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Feasibility Studies of Using Ghanaian-Nyamebekyere Calcined Clay as an

Artificial Pozzolan

Article  in  Aci Materials Journal · January 2019

DOI: 10.14359/51714458

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889ACI Materials Journal/November-December 2017

ACI MATERIALS JOURNAL TECHNICAL PAPER

There is a growing interest on the use of calcined clays as suitable supplementary cementitious materials (SCMs) for construction in recent times. However, the origin of clay presents some form of variations that influences their use as SCM. This study seeks to analyze clay obtained from the Nyamebekyere area of Ghana. The Ghanaian clay was calcined at temperatures of 600, 700, 800, 900, and 1000°C (1112, 1292, 1472, 1652, and 1832°F) in a labo-ratory furnace. The properties of the raw and calcined clay were characterized using thermal gravimetric analysis (TGA), 27Al and 29Si solid-state magic angle spinning nuclear magnetic resonance (SS MAS NMR), and Fourier transformed infrared (FTIR) spec-troscopic techniques. Pozzolanic strength activity indexes (PSAIs) were determined by replacing portland cement with 20% of the calcined materials. The results from the 27Al SS MAS NMR showed that the clay was a 1:1 kaolinitic clay type. The PSAI results were corroborated with the TGA, 27Al and 29Si SS MAS NMR, and the FTIR spectra results to achieve the optimum calcination tempera-ture, which indicated that clay calcined at 800°C (1652°F) attained a more reactive pozzolanic phase that consequently positively influenced the strength activity index. The study recommends calci-nation temperature of 800°C (1652°F) as the most appropriate temperature for the Ghanaian clay.

Keywords: calcined clay pozzolan; Fourier transformed infrared (FTIR); solid-state magic angle spinning nuclear magnetic resonance (SS MAS NMR) spectroscopy; strength activity; supplementary cementitious mate-rials; thermal gravimetric analysis.

INTRODUCTIONCalcined clay is an important and well-researched mate-

rial that is used as a supplementary cementitious material (SCM) in concrete production. The construction industry around the globe has embraced SCMs as cement substi-tutes in promoting sustainable construction. SCMs reduce harmful anthropogenic gases contributed by cement manu-facturing plants, reduce the dependence on natural resources for cement production, as well as significantly reduce the cost of concrete production.1-3 SCMs are classified into three categories: 1) fillers; 2) pozzolanic materials; and 3) hydraulic materials. Fillers are inert materials that contribute little to the hydration of cement. Pozzolanic materials are typically fine aluminosilicates that chemically react with calcium hydroxide to form additional calcium silicate hydrate and other cementitious compounds. Hydraulic materials chemically react with water to form cementitious compounds.4 Examples of filler materials are chalk and limestone, and examples of pozzolanic materials are fly ash, silica fume, and calcined clays; steel slag and ground- granulated blast-furnace slag (slag cement) are primarily characterized as hydraulic materials.

Clay minerals undergo thermal activation to become reac-tive with portland cement during hydration. The thermal activation process is usually achieved through calcination. At appropriate calcination temperatures, these thermally activated clays become more reactive with cement and can improve strength and durability of concrete. Generally, it has been found that temperatures between 500 and 900°C (932 and 1652°F) are suitable to produce reactive clays.5 However, the exact calcination temperature suitable to acti-vate clay thermally is dependent on the clay origin, chem-istry, and amount and type of impurities. Clays are classified into kaolinitic, smectite, and illite groups.6 The kaolinitic group includes kaolinite, nacrite, and nickite, whereas the smectite group includes montmorillonite, nontronite, biede-lollite. The illite group is made of illite and glauconite.7 Fundamentally, a clay mineral has different structures and compositions; however, the basic building blocks are all the same.8 The building blocks form sheets of tetrahedral and octahedral layers that define the atomic structure of every clay mineral. The kaolinitic group is made of a 1:1 layer—that is, a tetrahedral sheet and an octahedral sheet. Both the smectite and the illitic group also consist of a 2:1 layer—that is, an octahedral sheet between two opposing tetrahe-dral sheets.7 In a clay mineral, a tetrahedral sheet is always combined with an octahedral sheet.

