ARID ZONE JOURNAL OF ENGINEERING, TECHNOLOGY & ENVIRONMENT AZOJETE December 2021. Vol. 17(4):453-468 Published by the Faculty of Engineering, University of Maiduguri, Maiduguri, Nigeria. Print ISSN: 1596-2490, Electronic ISSN: 2545-5818 www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 453 ORIGINAL RESEARCH ARTICLE AN EXPERIMENTAL STUDY ON THE PERFORMANCE OF BITUMINOUS CONCRETE MIXTURES WITH SILICA SAND AS FILLER REPLACEMENT A. A. Shuaibu*, A. I. Mohammed, U. Hassan, B. H. S. Amartey, S. A. Wada, A. Mohammed and A. M. Rimi Department of Civil Engineering, Faculty of Engineering, Ahmadu Bello University, Zaria, Nigeria *Corresponding author’s email address: abdulshub4u@gmail.com 1.0 Introduction Bituminous concrete mixtures, also known as; (i) hot mix asphalt (HMA), (ii) warm mix asphalt (WMA), (iii) cold mix asphalt (CMA), (iv) plant mix, and (v) asphalt concrete (Speight, 2016). It is mainly composed of mineral aggregates (fine, coarse and filler), asphalt binder, and additive, and has been widely applied in pavement construction (Zhang et al., 2020). A typical bitumen concrete mixture contains 90 to 95% (w/w) of the total mixture as mineral aggregates and 5 to 10% (w/w) as binder (bitumen) (Speight, 2016). Filler in bituminous concrete mixes is defined as material with particle size less than 0.075 mm, which may originate from fines in the aggregate or added in the form of cement, lime and ground rock. Portland cement or hydrated lime is often added to natural filler (1 to 2 per cent by mass of total mix) to improve adhesion of bitumen and stiffening of bitumen-fine matrix (ORN 19, 2003). ‘‘The filler is an important constituent of bituminous concrete as the type and amount play a significant role in ensuring the quality and durability of the bituminous concrete in service’’ (Sutradhar et al., 2015). Although several materials have been used as filler, such as cement, lime dust, stone dust, granite powder, However, their production processes have detrimental effects on the environment and the use is expensive. Also due to the high cost, inconsistencies, scarcity and depletion of virgin construction materials as well as need to enhance the performance of bituminous concrete mixtures in service, such as ; resistance to permanent deformation, cracking, wear, stripping, ageing, there is dire need to seek alternative materials for sustainable construction and improved service life of the pavements. ARTICLE INFORMATION ABSTRACT This study investigates the performance of silica sand as a partial replacement for cement filler in bituminous concrete mixtures. The physical properties of bituminous concrete mixture constituent materials were tested in accordance with American Society for Testing and Materials ASTM and British standard BS specifications and were found to be satisfactory. Marshall stability method of bituminous concrete mix design was adopted to determine the optimum binder content at no silica sand replacement (control) within the bitumen content range prescribed by Nigerian General Specifications for Roads and Bridges and Asphalt Institute for bituminous courses in flexible pavements and an optimum binder content (OBC) of 6% was obtained. The Marshall stability-flow and void- density analysis of bituminous concrete mixtures prepared with 6% OBC at varying percentages replacement (5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, and 45%) of silica sand was conducted to obtain the mixture with the best performance in terms of strength and waste utilization. The results obtained from the experiment shows that the replacement of cement filler with silica sand up to 45% meets the standard specifications of Nigerian General Specifications for Road and Bridges, Hence, silica sand up to 45% could be partially adapted as cement filler replacement in bituminous concrete mixes. © 2021 Faculty of Engineering, University of Maiduguri, Nigeria. All rights reserved. Submitted 31 May, 2021 Revised 3 August, 2021 Accepted 10 August, 2021 Keywords: Silica sand bituminous concrete mixtures Marshall test optimum bitumen content and filler Arid Zone Journal of Engineering, Technology and Environment, December, 2021; Vol. 17(4):453-468. ISSN 1596-2490; e-ISSN 2545- 5818; www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 454 Extensive research have been conducted on the incorporation of agricultural waste such as; rice husk ash, groundnut husk ash, guinea corn stalk ash, bagasse ash, mesocarp fibre ash (Boon Hoe et al., 2014; Shuaibu et al., 2020a; Shuaibu et al., 2020b; Murana and Sani, 2015; Shuaibu et al., 2020c), industrial wastes such as fly ash, waste glass (Mistry and Roy, 2016; Simone et al., 2017) as well as a blend of agricultural-industrial waste such as rice husk ash and fly ash, rice husk ash and slag (Mistry et al., 2018; Akter and Hossain, 2017) in bituminous mixture. However, currently, attention has significantly shifted to the use of natural materials such as kaolin, metakaolin, waste foundry sand, foundry sand, silica sand etc; because of their abundance, low cost and