Ancient and Modern Pozzolanic Materials as Admixtures of Lime and Cement Composites: A Brief Review

Mortar is considered the oldest manufactured building material. The Egyptians first used a mixture of burnt gypsum, sandy silt from the Nile, and crushed limestone. The use of mineral admixtures has its historical and practical justification [1]. The colossal artificial harbour at Caesarea in 22-10BC was one of the most ambitious engineering feats of the ancient world. It was built of the so-called Roman concrete, which consisted of quicklime and volcanic ash. However, it is believed that knowledge of these binders and engineering skills originated with the Greeks or even with the ancient Egyptians and Persians with a slight influence of oriental culture through Mesopotamia and Mediterranean civilisations. In the Roman period, mortars of various compositions were widely used in the construction of buildings, harbours, bridges, aqueducts, roads, sewers, etc. Analysis of the surviving foundations, walls, and dams revealed very advanced technology and concrete composed of hydraulic lime, or air lime, and volcanic ash from Mount Vesuvius mined in the Pozzuoli region near Naples. Vitruvius recommended the ratio of one part lime to two parts fly ash in his work De Architectural libri decem, written around 27BC [2].

The state of practical knowledge and the views on lime and hydraulic mortars can be derived from the publications of Bélidor [3]. The use of blast furnace slag to produce binder was patented as early as 1728 by the Englishman John Payne. In the middle of the 19th century, slag cement began to be produced. John Smeaton in 1756, comparing various properties properties of limestone by chemical analysis, found that the most suitable for hydraulic binder production are limestones polluted with clays [4]. So, he prepared a concrete that hardened excellently under water and built a lighthouse out of it at Eddystone near Plymouth on the Cornish coast. This artificial stone, based on “Roman cement”, in colour resembled the building stone from the vicinity of Portland, which was considered to be of the finest quality. Here the silicate cement was later given the nickname ‘Portland cement.’ The tradition of using pozzolanic admixtures was considered a trade secret of the building families. The benefits of pozzolanic materials were rediscovered during the Industrial Revolution during the 18^th and 19th centuries. Engineers and scientists began to systematically study and apply industrial by-products such as fly ash and slag, recognising their pozzolanic properties [5-8]. As we can see from the analyses of the preserved mortars as pozzolanic admixtures in this period, ceramic tiles and bricks were also crushed [9-11], burnt clays [12], or natural zeolites [13].

The widespread industrial use of pozzolanic materials surged, driven by the need for durable and sustainable construction materials in the 20^th century. Advances in material science allowed for a better understanding of the chemical reactions and benefits provided by these admixtures. Modern pozzolanic admixtures continue to play a crucial role in enhancing the properties of cementitious materials. These materials are widely used in construction to improve the durability, strength, and environmental sustainability of concrete and mortars [14]. This also led to the development of High-Performance Concrete (HPC) in the 1960s and 1970s [15,16]. In the 1980s, pozzolans were incorporated as Supplementary Cementitious Materials (SCMs) to composite materials [17] and Ultra-High-Performance Concrete (UHPC) was proposed [18]. High-performance concretes are characterised by high strengths, resistance to water and salt penetration, frost resistance, etc. [19]. In this period of time, industrial by-products such as silica fume from silicon metal or ferrosilicon alloy production [20], fly ashes from coal combustion in power plants [21], Ground Granulated Blast Furnace Slag (GGBFS) a by-product of iron production in blast furnaces [22], or metakaolin derived from calcined kaolinite clay [23-25], rice husk ash [26], and of course natural pozzolans (volcanic ash, pumice, and certain sedimentary rocks [27,28]) were widely used.

Today, the exploration of pozzolanic admixtures involves extensive research and development to optimise their use in various applications. This includes mainly characterisation of natural and artificial pozzolans, performance testing, and sustainability studies. In the 21^st century, the construction industry is confronted with the environmental and economic impacts of cement production. For this reason, it is essential to design hydraulic binders using secondary raw materials. Fly ash from biomass combustion [29- 31], municipal waste [32,33], treated sewage sludge [34,35], and waste coal gangue [36,37] appear to be very promising. Additionally, these secondary waste materials may contain heavy metals and other dangerous chemicals that could be released into the environment by only landfilling. Therefore, its use in the form of active admixtures is highly desirable and contributes to the sustainable development of the construction industry.

