International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume 13 Issue 01 | Jan 2026
p-ISSN: 2395-0072
www.irjet.net
Enhancing the Geotechnical Properties of Clayey Soil Using Limestone Powder and Polypropylene Fiber Allaa saleh1, Prof. Mahmoud Abo Bakr Alsedik2, Lect. Mustafa merzk3 1MSc student, Dept of Civil Engineering Al-Azhar University, Cairo, Egypt
2Professor, Dept of Civil Engineering, Al-Azhar University, Cairo, Egypt 3 lecturer, Dept of Civil Engineering, Al-Azhar University, Cairo, Egypt
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Abstract - Many researchers have studied clayey soils
soils undergo periodic swelling and shrinkage due to moisture variations, primarily influenced by the presence of montmorillonite clay minerals. This cyclic swell-shrink behavior often leads to significant damage to structures built on such soils [1]. In fact, in the United States, damage caused by expansive clays surpasses the combined average annual damage from floods, hurricanes, and earthquakes [2]. Therefore, understanding the properties of these soils and developing effective treatment methods is crucial.
because they cause challenges in construction due to their low strength and high compressibility. This study investigates the effect of using limestone powder (LP) and polypropylene fiber (PPF) as soil stabilizers to improve the geotechnical properties of clayey soil. The soil sample was collected from the West Delta region in Tanta, Egypt. Limestone powder was added in different percentages (2%, 4%, 6%, 8%, 10%, 20%, 30%, and 40% by dry weight of soil), and various laboratory tests were conducted on both untreated and treated samples, including specific gravity, Atterberg limits, free swell, and standard Proctor compaction. Based on the results, 20% LP was found to be the optimum percentage for improvement. This percentage was then combined with different ratios of polypropylene fiber (0.2%, 0.4%, 0.6%, and 0.8%), and (10%,20%,30%,40) further tests—namely direct shear and one-dimensional consolidation—were performed. The shear tests were carried out immediately after mixing and after 14 and 28 days of curing. The results showed that adding 20% LP significantly improved soil properties: the free swell index decreased from 40% to 33%, optimum moisture content reduced from 21.04% to 18.8%, maximum dry density increased from 18.8 to 19 kN/m³, cohesion increased from 0.36 to 0.39 kg/cm², and internal friction angle raise from 18.33° to 25.27°. However, The addition of 0.4% polypropylene fibers (PPF) to clayey soil did not yield the expected improvement in shear strength. Instead, fiber clumping occurred due to excessive fiber length, leading to non-uniform distribution and reduced effectiveness. Cohesion remained nearly constant (0.31 to 0.30 kg/cm²), while the friction angle showed a modest increase (16.54° to 20.77°) after 14 days of curing. These results highlight the importance of optimizing fiber length and mixing techniques to avoid agglomeration and achieve effective soil reinforcement.
Soil stabilization can generally be achieved through two main approaches: chemical and mechanical methods. Chemical stabilization typically involves additives such as lime, cement, and granite powder, while mechanical stabilization uses reinforcement materials like polypropylene fibers and nylon [3]. Several studies have focused on the effects of polypropylene fibers (PPF) on clayey soils. It has been shown that incorporating PPF effectively reduces the soil’s swell potential and swelling pressure [2,4]. Research indicates that the optimum fiber content is approximately 2%, which maximizes the unconfined compressive strength (UCS) while minimizing swelling [3]. Additionally, increasing fiber aspect ratios leads to higher optimum moisture content, reduced maximum dry density, increased cohesion, and decreased internal friction angle [5]. Other investigations have explored combining polypropylene fibers with supplementary materials. For example, the addition of silica fume alongside PPF reduces the plasticity index and liquid limit of the soil while increasing the plastic limit, resulting in a reclassification from high-plastic clays (CH) to low-plastic clays (OH) [6]. Similarly, the use of rice husk ash (RHA), lime, and PPF has been shown to enhance soil strength, with pozzolanic reactions improving strength over curing time. [7].
Key Words: clayay soil, limestone powder, Polypropylene fiber, Shear strength; Consolidation , Compaction.
Further studies have examined the use of brick powder combined with PPF, identifying an optimum mix of 40% brick powder and 0.35% fiber for 60% soil content, which significantly improves the California Bearing Ratio (CBR) values [8]. The combination of marble dust, cement kiln dust, and PPF has also been found to enhance unconfined compressive strength [9]. Additionally, research on coir fiber
1. INTRODUCTION Clayey soils are commonly found in climatic regions characterized by alternating wet and dry seasons. These
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