pozzolanic activities. ‘‘Silica sand consists of small grains or particles of minerals and rock fragments with quartz (composed of silica dioxide SiO2) as the dominant mineral composition’’ (Duvuna and Ayuba, 2015). Thus, it is rich in silica necessary for hardness in bituminous mixes. ‘‘Silica sand deposits are most commonly surface-mined in open pit operations or obtained as riverine surface deposit due to erosion. Also, dredging and underground mining is also employed to obtain the sand’’ (Langer, 2003). Processing silica sand extracts to reduce impurities and sizing it to optimum particle size distribution is necessary for a wide range of applications (Langer, 2003). Silica sand with an adequate quality level may be used for glass production, casting moulds in foundries, ingredients of ceramics batches, proppants in shale hydrocarbons extraction, fillers and extenders in polymers, paints and rubber, for water filtration, and many other uses (Burkowicz et al., 2020). Our country Nigeria, is blessed with abundant silica sand deposits (Table 1) as cited by Chukwu (2019) in RMRDC, (2009) report. Table 1: Silica sand deposit locations in Nigeria S/No State Location 1 Abia Ukwa, Aba, IsialaNgwa, Azumili 2 Akwa Ibom Ikwo, Ukem, Ibeno 3 Anambra Onitsha, Coastal area of Ulasi River 4 Bayelsa Sagbama, Ijaw 5 Benue Buruku, Gboko, Guma, Kast 6 Bornu Dikwa, Gwoza, Jere 7 Cross River Ikom, Mfamosing 8 Delta Ughelli, Aniocha, Burutu, Ethiope 9 Enugu Enugu, Ekulu, Igbo Eze, Udi 10 Gombe Yamaltu-Deba, Dukku 11 Imo Ihiagwa, Obinze, Isu, Njaba 12 Jigawa Kangama, Kasaure 13 Kaduna Kaduna 14 Kano Dambatta, Makoda 15 Kastina Zango 16 Lagos Apapa, Badagry, Epe, Lekki 17 Nasarawa Lafia, Doma, Nasarawa 18 Niger Gbako, Gurara, Mokwa, Bida 19 Ondo Ogun waterside, Obafemi 20 Ogun Igbokada, Akata, Agbala 21 Rivers Etche, Obio, Okirika, Oyigbo 22 Sokoto Sabo, BiriniWamako 23 Taraba Jalilingo, Bali, Takum 24 Yobe Ngeji, Fita, Damaturu, Nguru, Tarmuwa 25 Zamfara Jamuri, Gumi S Source: RMRDC, (2009) Shuaibu et al: An Experimental Study on the Performance of Bituminous Concrete Mixtures with Silica Sand as Filler Replacement. AZOJETE, 17(4):453-468 ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 455 ‘‘Many of the Nigerian silica sands are associated with the coastal plain of sedimentary areas of the southern parts of the country. However, few deposits of the sand occur in the northern regions of the country as seen in Table 1 above (Chukwu, 2019)’’. Despite the huge deposits of silica sand in almost all Nigerian States, there are currently very scarce studies that have incorporated silica sand into bituminous concrete production in Nigeria. Employing silica sand as an admixture in bituminous concrete production will improve pavement performance and lead to the development of locally available materials for sustainable concrete production. This in turn will reduce cost and burden placed upon conventional construction materials.The aim of the current study is to experimentally evaluate the performance of bituminous concrete mixtures with the incorporation of silica sand as filler in wearing surfaces. The above aim was achieved through the following objectives: i. Determination of physical properties of mineral aggregates (fine, coarse), bitumen, and cement to ascertain their suitability for use in the bituminous concrete production; ii. Determination of the chemical properties (oxide composition) of silica sand using x-ray fluorescence and classify it based on ASTM C618, (2003) classification of pozzolanas; iii. Determination of OBC necessary for the production of bituminous concrete and find out the effect of adding the different percentage of silica sand on the stability-flow as well as void-density properties of bituminous concrete to be used in highway wearing course using the OBC. 2. Materials and Methods 2.1 Materials Materials used in the mix design of bituminous concrete include: i. Filler materials (Silica sand and Portland cement), ii. Aggregates (fine and coarse) and iii. binder (bitumen). The aggregates (fine and coarse) were locally sourced from Nagarta quarry, along Sokoto Road, Zaria, Kaduna State. The Cement which is Dangote 3X brand was obtained from open market, Zaria, Kaduna State. The bitumen used was obtained from Gidan Coal tar adjacent to NARICT, Basawa, Zaria, Kaduna State. Silica sand was obtained from Babban Mutum in Daura, Katsina State. 2.2 Methods Physical properties tests were conducted on bitumen, aggregates, cement, bitumen, silica sand as well as marshall test on bituminous concrete mixes in the Department of Civil Engineering, Ahmadu Bello University, Zaria, except oxide composition of Silica sand that was conducted in Chemistry Department, Ahmadu Bello University, Zaria. The test carried out on the constituent materials of bituminous mixture and code specifications are as follows: 2.2.1 Test on coarse aggregates Test conducted on coarse aggregates are; aggregate impact value/hardness test (BS 812 part 111, 1990), aggregate crushing value (BS 812 part 112, 1990), aggregate specific gravity (ASTM, C128, 2001), size and gradation analysis (BS 812-103.2, 1985) and water absorption (BS 812 2, 1995). 