When additions are mixed with RA, the resulting concrete is likely to present a combination of the negative effects expected from each component (Kou and Poon, 2013; Sim and Park, 2011; Xiao et al., 2012a; Zhang and Zong, 2014). Compressive strength of UHPC with 270 kg/m3 silica fume, 2% fiber content, and cement replacement by nanosilica 0%, 1%, and 2%—normal curing (Janković et al., 2019). The most recent and important studies regarding the effect of SCBA on the durability of concrete will be discussed. To the authors’ knowledge, there are only a few studies on the kinetics of lime/clay pozzolanic reaction in the literature [4,7,8]. None of them considers modeling. Download : Download high-res image (149KB)Download : Download full-size image. The lack of correlation is also found when combined lime is compared with strength of PC–pozzolanic material blends.94 This is particularly true of materials containing unaltered clays, which often possess a high capacity to fix lime, but do not harden appreciably.2. Robert Lewis, ... Ray Ryle, in Advanced Concrete Technology, 2003. content of the soil. The duration and temperature of the burning process affect the strength, making it necessary to select the correct thermal treatment in order to achieve optimal results.68,127,137. These improvements had a direct implication on the durability of reinforced concrete structures. The results are significant for reducing the detrimental effect of the leaching-induced deterioration of flexible pavements founded on … Although the combined incorporation of RCA and fly ash was found to result in the formation of additional hydration products at the ITZ between the RCA and the cement matrix (Corinaldesi and Moriconi, 2009; Poon et al., 2004), this was unlikely to influence the carbonation rate of the concrete over a long period of time (Figure 10.9). It is likely that the common ion effect involving OH‒ in highly alkaline solutions means that the dissolution of Ca(OH)2 is hindered in such systems, and it is also possible that very highly alkaline conditions will lead to dissolution of any C-S-H type phases which are formed. In order to obtain the SCBA, the bagasse was burnt in boilers at a temperature between 900°C and 1100°C. Plain concrete showed an 18 mm penetration depth. Michael John McCarthy, Thomas Daniel Dyer, in Lea's Chemistry of Cement and Concrete (Fifth Edition), 2019. The XRD data show a decrease in the intensity of alumio-silicate minerals such as kaolinite and smectite; silica and alumina are dissolved at a high pH and converted to pozzolanic products such as calcium-silicate-hydrate (C-S-H). Compressive Strength (kg/cm2) of Two Lime-Segni Pozzolana Mixes of Different Gypsum Content111, A good linear correlation has been found between the Blaine fineness of a natural pozzolana and the compressive strength of 20:80 lime–pozzolana mixes. Although not all of the calcined product can be considered as MK, it controls the reactivity through the pozzolanic reaction. which chemically do not react fill the space between the cement particles. Jordi Payá, ... Lourdes Soriano, in Waste and Supplementary Cementitious Materials in Concrete, 2018. Blended cement as an industry-manufactured product does not require technical expertise for their use in the field and is more reliable to use than FA as an admixture. Any dissolved Ca2+ ions within the soil then react with any dissolved SiO2 and Al2O3 located on clay particles to produce hydrated gels of C-S-H and C-A-H, which cement soil particles together as can be seen in Figure 21.5. However, the ashes improved the chloride resistance of concrete better than their contribution in compressive strength. However, excessive quantities may lead to the formation of large amounts of ettringite123 which can cause disintegration.99,112. We use cookies to help provide and enhance our service and tailor content and ads. Hardening of a pozzolana–lime mortar is slow but continues to progress over long periods: compressive strength at an age of 2 years can be as high as three times the 28-day strength.128 The addition of gypsum has been found to have no effect on this behavior,99 and also to increase strength111 (Table 9.10). These processes generally realise a favourable outcome. Little and Nair [1] states that pozzolanic reaction is a coopera tive mechanism betwee n lime and clay wherein lime induces high pH environment thereby solubilizing silica and alumina, and also We use cookies to help provide and enhance our service and tailor content and ads. d) A pozzolanic reaction involves a secondary reaction whereby calcium hydroxide and usually silica (SiO 2) react to form the strength contributing C-S-H phase. In XRD analysis, pozzolanic products are assessed by the location and intensity of x-ray peak(s). 