Dolomite is commonly used in the construction of highway pavement in the world. However, there are still no concrete specifications or regulations on the use of dolomite for highway construction. Dolomite is available in huge quantities in NinhBinh Province. This is a high potential material for grain bases of highway pavement structure. The alternative material could be a considerable contribution to diversify the supply of aggregate resources for highway pavement construction in the province, and thus contribute to the conservation of natural landscape heritages and limestone resources for related building materials manufacturing industries. In order to evaluate the use of dolomite in highway pavement construction, a research program is conducted to test the working capacity of the cement treated dolomite aggregate, which is intended to use as upper base material in pavement structure. The experimental results showed that the mechanical indicators of the mixture satisfy the requirements for the base layers of highway pavement structure

HIEP, Nguyen Trong

KHANG, Pham Huy

THANH, Bui Tien

English

Journal of Materials and Engineering Structures

 JOURNAL OF MATERIALS AND ENGINEERING STRUCTURES 9 (2022) 485–492 485     * Corresponding author.  E-mail address: phkhangdr@utc.edu.vn  e-ISSN: 2170-127X,  Research Paper Research on Using Dolomite Aggregate as Cement Treated Base for Highway Pavement Construction in Ninh Binh, Vietnam Nguyen Trong Hiepa, Pham Huy Khanga,*, Bui Tien Thanhb a University of Transport and Communications / UTC, Hanoi, Vietnam b Department of Transport, Ninh Binh, Vietnam  A R T I C L E  I N F O Article history: Received : 15 November 2022 Revised : 24 December 2022 Accepted : 29 December 2022  Keywords: Dolomite,  Base, Subbase  Cement treated base  Aggregate Pavement            A B S T R A C T Dolomite is commonly used in the construction of highway pavement in the world. However, there are still no concrete specifications or regulations on the use of dolomite for highway construction. Dolomite is available in huge quantities in NinhBinh Province. This is a high potential material for grain bases of highway pavement structure. The alternative material could be a considerable contribution to diversify the supply of aggregate resources for highway pavement construction in the province, and thus contribute to the conservation of natural landscape heritages and limestone resources for related building materials manufacturing industries. In order to evaluate the use of dolomite in highway pavement construction, a research program is conducted to test the working capacity of the cement treated dolomite aggregate, which is intended to use as upper base material in pavement structure. The experimental results showed that the mechanical indicators of the mixture satisfy the requirements for the base layers of highway pavement structure. F. ASMA & H. HAMMOUM (Eds.) special issue, 4th International Conference on Sustainability in Civil Engineering ICSCE 2022, Hanoi, Vietnam, J. Mater. Eng. Struct. 9(4) (2022) 1 Introduction With unique natural landscapes, many famous scenic spots and cultural and historical relics recognized by UNESCO, Ninh Binh has been identified as a national cultural, historical and tourist centre, with international significance of the country. In addition, the high quality and large reserves of limestone and clay quarries are a strong incentive and favourable conditions for the development of construction material industry, especially cement production. Therefore, the conservation of cultural heritages, limestone natural landscapes for tourism, and also the valuable raw material source for the construction material manufacturing industry should be concerned and put on top priority to ensure harmonious and sustainable development of the Province in future. Along with other provincial economic sectors, the highway 486 JOURNAL OF MATERIALS AND ENGINEERING STRUCTURES 9 (2022) 485–492  infrastructure network system is also to be developed to meet the increasing transport and travel demand, leading to increasing demand on construction materials, including aggregates for road pavement construction. While preserving the natural landscape and