Influence of Pozzolanic Additions on Durability of Reinforced Concrete Structures

Bertolini, L. Dipartimento di Chimica, Materiali e Ingegneria Chimica “G. Natta”, Politecnico di Milano (email: [email protected]) Carsana, M. Dipartimento di Chimica, Materiali e Ingegneria Chimica “G. Natta”, Politecnico di Milano (email: [email protected]) Frassoni, M. Holcim Italia SpA (email: [email protected]) Gelli, M. Istituto Italiano per il calcestruzzo (email: [email protected])

Abstract

Pozzolanic additions, used for partial replacement of portland cement clinker, generate an hydrated cement paste that, after suitable curing, shows a lower porosity and a refinement of the capillary pore structure. Consequently, these additions can improve the strength and durability of concrete structures. Most of pozzolanas used nowadays are residues of industrial processes and their use in concrete technology has the twofold advantage of enhancing the performance of concrete structures and improving the sustainability of the cement and concrete industries. For this reason, there is a great interest in studying the behaviour of new materials with potential pozzolanic activity. With this regard, tests procedures that allow to evaluate the beneficial effects of mineral additions in relation to concrete performance should be developed. Several tests have been proposed in the literature to assess different aspects of the pozzolanic behaviour of mineral additions, but these often do not give the same results when used to compare various additions.

This paper presents the results of a research aimed at the evaluation of the pozzolanic behaviour of different additions, such as natural pozzolanas, industrial residues (fly ash, silica fume) and recycled materials (grounded glass). For comparison, also inert additions of ground limestone and quartz were considered. The effect of fineness was studied by testing materials with different surface area. The potential pozzolanic behaviour was studied by means of chemical analysis and the Fratini test. The effects of the pozzolanic reaction was evaluated on mortar specimens, by studying the strength, the electrical resistivity, and the resistance to chloride penetration and sulphate attack. Compressive tests were also carried out on lime-pozzolana mortars. The paper compares the behaviour of the mineral additions and the results of different methods of testing.

Keywords: sustainability, durability, reinforced concrete, chloride, sulphate

252 1. Introduction

Pozzolanic additions, used as a partial replacement of portland cement contribute to the hydration of the cement paste, which, after a proper curing, shows a low capillary porosity and a refinement of the pore structure. Consequently, these mineral additions can improve the strength and durability of reinforced concrete (RC) structures (Bertolini et al., 2004). Specifically, pozzolanic additions may delay the penetration of ionic species through the concrete, thus preventing effects of sulphate attack of concrete and corrosion of embedded steel induced by chlorides. Most of the pozzalanic additions used nowadays are residues of industrial processes and their use in the concrete industry has the twofold beneficial effect of improving the durability of RC structures, due to the higher resistance of concrete to chloride penetration, and favouring a sustainable development of the cement and concrete industries (Bertolini et al., 2004, Neville, 1995). For these reasons, there is an increasing interest in the study of the behaviour of materials with pozzolanic behaviour, and tests aimed at the evaluation of the beneficial effects of these materials are needed. In the literature, different experimental procedures have been proposed with the aim of investigating the pozzolanic behaviour of mineral additions (Massazza, 1998), but sometimes they provide conflicting results when they are applied to different materials. This paper describes the results of an experimental study aimed at the comparison of the behaviour of different mineral additions with pozzolanic properties by means of different types of tests.

2. Experimental

Table 1 summarizes the mineral additions used for the tests and the designation adopted in this paper to identify them. Two natural pozzolanas from the centre of Italy were used, and they were identified by their colour, i.e. respectively red and black pozzolana (R-Pz and B-Pz). A silica fume (SF) and a coal fly ash (FA) were used as traditional wastes with pozzolanic behaviour. Also a green glass (G- Gl) obtained by grinding recycled bottles was considered as a possible innovative pozzolanic addition. Finally, a limestone filler (L), with maximum size of the particles of 100 m, and a quartz sand (QS) were studied, in order to have reference values for inert additions. To study the effect of the particle size, some of the mineral additions were grounded to different levels of fineness, in order to obtain a target specific surface of about 400 and 600 m2/kg. A portland cement of type CEM I 52,5R according to EN 197-1 standard was used as reference cement (CE).