The term pozzolanic activity covers all the reactions that take place between the active components of the pozzolan, lime, or calcium hydroxide, and water and practically defines the maximum amount of lime that the pozzolan can react with and the rate at which it does so. The activity of pozzolans has many variables, all depending on the nature of the pozzolan used, its quality, the amount of active ingredients contained, the ratio in the mixture, the specific surface, the water content, but also the chemical composition, the grain size, and of course the ambient conditions of the reaction, especially temperature, humidity, and partial pressure [38-40]. In recent years, researchers have proposed many methods for evaluating pozzolanic activity. Many countries have also selected different test methods and standardised them to provide the industry with a basis for assessing the activity of pozzolanic materials. The methods used for the determination of pozzolanic activity can be divided into two categories: direct and indirect. Direct methods monitor the presence of calcium hydroxide and its subsequent reduction during the pozzolanic reaction using analytical methods such as X-ray diffraction, thermogravimetric analysis, or classical chemical titration. Indirect methods include the measurement of physical properties such as the determination of the strength characteristics of the test specimens, electrical conductivity, or thermal conduction [41,42].

At first, it is necessary to characterise the material, which means determining the chemical composition, particle size distribution, and specific surface area. The values of these parameters can indicate whether a given material will be pozzolana active or how much. Subsequently, several methods can be used individually or in combination. Physical test methods, including the strength activity index method, electrical conductivity test, isothermal calorimetry test, thermal analysis method and bound water ratio method, indirectly reflect activity by measuring the conductivity of the solution, the strength of the mortar, heat release, or other factors [43,44]. These methods are defined by standards, specifically ASTM C331 [45], ASTM C1702 [46], and ASTM D8329 [47]. The chemical testing procedure quantitatively identifies the amount of Ca(OH)2 consumed or the content of SiO₂ and Al2O₃ in the material according to the nature of the pozzolanic reaction to precisely assess the activity, including the Frattini test [48], the lime absorption method, the Chappell test [49] and the acid/alkali dissolution method. Other methods include the determination of pozzolanic activity by microstructure analysis (degree of polymerisation) or the kinetic model method [50]. All these methods have their own advantages and disadvantages and will find their own specific applications. The appropriateness of using methods has been the subject of much research. In summary, chemical methods are more intuitive and precise than physical methods, which are more likely to be interfered with by the external environment.

From the point of view of practical use, it is essential to perform tests on concrete properties such as strength, durability, and environmental resistance. When designing new composite materials using pozzolans, it is crucial to determine the optimum amount of a given admixture. It can vary depending on several factors, including the type of pozzolan used, the specific application, and the desired properties of the composite material. It also depends on whether the pozzolan is added as a substitute or is added as a binder. For example, typically 15-30 % replacement of Portland cement is common. Silica fume is usually added at 5%-15% by weight of cement, and GGBFS is often used at replacement levels of 30-50% of the cement content. In some cases, up to 70% can be used for specific performance requirements. Typically, metakaolin is used as a replacement for cement and lime at 5-20%. It provides significant improvements in strength and durability.

The use of ancient pozzolanic admixtures revolutionised construction in antiquity, enabling the creation of enduring structures that still stand today. Understanding these materials offers valuable information on sustainable and durable construction practices that can guide the use of modern pozzolanic materials in contemporary engineering. Although general guidelines exist for the optimal amount of pozzolanic admixture in lime and cement composites, the specific requirements of each project should dictate the final proportions. Performance tests and consideration of environmental factors are crucial steps in determining the ideal mix design. Modern pozzolanic admixtures are integral to the advancement of concrete technology, providing solutions that address both performance and environmental challenges. By utilising these materials, the construction industry can produce more durable, sustainable, and cost-effective concrete structures. Substituting a portion of Portland cement with pozzolanic materials can lower the overall cost of concrete production while improving performance.

I can declare that there is no conflict of interest.

This research was funded by the CZECH SCIENCE FOUNDATION, grant No. 23-04744S-Research of heavy metals immobilization in alternative low-carbon composites.