2.2.2 Test on fine aggregates The tests conducted on the fine aggregates are; specific gravity (ASTM C127, 2005), sieve analysis (BS 812-103.2, 1985), and water absorption (BS 812 3, 1995). Arid Zone Journal of Engineering, Technology and Environment, December, 2021; Vol. 17(4):453-468. ISSN 1596-2490; e-ISSN 2545- 5818; www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 456 2.2.3 Test on Mineral aggregate (cement and silica sand) Test on cement are; Initial and final setting time (BS EN 196 part 3, 1995), Soundness test (BS EN 196 part 3, 1995), and specific gravity (ASTM C188, 2017). Test on silica sand are; bulk relative density (ASTM D854, 2014), and specific density (ASTM D854, 2014). Another test carried out on the silica sand is X-ray Fluorescence (XRF) to determine the oxide composition. Oxide composition analysis was carried out using in an energy dispersive spectrometer designed for detection and measurement of elements in a sample according to BS EN 196-2 (1995) in the Department of Chemistry, Ahmadu Bello University, Zaria. Furthermore, the classification of the silica sand into the pozzolana group was done based on ASTM C618, (2005) specifications. 2.2.4 Test on Bitumen Tests on bitumen are: Penetration test (ASTM D5, 2005), Solubility test (ASTM D2042, 2015), Ductility test (ASTM D113, 2007), Flash and fire point test (ASTM D92, 2005), Specific gravity test (ASTM D70, 2003) and softening point (ASTM D36, 2006). 2.3 Optimum binder content (OBC) To determine the optimum binder content, the relationships between binder content and the properties of bituminous concrete mixtures such as stability, flow, bulk density, voids filled with bitumen (VFB), void in mineral aggregate (VMA), and void in the mix (VIM) at no silica sand replacement (control) were established. Three (3) specimens each were prepared for five bitumen content (4.5, 5.0, 5.5, 6.0, and 6.5 %) in accordance with Asphalt Institute (1994) and FMWH, (1997) specifications. The optimum binder content is calculated as the average binder content for maximum density, maximum stability, and specified percentage air voids in the total mix. 2.4 Marshall test specimen preparation Asphalt Institute (1994) and FMWH, (1997) recommendations were used to prepare standard specimens with 1200g weight, 101.5 mm diameter, and 63.5 mm height compacted with 75 hammer blows on each side to simulate heavy traffic situation. To obtain the optimum blend of cement-silica sand in bituminous mixtures, various percentage replacement by weight (5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, and 45%) of cement with silica sand was used to produced bituminous mixes. The specimens were tested for bulk specific gravity in accordance with ASTM D1559 (2000). Furthermore, the specimens were kept immersed in water in a thermostatically controlled water bath at 60°C for 30 to 40 minutes before been transferred within 30 seconds to the Marshall test head and tested for Marshall stability and flow in accordance with ASTM D1559 (2000). Also, void analysis such as; Compacted Density of the Mix (CDM), void in mineral aggregate (VMA), void in mix (VIM) and void filled with bitumen (VFB) was carried out. Theoretical Maximum Specific Gravity of the Mix (Gmm) were determined using ASTM D 2041-95 and Bulk Specific Gravity or Compacted Density of the Mix (CDM) using ASTM D1188-96. ASTM D3203-94 was used to estimate Void in the Mix (VIM). ASTM D1559 (2004) was used to determine the stability and flow of specimens. Marshall stability-flow and void- density analysis were performed and checked against the limits specified by the Nigerian General Specifications for Roads and Bridges (FMWH, 1997) for use as wearing course of the heavily-trafficked road. Shuaibu et al: An Experimental Study on the Performance of Bituminous Concrete Mixtures with Silica Sand as Filler Replacement. AZOJETE, 17(4):453-468 ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 457 3. Results and Discussion 3.1 Result of test on aggregates Table 2 shows the results of the physical properties test on the aggregates (coarse and fine aggregates), standard specifications used for each test, and results obtained. Table 2: Aggregates physical properties Property Code Specifications Results obtained Code limits Remarks Aggregate crushing value (%) BS 812 part112 (1990) 20 Max. 25 OK Aggregate impact value (%) BS 812 part111 (1990) 22.2 Max. 25 OK Specific Gravity (Coarse) ASTM C127 (2005) 2.61 2.55-2.75 OK Specific Gravity (Fine) ASTM C128 (2001) 2.63 2.55-2.75 OK Water absorption (coarse) (%) BS 812 Part 2, (1990) 0.45 < 2 OK Water absorption (fine) (%) BS 812 Part 3, (1990) 8.62 < 15 OK From Table 2, all the results obtained from the tests conducted on aggregates fall within the specified limits provided in the specification of codes, therefore, the aggregate meets the requirement for use for the design of bituminous concrete mixtures. 