During heating, three processes occur: dehydroxyliza-tion, calcination, and crystallization. During dehydroxyl-ization, octahedral sheets lose water and transform into a meta-stable state.9 Produced amorphous materials in the metastable state are more reactive to free calcium hydroxide present during hydration. The end of the dehydroxyliza-tion process marks the calcination temperature. The calci-nation temperature also influences the environment of the layered silicate, which is also an indicative of the reactivity of calcined clays.10 At high temperature, the clay minerals begin to crystalize, which decreases reactivity. At approxi-mately 600°C (1112°F), kaolintic clays fully dehydroxylize, while the smectite and the illitic groups dehydroxylize above 600°C (1112°F).11 Hydroxyls are not as strongly bound in kaolinite clays compared to smectites and illites, which explains the differences in the calcination temperature. Qualitative techniques such as thermal gravimetric analysis

Title No. 114-M78

Investigation into Ghanaian Calcined Clay as Supplementary Cementitious Materialby Mark Bediako, Sudhaunshu Shrikant Purohit, and John Tristan Kevern

ACI Materials Journal, V. 114, No. 6, November-December 2017.MS No. M-2016-279.R3, doi: 10.14359/51700896 received January 11, 2017, and

reviewed under Institute publication policies. Copyright © 2017, American Concrete Institute. All rights reserved, including the making of copies unless permission is obtained from the copyright proprietors. Pertinent discussion including author’s closure, if any, will be published ten months from this journal’s date if the discussion is received within four months of the paper’s print publication.

890 ACI Materials Journal/November-December 2017

(TGA) and Fourier transform infrared spectroscopy (FTIR), and quantitative tools such as nuclear magnetic resonance (NMR), are able to provide meaningful characterization of thermally activated clays. TGA determines the extent of dehydroxylization, whereas FTIR determines the anionic functional groups.11,12 NMR is extremely helpful in quanti-fying the structural features of amorphous materials.10 NMR probes into the isotropic chemical shift of silicon tetrahe-dral and aluminum octahedral in either a calcined clay or a binder hydrate. Both qualitative and quantitative techniques uniquely support each other to limit the level of uncertainties in the characterization techniques and pozzolanic activity. In this study, clay from Ghana was thermally activated at temperatures of 600, 700, 800, 900, and 1000°C (1112, 1292, 1472, 1652, and 1832°F). The main objective was to charac-terize calcined clay using TGA, FTIR, NMR, and their rela-tion to pozzolanic activity to best understand the potential of this abundant resource to alleviate cement supply burdens.

RESEARCH SIGNIFICANCEGhana, a West African nation, and other neighboring coun-

tries do not have an abundance of commonly used SCMs such as fly ash, silica fume, metakaolin, and slag. However, the abundance of clay minerals in the country could provide a sustainable alternative with respect to SCM application.3 Previous research has characterized the strength performance of thermally activated clay.13,14 However, there is little infor-mation on the phase transformation of thermally activated Ghanaian clay and its relation with strength activity. In this regard, this work will help provide enough information on the structural transformation of the calcined clay, which could be used to explain strength performance.

MATERIALS AND METHODSMaterials

The materials used for the study were clay, cement, silica sand, polycarboxylate high-range water reducer (HRWR), and potable water. The clay was obtained from Nyame-bekyere in the Ashanti Region area of Ghana. The clay had a specific gravity of 2.61. Portland cement conformed to ASTM C150 Types I and Type II and was obtained from a cement plant in Chanute, KS. Table 1 shows the chem-ical compositions of the cement and the clay. Graded silica sand used conformed to ASTM. A polycarboxylate HRWR conforming to ASTM C595 was used.

MethodsThermal analysis—TGA results were obtained using a

analyzer heated to 1200°C (2192°F), ramping 15°C (59°F) per minute in N2 gas.

Clay calcination—Calcination of clay samples was performed in a laboratory furnace. A known mass was placed in ceramic bowls and heated at different tempera-tures of 600, 700, 800, 900, and 1000°C (1112, 1292, 1472, 1652, and 1832°F) for 3 hours. The calcined samples were then allowed to cool in the furnace to room temperature. The calcined material was sieved through the 75 µm using a sieve shaker. The 75 µm samples were used for the study.

FTIR—Attenuated total reflectance infrared spectros-copy was conducted using spectrometer equipped with a fast recovery deuterated triglycine sulfate (DTGS) detector and an extended KBr beamsplitter. Infrared spectrum was obtained from 4000 to 600 cm–1 (1574.8 to 236.1 in.–1), and 512 acquisitions were added at a spectral resolution of 2 cm–1 (0.79 in.–1). All spectral measurements were carried out at room temperature.