1. Collepardi M (1197) A historical review of development of chemical and mineral admixtures for use in stucco plaster and terrazzo floor. Symposium Paper 173: 673-694.
2. Pollo MV (2016) De architectura Libri Decem. Rose V (Ed.), The project Gutenberg E Book of De Architectura.
3. Bélidor BF (1737-1739) Hydraulic architecture or the art of leading, raising and providing resources for the different needs of life. Paris: Jombert. Advances in Historical Studies 9(2):
4. Morris MD (2012) American civil engineering history: The pioneering years. American Society of Civil Engineers, Reston, USA.
5. (1998) Standard specification for coal fly ash and raw or calcined pozzolan for use as mineral admixture in Portland cement concrete. ASTM standard.
6. (2023) Standard specification for coal fly ash and raw of calcined Natural pozzolan for use as in concrete. ASTM.
7. Suraneni P, Burris L, Shearer CR, Hooton RD (2021) ASTM C618 fly ash specification: Comparison with other specifications, shortcomings, and solutions. ACI Materials Journal 118(1): 157-167.
8. Mathapati M, Amate K, Prasad CD, Jayavardhana MI, Raju TH(2022) A review on fly ash utilization. Materials Today: Proceedings 50(5): 1535-1540.
9. Mansoor SS, Hama SM, Hamdullah DN (2022) Effectiveness of replacing cement partially with waste brick powder in mortar. Journal of King Saud University-Engineering Sciences.
10. Navrátilová E, Rovnaníková P (2016) Pozzolanic properties of brick powders and their effect on the properties of modified lime mortars. Construction and Building Materials 120: 530-539.
11. Pavlíková M, Volfová P, Pavlík Z, Keppert M, Černý R (2012) Effect of fine-ground ceramics admixture on the hydration process of cement paste. world academy of science. Engineering and Technology 6 (3): 521-524.
12. Sabir BB, Wild S, Bai J (2001) Metakaolin and calcined clays as pozzolanas for concrete, a review. Cement and Concrete Composites 23 (6): 441-454.
13. Mertens G, Snellings R, Balen KV, Simsir BB, Verlooy P, et al. (2009) Pozzolanic reactions of common natural zeolites with lime and parameters affecting their reactivity. Cement and Concrete Composites 39(3): 233-240.
14. Pavlíková M, Brtník T, Keppert M, Černý R (2009) Effect of metakaolin as partial Portland-cement replacement on properties of high performance mortars. Cement Wapno Beton 14(3): 113-122.
15. Aïtcin PC (1998) High Performance Concrete. 1^st (edn), CRC Press, USA.
16. Kostuch JA, Walters GV, Jones TR (2000) High performance concrete incorporation metakaolin: A review. Concrete 2(1993): 1799-1811.
17. Lothenbach B, Scrivener K, Hooton RD (2011) Supplementary cementitious materials. Cement and Concrete Research 41(3): 217-229.
18. Bajaber MA, Hakeem IY (2021) UHPC evolution, development, and utilization in construction: A review. Journal of Materials Research and Technology 10: 1058-1074.
19. Roy DM, Arjunan P, Silsbee MR (2001) Effect of silica fume, metakaolin, and low-calcium fly ash on chemical resistence of concrete. Cement and Concrete Research 31(12): 1809-1813.
20. Toutanji H, Houssam A, Korchi TE (1995) The influence of silica fume on the compressive strength of cement pastes and mortar. Cement and Concrete Research 25(7): 1591-1602.
21. Permatasari R, Sodri A, Gustina H (2023) Utilization of fly ash waste in the cement industry and its environmental impact: A Review. Jurnal Penelitian Pendidikan IPA 9(9): 569-579.
22. Ahmad J, Kontoleon KJ, Majdi A, Naqash MT, Deifalla AF, et al. (2022) A comprehensive review on the Ground Granulated Blast Furnace Slag (GGBS) in Concrete Production. Sustainability 14(14): 8783.
23. (2009) NF P18-513: Pozzolanic addition for concrete metakaolin. Definitions, specifications and conformity criteria. Annex A.
24. Khatib JM, Baalbaki O, Elkordi AA (2018) Metakaolin. Waste and supplementary cementitious materials in concrete, Elsevier Publishers, Netherlands, pp. 493-511.
25. Siddique R, Klaus J (2009) Influence of metakaolin on the properties of mortar and concrete: A review. Applied Clay Science 43(3-4): 392-400.
26. Della VP, Kühn I, Hotza D (2002) Rice husk ash as an alternate source for active silica production. Materials Letters 57(4): 818-821.