3.2 Results of particle size distribution for aggregates Aggregate grading is a very crucial factor in ascertaining the bond, interlocking packing and packing density The nature of the aggregate skeleton imparts greatly on the strength and resistance of the finished product in service (Otuoze and Shuaibu, 2017). Figures 1 and 2 shows the results of the gradation of the aggregates (fine and coarse) used in this study. Materials retained on sieve 2.36 mm are referred to as coarse aggregates while those that pass sieve 2.36 mm but retained in sieve 0.075 mm are referred to as fine aggregates (Shuaibu et al., 2020a). The grading of each of these constituent materials is very cardinal in ensuring a mix of desired engineering properties is obtained. Figure 1: Particle size distribution curve for coarse aggregate 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 100 Pe rc en t p as si n g (% ) Sieve size (mm) Arid Zone Journal of Engineering, Technology and Environment, December, 2021; Vol. 17(4):453-468. ISSN 1596-2490; e-ISSN 2545- 5818; www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 458 Figure 2: Particle size distribution curve for fine aggregate The results of the particle size distribution (Figures 1 and 2) obtained for the fine and coarse aggregates shows that the aggregates are well-graded and satisfy the specifications of BS 812- 103.2, (1985). Thus, suitable for the production of bituminous mixtures. 3.3 Results of test on Bitumen The test results on the physical properties test on bitumen are shown in Table 3. The results obtained fall within the limits of the ASTM code specifications, therefore, the bitumen can be adjudged suitable for use in the production of bituminous mixtures. Table 3: Preliminary test results on bitumen Test Conducted ASTM code Results Code Limits Remarks Penetration at 25°C, 0.1mm ASTM D5, (2005) 87.2 80-100 OK Flash & Fire Point (min) ASTM D92, (2005) 252 Min. 232 OK Solubility in trichloroethylene, (%) ASTM D2042, (2015) 99 99 OK Specific gravity at 25°C, (g/cc) ASTM D70, (2003) 0.98 0.97-1.02 OK Ductility at 25°C, cm ASTM D113, (2007) 115 Min. 100 OK Softening Point ASTM D36/D36M, (2009) 49.5 46-56 OK 3.4 Results of test on filler (Silica sand and cement) Test on the physical properties of cement and silica sand was performed. In addition, chemical properties of silica sand was performed to check the oxide composition necessary for classification into the groups of pozzolanas. The results obtained are as follows: 3.4.1 Physical properties of silica sand Table 4 and 5 present the results of the physical and chemical properties test on silica sand respectively. The physical properties (specific gravity and water absorption) obtained were compared to the code limits. The results obtained meet the limits of the code specifications. It is important to state at this point that for any material to be used as filler in bituminous mixtures more than 75 per cent of such material must pass through 0.075mm sieve and the silica sand meet these requirements. 0 20 40 60 80 100 120 0.01 0.1 1 10 100 P er ce n t p as si n g (% ) Sieve size (mm) Shuaibu et al: An Experimental Study on the Performance of Bituminous Concrete Mixtures with Silica Sand as Filler Replacement. AZOJETE, 17(4):453-468 ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 459 Table 4: Physical properties of Silica Sand Test conducted Code used Results Code Limits Remarks Specific gravity ASTM C128 (2001) 2.5 2.55-2.75 OK Water absorption (%) BS 812 Part 3, (1990) 8.92 < 15 OK 3.4.2 Oxide Composition of Silica Sand Table 5 shows the oxide composition of silica sand used in this study. The composition of the various oxides present in silica sand including the portion of loss on ignition to give a total of 100%. It is worth mentioning that the high SiO2 content above 95% is what make the silica sand special. Table 5: Chemical composition of silica sand Oxide Composition (%) Oxide Composition (%) Sodium Oxide (Na2O) 0.066 Sulphur trioxide (SO3) 0.659 Magnesium oxide (MgO) 0.313 Chloride (Cl) 0.046 Aluminium oxide (Al2O3) 5.913 Potassium oxide (K2O) 0.198 Silicon dioxide (SiO2) 91.221 Calcium oxide (CaO) 0.062 Diphosphorus pentoxide (P2O5) 0.406 Tetanium dioxide (TiO2) 0.729 Chromium III oxide (Cr2O3) 0.002 Manganese III oxide (Mn2O3) 0.009 Iron oxide (Fe2O3) 0.317 Zinc oxide (ZnO) 0.000 Strontium oxide (SrO) 0.005 Loss on ignition (LOI) 0.054 Based on the ASTM C 618, (2005) in Table 6 classification, the summation of Silica (SiO2), Alumina (Al2O3), and (Fe2O3) present in silica sand was compared to that of the code and the class of pozzolana which silica sand belongs to was deduced. From Table 5, the summation of these oxides in silica sand is 97.451%. i.e. (91.221+ 5.913+ 0.317). Also considering the low value of SO3 (≤ 5 %), silica sand can be classified as pozzolana in group N or F. Table 6: ASTM C 618, (2005) Classification of Pozolana Chemicals Class Test result N F C Silicon dioxide (SiO2), + Aluminium Oxide (Al2O3), + Iron Oxide (Fe2O3), min. (%) 70.0 70.0 50.0 97.451 Sulphur Trioxide (SO3), max,(%) 4.0 5.0 5.0 0.659 3.4.3 Results