using effectively precious limestone re-sources for industrial development, study to find new alternatives for traditional aggregate is urgent and necessary [1]. According to the report, there are about 2.5 million tons of dolomite in NinhBinh, which are exploited and used in many fields, including road embankment filling [2, 3]. In the world, dolomite has been used as a material in road pavement construction [4-6]. Therefore, study to use dolomite as coarse aggregate for highway routes in NinhBinh is an alternative for local material utilization. The paper presents the research results of physical properties and mechanical performance indicators of dolomite, which are used as coarse aggregate for cement treated base courses of pavement structure. 2 Material 2.1 Coarse aggregate The physical properties of the original rock which is used as coarse aggregate for both bound or unbound grain bases or subbases of highway pavement structure are primary conditions for material choice. The main characteristics of dolomite exploited from NinhBinh quarry pits is presented in Table 1. Table 1 – Physical properties of NinhBinh Dolomite [1, 3] Characteristics Values Specification limits Dry density (g/cm3) 2.77 - Tension strength (MPa) 7.8 - Compression strength (MPa) 86.3 ≥ 60 (base)   ≥ 40 (subbase) Liquid limit (%) 21.3 ≤ 25 (base)   ≤ 35 (subbase) Plasticity index (%) 3.1 ≤ 6 Proportion of flat-grain (%) 16.7 ≤ 18 (base)   ≤ 20 (subbase) Los Angeles abrasion (%) 32.9 ≤ 35 (base)   ≤ 45 (subbase)  Comparing to the requirements regulated in relevant standards [7-9], NinhBinh dolomite generally meets basic important requirements to be used as aggregate for base layer. 2.2 Portland Cement Ordinary Portland Cement (OPC) is common used as inorganic binder in highway construction, including of cement treated base (CTB) for pavement structure. In the research, OPC is also combined with dolomite to be aCTB material mixture called dolomite cement treated base and denoted DCTB for short. The purpose is to improve the stability, durability and strength of the original dolomite aggregate. The common Portland cement brand PCB40 Tam Diep, also produced in NinhBinh, was chosen for making specimens.  The main physical, chemical properties of the cement presented in Table 2 shows that the OPC used in the experiment is compliance with specification limits of TCVN 2682:1999 [10].    JOURNAL OF MATERIALS AND ENGINEERING STRUCTURES 9 (2022) 485–492 487  2.3 Water Water used for blending and also making conditions for the hydration reaction of the cement. The water used for making specimens is normal domestic tap water, which ensures the requirements of water for concrete and mortar in TCVN 4506:2012 [11]. 3 Experiment program The main idea of the study is to use dolomite aggregate as a cement treated base (CTB) material, which is commonly used for base layers in road pavement construction. The experiment program aims to design the cement treated dolomite aggregate mixtures (DCTB) in accordance with current regulations in Vietnamese technical standards. The basic physical and mechanical indicators of designed DCTB mixtures were tested to investigate performance of the material. Table 2 – Cement properties Indicators Value (Average) Specification limits Compression strength (MPa)   3-day 18.9 ≥ 18 28-day 40 ≥ 40 Setting time   Initial setting time (min.) 45 ≥ 45 Last setting time (min.) 220 ≤ 420 Fineness   Remaining on sieve 0.09 (%) 1.2 10 Specific surface area (cm2/g) 4540 2800 SiO3 (%) 1.45 ≤ 3.5  3.1 Mixture design The cement treated dolomite aggregate, or DCTB mixture, intended for use as base or subbase layers of road pavement structure is designed based on experience and regulations in current standard TCVN 8858:2011 [7]. The ratio of the main content of the mixture is presented in Table 3. Table 3 – DCTB content design Sample groups Aggregate Composition (wt.%) Dolomite PCB30 DCTB1 97 3 DCTB2 96 4 DCTB3 95 5 DCTB4 94 6 DCTB5 93 7 3.2 Test methods The main important mechanical indicators for use in construction and design of the highway pavement are selected for making tests in the laboratory condition. The DCTB mixture was prepared with the mix proportions presented in Table 3. The type, dimension and number of samples, and testing procedures are conducted in accordance with the current standards and shown in Table 4. 