Al and Si SS MAS NMR—A compact, modular, multiple- DSP-based console with 8.45 T magnet and homebuilt, single-channel, 4 mm wide-bore NMR probe was used to determine 27Al and 29Si spectra. Approximately 90 mg (0.000198 lb) of sample was taken for each analysis and signals are represented as chemical shift value, repre-sented as part per million (ppm). The 27Al and 29Si Larmor frequencies were 93.074 and 70.958 MHz, respectively. 27Al spectra were acquired with MAS spinning frequency, last delay and 90-degree pulse length of 8 KHz, 1 second, and 2.5 μs, respectively. 29Si spectra were acquired with MAS spinning frequency, last delay, and 60-degree pulse length of 8 KHz, 20 seconds, and 5.5 μs, respectively. Aluminum nitrate [Al(NO3)] and tetramethyl silane (TMS) were used as reference compounds for 27Al and 29Si NMR spectra, respec-tively. All experiments were performed at ambient tempera-ture without any corrections for sample heating.

Pozzolanic activity—The pozzolana activity was deter-mined according to the description of ASTM C618 and ASTM C311. This standard explains the determination of pozzolanic activity using the strength activity index (SAI) as well as pozzolana replacement dosage. SAI was determined on mortar samples. Mortar samples were prepared in accor-dance with ASTM C109 and cured in a lime water bath for a period of 7 and 28 days. As per ASTM C311, cement was replaced with calcined clay at 20%. The water-cement ratio (w/c) was maintained at 0.485 and the ratio of cementitious material (portland cement plus calcined clay) to sand was set at a ratio of 1 to 2.75. To achieve the desired flow according to ASTM C1437, the polycarboxylate HRWR was used. SAI

Table 1—Compositions of portland cement and raw clay

Chemical Portland cement Raw clay

SiO2, % 20.49 59.7

Al2O3, % 4.26 25.53

Fe2O3, % 3.14 5.22

CaO, % 63.48 0.16

MgO, % 2.11 1.37

SO3, % 2.9 0.07

Na2O + K2O, % 0.49 2.41

Loss on ignition, % 2.2 4.5

Mineralogy

C3S, % 56

C2S, % 15

C3A, % 6

C4AF, % 9

891ACI Materials Journal/November-December 2017

was measured on an average of three mortar specimens. The SAI was calculated based on this formula

SAI = −−

×1 100

CS CSCSo i

o

%

where CSo is the compressive strength without pozzolan; and CSi is the compressive strength with calcined clay.

RESULTS AND DISCUSSIONCalcined clay characterization

Thermal analysis—Figure 1 presents the TGA results of the clay powder showing that four different processes occurred. The first two peaks, A and B, that preceded the dehydroxylization peak (C) represented the evaporation of adsorbed water and decomposition of organic particles. The dehydroxylization of the clay started from 325°C (617°F) to approximately 731°C (1348°F). The figure shows that the effective calcination temperature was at 731°C (1348°F). The temperatures between 731 and 905°C (1348 and 1661°F) showed a complete dehydroxylization of the clay material. Complete dehydroxylization of clay mineral, indicated between 731 and 904°C (1348 and 1659°F), shows that octa-hedral aluminium sheets dehydroxylized into a metastable disordered state, collapsing a higher quantity of crystalline clay minerals to produce a more reactive calcined clay.9 The temperature between 905 and 1036°C (1661 and 1897°F), labeled as D, also showed the formation of crystal growth of mullite phases. The growth of crystals shown between 905 and 1036°C (1661 and 1897°F) support the argument of Fernandez et al.11 that, at higher temperatures, a metastable state transforms from amorphous condition into crystalline units, which inhibits reactivity of calcined clays.

FTIR analysis—Figure 2 presents the FTIR results of the raw and clay calcined between 600 and 1000°C (1112 and 1832°F). The figure shows vibration band occurring between approxi-mately 690 and 1800 cm–1 (272 and 709 in.–1), and molecular

vibration from 1800 to 3700 cm–1 (709 to 1457 in.–1). The raw clay showed distinctive vibration bands at 3693, 3651, and 3619 cm–1 (1454, 1437, and 1424 in.–1), conforming a metal bonded to hydroxide group. This is most likely to

Fig. 1—DTA results of powdered clay.

