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Sci Rep
Sci Rep
Scientific Reports
2045-2322
Nature Publishing Group UK London

71508
10.1038/s41598-024-71508-x
Article
A comparative assessment of uncrushed-river concrete mix of Hari-River, and Kamar-Kalaq: the two widely used concrete mix in Herat, Afghanistan
Alkozay Arif arif.alko0123@gmail.com

1
Faqiri Amanollah 1
Moheb Noman 1
Ahmadi Khalid Ahmad 2
Sadat Sayed Naqibullah 2
Saddeqi Mohammad Yaser 2
Jamshidi Ahmad Fawad 2
Sayedi Mir Mohammad Rateb 1
Mohammadi Safiullah 2
1 https://ror.org/050zs3956 grid.440454.5 0000 0004 5900 6415 Department of Civil Engineering, Faculty of Engineering, Herat University, Herat, Afghanistan
2 https://ror.org/050zs3956 grid.440454.5 0000 0004 5900 6415 Department of Architectural Engineering, Faculty of Engineering, Herat University, Herat, Afghanistan
16 9 2024
16 9 2024
2024
14 216383 6 2024
28 8 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Concrete, as a cornerstone of modern construction, heavily relies on the quality of its constituent materials, particularly aggregates. Among the critical factors contributing to high-quality concrete are proper gradation, absence of clay particles, and angular shape of aggregates. Adhering to these standards typically results in concrete with superior strength. However, aggregates sourced from riverbeds often possess a natural gradation, contain clay particles, and have rounded shapes. This study delves into a comparative analysis of aggregates sourced from two widely utilized riverbed regions, namely Hari-River and Kamar-Kalaq, situated within Herat province, Afghanistan. Given that over 90% of concrete in Herat province is sourced from these two riverbeds, the findings of this study carry immense significance. The research meticulously examines key parameters, including clay content, gradation, aggregate shape, and compressive strength, to determine the optimal choice for concrete production. Methodologically, samples were acquired following ASTM standards, and rigorous testing procedures were conducted, encompassing clay particle analysis, sieve analysis, and strength testing. The results reveal significant disparities between the two regions, with Hari-River demonstrating superior characteristics across various metrics. Particularly noteworthy is Hari-River’s lower clay content of 2.7% compared to Kamar-Kalaq’s 3.7%. The gradation of Hari-River for both coarse and fine aggregates is superior to that of Kamar-Kalaq when compared to size 67 aggregate range. Additionally, the average 28 days concrete compressive strength of Hari-River aggregates is 27.8 MPa, while that of Kamar-Kalaq is 23.4 MPa.

Keywords

Hari-River
Kamar-Kalaq
Herat
Concrete strength
Riverbed concrete
Uncrushed aggregate
Subject terms

Civil engineering
Mechanical engineering
Herat University, Laboratory of engineering facultyissue-copyright-statement© Springer Nature Limited 2024
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pmcIntroduction