of test on Cement The results of the physical properties tests carried out on the cement are presented in Table 7. It can be seen that the cement used in this study meet all the code specified limits of Portland cement, Thus, it can be concluded that the Dangote 3x brand of cement used in this study is Portland cement. Arid Zone Journal of Engineering, Technology and Environment, December, 2021; Vol. 17(4):453-468. ISSN 1596-2490; e-ISSN 2545- 5818; www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 460 Table 7: Physical properties of cement Test Code used Results Code limits Remarks Initial Setting Time (minutes) BS EN 196 part 3, (1995) 125 > 45 OK Final Setting Time (hr) BS EN 196 part 3, (1995) 3.42 hrs < 10 hrs. OK Soundness (mm) BS EN 196 part 3, (1995) 3.0 < 10 OK Specific Gravity ASTM 188, (2017) 3.10 3.15 OK 3.5 Aggregate Proportioning and Blending for production of bituminous mix The aggregates materials were sampled according to the recommendation of BS EN932-1 (1996) and particle size distribution was conducted according to BS EN 933-1 (2012). To obtain proportion and blending of individual constituent material; coarse aggregate (material retained on 4.75 mm sieve with a maximum aggregate size of 25 mm), fine aggregate (material passing 4.75 mm sieve and retained on 200 μm sieve), and mineral filler (material passing 200 μm sieve) necessary for the production of the bituminous concrete mix were achieved by trial and error and blended until an all-in-aggregate satisfying code requirement is obtained as presented in Table 8 below. The results of combined material mixes fall within the lower and upper limits specified by Asphalt Institute (1997), thus, adjudged suitable for use in the production of bituminous concrete mixtures that meets strength and durability requirements in practice. Table 8: Result of the combined material mix (coarse aggregate, fine aggregate, and silica sand/cement) with limits of code specifications BS Sieve size (mm) Percentage retained (%) Cumulative percentage retained (%) Cumulative percentage passing (%) Asphalt Institute, (1997) 25.4 100 100 19.05 6.6 6.6 93.4 90 - 100 12.7 14.9 21.5 78.5 - 9.52 7.2 28.7 71.3 56 - 80 6.32 11.7 40.7 59.3 - 4.76 7.2 47.6 52.4 35 - 65 2.36 5.6 53.2 46.8 23 - 49 1.18 10.8 64.0 36.0 - 0.6 22.4 86.4 13.6 - 0.3 5.9 92.3 7.7 5 – 19 0.15 0.7 93.0 7.0 - 0.075 0.4 93.4 6.5 2 - 8 Pan 6.5 99.9 0.1 - 3.6 Determination of Optimum Binder Content (OBC) To obtain the optimum binder content necessary for the asphalt paving mixtures at different silica sand replacements, the relationships between binder contents and the properties of bituminous mixtures such as stability, flow, and bulk density, void in mix, void in mineral aggregate, and void filled with bitumen at no replacement (control) were established. Three samples were produced at each bitumen content (5, 5.5, 6, 6.5, 7.0%) as specified by Asphalt Shuaibu et al: An Experimental Study on the Performance of Bituminous Concrete Mixtures with Silica Sand as Filler Replacement. AZOJETE, 17(4):453-468 ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 461 Institute (1997) and ORN 19, (2003) and the average of the results obtained for the strength and void properties are presented in Table 9. Table 9: Summary of the Marshall Test Results for Control Specimens Bitumen Content (%) Stability (kN) Flow (mm) Bulk specific gravity (G) (g/cm3) VIM (%) VMA (%) VFB (%) 5.0 8.30 2.40 2.29 6.30 18.00 68.60 5.5 8.45 3.10 2.31 5.00 18.00 75.30 6.0 8.51 4.23 2.24 3.00 17.30 84.70 6.5 8.10 6.84 2.33 2.40 17.90 91.60 7.0 7.81 8.16 2.31 2.80 19.20 93.00 The optimum binder content is calculated as the average binder content that corresponds to maximum stability, maximum unit weight, and 4 % air voids.  Bitumen content at the maximum stability = 5.5 %  Bitumen content at the maximum value of bulk density = 6.5%  Bitumen content at 4 % air voids = 5.25 % (obtained by interpolation from table 6) Thus, Optimum Bitumen Content (OBC) = 5.5 + 6.5 + 5.25 /3 = 5.75% An optimum binder content of 6.0% was adopted for the production of bituminous concrete mixtures at varying silica sand/cement contents. The OBC used in this study is within the limits of 5.0 – 8.0% specified by FMWH, (1997). 3.7 Marshall test results for various replacements of cement with Silica sand at optimum binder content Figures 3 to 8 show the results of Marshall stability-flow, and void-density properties at various percentage replacement by weight of Portland cement with silica sand (5%,10%,15%, 20%,25%, 30%,35%, 40%, and 45%) using the optimum binder content of 6%. Figure 3: Variation of stability with silica sand content 4.5 5 5.5 6 6.5 7 7.5 8 5 15 25 35 45 55 St ab ili ty (k N ) Silica sand content (% ) Arid Zone Journal of Engineering, Technology and Environment, December, 2021; Vol. 17(4):453-468. ISSN 1596-2490; e-ISSN 2545- 5818; www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 462 Figure 3 shows the variation of Marshall Stability with different silica sand content. Marshall Stability is a measure of HMA resistance to