Comparing New Formulated Calcium

Aluminate Cement (C12A7 Rich) with (CA Rich)

in CAC-ggbs Blending System

Programme: MSc Civil Engineering

Name of Student: Shaoyan Li

Supervisor: Dr. Bai Yun

UCL Department of Civil, Environmental &

Geomatic Engineering, Gower St, London,

WC1E 6BT

Introduction

Calcium aluminate cements (CAC) are range of cements in which calcium

aluminate are the principle constituents[1,2]. The raw materials are calcium

carbonate (limestone) and alumina (bauxite) both of which may be impure and

contain iron, silicon and titanium oxides as minor contaminants together with

traces of alkalis etc. CAC is manufactured by fusion or sintering process, the

kiln temperature is 1450-1600 ℃, the clinker formed in the kiln is cooled and

ground in the grinding mill to a specific surface area (see Figure 2). The phases

produced in cement production will include C12A7, CA, C2AS, C4AF-CF2 solid

solution (fss), CT, C2S, wustite (FeO), C22A17F2S3 (pleochroite or fibre) and

glass. It’s an alternative to Portland cement (PC) in certain applications[3].

Figure 1 shows the composition of CAC compared with Portland cements.

Figure 2 shows the CAC manufactory process [4].

Figure 1 CAC Composition[3

Figure 1 CAC composition compared with PC Figure 2 Manufacture of CAC

Aims and Objectives

The aim of this investigation is to study the hydration, chemical and physical

properties of traditional CAC based on CA rich and new formulation based

on C12A7 rich by blending with ground granulated blast furnace slag (ggbs).

• Literature review on properties of CAC, ggbs and CAC-ggbs blending

system is presented.

• Recommend optimal paste and mortar formulation investigated in the

research based on setting time control, heat evolution, conversion effect,

strength development.

Methodology: Materials, apparatus and experimental

Materials used are TERNAL RG, TERNAL EP and ggbs.

Apparatus used were:

I. Workability – Mini slump test & Flow Table Test

II. Setting time – Vicat Needle Test

III. Rheological property – Rheometer Test

IV. Compressive strength – Compression Test (Figure 3)

V. Thermogravimetric analysis – TG Test (Figure 4)

VI. Heat evolution of hydration process – Isothermal Conduction

Calorimetry (ICC) Test (Figure 5)

VII.Microstructure analysis – X-Ray Diffraction Test (Figure 6)

CAC was blended with ggbs in different proportions with fixed water/solid

ratio 0.4 and carried out at 20℃.

Figure 3 Compression Machine Figure 4 TG Test

Figure 5 TG Test Figure 6 XRD Test[5]

References:[1] Robson, T D., (1962), High-Alumina Cements and Concretes, John Wiley and Sons.

[2] George, C M., (1983), Industrial aluminous cements in Structure and Performance of Cements (ed. P Barnes), Applied Science Publishers,

London, pp. 415-470.

[3] Fentiman, C H., Mangabhai R J. and Scrivener, K L., (2014), Calcium Aluminate Cements: Proceedings of the Centenary Conference, IHS

BRE Press, London. [4] Calcium Aluminate Technology Briefing, (2016), Kerneos,. [5] STOE STADI P, Product briefing.

Acknowledgements:This work was undertaken at the University College London under supervision of Yun Bai

and Raman Mangabhai, their help is gratefully acknowledged. The author would like to thank

Tony Newton from Kerneos for providing the materials and valuable information.

Results Mortar setting time

Table 1 Setting time of mortar for (a) TERNAL RG and (b) TERNAL EP

Isothermal Conduction Calorimetry Test

Figure 7 Normalized heat flow vs Time (solid & cement) for (a) TERNAL RG and (b)

TERNAL EP

Compressive strength (1 Day paste & mortar)

Figure 8 Effect of blending TERNAL RG & EP with ggbs on strength development for (a)

paste and (b) mortar

Thermogravimetric Analysis

Figure 9 Thermogravimetric analysis for (a) TERNAL RG and (b) TERNAL EP

Discussion and Conclusion• Setting time of paste blends (TERNAL EP/RG) varies with ggbs content. Results indicate

TERNAL EP is more reactive than TERNAL RG.

• Mortar blends show setting time does not significantly affected by ggbs content. Results

indicate TERNAL EP is more reactive than TERNAL RG. Observations carried out during

the preparation indicate that TERNAL EP is less workable than RG (Table 1).

• Effect of blending ggbs with TERNAL RG and EP shows decrease in tmax and Qmax with

increase in ggbs content (Figure 7).

• tmax for RG is reduced from 8 to 4.3 hours with increase in ggbs content, whilst for EP

reduced from 5.3 to 4 hours.

• Qmax is reduced from 23 to 4.2 mw/g for RG, whilst for EP it is reduced from 25.6 to 5.5

mw/g, with increase in ggbs content.

• In both cases, the hydration is accelerated with increase in ggbs content.

• Compressive strength decreases with increase in ggbs content at 24 hours for RG, whilst for

EP shows maximum at 20% ggbs (Figure 8).

• Effect of ageing show increase in strength for RG (data not shown), whilst EP shows

variable strength.

• Effect of blending ggbs with TERNAL EP and RG shows variable strength with increase in

ggbs content at 1 day. EP shows higher strength than RG, indicating higher reactivity as

shown with setting time results.

• Thermal analysis results shows changes in the hydration process (Figure 9) and are being

evaluated with XRD data to confirm the changes in hydration phases.

• It is recommended TERNAL® EP with 80% GGBS addition by mass for rapid setting and

hardening, as well as long-term strength requirement for paste, and 80% GGBS replacement

to limestone is recommended for mortar.

• Future development: Impact of curing temperature and admixtures on (C12A7 rich) CAC-ggbs

blending systems, as well as chemical reaction between CAC and ggbs.

TERNAL EP Setting time (min)

ggbs (%) Initial Final

0 28 51

20 38 53

50 34 47

80 24 34

100 30 45

TERNAL RG Setting time (min)

ggbs (%) Initial Final

0 50 87

20 45 76

50 46 106

80 33 78

100 45 90

tmax, Qmax