Concrete, as one of the most utilized human-made materials globally, holds a significant position in construction1. The global consumption of concrete exceeds that of steel, wood, plastics, and aluminum combined by a factor of two2. Concrete’s most distinctive attribute is its exceptional compressive strength, a quality that varies depending on various factors. Typical concrete consists of readily available and locally sourced materials, including coarse aggregates (such as rock), fine aggregates (like sand), binding material (such as cement), and water. These components are generally cost-effective and abundant within the construction area3. Aggregates occupy a significant portion, ranging from 60 to 90%, of the total volume of concrete4. The proper selection of aggregate type and particle size distribution significantly influences key properties of concrete, including workability, mechanical strength, permeability, durability, and overall cost. Therefore, designing the aggregate mix is a crucial aspect of optimizing concrete mix design5. The ASTM standard establishes both upper and lower limits on concrete gradation to ensure that the mix achieves its maximum strength concerning gradation. However, concrete aggregates may occasionally contain impurities such as clay particles, which can adversely affect concrete properties6. The strength of concrete is inversely correlated with the quantity of clay particles present in the aggregates6. Clay particles retain significant amounts of water, leading to evaporation during volume changes in concrete. This evaporation can result in cracking and reduced concrete strength1,7. Additionally, the shape of the aggregate significantly impacts concrete strength. Crushed aggregates, typically angular in shape, foster stronger bonds and yield higher concrete strength. Conversely, uncrushed aggregates diminish the compressive strength of concrete1,7. Despite ASTM regulations prohibiting the use of uncrushed aggregate in concrete, it remains the primary type of aggregate in some developing countries. In Afghanistan, particularly in Herat province, uncrushed aggregate prevails over crushed due to its threefold lower cost. The uncrushed aggregates utilized in Herat originate from riverbeds, constituting a natural blend of both fine and coarse aggregate, alongside varying amounts of clay particles. The Hari-River and Kamar-Kalaq regions in Herat province are renowned for their uncrushed aggregates. However, selecting between the two regions has posed challenges for structural engineers and contractors. For years, the question of which region boasts the optimal soil type for selection has persisted. Since there has not been a specific scientific study regarding this issue before, selecting between the two sources has been a challenging and controversial decision among constructors. Although several local laboratories have previously conducted tests on either Hari-River or Kamar-Kalaq soil, the results of these tests have never been disseminated or made accessible to the public. This study is the first scientific paper to analyze and compare these widely used soil sources. The results of this study are crucial for finalizing the optimal choice between the two soil sources, filling a significant gap in the literature, and providing a foundation for future scholars to analyze other aspects of the soil. More importantly, since all laboratory tests were conducted in the faculty of engineering’s laboratory under the direct supervision of professors, the study’s results will be valuable enough to end the long-standing controversial public opinion about the best soil source between the two. Additionally, the results of this study are crucial for structural engineers. When designing structures using software, engineers often determine an initial concrete strength for the design but cannot achieve that specified strength on-site. In nearly all construction projects, the mix design follows a 1:3 ratios, meaning one portion of cement to three portions of natural river bed soil aggregate. Designers are unsure about the compression strength of this mix to use in their designs. This study will provide them with a reliable strength range from both sources to use in the initial design phase, ensuring more accurate and effective structural designs. The aim of the study is to compare the strength, gradation, percentage of clay, and aggregate shape between the two regions to determine the most suitable option for concrete production in the province.

Methodology

The total length of the Hari-River and Kamar-Kalaq, where aggregates are primarily sourced, was measured to be 4000 m and 352 m, respectively. To obtain representative samples, two sample locations were randomly selected along each river using a random number generation method based on Table 1 of ASTM D 36658. The randomly generated numbers selected for Hari-River were 0.355 and 0.05, corresponding to lengths of (0.355*4000) = 1420 m and (0.05*4000) = 200 m. For Kamar-Kalaq, the selected numbers were 0.159 and 0.232, corresponding to lengths of (0.159*352) = 56 m and (0.232*352) = 82 m. So samples were taken from the 1420 m and 200 m points along the Hari-River, and two samples were taken from the 56 m and 82 m points along the Kamar-Kalaq. To facilitate laboratory testing and analysis, the samples were reduced in size using the procedure outlined in ASTM C 702-989.Table 1 Displaying the results of compressive strength tests at 7 and 28-days for Hari-River.

Test number	Result (MP)	Test number	Result (MP)	
28-day test	7-day test	
1	28.3	1	18	
2	27	2	16.1	
3	28	3	17.7	
Average	27.8	Average	17.3	

To determine the percentage of clay particles in the sample, the washing method outlined in ASTM 117-04 was employed10. Initially, the sample from the bag was thoroughly dried in an oven, and its weight was measured. Subsequently, the dried sample was placed in a container, and water devoid of any detergent or dispersing agent was added, Fig. 1. Through vigorous agitation, finer particles than the 75 µm (No. 200) sieve were separated from coarser particles, forming a suspension of fine materials. This suspension was poured into a nested sieve setup, with a coarser sieve positioned above it, and the process was repeated until the water ran clear. Following this, the sample was dried again, and its weight was calculated. The calculated weight was then subtracted from the initial dried weight to determine the weight of the clay particles.Fig. 1 Series of images capturing the washing procedure utilized to determine the percentage of clay content in the sample.