Different standardized test procedures were used in order to characterise the mineral additions. Chemical composition of the additions and the reference cement was studied with X-ray fluorescence spectrography (XRF), and it was expressed as percentage by mass of oxides. Then the additions were characterised by means of XRD analysis, using a X-ray diffractometer with CuK radiation and scanning rate of 2.4°/min. The pozzolanicity test (also named Fratini test) proposed by EN 196-5 standard for pozzolanic cement was also conducted. The test was performed on blends obtained by mixing 70% of the reference cement and 30% of the mineral addition. According to this test, the pozzolanic behaviour was evaluated by the ratio between the quantity of calcium hydroxide

(Ca(OH)2) required to saturate an aqueous solution in contact with the blend cement and the quantity

253 of Ca(OH)2 required to saturate a solution of the reference portland cement. The fineness of the mineral additions was evaluated by means of grading curves obtained by laser granulometry. The specific surface was then calculated from the grading curve. The specific surface was measured by means of the Blaine test (see EN 196-6 standard) as well.

Standard cement-pozzolana mortars were cast according to EN 196-1 standard. Blends of the reference cement with 30% by mass of the mineral additions (10% for silica fume) were used as binders. Compressive strength was measured on 40x40x160 mm3 prisms following the standard procedure of EN 197-1 standard. Specimens were wet cured (immersed in water) for different periods of time. Similar tests were also carried out on lime-pozzolana mortars, made with a binder obtained by blending lime and the mineral additions, at the same curing time. Electrical resistivity of cement mortars was monitored during curing on the immersed specimens.

Tests were carried out to asses role of the mineral additions on the resistance of the cement-pozzolana mortars to the penetration of chloride and sulphate ions. The resistance to the penetration of chlorides was studied using cylinder specimens with height of 60 mm and diameter of 100 mm, following the procedure proposed by NT Build 443 standard. After 28 days of wet curing, the side surface and one of the flat surfaces of the cylinders were masked with epoxy. Then the specimens were immersed for 35 days in a solution with 165 g/L of NaCl. Chloride profiles were measured on powder samples ground at different depth, which were digested in nitric acid and analysed by potentiometric titration with silver nitrate. Sulphate resistance was evaluated on prism specimens (25 25 280 mm3) immersed in 5%Na2SO4 according to ASTM C1012-95a standard. The length of the specimens was monitored with a precision of 1 m throughout the immersion period, in order to detect the expansion in time of the specimens.

Table 1: Designation and activity index from Fratini test of the mineral additions

Mineral addition Grinding Designation Activity index Red natural pozzolana ~ 400 m2/kg R-Pz4 0.8 ~ 600 m2/kg R-Pz6 0.75 Black natural pozzolana ~ 400 m2/kg B-Pz4 0.70 ~ 600 m2/kg B-Pz6 0.86 Coal fly ash none FA 0.67 Silica fume none SF - Green glass ~ 400 m2/kg G-Gl-4 0.51 ~ 600 m2/kg G-Gl-6 0.32 Limestone filler none L - Quartz sand ~ 400 m2/kg QS 1.54

254 3. Results and discussion

3.1 Characterization of mineral additions

The first requisite for a mineral addition to have a pozzolanic behaviour is the presence of silica compounds. Figure 1 plots the composition of the additions on a ternary diagram and shows that green glass (G-Gl), silica fume (SF) and quartz sand (QS) are characterised by a high silica content (ranging from 68.6% to 96.7% by mass). CaO content is comparable for green glass and silica fume (respectively 11.3% and 10.1%), while it is lower for quartz sand (1.1%). Natural pozzolanas (R-Pz,

B-Pz) and coal fly ash (FA) show a similar composition, characterised by a major content of SiO2 and

Al2O3 and low content of CaO.

Besides the presence of high amount of SiO2 and Al2O3, an amorphous structure is required for a mineral addition to have a pozzolanic behaviour. XRD analysis is useful to discriminate between crystalline and amorphous substances. For instance, Figure 2 compares the XRD analyses of quartz sand and green glass. The amorphous nature of the former compared to the crystalline nature of the latter is clearly evident.

The reactivity of an addition also depends on its fineness, which is measured by the particle size distribution or the specific surface. Figure 3 shows, as an example, the particle size distribution of some selected additions.

To study the pozzolanic reactivity of the mineral addition the pozzolanicity tests proposed in the fifties by Fratini was carried out (Figure 4).

