Concretes containing SCBA were exposed to alternative dry–wet cycles in 3% NaCl solution for 18 months to study the corrosion behavior of carbon steel. The results are significant for reducing the detrimental effect of the leaching-induced deterioration of flexible pavements founded on tropical floodplains. bilization methods utilizing the pozzolanic reaction. (2012) assessed the corrosion rate of steel in reinforced concrete, in which 20% (by mass) of cement was replaced by SCBA. Studies indicate that blended cement performs comparably to OPC and indicate the optimum proportion of the blend. 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. This behavior was due to the pozzolanic activity that produces a refinement in the pore size distribution compared to the control concretes. 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). L. Black, in Sustainability of Construction Materials (Second Edition), 2016. However, the introduction of an additional alkali source, as is the case in calcium-containing metakaolin geopolymers, introduces additional complexity into the range of phases that can form in this reaction system. The quantification of the kinetics of lime/clay interactions is, therefore, a key step to optimize soil stabilization but also to estimate their durability on the long term. If it is assumed that the reaction of Pozzolan and lime produces the same hydration products as cement consider the following reaction: 3 [ Ca(OH) 2) ] + 2 [ SiO 2] = [ 3(CaO) 2(SiO 2) 3(H 2O) ] (1) 222 120 = 342 In this reaction 222 parts lime reacts with 120 parts silica for a mass ratio of 222/120 = 1.85. 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). The most recent and important studies regarding the effect of SCBA on the durability of concrete will be discussed. As with Portland cement, this hydration reaction produces free lime. However, heterogeneous soil chemistry and mineralogy may result in important changes to the nature of reactions between lime and soil. The strength of lime–natural pozzolana pastes initially increases with the lime/pozzolana ratio, but eventually decreases127,128 (Fig. An increase in strength of about 10% with the increase in silica fume from 135 to 270 kg/m3 was achieved. (2008) found that the replacement of 20% of the metakaolin in a geopolymer mix had varying effects depending on the specific nature of the calcium silicate source and also the alkalinity of the geopolymer-forming system. Specifically, x-ray diffraction (XRD) and differential thermogravimetric analysis (DTA) are used for this testing. This is preferable in terms of engineering performance of the stabilised soil, as the material becomes stiffer and less susceptible to volume shrinkage/swelling. (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. The corrosion rate using the linear polarization technique exhibited a seven times decrease compared to the control concrete for the system with 10% cement replacement by SCBA. Lime-treated soil 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). Whereas permanent pozzolanic reactions occurred at lime contents above the LSO and thus resulted in a 45-fold increase in strength and durability. Argical M-1000 is a metakaolin which we use today to have the same effect. The advantages and disadvantages of CSMs as the ground stabilizing agent are succinctly pre… The pozzolan-lime reactions, and the hydration and carbonation processes are important factors that influence the final properties of any lime-pozzolan mortars. 2.1 and 2.2 show the effect of increasing the compressive strength on UHPC which is cured at a standard temperature with 2% fibers and without fibers. 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URL: https://www.sciencedirect.com/science/article/pii/B9781782422761500216, URL: https://www.sciencedirect.com/science/article/pii/B9780081007730000095, URL: https://www.sciencedirect.com/science/article/pii/B9780128189610000211, URL: https://www.sciencedirect.com/science/article/pii/B9780081003701000172, URL: https://www.sciencedirect.com/science/article/pii/B9781845694494500059, URL: https://www.sciencedirect.com/science/article/pii/B9780750656863502792, URL: https://www.sciencedirect.com/science/article/pii/B9780081026410000025, URL: https://www.sciencedirect.com/science/article/pii/B9780081009857000108, URL: https://www.sciencedirect.com/science/article/pii/B9780081021569000171, Developments in the Formulation and Reinforcement of Concrete (Second Edition), 2019, The development of alkali-activated mixtures for soil stabilisation, Handbook of Alkali-Activated Cements, Mortars and Concretes, Michael John McCarthy, Thomas Daniel Dyer, in, Lea's Chemistry of Cement and Concrete (Fifth Edition), Use of fly ash for the development of sustainable construction materials, Low clinker cement as a sustainable construction material, Sustainability of Construction Materials (Second Edition), The refined pore structure induced in concrete containing silica fume as a result of the, Nanostructure/microstructure of metakaolin geopolymers, The calcium hydroxide-metakaolin system is in itself of interest as a means of analysing the, Influence of nanoparticles on the strength of ultra-high performance concrete, Ksenija Janković, ... Marko Stojanović, in, Nanotechnology in Eco-efficient Construction (Second Edition), Standard room temperature curing is the most common, economical, and environmentally friendly process, which can be applied to practice. pozzolanic reaction). 