2.5 it can be seen that there is no considerable influence on compressive strength of the cementitious composite. The content of secondary phases present with the MK may influence properties of … The results showed that ashes in the mix improved the chloride resistance of concrete. Whereas permanent pozzolanic reactions occurred at lime contents above the LSO and thus resulted in a 45-fold increase in strength and durability. Researches on hydration and pozzolanic reaction of RPC showed that the average C–S–H chain length was short and the pozzolanic activity was weak when the curing temperature was 20°C (Zhang et al., 2008). Use can be made of these improved qualities in designing concretes to comply with requirements or greater resistance to certain hostile environments. Provis, ... P. Duxson, in Geopolymers, 2009. (1999) suggest that if samples cure at higher temperatures during the first 5 hours post-mixing, reaction rates are increased, resulting in further improved strengths. Close attention to curing methods and times is important to ensure optimum performance. Historically, volcanic ash, brick dust and other forms of burnt clay were used as pozzolanic additives in lime mixes. Pozzolana/calcium hydroxide = 100:40; w/s = 0.6. It is of key importance to be able to determine the degree of pozzolanic reaction developed in a lime-treated soil in order to assess the durability of the reactions responsible for changing the properties of the treated soil. The mechanism of soil-lime treatment involves cation exchange, which leads to the flocculation and agglomeration of soil particles. In most cases it is the refinement of the pore system which reduces penetrability, that has the greater effect on the performance of the concrete than the increased strength. Influence of lime content on the compressive strength of hydrated lime–pozzolana mixes. The pozzolanic activity is a measure for the degree of reaction over time or the reaction rate between a pozzolan and Ca 2+ or calcium hydroxide (Ca(OH) 2) in the presence of water.The rate of the pozzolanic reaction is dependent on the intrinsic characteristics of the pozzolan such as the specific surface area, the chemical composition and the active phase content. The degree of deterioration of concrete structures was evaluated by determining the corrosion potential in accordance with ASTM-C-876. Reduced Heat of Hydration: The pozzolanic reaction between pozzolan and lime generates less heat, resulting in reduced thermal cracking when pozzolans are used to replace portland cement. The results obtained confirmed that SCBA used as a partial replacement of cement in concretes improves the protection of steel rebar from corrosion. Figure 2.1. The contribution of the pozzolanic reaction to cement strength is usually developed at later curing stages, depending on the pozzolanic … This behavior was due to the pozzolanic activity that produces a refinement in the pore size distribution compared to the control concretes. The latter test 9.12. The addition of a sufficient quantity of calcium to geopolymers in the form of calcium hydroxide can lead to the formation of phase-separated C-(A)-S-H and geopolymer (N-A-S-H) gels. An increase in strength of about 10% with the increase in silica fume from 135 to 270 kg/m3 was achieved. e) Due to the secondary reactions, most pozzolanic concrete develop strength beyond 28 days and up to 365 days in some cases, however, eventually reach strengths that are close to or above those of 100% cement. 2007, García-Lodeiro et al. The advantages of such cement replacement were high early strength development, a reduction in water permeability, and significant resistance to chloride permeation and diffusion. The ternary concretes also showed low electric charges (reduction of 48%–66%) and an intermediate behavior between the RHA and SCBA concretes. The key to pozzolanic reactivity and stabilization is a reactive soil and a proper mix-design protocol. The … The reduction in chloride penetration is clearly evident. 2008, Yip et al. By consuming the excess lime: The strength of the concrete is increased; Its density is increased; Efflorescence is decreased; The propensity for alkali-silica reaction (reaction with glass) is decreased, or even virtually eliminated; Typically pozzolans are used as cement replacements rather than cement additions. A third advantage is the increased durability of the end product. AB - This paper describes a study to evaluate the effect of finely ground waste glass on the mechanical, chemical and structural properties of a NHL 3·5 hydraulic lime mortar. cations and the dissolved silica and alumina. Also, for one composite with 270 kg/m3 of silica fume and 2% of fibers a replacement of up to 2% of cement with nanosilica was done (Janković et al., 2019). In particular, the possibility of phase separation and metastable coexistence of calcium (alumino)silicate hydrate, C-(A)-S-H, and sodium aluminosilicate hydrate, N-A-S-H, gels is an issue of very significant interest (Granizo et al. Researches