deformation and distortion under traffic loading. This resistance is mainly derived from cohesion (provided by the binder material) and internal friction (provided by interlocking and frictional resistance of aggregates) (Shuaibu et al., 2020b). From Figure 3, the Marshall stability increases with the increase in the silica sand content. This could be attributed to the ability of silica sand to fill void spaces in the bituminous concrete mix by gaining increased contact points with other constituent materials, thereby, resulting in a denser mix. Also, the presence of high content of Sio2 enhances hardness. It should be noted that at silica sand content above 40%, the stability started dropping and this could be attributed to excess silica sand content in excess of the optimum which resulted in weak cohesion. However, the Marshall stability results obtained at all the silica sand contents satisfied the requirements for Nigerian Specification for roads and bridges (FMWH, 1997). Figure 4: Variation of flow with silica sand content Figure 4 shows the result of flow variation at varying silica sand content. Flow is the measure of flexibility by the change in diameter of the test sample in the direction of load application between the start of loading and the time of maximum load (Shuaibu et al., 2019). The flow value increases gradually at 5% (2.97mm) silica sand content until it peaked at 25% (3.8mm) silica sand content, then, it gradually started to decrease. The initial increase in flow could be due to the insufficient content of silica sand in the mix to retard the flow. However, as the silica sand content increases, the stiffening of filler-bitumen mastic occurred, consequently reducing the flow. The flow values obtained at all the silica sand contents falls with the 2 to 4mm Nigerian General Specifications for Roads and Bridges specification FMWH, (1997) margin for use in wearing course of the heavy-trafficked road. 2 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4 5 15 25 35 45 55 Fl o w ( m m ) Silica sand content (% ) Shuaibu et al: An Experimental Study on the Performance of Bituminous Concrete Mixtures with Silica Sand as Filler Replacement. AZOJETE, 17(4):453-468 ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 463 Figure 5: Variation of Void in the Mix (VIM) with silica sand content Figure 5, show the variation of void in mix (VIM) at different silica sand contents. The void in mix increases gradually from 5% silica sand until it peaked at 25% silica sand content then gradually started decreasing. This initial increase could be attributed to silica sand particles' having greater ability to convert free bitumen to structural bitumen than Portland cement (P.C) particles. Structural bitumen here refers to the bitumen that fills the voids among filler particles. This conversion reduces the amount of free bitumen required to lubricate aggregates and fill inter-granular voids (Shuaibu et al., 2020b). The reduction in percent air voids beyond 25% could be due to the sufficient filling of the void space between aggregates. It is important to note that a balance must be attained with the percentage air void content to achieve desirable engineering properties in service. The Nigerian General Specifications for Roads and Bridges specification FMWH, (1997) specifies a margin of 3 to 5% air void in mix, however, the values of VIM obtained at 25, 30 and 35% silica content does not meet this specification. Figure 6: Variation of bulk density with silica sand content 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 5 10 15 20 25 30 35 40 45 50 V o id in m ix ( % ) Silica sand content (% ) 2.00 2.10 2.20 2.30 2.40 2.50 5 15 25 35 45 55 B u lk d en si ty ( g/ cm 3 ) Silica sand content (%) Arid Zone Journal of Engineering, Technology and Environment, December, 2021; Vol. 17(4):453-468. ISSN 1596-2490; e-ISSN 2545- 5818; www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 464 Figure 6 show the result of bulk density at varying silica sand contents. The bulk density decreases with the increasing content of silica sand. The maximum value of bulk density recorded is 2.38g/cm3 at 5% silica sand content. The reduction in bulk gravity could be due to the lower specific gravity/large surface area (i.e higher volume) of the silica sand compared to that of cement (Shuaibu et al., 2020a) . Silica sand has large surface area and it requires more binder for coating, hence, the bulk density dropped. Figure 7: Variation of void filled with bitumen (VFB) with silica sand content Figure 7 shows the result of VFB at varying silica sand contents. The void filled with bitumen VFB is defined as the portion of the volume of void space between the aggregates particles that is occupied by the effective bitumen (Shuaibu et al., 2020c). The void filled with bitumen decreases as percentage replacement of silica sand increases and this is because the particles of the silica sand take up the effective bitumen and in turn reduces it. Only the VFB results obtained at silica sand contents of 5, 10, 15 and 20% conformed