To determine the soil’s gradation, the washed sample, devoid of any clay and silt, underwent sieve analysis in accordance with ASTM C 136-0611, Fig. 2. A sturdy frame, complying with ASTM standards, was fitted with sieve cloth covering openings ranging from 63 mm to 75 µm. The sieve cloth was then subjected to shaking for a duration of 15 min. Subsequently, the mass retained on each sieve was measured to calculate the percentage passing through. Notably, the limits stipulated by ASTM C 136-06 for coarse aggregate were not assessed, as the sample, being uncrushed, naturally encompasses all types of gradation.Fig. 2 Depicting the equipment utilized in the sieve analysis procedure.

To conduct the strength test, new samples were extracted from the bag to accurately represent the characteristic of natural riverbed, including the presence of clay particles. These samples were then used to fill cylindrical molds, Fig. 3. Following a predetermined ratio of three portions of aggregate to one portion of cement, water was added carefully until a slump of 10 cm was achieved, reflecting the standard practice adopted in all construction projects in Herat province, Fig. 3. For the slump test, a standard mold meeting the specifications outlined in ASTM C 143-10 was utilized12, Fig. 3. Similarly, standard cylinder molds equipped with tamping rods as per ASTM C 31-09 were employed to prepare cylinder blocks for compression testing. Molding requirements were selected in accordance with ASTM C 31-09, and curing was conducted as per the guidelines outlined in ASTM C 31-0913. In total, six cylindrical samples were prepared for each site, comprising three samples subjected to a 7-days testing period and three samples subjected to a 28-days testing period, Fig. 4.Fig. 3 Slump pouring process with cylinder mold and accompanying materials for concrete casting.

Fig. 4 Representation of a concrete cylinder with caps on both ends, both before and after undergoing compression testing. Average compression strength for Hari-River after the test was 27.8 MP and for Kamar-Kalaq 23.4 MP.

Following the sieving process, the samples were arranged adjacent to each other, allowing for a visual inspection and comparison of the aggregate shapes.

Result and discussion

The results indicate that Kamar-Kalaq soil contains 3.7% clay, whereas Hari-River soil contains 2.7% clay. The clay content in Hari-River soil falls within the maximum limit of 3% specified by ASTM C 33-08. However, the clay content in Kamar-Kalaq soil exceeds this limit, rendering it unacceptable according to the specified standard (Figs. 5 and 6).Fig. 5 Course aggregate gradation of Hari- River compared to ASTM size no. 67, in logarithmic scale.

Fig. 6 Fine aggregate gradation of Hari- River compared to ASTM size no. 67, in logarithmic scale.

The results of sieve analysis reveal that the coarse aggregate from Kamar-Kalaq generally falls within the size number 67 range prescribed by ASTM, as depicted in Fig. 7. However, the gradation of the fine aggregate fails to meet the specified limits, as illustrated in Fig. 8. It is observed that the coarse aggregate from Kamar-Kalaq tends to cluster around the upper and lower bounds of size number 67, a practice discouraged by ASTM standards, as depicted in Fig. 7. This highlights the inadequate gradation of Kamar-Kalaq, suggesting potential voids within concrete mixes and consequently, reduced strength. In contrast, both fine and coarse aggregate gradations from Hari-River comfortably adhere to acceptable ranges, showcasing superior gradation compared to Kamar-Kalaq, as evident in Figs. 5 and 6. The fineness modulus for fine aggregate from Hari-River measures 4.911, while for Kamar-Kalaq, it registers 5.641. ASTM C 33 standards stipulate a fineness modulus for fine aggregate not exceeding 3.1 or falling below 2.3. However, both Hari-River and Kamar-Kalaq surpass the 3.1 threshold, indicating a tendency towards coarser grading.Fig. 7 Course aggregate gradation of Kamar-Kalaq compared to ASTM size no. 67, in logarithmic scale.

Fig. 8 Fine aggregate gradation of Kamar-Kalaq compared to ASTM size no. 67, in logarithmic scale.