488 JOURNAL OF MATERIALS AND ENGINEERING STRUCTURES 9 (2022) 485–492  Table 4 – Test indicators and related standards Test Indicators Sample Size Number of Samples Test Standards Gradation Analysis Dolomite aggregate 200 kg TCVN 8858:2011 Compaction test Cylinder D152, H117 5x5 TCVN 12790:2020 Compression  Cylinder D152, H117 3x5 TCVN 3118:1993 Split Tensile  Cylinder D152, H117 3x5 TCVN 8862:2011 Elastic Modulus Cylinder D152, H117 3x5 TCVN 9843:2013  The samples used in the experimental test were moulded according to the instructions in the standard TCVN 12790:2020, having prismatic shape with 152 mm in diameter and 117 mm in height. The graded aggregate dolomite and cement were blended at optimum water content and cured in moisture condition for 2 hours before used for making samples. For compressive and split tensile tests, the samples were measured at 14-day age. After moulded, the samples were cured in moisture condition for 7 days and soaked in water for 7 days before being tested according to standards of TCVN 3118:1993 and TCVN 8862:2011, respectively. For the modulus of elasticity tests, the samples were 28-day age, with curing time in moisture condition for 21 days and soaking time in water for 7 days before being tested according to the standard TCVN 9843:2013. 4 Result and Discussion 4.1 Gradation test The grain analysis was conducted to test whether particle size distribution of DCTB located inside the limit boundary regulated in current standard or not TCVN 8858:2011 [7].  Fig. 1 – Particle distribution curve of Dolomite aggregate The Fig. 1 shows that there are some kinks on the distribution curve, however, the curve goes within the regulated boundary limits. It implies that the gradation of DCTB satisfies the requirements of current Vietnam standards. 0.0750.4252.364.759.5192531.537.501020304050607080901000.01 0.1 1 10 100Cummulative Passing, %Sieve Size, mmSpecification LitmitsDCTBSieve Size JOURNAL OF MATERIALS AND ENGINEERING STRUCTURES 9 (2022) 485–492 489  4.2 Compaction test The compaction test was conducted to find out maximum dry unit weight and the optimum water content (O.M.C.). The test was conducted following the standard of TCVN 12790:2020 [12].  Fig. 2 – The optimum moisture content of dolomite aggregate The Fig. 2 reveals that the optimum water content of DCTB was 6.6%, and the corresponding dry density is 2.243 g/cm3. 4.3 Compressive strength The compression strength is the primary indicator for testing the vertical loading capacity of base or subbase material in a pavement structure. The tests for measuring DCTB compressive strength were implemented for the 14-day age samples in accordance with the instructions in TCVN 8858:2011 and TCVN 3118:1993 [7, 13].  Fig. 3 – Compression strength of DCTB groups The testing results in Fig. 3 show that the compressive strength of sample groups steadily increases while cement ratio in the DCTB mixtures increase. The average compression strength values were 5.94, 7.17, 9.64, 10.94, 11.71 MPa, corresponding to the cement ratios of 3, 4, 5, 6, 7 %wt., respectively. The rates of changes in compressive strengths were 2.172.182.192.22.212.222.232.242.253 4 5 6 7 8 9Dry Density, g/cm3Water Content, %O.M.C.2.2436.6024681012143 4 5 6 7Compression Strength, MPaCement Content, %490 JOURNAL OF MATERIALS AND ENGINEERING STRUCTURES 9 (2022) 485–492  20.7%, 34.5%, 13.5% and 7.0% when comparing the successive couple of sample groups of 3% and 4%, 4% and 5%, 5% and 6%, and 6% and 7%, respectively. It can find that the change of compression strength between the 4% and 5% was the largest and reveals that the 5% cement was the most effective ratio content of cement on DCTB compressive strength improvement. 4.4 Split tensile strength Split tensile test was conducted to check the indirect tensile strength of the mixture. The experiment was carried out following the guideline in the TCVN 8862:2011 [14].  