CE SiO2 R-Pz B-Pz FA SF QS G-Gl L

CaO Al2O3

Figure 1: Chemical composition of the tested materials plotted on a ternary diagram

255

Figure 2: XRD analyses of quartz sand (QS) and green glass (G-Gl)

100 FA 90 CE 80 G-Gl-4 70 G-Gl-6 60 50

40 Passing(%) 30 20 10 0 1 10 100 Size ( m)

Figure 3: Particle size distribution of G-Gl-4, G-Gl-6, FA mineral additions and CE (cement)

This test is based on the ability of the mineral addition to consume the calcium hydroxide produced by the hydration of the clinker of Portland cement, namely due to the pozzolanic reaction: pozzolana

+ Ca(OH)2 + H2O C-S-H. Blends of 70% of portland cement and 30% of mineral additions were immersed in an aqueous solution for 8 days. The higher is the quantity of lime consumed by the pozzolanic reaction, the lower is the concentration of hydroxyl ions (OH-) found in the testing solution. The dashed line in Figure 4 is the saturation curve for portland cement proposed by EN 196- 5 standard. An activity index was calculated for each addition from this graph as the ratio between the concentrations of calcium ions (expressed as CaO) in the test solution of the specimen with the blend of 70% portland cement and 30% mineral addition and the concentration of calcium ions on the saturation curve correspondent to the concentration of OH- ions found in the tested sample.

256 25 R-Pz 4 Saturation R-Pz 6 20 curve B-Pz 4 (EN 196-5) B-Pz 6 15 G-Gl 4 G-Gl 6 10 FA

mmol/l CaO mmol/l CaO QS

5

0 20 40 60 80 100 120 mmol/l OH-

Figure 4: Results of pozzolanicity tests

All the pozzolanic additions (i.e. except ground quartz sand) have an index lower than 1 (Table 1), but the index is influenced by the type of addition and its fineness. For instance, the index of the red pozzolana increased from 0.80 to 0.75 when the fineness increased from about 400 m2/kg (R-Pz4) to about 600 m2/kg (R-Pz6), suggesting a higher reactivity of the latter. Surprisingly, the lowest values of this index, corresponding to potentially higher pozzolanic reactivity, were found for the ground green glass. The index had values of 0.51 and 0.32 for fineness values of 400 m2/kg and 600 m2/kg respectively.

3.2 Characterization of mortars with mineral additions

The compressive tests on the mortars made with a binder obtained by replacing 30% of the reference cement with the different mineral additions (only 10% of cement was replaced in the case of silica fume) was compared to the strength of the reference mortar (CE). Mortars with mineral additions were designated by the letter M followed by the name of the addition used to replace the reference cement. The effect of the mineral addition may be evaluated through a pozzolanic reactivity index (P.R.I.) that is calculated as the ratio between the compressive strength of a mortar obtained with the cement blended with the mineral addition (Rpoz) and the strength of a mortar made with the reference cement only (RCE). Figure 5 shows the values of P.R.I. determined after 28 days and 6 months of curing, as a function of the mineral addition and its specific surface (for CE, L, QS and SF P.R.I. values were plotted on the left or right axes by means of an horizontal line). P.R.I. values higher than 100% were reached even at 28 days of wet curing by the mortar with 10% of silica fume (MSF). This result has to be attributed to the well known high reactivity as well as possible filler effect of this extremely fine addition (ACI, 1996). The mortar with limestone (ML) shows a P.R.I. just above 55%; the performance of the mortars with fly ash and ground quartz sand (respectively equal to 75% e 76%) are comparable. P.R.I measured for mortars with green glass (respectively equal to 80% for MG-Gl-4 and 86% for MG-Gl-6) is comparable with those of mortars with black pozzolana

257 (respectively 80% for MB-Pz-4 and 84% for MB-Pz-6). The performance of mortars with red pozzolana are lower than those with black pozzolana; in fact, indexes of 78% and 83%, respectively for MR-Pz-4 and MR-Pz-6, were measured. The different behaviour in relation to the fineness of mortars with pozzolanic additions can be observed: reactivity of mortars with green glass and natural pozzolanic coarsely ground is lower than the same additions finely ground (Shao and Leoux, 2001). Prolonged curing allows a significant increase in term of P.R.I., especially for the mortars with ground glass which had strength values slightly higher than the reference mortar. A good behaviour could be observed for the mortars with fly that showed a P.R.I. index of 92%.