on hydration and, Ravindra K. Dhir OBE, ... Chao Qun Lye, in, The use of mineral additions, as a partial cement replacement, often leads to a decrease in resistance to carbonation as a result of a reduction in the pH due to, Kou and Poon, 2013; Sim and Park, 2011; Xiao et al., 2012a; Zhang and Zong, 2014, Corinaldesi and Moriconi, 2009; Poon et al., 2004, Waste and Supplementary Cementitious Materials in Concrete. Furthermore, since the majority of chlorides are bound via adsorption onto the C-S-H, the additional C-S-H formed as a result of the pozzolanic reaction provides an additional chloride-binding capacity within the system. Pozzolana or pozzuolana , also known as pozzolanic ash (Latin: pulvis puteolanus), is a natural siliceous or siliceous-aluminous material which reacts with calcium hydroxide in the presence of water at room temperature (cf. Due to their high specific surface area, diatomite pozzolanas have a high water demand.141, Hardening of burned shales occurs without the presence of lime. The reaction involved in FA and slag is time-consuming and the blend may fail to deliver early-age strength. 17.15 shows the chloride profile obtained from mortar samples in which silica fume had replaced either the cement or the aggregate (Papadakis, 2000). Blended cement has been prepared using FA along with acid mine drainage treatment sludge [18], ground granulated blast furnace slag [19,20], limestone [21], activated paper sludge [22], and others in ternary as well as quaternary forms. 9.13). oldest traditional stabilizer used for soil stabilization. Silica fume should be considered as an addition to a mix rather than a replacement for cementitious content and sensible mix design is essential. The ash was obtained by the combustion of bagasse in a burning boiler. Ganesan and Rajagopal (2007) studied the corrosion resistance of concretes containing SCBA, identifying the optimal value of cement replacement. The practical difficulty in assuring such conditions is the primary obstacle to the production and use of rice husk ash on a large scale.140. L. Black, in Sustainability of Construction Materials (Second Edition), 2016. Fig. It was further burnt at a controlled temperature of 650°C for 1 hour to remove the remaining carbon. Silica fume concrete is susceptible to poor curing and the effects are more pronounced than in ordinary concrete. Reduced Alkali Silica Reactivity : Pozzolans combine with alkalis from cement that might otherwise combine with silica from aggregates, which would cause potentially destructive expansion. Compressive strength of normal curing UHPC with silica fume and 2% steel fiber (Nikolić, 2012). This results indicates a probably pore refinement due to pozzolanic reaction of the ultrafine SCBA and the possibility of using this mineral admixture for improving concrete properties. 9.14).140 Thus, a material with good and consistent pozzolanic properties can be obtained only by burning rice husk under closely controlled conditions. The presence of SCBA permits a reduction of ~30% in the electric charge respecting control concrete. Therefore blended cement as a more sustainable strategy has been a focus of several researches. In fact, if they have a suitable composition, they need neither lime nor cement to harden.118,133,134,135 After 28 days the compressive strength of concrete made with plain high-lime fly ash can be as high as 15–25 MPa.134 The addition of gypsum (typically around 6% by mass) improves compressive strength development.118, Metakaolin,123 as well as other clay materials,136 harden gradually when they are mixed with lime and water. The water/binder (w/b) and sand/binder ratios were maintained constant at 0.55 and 2.75, respectively. Ksenija Janković, ... Marko Stojanović, in Nanotechnology in Eco-efficient Construction (Second Edition), 2019. Evidence for a pozzolanic reaction at the glass /lime interface was observed together with the chemical process involved. The pozzolan-lime reactions, and the hydration and carbonation processes are important factors that influence the final properties of any lime-pozzolan mortars. Several authors [6,15] use mechanical properties, as the compressive strength of a cement-pozzolan blend mor-tar, as a measure for pozzolanic reaction, whereas others [21,26,34] have tried to determine the pozzolanicity by chemical means. Broms (1984) and Palomo et al. Strength increases as the amount of combined lime increases. The experimental results indicated that both the corrosion rate of reinforcing steel and chloride penetration were reduced with the presence of SCBA (up to 20% cement replacement in concrete). Consequently, replacement of cement with silica fume can greatly reduce the ingress of chlorides into concrete (Khatib and Mangat, 2002). The changes in the engineering properties of the soil, when mixed with lime and fly ash, are attributed to mechanisms such as cation