Assessment of the effects of sodiumhexametaphosphate and sodium carbonate on particle size distribution on soil with varying plasticity

Samwel Charles Kawegele; Dr. Mgaza Somo Muya

doi:10.36948/ijfmr.2026.v08i05.87249

Assessment of the effects of sodiumhexametaphosphate and sodium carbonate on particle size distribution on soil with varying plasticity

Author(s)	Mr. Samwel Charles Kawegele, Dr. Mgaza Somo Muya
Country	Tanzania
Abstract	Accurate determination of particle size distribution (PSD) is fundamental in geotechnical engineering because soil classification governs the prediction of permeability, compressibility, shear strength, settlement behavior, pavement performance and foundation design. Conventional hydrometer analysis assumes complete dispersion of soil particles before sedimentation. However, naturally occurring fine-grained soils possess electrochemical attractions that promote aggregation, thereby producing inaccurate PSD results when dispersing agents are inadequately selected or improperly dosed. Although international standards recommend the use of sodium hexametaphosphate (SHMP) combined with sodium carbonate (Na₂CO₃), a constant dosage is commonly applied irrespective of soil mineralogy or plasticity characteristics. This practice may lead to considerable errors in the measured clay and silt fractions. This article explores soil classification methods and the influence of using dispersing agents in various amounts for the soil particle size analysis. Laboratory testing with different dispersing agents was conducted to analyze the effects of sodium hexametaphosphate and sodium carbonate for four different soils with plasticity indices indicating one to be with (PI = 10.7 %), (PI=16%), (PI=19%) and the other with high plasticity (PI = 36 %). The article highlights differences in the granulometric fractions reported for each soil and usage of the same dispersing agent but in various amount. Thus, the classification of soils is influenced by the amount of the used dispersing agents, recommendations of standards being different in time and countries. These findings contribute to a better understanding of the anticipated behavior of fine soils and provide useful insights for various geotechnical applications. This study evaluated the influence of sodium hexametaphosphate and sodium carbonate on the particle size distribution of soils with varying plasticity. Laboratory investigations were performed on representative fine-grained soils collected from different locations exhibiting high, medium and low plasticity characteristics. Soil characterization included natural moisture content determination, Atterberg limits, specific gravity, wet sieve analysis and hydrometer analysis conducted under varying dispersing-agent concentrations. Different combinations of sodium hexametaphosphate and sodium carbonate were investigated to determine their effectiveness in promoting complete particle dispersion.
Keywords	Particle Size Distribution, Hydrometer Analysis, Sodium Hexametaphosphate, Sodium Carbonate, Soil Plasticity, Fine-Grained Soil, Dispersing Agent, Geotechnical Engineering.
Field	Engineering
Published In	Volume 8, Issue 5, September-October 2026
Published On	2026-10-07
DOI	https://doi.org/10.36948/ijfmr.2026.v08i05.87249

View / Download PDF File

About IJFMR Fees & Payment Current Issue Publication Archive	Submit Research Paper Track Submission Status Publication Guidelines Publication Ethics Peer Review & Plagiarism	Join as a Reviewer Editors & Reviewers Reviewer Referral Program Get Reviewer Membership Certi.	Website/Journal Policies Usage Policy Content Policies Privacy Policy

Contact Us		+91-9687-828-838	editor@ijfmr.com

International Journal For Multidisciplinary Research

A Widely Indexed Open Access Peer Reviewed Multidisciplinary Bi-monthly Scholarly International Journal

Assessment of the effects of sodiumhexametaphosphate and sodium carbonate on particle size distribution on soil with varying plasticity

Share this