Fig. 2—FTIR spectra of raw clay and clays calcined at temperatures of 600 to 1000°C (1112 to 1832°F).

892 ACI Materials Journal/November-December 2017

be a kaolinite structure.15 Absorption bands corresponding to Al-O and Si-O were also observed at 1162, 1109, 1025, 999, 910, 777, and 692 cm–1 (457, 437, 404, 393, 358, 306, and 272 in.–1).16 The clay calcined between 600 and 1000°C (1112 and 1832°F) showed the disappearance of the kaolinite structures as well as the water molecules. This indicates a change from a crystalline structure to an amorphous or meta-stable structure.17 The vibrational atoms that corresponded to Al/Si-O at 1162, 1109, 1025, 999, and 910 cm–1 (457, 437, 404, 393, and 358 in.–1) were seen disappearing after calci-nation; however, absorption bands at 777 and 692 cm–1 (306 and 272 in.–1) did not disappear. The disappearance of the absorption bands meant a change from octahedral coordina-tion of Al+3 to a tetrahedral coordinated environment.18

27Al and 29Si SS MAS NMR—27Al is a quite sensitive nucleus to perform NMR studies on and, hence, can be readily detected; therefore, 27Al SS MAS NMR spectros-copy is widely used to characterize aluminate phases. One must also understand the disadvantage of using 27Al MAS NMR spectroscopy because 27Al is a quadrupolar nucleus and thus is additionally affected by electric field gradients within the sample. This can pose difficulties in spectral interpretation. The spectra become difficult to interpret, as the 27Al nucleus is affected by the quadrupolar interaction, which leads to a field-dependent shift in resonance position and a broadening of the peaks. Nevertheless, four-coordinate and six-coordinate aluminium can readily be distinguished.

The 27Al solid-state mass angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of raw and calcined

clay from 600 to 1000°C (1112 to 1832ºF) are presented in Fig. 3. The raw clay showed two distinct peaks that reso-nated at 68 and –0.8 ppm, respectively, and indicated a 1:1 kaolinite group of clay. As has already been explained from literature, a 1:1 group represents an octahedral and a tetrahe-dral sheet. Hanna et al.19 confirmed that a tetrahedral sheet resonates from 50 to 80 ppm, whereas the octahedral sheet resonates from –20 to 20 ppm.

Calcined clays exhibited an increase in the intensities at the tetrahedral environment (Al(iv)) and a decrease in the intensities at the octahedral environment (Al(vi)) with refer-ence to the raw clay, which indicated greater reactivity of calcined clays.20,21 It was observed that calcined clays at 900 and 1000°C (1652 and 1832°F) had low and similar intensi-ties at the Al(vi) environment. Again, from the results of the TGA shown in Fig. 1, the most appropriate temperature that may give higher amorphousness or disorderliness of calcined clay is either at 700 or 800°C (1292 or 1472°F). The inten-sities of the results at the four-coordinate environment of 27Al were very difficult to attain because of the nature of the reference clay peak. The nature of the peak shown at 68 ppm on the spectra of the reference clay is subjected to produce higher error of margin being merged with the adjacent spin-ning side band (indicated by an asterisk). This limitation hindered the authors’ interest in calculating the respective peak areas of all the peaks at 68 ppm at various temperatures of calcination.

29Si NMR spectra are normally interpreted in terms of the different silicon environments and are usually denoted as Qn, where “Q” represents the silicon tetrahedron bonded to four oxygen atoms and “n” denotes the number of SiO4 units connected to the silicon tetrahedron under consider-ation. 29Si SS MAS NMR spectroscopy has proven to be extremely useful in the structural characterization of sili-cates and typical ordinary portland cements, and to investi-gate the hydration of pure C3S and β-C2S phases. In hydrated cements, these show the presence of Qo units due to ortho-silicate groups, Q1 units from Si-O-SO3 groups in dimers or terminating polymers, and Q2 units from Si-O-Si-O-Si groups in trimers and higher polymers.