to the Nigerian General Specifications for Roads and Bridges specification FMWH, (1997) of 75 to 82% for use in wearing course. Figure 8: Variation of voids in mineral aggregate (VMA) with silica sand Content 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 5 10 15 20 25 30 35 40 45 50 V F B ( % ) Silica sand content (%) 16.0 17.0 18.0 19.0 20.0 21.0 22.0 5 10 15 20 25 30 35 40 45 50 V M A ( % ) Silica sand content (%) Shuaibu et al: An Experimental Study on the Performance of Bituminous Concrete Mixtures with Silica Sand as Filler Replacement. AZOJETE, 17(4):453-468 ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 465 Figure 8 shows the results of void in mineral aggregate with silica sand content. Voids in mineral aggregate (VMA) is bituminous concrete design parameter that defines the sum of the volumes of air voids (voids in total mix) and the unabsorbed bitumen (effective binder content) in a compacted bituminous concrete sample (Shuaibu et al., 2020b). Minimum requirements on VMA are set to ensure that sufficient voids are present in the compacted mix to avoid durability problems. The VMA aggregates increases gradually from 5% silica sand content, peaked at 25%, and gradually decreased. The later decreasing trend observed in VMA is due to the ability of silica sand to fill up spaces between the mineral aggregates. 4. Conclusions From the results of the experimental study, the following conclusions can be deduced; i. The preliminary test conducted on bituminous concrete constituent materials (cement, fine and coarse aggregates, bitumen) conforms to the ASTM and BS code specifications, therefore, adjudged suitable for the production of bituminous mixtures for wearing course. ii. Oxide composition test conducted on silica sand confirmed that it is pozzolanic in group N or F, thus, can be used as an admixture in the bituminous concrete mix. iii. Marshall stability results showed that of bituminous concrete mix containing up to 45% silica sand improved the stability value beyond 3.5kN specified by the code. Also, the flow values recorded at all silica sand contents are within the 2-4mm limits specified by codes. 5. Acknowledgement The authors are sincerely grateful to the Department of Civil Engineering Department, Ahmadu Bello University, Zaria, Kaduna State, Nigeria for providing an enabling environment to carry out this research. The work described in this paper is not supported by any grant. Reference Akter, H. and Hossain, K. 2017. Influence of Rice Husk Ash and Slag as Fillers in Asphalt Concrete Mixes. American Journal of Engineering Research (AJER), 6(1): 303-311. Asphalt Institute, 1997, Mix Design Methods for Asphalt, Manual Series No. 2 (MS-02). The Asphalt Institute. Lexington, KY. ASTM C117 2017, Standard Test Method for Materials Finer than 75-μm (No. 200) Sieve in Mineral Aggregates by Washing, ASTM International, West Conshohocken, PA, USA. ASTM C127, 2015, Standard Test Method for Relative Density (Specific Gravity) Absorption of Coarse Aggregate, ASTM International, West Conshohocken, PA, USA. ASTM C128, 2001, Standard Test Method for Density, Relative Density (Specific Gravity), and Absorption of Fine Aggregate, ASTM International, West Conshohocken, PA, USA. ASTM C618, 2005, Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete, ASTM International, West Conshohocken, PA, USA. ASTM D113 - 2007, Standard Test Method for Ductility of Bituminous Materials, West Conshohocken, ASTM International, Philadelphia, PA, USA. Arid Zone Journal of Engineering, Technology and Environment, December, 2021; Vol. 17(4):453-468. ISSN 1596-2490; e-ISSN 2545- 5818; www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 466 ASTM D113, 2007. Standard Test Method for Ductility of Bituminous Materials. West Conshohocken, ASTM International, Philadelphia, PA, USA. ASTM D2042 2015, Standard Test Method for Solubility of Asphalt Materials in Trichloroethylene, ASTM International, West Conshohocken, PA, USA. ASTM D2042, 2015. Standard Test Method for Solubility of Bituminous Materials. West Conshohocken, ASTM International, Philadelphia, PA, USA. ASTM D36 2006, Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus), ASTM International, West Conshohocken, PA, USA. ASTM D5, 2005, Standard Test Method for Penetration of Bituminous Materials. West Conshohocken, ASTM International, Philadelphia, PA, USA. ASTM D70, 2003. Standard Test Method for specific gravity and density of asphalt binder (Pycometer method). West Conshohocken, ASTM International, Philadelphia, PA, USA. ASTM D854, 2014, Standard Test Methods for Specific Gravity of Soil Solids by Water Pycnometer, ASTM International, West Conshohocken, PA, USA. ASTM D92, 2005. Standard test method for flash and fire points by Cleveland Open Cup Tester. West Conshohocken, ASTM International, Philadelphia, PA, USA. Boon Hoe, H., Sunnasee, P., Kok Hon, C., Byung Gyoo, K. and Sien Ti, K. 2014. Utilisation of Rice Husk Ash in Asphaltic Concrete Pavement. Advanced Materials Research, TransTech Publications, Switzerland, 1030-1032(961-964). BS 