By comparing mortars with the same addition but different fineness, it can be observed that the role of fineness becomes less evident after long curing; for example, the mortars with red pozzolana, grounded at 400 e 600 m2/kg (R-Pz-4 e R-Pz-6), reach comparable values of P.R.I after six months of curing, equal respectively to 87 e 91%.

Since the pozzolanic reaction occurs in the presence of lime, mortar specimens were also made by mixing each addition with hydrated lime, in order to measure directly their reactivity. Figure 6 shows that the compressive strength of lime-pozzolana mortars can be correlated to that of cement- pozzolana mortars, at the same curing time (1 and 12 months). The results of tests on specimens of lime-pozzolana mortars show that, in general, the strength of the mortar improves as the additions are more finely grounded, especially for long curing, beyond 28 days. After one year of curing, lime- mortars achieved rather high strength, especially those made with the natural pozzolana more finely grounded (e.g. compressive strength equal to 13.9-15.8 MPa was measured on MR-Pz-6 and 12.2- 12.6 MPa on MB-Pz6) and with fly ash. In particular, it can be observed that the lime-mortar with fly ash achieved a compressive strength of about 20 MPa after 12-month curing, despite this mortar had at early curing (28 days) a strength lower than the mortars with other pozzolanic additions.

120 120

110 110 MCE MSF MC 100 100

90 90

80 MQS 80 MQS

70 P.R.I. (%) 70 P.R.I. (%) MR-Pz-4 MR-Pz-6 MR-Pz-4 MR-Pz-6 60 ML MB-Pz-4 MB-Pz-6 60 MB-Pz-4 MB-Pz-6 MG-Gl-4 MG-Gl-6 MG-Gl-4 MG-Gl-6 50 50 MFA MFA 40 40 150 250 350 450 550 650 750 150 250 350 450 550 650 750 2 2 a ) Specific surface (m /kg) b ) Specific surface (m /kg)

Figure 5: Relationship between specific surface and P.R.I. evaluated on cement-addition mortars after 28 days (a) and 6 months (b) of curing

258 Figure 6 shows that after one year of curing the coal fly ash led to the highest strength both for cement-pozzolana and lime-pozzolana mortars. To evaluate the changes in the capillary porosity of the different cement-pozzolana mortars as a function of curing, electrical resistivity measurements were carried out on water-saturated specimens. Figure 7 shows that the reference-cement mortar (MCE) reached resistivity values of about 70 Ω m after 2 years of curing. Comparable or lower values of electrical resistivity were reached by mortars with ground quartz sand (MQS) or limestone (ML). Conversely, mortars with pozzolanic additions showed a higher resistivity. This can be attributed to the well-known effect of pore refinement brought about by the pozzolanic reaction (Neville, 1995).

25 MR-Pz4 1 month MR-Pz6 20 MB-Pz4 MB-Pz6 MFA MG-Gl4 15 MG-Gl6 Serie8 MR-Pz4 12 months 10 MR-Pz6 MB-Pz4 MB-Pz6

C.S.mortar lime (MPa) 5 MFA

0 40 45 50 55 60 65 70 75 C.S. cement mortar (MPa)

Figure 6: Relationship between compressive strength of cement-pozzolana and lime-pozzolana mortars

1000 m)

100

MR-Pz-4 MR-Pz-6 MB-Pz-4 MB-Pz-6 MG-Gl-4 MG-Gl-6

Electrical resistivity ( Electrical MFA MCE MQS ML MSF 10 0 100 200 300 400 500 600 700 800 Time (days)

Figure 7: Electrical resistivity of cement-addition mortars as a function of time (specimens immersed in water)

259 Mortars with silica fume (MSF), coal fly ash (MFA) and ground green glass (MG-Gl) showed the highest values of resistivity. For instance values higher than 200 Ω m were reached after three months of curing. These high values of resistivity confirmed the higher reactivity of these additions compared to natural pozzolanas. As a matter of fact, fly ash contributed to reach high resistivity values, approaching 500 Ω m after 1 year of curing. Mortars with ground glass initially showed resistivity values intermediate between those of silica fume and fly ash; nevertheless, after long curing they reached values comparable to those of the latter. As far as natural pozzolanas are concerned, the red pozzolana led to higher values of the resistivity of the mortar compared to the black pozzolana. Anyway, even after two years of wet curing, none of the mortars with natural pozzolanas could approach the resistivity value of the mortar with fly ash.