Figure 4 presents the 29Si solid-state mass angle spin-ning (MAS) nuclear magnetic resonance (NMR) of raw and calcined clay from 600 to 1000°C (1112 to 1832°F). Raw clay showed a chemical shift at –110 and –126 ppm. This shift corresponds to silicon coordinated environment which is Q4.22 Q4 shows that the central silicon tetrahedron is linked to four SiO4 units. The process of calcination collapsed one of the Q4 population in the raw clay remaining another one Q4 popula-tion, which increased progressively in intensities as calcined temperatures increased. Calcined temperatures at 900 and 1000°C (1652 and 1832°F) indicated higher intensities, which could be due to the presence of recrystallized quartz shown in the TGA graph. TGA results have already shown that calcined clay between 900 and 1000°C (1652 and 1832°F) may be less reactive because of crystalline products. Moreover, the TGA has also shown that calcined materials at 700 and 800°C (1292 and 1472°F) may be more reactive. However, Fig. 4 confirms that calcined clay at 800°C (1472°F) could possess more reac-tive phases than calcined materials at 700°C (1292°F) due to

Fig. 3—27Al SS MAS NMR spectra of raw clay and clays calcined at temperatures of 600 to 1000°C (1112 to 1832°F). Spinning side-bands are indicated by asterisk.

893ACI Materials Journal/November-December 2017

the high intensity obtained at the Q4 silicon population. Table 2 presents a summary of the concentrations and peak areas of the 27Al and 29Si environments. Peak areas are calculated considering raw clay as the control.

Pozzolanic activity—Table 3 shows the mortar mixture proportions of calcined clay pozzolan. The table shows that the flow for the mortar mixtures were between 106 and 116, which was within the acceptable range specified in the ASTM C1437. HRWR content reduced at temperatures of 900 and 1000°C (1652 and 1832°F) compared with materials calcined from 600 to 800°C (1112 to 1472°F). The reduc-tion of HRWR at 900 and 1000°C (1652 and 1832°F) indi-cate a reduction in the particle surface area and absorption properties of the powder materials, which is confirmed from the TGA results. The formation of crystalline substances reduces the surface area and porosity.23,24 Table 4 presents the compressive strength of the control and the calcined mortars at 7 and 28 days.

Figure 5 provides the results of the SAI of the calcined clay pozzolan. Calcined clay at 800°C (1472°F) attained the maximum strength at 7 and 28 days as compared to the control mortar mixture. This shows that at 800°C (1292°F), the clay powder was completely calcined forming active pozzolanic phases, which are very reactive with cement in comparison with the other temperatures used to calcine the clay. Tironi et al.17 indicated that at optimum calcination temperature strength improves due to the pozzolanic active phases (amorphous phases) formed.

Influence of calcined clay on cement hydration using 27Al SS MAS NMR spectroscopy

Figures 6, 7, and 8 present the 27Al SS MAS NMR results of hydrated binder paste mixture of the unblended cement as well as blended mixtures between cement and calcined clay at 800°C (1292°F). Figures 6, 7, and 8 show hydration at 3, 7, and 28 days, respectively, indicating two distinct peaks. The studies of Skibsted et al.25 and Anderson et al.26 have shown that a chemical shift between 8 and 11.8 ppm corresponds to monosulfates, whereas chemical shifts between 66 and 72 ppm corresponds to Al environment replacing silicon in the tetrahedral environment of aluminum. The diffused peaks around 8 ppm shown in Fig. 6 represents monosulfate (AFm) present in the aluminosilicate hydrates or stratlingite formed, whereas around 68 ppm, it could be seen that Al substituted silicon in the tetrahedral environment. The peak relating to Afm grew with age from 3 to 28 days, and this is indicative of more aluminum passing into cement solution forming strat-lingite containing Afm phases.11 The intensity of the cement and calcined clay at 3 days, which gave 114%, versus 100% of

Fig. 4—29Si SS MAS NMR spectra of raw and calcined clays.

Table 2—SS NMR spectra indicating position and peak areas of respective peaks of 27Al and 29Si

Dry cement

27Al SS NMR 29Si SS NMR

ppm Peak area, % ppm Peak area, %

Raw clay –0.8 100 –126 100

600°C –0.3 13 –126 320

700°C –1.8 6 –126 328

800°C –0.3 9 –126 335

900°C –2.8 2 –126 800

1000°C –6.3 2 –126 726

Note: T(°F) = T(°C) × 1.8 + 32.