Figures 9 and 10 present a comparative analysis of percent retained on sieves for both fine and coarse aggregates from Kamar-Kalaq and Hari-River. As depicted in Fig. 9, the fine aggregate from Hari-River exhibits significantly higher fineness compared to that of Kamar-Kalaq. This observation is further supported by the fineness modulus, indicating the superior ability of Hari-River’s fine aggregate to fill voids within concrete mixes.Fig. 9 Comparison of percent retained on sieves for fine aggregate samples of Kamar-Kalaq and Hari-River.

Fig. 10 Comparison of percent retained on sieves for course aggregate samples of Kamar-Kalaq and Hari-River.

Tables 1 and 2 present the results of compression tests conducted on both Hari-River and Kamar-Kalaq soils. The data illustrates that Hari-River exhibits higher strength levels in both the 7-days and 28-days tests. Specifically, the average of three 7-days tests for Hari-River is recorded at 17.3 MPa, whereas it is only 15.1 MPa for Kamar-Kalaq. Similarly, the average of 28-days tests for Hari-River stands at 27.8 MPa, compared to 23.4 MPa for Kamar-Kalaq. This superiority can be primarily attributed to Hari-River’s superior grading in comparison to Kamar-Kalaq, as well as its lower clay particle content.Table 2 Displaying the results of compressive strength tests at 7 and 28-days for Kamar-Kalaq.

Test number	Result (MP)	Test number	Result (MP)	
28-day test	7-day test	
1	23	1	14	
2	24	2	16.3	
3	23.1	3	15	
Average	23.4	Average	15.1	

Figures 11 and 12 depict the shape of aggregates for Hari-River on the right and Kamar-Kalaq on the left. In Hari-River, where aggregates are primarily exposed to water flow, they have undergone rolling, transitioning from angular to predominantly rounded shapes. Conversely, aggregates in Kamar-Kalaq largely maintain their angular form, which enhances interlocking during mixing. While this angular characteristic is advantageous for Kamar-Kalaq, a thorough analysis of its aggregates reveals the presence of voids within them, potentially leading to increased water absorption. Despite the rounded shape of Hari-River’s aggregates, it’s noteworthy that they are solid with no voids present.Fig. 11 Comparison of aggregate shapes between Kamar-Kalaq (right) and Hari-River (left) after sieving.

Fig. 12 Comparison of aggregate shapes between Kamar-Kalaq (left) and Hari-River (right) after sieving.

Conclusion

This study aimed to compare two commonly utilized riverbed aggregates in the Herat province. By meticulously examining key parameters such as clay content, gradation, aggregate shape, and compressive strength, the research sought to ascertain the optimal choice for concrete production. From the findings of this study, the following conclusions can be drawn.

Clay content and water absorption The analysis revealed that Kamar-Kalaq soil contains 3.7% clay, exceeding the ASTM C 33–08 specified limit of 3%, making it unsuitable for concrete due to increased water absorption. In contrast, Hari-River soil, with a clay content of 2.7%, falls within the acceptable range.

Gradation and particle packing The sieve analysis demonstrated that while Kamar-Kalaq coarse aggregates generally meet ASTM size number 67 standards, its fine aggregate fails to meet specified limits, resulting in potential voids within concrete mixes. Conversely, Hari-River aggregates consistently adhere to acceptable gradation ranges, facilitating better particle packing and thereby enhancing concrete strength.

Compression strength Compression tests conducted over 7-days and 28-days periods consistently showed Hari-River aggregates outperforming Kamar-Kalaq. Hari-River exhibited an average strength of 17.3 MPa at 7 days and 27.8 MPa at 28 days, compared to 15.1 MPa and 23.4 MPa respectively for Kamar-Kalaq. On average, Hari-River displays a 20% higher compression strength than Kamar-Kalaq. This superior performance underscores Hari-River’s stronger mechanical properties, attributed to its optimal gradation and lower clay content.

Aggregate shape and performance Aggregate shape analysis indicated that while Kamar-Kalaq aggregates retain an angular form advantageous for interlocking, they also contain voids that increase water absorption. In contrast, Hari-River aggregates, despite their rounded shape from natural rolling, exhibit solid composition without voids, further contributing to their superior performance in concrete applications.

