducing their storage capacity. To extend the lifespan of these structures, dam dredging is an essential solution. However, the extraction of enormous amounts of mud through the dam's bottom outlets, which remain unused, currently poses an environmental problem.

The primary objective of this research is to study the influence of mud, after thermal treatment at 850°C, added as an additive on the behavior of self-compacting concrete (SCC).

The first section of this article aims to detail the steps and essential processes for obtaining high-quality self-compacting concrete, incorporating calcined mud as an additive while adhering to current standards. The second part presents results related to mechanical compressive strength and split tensile strength concerning age.

Optimization of Calcined Beans Pod Ash – Cement Blended Concrete Mix Using Taguchi Method

Oluwatoyin P Joseph — 2023-12-31

This study investigated the optimization of calcined beans pod ash (BPA) - cement concrete mix using the Taguchi method. Concrete is a widely used building material with various performance requirements. These requirements are mostly influenced by concrete constituent materials and mixtures proportion obtained from concrete mix design. But improper mix design can result in inherent defects or local imperfections, which can significantly deteriorate the performance properties of concrete and jeopardize the structural integrity and durability of concrete structure. Taguchi method of optimization was employed to address these challenges. It involves identifying key factors (water – cement ratio, percentage of BPA – cement replacement, fine to total aggregate ratio and super-plasticizer dosage), selecting suitable levels for these factors, and conducting experiments to determine the optimum combination of factors. The effects of these variables on concrete slump flow (SF), compressive strength (F_cu), and split tensile strength (F_y) were evaluated. The results of SF, F_cu and F_y of BPA – cement concrete show significant improvement of 23.74%, 21.72% and 21.43% respectively, when cement was partially replaced with BPA from 5% to 20%. Likewise, an improvement of 5.97%, 5.69% and 5.37% for SF, F_cu and F_y of BPA – cement concrete, when the dosage of super-plasticizer in concrete mix was varied from 6% to 12%. A respective optimal parameter combination for BPA – cement concrete slump and strengths were obtained at 0.40, 5%, 0.4, 6 ml/kg of cement and 0.35, 5%, 0.4, 6 ml/kg of cement for W-C, BPA, F-T Agg, SP respectively.

Assessment of Non-destructive Methods for Evaluating the Performance of Surface Treatments on Concrete

Sunday O. Nwaubani — 2023-12-31

Hydrophobic films are frequently applied to concrete structures to reduce water ingress and provide protection against weathering and chemical attacks. However, these waterproof coatings tend to deteriorate with time and require reapplication to maintain their effectiveness. Deciding when the retreatment should be applied and how to assess existing treated surfaces can sometimes be a challenging task for owners of concrete structures. Consequently, this paper presents findings on the assessment of absorption characteristics of surface-treated concrete using several techniques. Three non-destructive test methods were used to evaluate the efficacy of surface treatment under different curing conditions and with varying numbers of treatments. The methods employed were the initial surface absorption test, Karsten tube test and electrical conductivity test (wet method). The results show that the employed methods were all able to distinguish between treated and untreated surfaces. Treated samples exhibited better resistance to water absorption and electrical conductivity than untreated ones, and the absorption characteristics were found to be influenced by the number of treatments and curing regimes. All three test methods were effective in assessing surface treatment quality, with the Karsten tube test being the most practical for in-situ evaluation due to the simplicity of its setup.