The improved microstructure of mortars with addition of pozzolanic materials also led to a higher resistance to the penetration of chlorides. This was measured by means of ponding tests with a solution of 165 g/L NaCl for 35 days. Chloride profiles were measured and an apparent diffusion coefficient (Dapp) was calculated by fitting the profiles with the „erf-function‟ derived from Fick‟s second law (Collepardi et al., 1972). Even though the value of Dapp depends on the testing conditions (Bertolini et al., 2004), this parameter is normally used to compare the resistance to chloride penetration of cementitious materials. Therefore, results of these accelerated chloride penetration tests allow a comparison of the different mineral additions in terms of their contribution to increasing the resistance to chloride penetration. Figure 8 shows the apparent diffusion coefficient measured as a function of the type of mortar and the fineness of the mineral addition. The low resistance to chloride penetration of the mortars with the inert additions of ground quartz sand (MQS) and limestone (ML) -12 2 -12 2 is confirmed (Dapp is about 20 10 m /s and 11 10 m /s respectively). Significantly lower diffusion coefficients were obtained for the mortars with pozzolanic additions. Values of Dapp much lower were obtained for the mortars with fly ash (MFA), ground green glass (MG-Gl-4 and MG-Gl-6) and silica fume (MSF), which showed values in the range of 0.25-1.8 10-12 m2/s.

25 Curig MR-Pz-4 MR-Pz-6 28 days 20 MB-Pz-4 MB-Pz-6 MQS

/s) /s) MG-Gl-4 MG-Gl-6

2 15 m

-12 MFA

(10 10 ML

app D 5 MCE MSF 0 150 250 350 450 550 650 750 Specific surface (m2/kg)

Figure 8: Apparent diffusion coefficient (Dapp) as a function of the type of addition and its fineness

260 As far as the mineral additions studied with different fineness are concerned, no significant influence of the specific surface on Dapp was observed with these tests.

The pozzolanic additions also showed a beneficial effect on the resistance of the mortars to sulphate attack. Figure 9 shows the average expansion of two specimen of each type of mortar. Mortars with silica fume and ground glass showed a negligible expansion even after more than 1 year of immersion in the 5%Na2SO4 solution. Conversely, the mortars with the inert additions (MQS and ML) showed a sharp increase in the sulphate-induced expansion just after a few months of tests, i.e. before the reference mortar (MCE). An intermediate behaviour was observed for the mortars with natural pozzolanas, which showed to improve the sulphate resistance of the mortars, especially when they are finely grounded. In fact, mortars with both red and black pozzolanas grounded at 600 m2/kg (MPz-R- 6 and MPz-B-6) showed average values of expansion of 0.10 and 0.15% respectively, even after 20 months of immersion. A similar behaviour was observed for the mortar with coal fly ash (MFA).

3.3 Correlations

The previous results showed, according to a large amount of available literature, that different mineral additions with pozzolanic properties used to replace part of the portland cement may improve the performances of mortars in terms of resistance to aggressive environments. The beneficial effects of pozzolanic additions, therefore, could be taken into consideration in a performance-based design of reinforced concrete structure. The selection of a suitable type of mineral addition could be part of the design stage and its role in delaying the degradation of the structure, thus increasing its service life, could be considered. Nevertheless, it clearly appears that the contribution of a specific pozzolanic addition depends on several parameters related to its composition and microstructure, as well as on its fineness. Consequently, any specific mineral addition should be tested in order to evaluate its actual behaviour, possibly through appropriate performance indexes.

0.8 MR-Pz-4 MR-Pz-6 MB-Pz-4 MB-Pz-6 MCE MFA MQS MG-Gl-4 0.6 MG-Gl-6 ML MSF

0.4

Expansion(%) 0.2

0 0 100 200 300 400 500 600 700 Time (days)

Figure 9: Expansion of specimens as a function of time during sulphate tests

261 Besides the use in the qualification phase, performance tests would also be useful for quality controls of materials during construction.