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. Figure 2.1. 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. 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. Ravindra K. Dhir OBE, ... Chao Qun Lye, in Sustainable Construction Materials, 2019. These improvements had a direct implication on the durability of reinforced concrete structures. Ganesan et al. These pozzolanic reaction products fill in pores and result in a refining of the pore size distribution or pore structure. Use can be made of these improved qualities in designing concretes to comply with requirements or greater resistance to certain hostile environments. At low alkalinity, the compressive strength of geopolymer matrices prepared with predominantly amorphous calcium silicates (blast furnace slag) or containing crystalline phases specifically manufactured for reactivity (cement) was much higher than when the calcium was supplied as crystalline silicate minerals. Nuñez-Jaquez et al. (1965), pozzolanic reactions only occur when soil pH is ≥ 10.5, as this is when SiO2 and Al2O3 become soluble. 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. The high pH environment then causes a pozzolanic reaction between the free Ca +2. In literature this phenomenon is called particle packing model or microfiller effect and is similar to a small aggregate packing model in the pores of a large aggregate. The results obtained confirmed that SCBA used as a partial replacement of cement in concretes improves the protection of steel rebar from corrosion. Concrete durability was evaluated by measuring chloride ion penetrability (ASTM C1202-97) on 30 and 70 MPa concretes. Copyright © 2021 Elsevier B.V. or its licensors or contributors. 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. Cordeiro et al. Fig. 9.12, there is no general relationship between the two parameters, although there is a correlation for a given type of pozzolanic material. 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). Copyright © 2021 Elsevier B.V. or its licensors or contributors. A decrease of expansion was observed with increasing ash content (0.0361% for control concrete and 0.0167 for concrete with 50% GBA). Fig. Ganesan and Rajagopal (2007) studied the corrosion resistance of concretes containing SCBA, identifying the optimal value of cement replacement. appears that lime contents greater than 10% have little effect on the maximum dry density. In order to obtain the SCBA, the bagasse was burnt in boilers at a temperature between 900°C and 1100°C. Concrete with SCBA showed two to three times higher resistance to chloride ion penetration than the control concrete after 28 and 90 days of curing. ● Analysis of XRD results and DTA analysis. Published by Elsevier B.V. https://doi.org/10.1016/j.mex.2020.100928. The refined pore structure induced in concrete containing silica fume as a result of the pozzolanic reaction and densification of the cement matrix leads to a marked reduction in permeability. The difference in compressive strength between matrices synthesised using different calcium silicate sources was significantly reduced at high alkalinity. Table 9.10. For this reason the technical assessment of pozzolanic materials requires the measurement of strength development in the presence of lime or PC, rather than determination of the amount of fixed lime present. 2007). The compressive strength achieved by rice husk ash/lime mixes depends on the ash:lime ratio, with optimum performance typically observed between ratios of 1:1 and 1.5:1. Figure 21.5. The advantages of such cement replacement were high early strength development, a reduction in water permeability, and significant resistance to chloride permeation and diffusion. 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. Lime reactivity of rice husk ash produced at different temperatures and firing times, according to Standard IS 1727. Cordeiro et al. A characteristic advantage of FA utilization is its pozzolanic reaction with lime formed during the hydration of cement. 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). 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