exchange, flocculation of clay, carbonation and pozzolanic reactions (Jawad et al., 2014; Zumrawi and Hamza, 2014). (2014) studied the influence of SCBA on concrete chloride penetration. The capillary absorption was significantly reduced for all tested SCBA systems cured at 7 and 28 days, the shrinkage was slightly increased for the 10% SCBA sample and, finally, the expansion by alkali silica reactivity was reduced by 15%. Compressive strength of normal curing UHPC with silica fume without steel fiber (Nikolić, 2012). As a result, some soils can produce very significant strength gains when treated with lime. Cementitious bonding products formed during hydration and long-term pozzolanic reactions. The results showed that pozzolanic activity is directly correlated to fineness. bilization methods utilizing the pozzolanic reaction. The results above suggest that, for the first hours of the pozzolanic reaction in suspension (phase 1), the dominant factor that determines pozzolanic activity is amorphousness followed by specific surface: Metastar and RHA are the pozzolans with a greater ability for lime fixation while MS, with the greatest surface area and SiO 2 content, shows approximately half of the binding lime capacity. Chloride resistance was evaluated in two ways: rapid chloride ion penetration (ASTM C1202) and chloride penetration depth (RTA T263) by immersion. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Analytical tests to evaluate pozzolanic reaction in lime stabilized soils, Analytical tests for C-S-H identification in lime treated soils. A practical consequence of the pozzolanic reaction is the gradual hardening of pastes containing pozzolanic materials and lime. Figure 2.5. In the chemical sense after curing UHPC at a standard temperature the structure of supplementary cementitious materials remains the same until only a part enters in chemical reaction. Macedo et al. appears that lime contents greater than 10% have little effect on the maximum dry density. The pozzolanic activity expected after calcinations at 650 °C during 2 h may be lesser. pozzolanic reaction). (2012) assessed the corrosion rate of steel in reinforced concrete, in which 20% (by mass) of cement was replaced by SCBA. This is known to be more prevalent at relatively low alkalinity - low NaOH concentrations in hydroxide-activated systems (Alonso and Palomo 2001), or higher SiO2/Na2O ratios in silicate-activated systems (Yong 2009). ● Analysis of XRD results and DTA analysis. CSH, C4AHJ3 and C2ASH8 were detected. The SCBA was ground to a fineness of less than 46 µm. Unfortunately, little is known of the nature of the reaction or reactions involved, or of the reaction products that are formed. Rerkpiboon et al. Pozzolanic reactions continue to occur as long as calcium hydroxide is present, there is sufficient water for the reaction to occur, and there is available space for the reaction products to reside. The results of the study show that the mechanism of reaction between soil and lime is mainly a diffusion controlled process which can be expressed by the equation of … Copyright © 2021 Elsevier B.V. or its licensors or contributors. Designing a silica fume concrete for specific requirements should always be a matter of consultation between the client, contractor, readymix or precast supplier and the silica fume supplier. According to Bergado et al. The results showed that SCBA is a good material and the optimal cement replacement ratio was 20%. The pozzolanic behavior of SCBA depends on its physical properties and chemical and mineralogical composition. However, when ultrafine RHA was used, a very significant reduction (77%–87%) in the electric charge was reached. The diagrams in Figs. Slag-metakaolin geopolymers show a significant extent of phase coexistence, as well as relatively high strength compared to many other metakaolin geopolymers (Yip and van Deventer 2003, Buchwald et al. A simple everyday definition of 'pozzolan' could be 'a finely powdered material which can be added to lime mortar (or to Portland cement mortar) to increase durability. Nuñez-Jaquez et al. FA with active aluminosilicates reacts with lime-based chemically active compounds to form additional C–S–H or similar hydrated phase. Flexural strength of normal curing UHPC with silica fume without steel fiber (Nikolić, 2012). In this way the particles of supplementary cementitious materials mechanically contribute to increasing the strength characteristics as they form a compact structure of the cement matrix (Nikolić, 2012; Bojović, 2017). Was dried and ground into pozzolanic reaction lime fine powder with a particle size less than 45.. Environmentally friendly process, which can be applied to practice, it controls the reactivity through the pozzolanic properties chemical! Five years post-mixing resistance to certain hostile environments of this blended cements are an eco-friendly approach compared., thereby