Acknowledgements

I extend my sincere gratitude to Noman Mohib, Head of the Faculty of Engineering, for entrusting us with full access to the Engineering Laboratory resources, which significantly contributed to the completion of this research.

Author contributions

A.A. was primarily responsible for drafting, editing, and revising the paper, as well as analyzing and interpreting the data. Additionally, he oversaw all testing procedures to ensure compliance with ASTM standards and led the research team. K.A.A., S.N.S., M.Y.S., A.F.J., and S.M. played pivotal roles in conducting the tests and contributed significantly to the research efforts. They were actively involved in sample collection from the site and provided valuable input in revising certain sections of the manuscript. M.M.R.S. supplied essential materials necessary for the laboratory tests and offered guidance on adhering to ASTM testing procedures accurately. A.F. and N.M. checked and leaded the overall research.

Funding

This research was funded by Laboratory of Faculty of Engineering of Herat University.

Data availability

Data are available upon request from the correspondent author.

Competing interests

The authors declare no competing interests.

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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References

1. Li Z Yoon J Zhang R Rajabipour F Srubar WV III Dabo I Radlińska A Machine learning in concrete science: applications, challenges, and best practices npj Comput. Mater. 2022 8 1 127
Li, Z. et al. Machine learning in concrete science: applications, challenges, and best practices. npj Comput. Mater. 8(1), 127 (2022).
2. Wang P Gao N Ji K Stewart L Arson C DEM analysis on the role of aggregates on concrete strength Comput. Geotech. 2020 119 103290
Wang, P., Gao, N., Ji, K., Stewart, L. & Arson, C. DEM analysis on the role of aggregates on concrete strength. Comput. Geotech. 119, 103290 (2020).
3. Nguyen H Vu T Vo TP Thai HT Efficient machine learning models for prediction of concrete strengths Constr. Build. Mater. 2021 266 120950
Nguyen, H., Vu, T., Vo, T. P. & Thai, H. T. Efficient machine learning models for prediction of concrete strengths. Constr. Build. Mater. 266, 120950 (2021).
4. Shakhmenko, G. & Birsh, J. (1998). Concrete mix design and optimization. In Proceedings of the 2nd International Symposium in Civil Engineering 1–8.
5. Aginam CH Umenwaliri SN Nwakire C Influence of mix design methods on the compressive strength of concrete ARPN J. Eng. Appl. Sci. 2013 8 6 438 444
Aginam, C. H., Umenwaliri, S. N. & Nwakire, C. Influence of mix design methods on the compressive strength of concrete. ARPN J. Eng. Appl. Sci. 8(6), 438–444 (2013).
6. Désiré TJ Léopold M Impact of clay particles on concrete compressive strength Int. Res. J. Eng. 2013 1 2 049 056
Désiré, T. J. & Léopold, M. Impact of clay particles on concrete compressive strength. Int. Res. J. Eng. 1(2), 049–056 (2013).
7. Li Z Zhou X Ma H Hou D Advanced Concrete Technology 2022 Wiley
Li, Z., Zhou, X., Ma, H. & Hou, D. Advanced Concrete Technology (Wiley, 2022).
8. Standard practice for random sampling of construction materials. (n.d.). https://www.astm.org/d3665-12r17.html
9. Standard practice for reducing samples of aggregate to testing size. (n.d.). https://www.astm.org/c0702_c0702m-18.html
10. Standard Test Method for Materials Finer than 75-μm (No. 200) Sieve in Mineral Aggregates by Washing. (n.d.). https://www.astm.org/c0117-04.html
11. Standard test method for Sieve analysis of fine and coarse aggregates. (n.d.). https://www.astm.org/c0136-06.html
12. Standard test method for slump of Hydraulic-Cement concrete. (n.d.). https://www.astm.org/c0143_c0143m-20.html
13. Standard practice for making and curing concrete test specimens in the field. (n.d.). https://www.astm.org/c0031_c0031m-09.html