27. Pavlíková M, Rovnaníková P, Záleská M, Pavlík Z (2022) Diatomaceous earth-lightweight pozzolanic admixtures for repair mortars-complex chemical and physical assessment. Materials 15(19): 6881.
28. Pavlík Z, Záleská M, Pavlíková M, Pivák A, Lauermannová AM, et al. (2023) Utilization of extracted carbonaceous shale waste in eco-friendly cementitious blends. Construction and Building Materials 394.
29. Olatoyan OJ, Kareem MA, Adebanjo AU, Olawale SOA, Alao KT (2023) Potential use of biomass ash as a sustainable alternative for fly ash in concrete production: A review. Hybrid Advances 4.
30. Agrela F, Cabrera M, Morales MM, Zamorano M, Alshaaer M (2019) Biomass fly ash and biomass bottom ash. New trends in eco-efficient and recycled concrete. Elsevier Publishers, Netherlands, pp. 23-58.
31. Aprianti E, Shafigh P, Bahri S, Farahani JN (2015) Supplementary cementitious materials origin from agricultural wastes-a review. Construction and Building Materials 74: 176-187.
32. Lam CHK, Ip AWM, Barford JP, McKay G (2010) Use of incineration MSW Ash: A Review. Sustainability 2(7): 1943-1968.
33. Siddique R (2010) Use of municipal solid waste ash in concrete. Resources, Conservation and Recycling 55(2): 83-91.
34. Lin KL, Lin CY (2005) Hydration characteristics of waste sludge ash utilized as raw cement material. Cement and Concrete Research 35(10): 1999-2007.
35. Pavlík Z, Fořt J, Záleská M, Pavlíková M, Trník A, et al. (2015) Energy-efficient thermal treatment of sewage sludge for its application in blended cements. Journal of Cleaner Production 11(1): 409-419.
36. Li J, Wang J (2019) Comprehensive utilization and environmental risks of coal gangue: A review. Journal of Cleaner Production 239.
37. Zhang Y, Ling YTCH (2020) Reactivity activation of waste coal gangue and its impact on the properties of cement-based materials- A review. Construction and Building Materials 234.
38. Wang H, Liu X, Zhang Z (2023) Pozzolanic activity evaluation methods of solid waste: A review. Journal of Cleaner Production 402.
39. Záleská M, Pavlíková M, Pavlík Z (2015) Classification of a-SiO₂ rich materials. Materials Science Forum 824: 33-38.
40. Donatello S, Tyrer M, CHeeseman CR (2010) Comparison of test methods to assess pozzolanic activity. Cement and Concrete Composites 32(2): 121-127.
41. Ayub T, Khan SU, Memon FA (2014) Mechanical characteristics of hardened concrete with different mineral admixtures: A review. The Scientific World Journal 2014: 875082.
42. Záleská M, Pavlíková M, Pavlík Z, Jankovský O, Pokorný J, et al. (2018) Physical and chemical characterization of technogenic pozzolans for the application in blended cements. Construction and Building Materials 160: 106-116.
43. Thorstensen TR, Fidjestol P (2015) Inconsistencies in the pozzolanic Strength Activity Index (SAI) for silica fume according to EN and ASTM. Materials and Structures 48(12): 3979-3990.
44. Pavlík Z, Trník A, Kulovaná T, Scheinherrová L, Rahhal V, et al. (2016) DSC and TG analysis of a blended binder based on waste ceramic powder and Portland cement. International Journal of Thermophysics 37: 32-37.
45. (2024) Standard test methods for sampling and testing fly ash or natural pozzolans for use in Portland-cement concrete. ASTM.
46. (2023) Standard test method for measurement of heat of hydration of hydraulic cementitious materials using isothermal conduction calorimetry. ASTM.
47. (2021) Standard test method for determination of water/cementitious materials ratio for Geosynthetic Cementitious Composite Mats (GCCMs) and measurement of the compression strength of the cementitious material contained within. ASTM.
48. Raverdy M, Brivot F, Paillére AM, Dron R (1980) Appreciation of the pozzolanic activity of secondary constituents, 7^th International Congress on the Chemistry of Cement 3: 36-41.
49. Quarcioni VA, Chotoli FF, Coelho ACV, Cincotto MA (2015) Indirect and direct Chapelle's methods for the determination of lime consumption in pozzolanic materials. Revista IBRACON de Estruturas e Materiais 8(1): 1-7.
50. Bayiha BN, Bahel B, Kenmogne F, Yemetio UN, Yamb E, et al. (2023) Comparative study of the effects of a natural pozzolan and an artificial pozzolan on the hydraulic properties of Portland cement mortar. Global Journal of Engineering and Technology Advances 14(1): 107-119.