Comparing New Formulated Calcium Supervisor: Dr. Bai … Civil... · Calcium aluminate cements...
Transcript of Comparing New Formulated Calcium Supervisor: Dr. Bai … Civil... · Calcium aluminate cements...
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