A series of tests proposed in the literature for studying the pozzolanic properties of mineral additions were considered in this work and they were applied to several types of additions. From the results discussed in the previous sections it appears clear that there is no a single test or a single parameter that can provide a thorough description of the role of a mineral addition when it is used to replace portland cement. A specific tests should be carried out in order to evaluate the contribution of the mineral addition to any given property of the concrete (e.g. P.R.I. could be considered if the compressive strength is concerned or Dapp if resistance to chloride penetration is considered). Nevertheless, relationships can be found among some of the parameters. Correlations were found between the electrical resistivity and other properties of the cement based mortars. Figure 10 shows the relationship between the resistivity and P.R.I. or Dapp of the mortars, measured after 28 days of curing. Reasonable linear correlations were found in both cases, showing that the resistivity is able to distinguish the role of the type of addition and of its fineness on the compressive strength and the resistance to chloride penetration. Indeed, resistivity of water saturated mortars is strictly related to the pore microstructure and, thus, it is able to detect the pore refinement possibly induced by the hydration of a pozzolanic addition. Being electrical resistivity of a mortar or concrete specimen rather easy to be measured, this parameter could be considered as a possible simple way for a preliminary classification of mineral additions. For instance, Figure 10 shows that mortars with pozzolanic -12 2 additions, which had P.R.I. values higher than 75% and Dapp higher than 10 10 m /s, had electrical resistivity values higher than 40 Ω m. The mortars with the most reactive mineral additions (MSF, -12 2 MFA, MG-Gl) showed resistivity values higher than 75 Ω m and Dapp lower than 2 10 m /s. The electrical resistivity of the mortar also evidenced the good performance of mortars with 30% of ground glass that showed both resistivity values and durability performances similar to those of mortars with 30% fly ash.

105 100 MCE MR-Pz-4 100 MR-Pz-6 MB-Pz-4 MB-Pz-6 MFA 95 MG-Gl-4 MSQ

/s) 10

2 MG-Gl-6 MSF

90 m -12 MR-Pz-4 MR-Pz-6

85 (10

P.R.I. (%) MB-Pz-4 MB-Pz-6 app MG-Gl-4 MG-Gl-6 1 80 D MSF MFA 75 MQS Curing 28 days Curing 28 days 70 0.1 0 100 200 300 10 100 1000 Electrical resistivity ( m) a ) b ) Electrical resistivity ( m)

Figure 10: Relationship between the electrical resistivity and: (a) P.R.I. or (b) the apparent diffusion coefficient (Dapp)

262 4. Conclusions

Results confirmed that partial replacement of portland cement with pozzolanic additions, such as silica fume or coal fly ash, can significantly improve the resistance of mortars to chloride penetration and sulphate attack. The use of natural pozzolanas also showed to increase the imperviousness of the hardened cement paste but these additions showed a lower reactivity, which is influenced by the composition of the pozzolana and its fineness. An excellent pozzolanic behaviour was observed on ground green glass, which improved as the fineness increased.

The pozzolanic behaviour of different mineral additions and their role on the behaviour of hardened mortar or concrete cannot be investigated by means of a single test. A combination of methods appears to be more appropriated to evaluate the actual role of pozzolanic additions on the strength and durability of concrete. The chemical analysis is useful to detect the presence of chemical compounds essential for the pozzolanic behaviour (SiO2 and Al2O3), but the chemical composition cannot be related to the actual performance of the addition. Both the pozzolanic reactivity index (P.R.I.) and the electrical resistivity of water saturated mortars provide a good evaluation of the reactivity of a mineral addition, showing the development of the microstructure of the hardened cement paste respectively in terms of strength and imperviousness. The effect of curing can also be studied by means of these parameters. Electrical resistivity of mortars was also correlated to apparent diffusion coefficient; thus this simple parameter could be proposed for a classification of pozzolanic additions also in relation to durability issues.

References

Bertolini L., Elsener B., Pedeferri P., Polder R. B. (2004), Corrosion of steel in concrete – Prevention, diagnosis, repair, Wiley-VCH, Weinheim.

Neville A.M. (1995) Properties of concrete, Longman Group Limited, Harlow, Essex, UK.

Massazza F. (1998) “Pozzolana and Pozzolanic cements”, Chapter 10 of Lea’s chemistry of cement and concrete, Arnold Publishers, 1998.

American Concrete Institute (1996) Guide of the use of silica Fume in concrete, ACI 234R-96.

Shao Y., Lehoux P. (2001) Feasibility of using ground waste glass as a cementitious material, Thomas Telford, London, pp.209-219.

Collepardi M., Marcialis A., Turriziani R. (1972), Penetration of chloride ions into cement pastes and concretes, Journal of American Ceramic Society, Vol. 55, pp. 534-535.

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