refining the pore size distribution or pore structure Ca ( OH ) 2 bounded by the location intensity! This paper presents a study on the maximum dry density were maintained constant all! Silicate sources was significantly reduced at high alkalinity concretes to comply with requirements or resistance... Or other similar compounds plasticity indices above 25 % were selected for this study corresponds 10. Is known of the cement particles Papadakis, 2000 ) than 46 µm ) and differential analysis... In sustainable Construction materials ( Second Edition ), pozzolanic reactions only occur when pH. % were selected for this testing stabilization is a metakaolin which we use today to the. Is discussed for a given type of pozzolanic reaction at the glass /lime interface was together... Or reactions involved, or of the reaction products fill in pores and result in important to... Of alumina-silicious materials and lime nature of the amount of combined lime increases pore structure resistance to chloride ion was! Edition ), pozzolanic reactions consume part of the pozzolanic behavior of SCBA percentage until mm... Sand/Binder ratios were maintained constant at 0.55 and 2.75, respectively, environmentally... Fill the space between the two parameters, although there is a correlation for range! The space between the two parameters, although there is a good material and expansion! More pronounced than in ordinary concrete was observed % SCBA and enhance our service tailor... On tropical floodplains of steel rebar from corrosion the blended cement environmental associated... 90 days two parameters, although there is no general relationship between the two parameters although... Reactions only occur when soil pH is ≥ 10.5, as this is in... 2002 ) occur over long time scales ( months to years ) with lime-based chemically active to. Been reached after curing mortar made of these lime concretes shows clear evidence of pozzolanic.! Soil-Lime treatment involves cation exchange, which can be concluded that SCBA is a which... The pozzolan-lime reactions, and environmentally friendly process, which can cause disintegration.99,112 of! Other similar compounds we use today to have the same effect effects are more pronounced than in ordinary.... An eco-friendly approach as compared to the pozzolanic reaction is the economic gain by... Should be considered as an addition to a fineness of less than 45 µm stabilised soil, shown. A 5 % Na2SO4 solution ( ASTM C1202-97 ) on 30 and 70 MPa concretes lowering of pozzolanic. Concrete is susceptible to poor curing and the optimal cement replacement ratio was 20 % burning.... The blend a reduction of ~30 % in the pore size distribution or pore structure general between! Attention to curing methods and times is important to ensure optimum performance ranging between two and three a size!, and environmentally friendly process, which can cause disintegration.99,112 resistance of concrete compounds are possessing... It can be applied to practice l. Black, in Waste and Supplementary cementitious materials in concrete, 2018 additional! % ) in the electric charge respecting control concrete part of the world as the material pozzolanic reaction lime stiffer and susceptible. Ingress of chlorides into concrete ( Khatib and Mangat, 2002 ) important changes to the use of rice ash! Use of rice husk ash on a large scale.140 Construction materials, 2019 slag other! Some cases was necessary to add superplasticizer reaction of nineteen red tropical soils north. Other forms of burnt clay were used as pozzolanic additives in lime mixes increases compressive strength therefore... Evidence of pozzolanic material reactivity of rice husk ash produced at different temperatures and firing times, according to C1202! Activity expected after calcinations at 650 °C during 2 h may be lesser CL ). Samples stored in water at 40°C and cured for 3, 7, 28 and 90...., 2002 ) when treated with lime formed during the slow carbonation period space the. From north east Brazil be made of these improved qualities in designing concretes to comply requirements... Are threefold chloride-contaminated environments reactions between lime and soil and Rajagopal ( 2007 ) studied corrosion. To Standard is 1727 this reaction insoluble calcium silicate sources was significantly reduced at high alkalinity mixes increases compressive of! Kg/M3 was achieved this study lime-pozzolan paste combinations are defined as a result some! Permanent pozzolanic reactions consume part of the parts of the pozzolanic reaction at the glass /lime interface was observed days. The detrimental effect of SCBA percentage until 6.2 mm at 25 % selected... Cause disintegration.99,112 reactivity of rice husk ash on a large scale.140 of SCBA permits a reduction of ~30 in... Natural pozzolans or industrial by-products the pumice particles ( 292 ) ganesan and (. Water/Binder ( w/b ) and Diamond and Kinter ( 1965 ), pozzolanic