Table 3—Mortar mixture proportion for strength activity index of calcined clays at 7 and 28 days

Temperature, °C Mixture name

Mass, g

w/b HRWR, % Flow, %Cement Clay Sand Water

Control C 500 0 1375 242 0.485 0 106

600 20P600 400 100 1375 242 0.485 0.4 111

700 20P700 400 100 1375 242 0.485 0.4 110

800 20P800 400 100 1375 242 0.485 0.4 110

900 20P900 400 100 1375 242 0.485 0.3 115

1000 20P1000 400 100 1375 242 0.485 0.2 116

Notes: T(°F) = T(°C) × 1.8 + 32; 1 g = 0.0022 lb.

894 ACI Materials Journal/November-December 2017

the control, showed that the material was very reactive at early ages and even at the 7-day period of hydration.

The performance of the cement blended mixture at early ages indicated that the calcined clay behaved as a filler mate-

rial. The filler effect accelerates early hydration. The accel-eration of the hydration process generates more calcium hydroxide to react with the active silica and aluminate phases of pozzolans to produce secondary calcium aluminosilicate

Fig. 6—27Al SS MAS NMR spectra of hydrated cement “20 Clay Pozzolan” at 3 days.

Fig. 7—27Al SS MAS NMR spectra of hydrated cement “20 Clay Pozzolan” at 7 days.

Fig. 8—27Al SS MAS NMR spectra of hydrated cement “20 Clay Pozzolan” at 28 days.

Table 4—Compressive strength and coefficient of variation (COV) of mortars

Mixture name

Compressive strength, MPa Coefficient of variation (COV)

7 days 28 days 7 days 28 days

Control 32.5 44.1 3% 0%

20P600 32.5 44.1 3% 1%

20P700 35.9 42.3 8% 5%

20P800 40.1 47.5 3% 2%

20P900 30.9 41.4 9% 4%

20P1000 31.3 41.1 2% 3%

Fig. 5—Strength activity index of calcined pozzolan.

895ACI Materials Journal/November-December 2017

hydrates at early ages.27 The formation of these secondary products enhances strength performance. At 28 days, the cement blended material showed the highest intensity of 194% as compared to 100% intensity of plain cement. This shows that pozzolanic reaction occurred at the late stage of 28 days, forming more of the stratlingite phases. The figure also indicated that the presence of the Afm phases virtually diminished the presence of ettringite phases (Afm). This is very important because expansion due to ettringite was seen to be eliminated in the case of using cement and calcined clay as alternative binder materials.

CONCLUSIONSThe following conclusions could be drawn from the studies:1. Nyamebekyere clay used for the study could be clas-

sified as a 1:1 kaolinitic clay type from the 27Al SS MAS NMR studies.

2. The optimum temperature that yielded more reactive pozzolanic phases was obtained at 800°C (1472°F).

3. The influence of calcined clay in the cement blended material showed that the calcined material behaved partly as a filler and partly as a pozzolanic material. The filler effect accelerates portlandite growth, which enhances early strength, whereas the pozzolanic effect enhances late strength.

4. Calcined clays at 800°C (1472°F) used to replace port-land cement at 20% gave the maximum strength. This was attributed to the influence of the calcined clay, which produced more stable aluminate phases, including calcium aluminate hydrate (CAH) and stable form of monosulfate (AFm).

AUTHOR BIOSMark Bediako is a Research Scientist in the Materials Development and Engineering Division at the Building and Road Research Institute (BRRI) of the Council for Scientific and Industrial Research (CSIR) in Ghana. He received his BSc in chemical engineering, his MPhil in materials engineering, and his PhD in Materials Science Engineering from Kwame Nkrumah University of Science and Technology, Kumasi, Ghana, in 2003, 2010, and 2016, respectively. His research interests include sustainable construction materials related to concrete, cementitious materials research with emphasis on supplementary cementitious materials, X-ray reviews of cement-based materials including scanning electron microscopy, X-ray diffraction, and X-ray florescence, as well as durability of cement-based materials.

Sudhaunshu Shrikant Purohit is a Doctoral Candidate in the Department of Chemistry at the University of Missouri-Kansas City, Kansas City, MO. He received his BSc in chemistry from Ruia College, India, in 2004, and his MSc in inorganic chemistry at Ramnarain Ruia College, University of Mumbai, India. His research interests include spectroscopy, which includes infrared and Raman spectral studies and nuclear magnetic resonance spec-troscopy (NMR).