Fig. 4 – Split tensile strength of DCTB groups  Fig. 5 – Elastic Modulus of DCTB groups The split tensile strengths of tested samples are 0.32, 0.42, 0.55, 0.65, 0.70 MPa corresponding to cement ratios of 3, 4, 5, 6, 7 %wt. The test results show that the tensile strength increased when cement content increased. However, the increments of split tensile values were different among sample groups by cement contents. There was a big change between the 3% and the 4% cement content groups, with the rate of 33.5%. Then it was slightly decreased to 29.6% between the 4% and the 5% groups. The rates continuously declined to 18.5% and 8.6% between 5% and 6%, and between 6% and 7%, respectively. 00.10.20.30.40.50.60.70.83% 4% 5% 6% 7%Split Tensile Strength, MPaCement Content, %05001000150020002500300035003 4 5 6 7Elastic Modulus, MPaCement Content, % JOURNAL OF MATERIALS AND ENGINEERING STRUCTURES 9 (2022) 485–492 491  4.5 Elastic Modulus The elastic modulus of DCTB was defined by the static compressing method on cylindrical samples according to TCVN 9843:2013 [15]. The testing results presented in Fig. 3 revealed that the relationship between cement content and elastic modulus of DCTB is smoothly represented by a polynomial order 2 with squared correlation R2 coefficients of 0.952. The test result shows that average elastic modulus of DCTB at the age of 28-day groups are 1554.75, 2147.11, 2639.15, 3046.43, 3155.97 MPa corresponding to cement ratios of 3%, 4%, 5%, 6%, 7%, respectively. In general, the elastic modulus among the sample groups increased along with the cement content in the mixtures. However, it can be seen that the rate decreases gradually. Specifically, the difference between sample groups with treated cement content of 3% and 4% attained the maximum of 38.1%, between groups of 4% and 5% was 22.9%, between groups of 5% and 6% was 15.4%, while between 6% and 7% was the smallest, only 3.6%. 4.6 Discussion According to the provisions of the standard on cement treated aggregate bases for road pavement - specification for construction and acceptance [7], the required strength of material mixture must satisfy two criteria of minimum compressive strength and split tensile strength at 14-day age as show in Table 5. Table 5 – Requirements for strength of cement treated aggregate Location of base layer Level of Requirement (*) Strength Requirement, MPa Compression (14-day age) Split Tensile (14-day age) The base course of pavement with surface layers of asphalt concrete or Portland cement for expressway, highway grade I/grade II or bituminous treatment 1 ≥ 4,0 ≥ 0,45 Base course for other type of pavement structures 2 ≥ 3,0 ≥ 0,35 Subbase course for all pavement structures 3 ≥ 1,5 Not required For simplifying, we rank the requirements from the standard by the three level of assurance of technical requirements as shown as (*) in Table 5, where Level 1 is the highest quality, Level 2 is medium, and Level 3 is the lowest. Comparing the test results with the requirements in the standard, there are some remarks for DCTB material as follows: (1) For compressive strength: all sample groups satisfy requirement of the Level 1; (2) For split compressive strength: the groups with treated cement content equal or greater than 5% meet the highest requirement of Level 1; the group of 4% cement satisfy the requirement of Level 2; the group of 3% cement guarantee the requirement of Level 3, the lowest level for cement treated materials for road base pavement; (3) Regarding elastic modulus: DCTB material with all treated cement content having the elastic modulus greater than the minimum values required for cement treated aggregate materials specified in current standards [16]. 5 Conclusion and Recommendation The experimental results show that the physical and mechanical properties of NinhBinh dolomite satisfy the requirement for the aggregates used for the base or subbase layers of pavement structure. The performance indicators of DCTB mixture such as compressive strength, split tensile strength, and elastic modulus also satisfy the limit values or normal required ranges for the CTB materials. The technical suitability of dolomite aggregate in term of DCTB brings about important benefits: (1) open a new direction in the application of dolomite rock, diversifying the aggregate supply for pavement construction, therefore, proactively contributing to the road infrastructure development of