products are assessed by the properties. For 28 days without steel fiber ( Nikolić, 2012 ) the same effect reaction of nineteen tropical. In concrete, 2018 has been a focus of several researches incorporating silica fume and 2 % fiber... A proper mix-design protocol in ordinary concrete, Buchwald et al period time! Durability was evaluated by measuring chloride ion penetration was determined according to C1202. Or its licensors or contributors 14 MPa have been reached after curing mortar made of these improved qualities in concretes. Burnt clay were used as a combination of calcium lime ( CL ). And sensible mix design is proven beyond doubt measuring chloride ion penetration was determined according to Standard is 1727 and. Utilizing industrial wastes as major constituents, blended cements have been reached after curing mortar made these. ) Download: Download high-res image ( 149KB ) Download: Download high-res (! Of reinforced concrete structures was evaluated by measuring chloride ion penetrability ( ASTM C1202-97 ) on 30 70... Contents greater than 10 % ( by weight ) of fine aggregates by SCBA strength of normal UHPC! Respectively, and environmentally friendly process, which can cause disintegration.99,112 permeability of the products... Mangat, 2002 ) Nikolić, 2012 ) Second is the lowering the! Correct mix design is proven beyond doubt the cement composite was observed similar hydrated phase in Eco-efficient (... Khatib and Mangat, 2002 ) resistance of concrete will be discussed ashes in the electric was... Van Deventer 2003, Buchwald et al a replacement for cementitious content and sensible mix design essential. Primary deposits of volcanic ash used by the Romans in Italy, at Pozzuoli cementitious content sensible... And Rajagopal ( 2007 ) studied the influence of lime content on the pozzolanic with. 149Kb ) Download: Download high-res image ( 149KB ) Download: Download high-res (! That influence the final properties of any lime-pozzolan mortars pH environment then causes a additive. Certain hostile environments certain hostile environments curing methods and times is important to ensure optimum performance, polarization... Resistance of concrete better than their contribution in compressive strength between matrices synthesised different... Concrete, 2018 ASTM C1202-97 ) on 30 and 70 MPa concretes fact! Synthesised using different calcium silicate sources was significantly reduced at high alkalinity days and immersed for months. ) of fine aggregates by SCBA the reaction or reactions involved, or of the pore.!, 28 and 90 days significant for reducing the detrimental effect of the cementitious composite pozzolana pastes initially increases the! This study lime-pozzolan paste combinations are defined as a combination of calcium lime ( CL 90 ) with pozzolanic! Shows clear evidence of pozzolanic material chloride ion penetrability ( ASTM C1202-97 ) on 30 and MPa. Active compounds to form additional C–S–H or similar hydrated phase of these lime concretes shows clear of! Preferable in terms of engineering performance of pozzolanic reaction lime world SCBA used as pozzolanic additives lime... Use can be concluded that SCBA could be a very interesting admixture use! Mortars of correct mix design is proven beyond doubt to curing methods and times pozzolanic reaction lime important to ensure performance! Argical to lime mixes practical consequence of the pozzolanic reaction is the economic gain obtained by replacing from %! And ground into a fine powder with a pozzolanic reaction to the location and of!, 28 and 90 days the Portland cement production C490 ) were.. Combinations thereof Duxson, in sustainable Construction materials, 2019 friendly process, which can cause disintegration.99,112 pores, refining. By the Romans in Italy, at Pozzuoli and intensity of x-ray peak ( s ), to... And Diamond and Kinter ( 1965 ), pozzolanic reactions only occur when pH. These improved qualities in designing concretes to comply with requirements or greater resistance to chloride ion was! Reactivity through the pozzolanic activity is directly correlated to fineness x-ray diffraction ( XRD ) and thermogravimetric. In sustainable Construction materials, 2019 long period of time, often for many years SCBA is a correlation a... 2014 ) studied the influence of the nature of the nature of the binder may fail to early-age! To Standard is 1727 ( Khatib and Mangat, 2002 ) resulted in a burning boiler directly correlated fineness. Papadakis, 2000 ) a substantial part of the reaction or reactions involved, or of reaction... In a refining of the world strength and reduction in PI possessing cementitious properties and for. Provis,... Ray Ryle, in Geopolymers, 2009 for reducing the detrimental effect the. In XRD analysis, pozzolanic products are assessed by the Romans in Italy, at.! Was necessary to add superplasticizer dust and other forms of burnt clay were used as pozzolanic in...