ACI member John Tristan Kevern is an Associate Professor in the Civil and Mechanical Engineering Department at the University of Missouri- Kansas City. His research interests include improving water quality using pervious concrete and the incorporation of industrial by-products in cement and concrete.

REFERENCES1. Sabir, B. B.; Wild, S.; and Bai, J., “Metakaolin and Calcined Clays as

Pozzolans for Concrete: A Review,” Cement and Concrete Composites, V. 23, No. 6, 2001, pp. 441-454. doi: 10.1016/S0958-9465(00)00092-5

2. Samet, B.; Mnif, T.; and Chaabouni, M., “Use of Kaolinitic Clay as a Pozzolanic Material for Cements: Formulation of Blended Cement,” Cement and Concrete Composites, V. 29, No. 10, 2007, pp. 741-749. doi: 10.1016/j.cemconcomp.2007.04.012

3. Bediako, M.; Gawu, S. K. Y.; and Adjaottor, A. A., “Suitability of Some Ghanaian Mineral Admixtures for Masonry Mortar Formulation,”

Construction and Building Materials, V. 29, 2012, pp. 667-671. doi: 10.1016/j.conbuildmat.2011.06.016

4. Kosmatka, S. H.; Kerkhoff, B., and Pananese, W. C., Design and Control of Concrete Mixtures, 14th edition, Portland Cement Association, Skokie, IL, 2002, p. 39.

5. Hellar-Kallai, L., “Thermally Modified Clay Minerals,” Handbook of Clay Science: Development in Clay Science, B. K. G. Bergaya Theng and G. Legaly, eds., Elsevier, 2006, pp. 289-308.

6. Guggenheim, S., and Martin, R. T., “Definition of Clay and Clay Minerals: Joint Report of the AIPEA Nomenclature and CMS Nomencla-ture Committee,” Clays and Clay Minerals, V. 43, No. 2, 1995, pp. 255-256. doi: 10.1346/CCMN.1995.0430213

7. Guggenheim, S.; Adams, J. M.; Bain, D. C.; Bergaya, F.; Brigatti, M. F.; Drits, V. A.; Formoso, M. L. L.; Galan, E.; Kogure, T.; and Stanjek, H., “Summary of Reommendations of Nomenclature Committees Rele-vant to Clay Mineralogy: Report of the Association 209 Internationale Pour L’etude des Argiles (AIPEA) Nomenclature Committee 2006,” Clays and Clay Minerals, V. 54, No. 6, 2006, pp. 761-772. doi: 10.1346/CCMN.2006.0540610

8. Zhou, C. H., and Keeling, J., “Fundamental and Applied Research on Clay Minerals: From Climate and Environment to Nanotechnology,” Applied Clay Science, V. 74, 2013, pp. 3-9. doi: 10.1016/j.clay.2013.02.013

9. Mendelovici, E., “Comparative Study of the Effect of Thermal and Mechanical Treatments on the Structures of Clay Mineral,” Journal of Thermal Analysis, V. 49, No. 3, 1997, pp. 1385-1397. doi: 10.1007/BF01983697

10. Mendes, A.; Gates, W. P.; Sanjayan, J. G.; and Collins, F, “NMR, XRD, IR and Synchrotron NEXAFS Spectroscopic Studies of OPC and OPC/Slag Cement Paste Hydrates,” Materials and Structures, V. 44, No. 10, 2011, pp. 1773-1791. doi: 10.1617/s11527-011-9737-6

11. Fernandez, R.; Martirena, F.; and Scrivener, K. L., “The Origin of the Pozzolanic Activity of Calcined Clay Minerals: A Comparison between Kaolinite, Illite and Montmorillonite,” Cement and Concrete Research, V. 41, No. 1, 2011, pp. 113-122. doi: 10.1016/j.cemconres.2010.09.013

12. Ylmen, R.; Wadso, L.; and Panas, I., “Insights into Early Hydra-tion of Portland Limestone Cement from Infrared Spectroscopy and Isothermal Calorimetry,” Cement and Concrete Research, V. 40, No. 10, 2010, pp. 1541-1546. doi: 10.1016/j.cemconres.2010.06.008

13. Bediako, M., and Frimpong, A. O., “Alternative Binders for Increased Sustainable Construction in Ghana—A Guide for Building Professionals,” Materials Sciences and Applications, V. 4, No. 12, 2013, pp. 20-28. doi: 10.4236/msa.2013.412A004

14. Bediako, M., and Atiemo, E., “Influence of Higher Volumes of Clay Pozzolana Replacement Levels on Some Technical Properties of Cement Pastes and Mortars,” Journal of Scientific Research and Reports, V. 3, No. 23, 2014, pp. 3018-3028. doi: 10.9734/JSRR/2014/9046

15. van der Marel, H. W., and Beutelspacher, H., Atlas of Infrared Spec-troscopy of Clay Minerals and Their Admixtures, Elsevier, Amsterdam, the Netherlands, 1974, 396 pp.