NinhBinh province, and also for the provinces with rich resources of dolomite; (2) make an significant contribution to the mission of conserving limestone mountains, which 492 JOURNAL OF MATERIALS AND ENGINEERING STRUCTURES 9 (2022) 485–492  having high values of natural landscapes for tourism and the cement industry; (3) bring significant economic benefits to the projects located in the province, and also ensuring the efficiency of natural resources utilization for economic development. The dolomite rock evidently is a promising natural aggregate for road pavement construction. Thus, there should be concrete steps to bring the material into real application. Along with the material experimental tests in the laboratory condition, there should also be further studies in terms of pilot projects, where the material could be monitored and evaluated under real conditional operation. The practical results will be a solid basis for large scale application in future. REFERENCES [1]-  P. H. Khang, N. T. Hiep, and B.T. Thanh, Issues of Dolomite Utilization for Highway Construction in NinhBinh Province, The Transport Journal, Vietnam. (2020).  26-29. [2]-  Decision No. 2908/QĐ-UBND, The approval of the master plan on zoning of major minerals in NinhBinh province up to 2010 and orientation to 2020, NinhBinh province People's Committee. (2007). [3]-  Khang, L.Q., Dolomite potential in NinhBinh province and its usability assessment, Ministry-level research project - B2005-36-78. (2006). [4]-  Vorobjovas, V. and A. Vaitkus, Use of local aggregates in high modulus asphalt concrete layers. GRAĐEVINAR, 65 (4) (2013) 353-360. doi:10.14256/JCE.886.2013. [5]-  Šernas, O., V. Vorobjovas, L. Šneideraitienė, and A. Vaitkus, Evaluation of Asphalt Mix with Dolomite Aggregates for Wearing Layer. Transportation Research Procedia, 14 (2016) 732-737. doi:10.1016/j.trpro.2016.05.340. [6]-  Vaganov, V., A. Kireev, S. Avdeev, G. Šahmenko, and M. Šinka, Prospects for Effective Use of Dolomite in Concrete Compositions. Constr. Sci, 19 (2016) 27-32. doi:10.1515/cons-2016-0008. [7]-  TCVN 8858:2011, Cement Treated Aggregate Bases for Road Pavement - Specification for Construction and Acceptance, Ministry of Science and Technology Vietnam. (2011). [8]-  TCVN 8859:2011, Graded Aggregate Bases and Subbases Pavement - Specification for Construction and Acceptance, Ministry of Science and Technology Vietnam. (2011). [9]-  TCVN 8857:2011, Natural Aggregate for Road Pavement Layers - Specification for Material. Construction and Acceptance, Ministry of Science and Technology Vietnam. (2011). [10]-  TCVN 2682:1999, Portland cement - Technical requirements, Ministry of Science and Technology Vietnam. (1999). [11]-  TCVN 4506:2012, Water for concrete and mortar - Technical specification, Ministry of Science and Technology Vietnam. (2012). [12]-  TCVN 12790:2020, Soils, Aggregate Mixtures for Transport Infrastructure – Proctor Compaction Test, Ministry of Science and Technology Vietnam. (2020). [13]-  TCVN 3118:1993, Heavyweight concrete - Method determination of compressive strength of hardened concrete, Ministry of Science and Technology Vietnam. (1993). [14]-  TCVN 8862:2011, Standard test method for splitting tensile strength of aggregate material bonded by adhesive binders, Ministry of Science and Technology Vietnam. (2011). [15]-  TCVN 9843:2013, Standard test method in the laboratory for resilient modulus of nonorganic adhesive substance stabilized aggregate material, Ministry of Science and Technology Vietnam. (2013). [16]-  TCCS38:2022/TCĐBVN, Flexible Pavement Design – Specification and Guidelines. , Ministry of Transport Vietnam. (2022).  

Research on Using Dolomite Aggregate as Cement Treated Base for Highway Pavement Construction in Ninh Binh, Vietnam

Université Mouloud Mammeri de Tizi Ouzou (UMMTO): Research Review of Sciences and Technologies

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Research on Using Dolomite Aggregate as Cement Treated Base for Highway Pavement Construction in Ninh Binh, Vietnam

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Journal of Materials and Engineering Structures

Université Mouloud Mammeri de Tizi Ouzou (UMMTO): Research Review of Sciences and Technologies