812 110, 1990. Methods for Determination of Aggregate Crushing Value (ACV). British Standard Institution, London, United Kingdom. BS 812 112, 1990. Methods for Determination of Aggregate Impact Value (AIV). British Standard Institution, London, United Kingdom. BS 812 2, 1995. Methods for Determination of Density, Water Absorption, British Standard Institution, London, United Kingdom. BS EN 933-1, 2012, Tests for Geometrical Properties of Aggregates. Determination of Particle Size Distribution, Sieving Method, British Standard Institution, London, United Kingdom. BS EN 933-2, 1996 Tests for geometrical properties of aggregates. Determination of particle size distribution. Test sieves, nominal size of apertures, British Standard Institution, London, United Kingdom. BS EN196-3, 1995, Methods of testing cement — Part 3: Determination of setting time and soundness, British Standard Institution, London, United Kingdom. Burkowicz, A., Krzysztof Galos, K. and Guzik, K. 2020. The Resource Base of Silica Glass Sand versus Glass Industry Development: The Case of Poland, Multi-discplianry Publishing Institute, Basel, Switzerland. Chukwu, P. 2019. Exposition on Silica Sand Reserves In Nigeria and Its Impact on Metallurgical Industries. COOU Journal of Physical Sciences, 1(2): 810-816. Shuaibu et al: An Experimental Study on the Performance of Bituminous Concrete Mixtures with Silica Sand as Filler Replacement. AZOJETE, 17(4):453-468 ISSN 1596-2490; e-ISSN 2545-5818, www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 467 Duvuna, GA. and Ayuba, A. 2015. A Study on Silica Sand Quality in Yazaram and Mugulbu Deposits for Glass Making. Nigerian Journal of Technology, 34(1): 109 – 112., http://dx.doi.org/10.4314/njt.v34i1.13 FMWH, 1997. General Specifications for Roads and Bridge. Federal Ministry of Work sand Housing, Federal Republic of Nigeria. Abuja, Nigeria. Langer, WH. 2003. A general overview of the technology of in-stream mining of sand and gravel resources associated potential environmental impacts, and methods to control potential impacts. U.S. Geological Survey Open File Report OF-02-153. Mistry, R. and Roy, TK. 2016. Effect of using fly ash as alternative filler in hot mix asphalt. Perspectives in Science, 8: 307—309. Mistry, R., Karmakar, S. and Roy, TK. 2018. Experimental evaluation of rice husk ash and fly ash as alternative fillers in hot-mix asphalt. Road Materials and Pavement Design, DOI:10.1080/14680629.2017.1422791. Murana, AA. and Sani, A. 2015. Partial Replacement of Cement with Baggase Ash in Hot Mix Asphalt. Nigerian Journal of Technology, 34(4): 699-704. ORN 19, 2003. A guide to the Design of Hot Mix Asphalt in Tropical and Sub-tropical Countries, Overseas Road Note 1. Berkshir, England Otuoze, HS. and Shuaibu, AA. 2017. An Experimental Study on the Use of Polypropylene waste in bituminous mix. Nigerian Journal of Technology, 36(3): 677-685. RMRDC, 2009. Survey Series 061 Raw materials Sourcing for Manufacturing in Nigeria 4th Edition. Publishers: Raw Materials Research and Development Council, Abuja Nigeria. Shuaibu, AA., Otuoze., HS., Mohammed, A. and Lateef, MA. 2019. Properties of asphalt concrete containing waste foundry sand (WFS) as filler material. Arid Zone Journal of Engineering, Technology and Environment (AZOJETE), 15(3): 662-677. Shuaibu, AA., Otuoze, HS., Ahmed, HA. and Musa, B. 2020a. Experimental Study on the Use of Groundnut Shell Ash as Mineral Filler in Hot Mix Asphalt. Nigerian Journal of Engineering, 27(3), 61-68. Shuaibu, AA., Umar, AM., Otuoze, HS., Mohammed, A. and Abba, AM. 2020b. Optimum Portland Cement-Guinea Corn Husk Ash Blend as Filler in Hot Mix Asphalt. Covenant Journal of Engineering and Technology, 4(2): 56 - 66. Shuaibu, AA., Otuoze, HS., Iliyasu, I. and Maska, US. 2020c. Effect Of Oil Palm Mesocarp Fibre Ash (OPMFA) On The Strength Properties Of Hot Mix Asphalt. Journal of Science Technology and Education, 8(2), 330 - 350. Simone, A., Mazzotta, F., Eskandarsefat, S., Sangiorgi, C., Vignali, V., Lantieri, C. and Dondi, G. 2017. Experimental application of waste glass powder filler in recycled dense grade asphalt mixtures. Road Materials and Pavement Design, 20(3): 592-607 DOI:10.1080/14680629.2017.1407818. http://dx.doi.org/10.4314/njt.v34i1.13 Arid Zone Journal of Engineering, Technology and Environment, December, 2021; Vol. 17(4):453-468. ISSN 1596-2490; e-ISSN 2545- 5818; www.azojete.com.ng Corresponding author’s e-mail address: abdulshub4u@gmail.com 468 Sutradhar, D., Miah, M., Chowdhury, GJ. and Abdus, S. 2015. Effetct of using waste materials as in bituminous mix design. American Journal of Civil Engineering, 3(3): 88-94. Speight, JG. 2016. Nomenclature and Terminology Asphalt Materials Science and Technology, Butterworth-Heinemann, United Kingdom, 3-43, doi.org/10.1016/B978-0-12 800273-5.00001-5. Zhang, H., Chen, Z., Zhu, C. and Wei, C. 2020. An innovative and smart road construction material: thermochromic asphalt binder. New Materials in Civil Engineering, Butterworth Heinemann, 2020, 691-716, doi.org/10.1016/B978-0-12-818961-0.00022-3