16. Russell, J. D., “Infrared Spectroscopy of Inorganic Compounds,” Laboratory Methods in Infrared Spectroscopy, Wiley, New York, 1987.

17. Tironi, A.; Trezza, M. A.; Irassar, E. F.; and Scian, A. N., “Thermal Treatment of Kaolin: Effect on the Pozzolanic Activity,” Procedia Mate-rials Science, V. 1, 2012, pp. 343-350. doi: 10.1016/j.mspro.2012.06.046

18. Ilic, B. R.; Mitrovic, A. A.; and Milicic, L. R., “Thermal Treatment of Kaolin Clay to Obtain Metakaolin,” Hemijska Industrija, V. 64, No. 4, 2010, pp. 351-356. doi: 10.2298/HEMIND100322014I

19. Hanna, R. A.; Barrie, P. J.; Cheeseman, C. R.; Hills, C. D.; Buchler, P. M.; and Perry, R., “Solid State 29Si and 27Al NMR and FTIR Study of Cement Pastes Containing Industrial Wastes and Organics,” Cement and Concrete Research, V. 25, No. 7, 1995, pp. 1435-1444. doi: 10.1016/0008-8846(95)00138-3

20. Klimesch, D. S.; Lee, G.; Ray, A.; and Wilson, M. A., “Metakaolin Addition in Autoclaved Cement-Quartz Pastes: A 29Si and 27Al MAS NMR Investigation,” Advances in Cement Research, V. 10, No. 3, 1998, pp. 93-99. doi: 10.1680/adcr.1998.10.3.93

21. Pena, P.; Rivas-Mercury, J. M.; de Aza, A. H.; Turrillas, X.; Sobrados, I.; and Sanz, J., “Solid State 27Al and 29Si NMR Characteriza-tion of Hydrates Formed in Calcium Aluminate-Silica Fume Mixtures,” Journal of Solid State Chemistry, V. 181, No. 8, 2008, pp. 1744-1752. doi: 10.1016/j.jssc.2008.03.026

22. Stebbins, J. F., and Kanzaki, M., “Local Structure and Chemical Shifts for Six-Coordinated Silicon in High-Pressure Mantel Phases,” Science, V. 251, No. 4991, 1991, pp. 294-298. doi: 10.1126/science.251.4991.294

23. Kartina, K., “Rice Husk Ash-Pozzolanic Material for Sustainability,” International Journal of Applied Science and Technology, V. 1, No. 6, 2011, pp. 169-178.

896 ACI Materials Journal/November-December 2017

24. Moodi, F.; Ramezanianpour, A. A.; and Safavizadeh, A. S., “Evalu-ation of the Optimal Process of Thermal Activation of Kaolins,” Scientia Iranica A, V. 18, No. 4, 2011, pp. 906-912. doi: 10.1016/j.scient.2011.07.011

25. Skibsted, J.; Henderson, E.; and Jakobsen, H. J., “Characterization of Calcium Aluminate Phases in Cements by 27Al MAS NMR Spectroscopy,” Inorganic Chemistry, V. 32, No. 6, 1993, pp. 1013-1027. doi: 10.1021/ic00058a043

26. Anderson, M. W.; Teisl, M.; and Noblet, C., “Giving Voice to the Future in Sustainability: Retrospective Assessment to Learn Prospective Stakeholder Engagement,” Ecological Economics, V. 84, 2012, pp. 1-6. doi: 10.1016/j.ecolecon.2012.09.002

27. Bediako, M.; Gawu, S. K. Y.; Adjaottor, A. A.; and Ankrah, J. S., “Early and Late Strength Characterization of Portland Cement Containing Calcined Low-Grade Kaolin Clay,” Journal of Engineering, V. 2016, 2016, 5 pp. doi: 10.1155/2016/721089110.1155/2016/7210891

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