RICE HUSKS-DERIVED SILICA AEROGEL AND THE EFFECTS ON THE STRENGTH AND THERMAL PROPERTY OF ORDINARY
PORTLAND CEMENT
INSTITUT PENYELIDIKAN, PEMBANGUNAN DAN PENGKOMERSILAN UNIVERSITITEKNOLOGI MARA 40450 SHAH ALAM, SELANGOR
MALAYSIA
BY
UMI SARAH BT JAIS HAMIDAH MOHD. SAMAN
JANUARY 2006
COPYRIGHT UiTM
B U R E A U OF R E S E A R C H &
Biro Penyelidikan dan Perundingan Universiti Teknologi MARA 40450 Shah Alam, Malaysia Tel: 03-55442094 / 5 / 3 / 2 Fax : 03-55442096 Website: www.uitm.edu.my/brc
UNIVERSITI TEKNOLOGI
25SJMARA
Penolong Naib Canselor (Penyelidikan) 03-55442094/5 [email protected]
Koordinator Penyelidikan (Sains dan Teknologi) 03-55442091 [email protected]
Koordinator Penyelidikan (Sains Kemasyarakatan & Kemanusiaan) 03-55442097 [email protected]
r Koordinator Perundingan (Kewangan) 03-55442090 [email protected]. edu. my
Koordinator Perundingan 03-55432100 aro @salam. Urn. edu. my
Penolong Pendaftar 03-55442092 dapeah [email protected]. edu.my
Pegawai Eksekutif 03-55442098 [email protected]
Pentadbiran 03-55442093
Unit Kewangan Zon 17 03-55442099 03-55443440 [email protected]
Surat Kami Tarikh
600 - BRC/ST. 5/3/545 ft Mac 2003
Prof. Madya Dr Umi Sarah Jais Pensyarah Fakulti Sains Gunaan Universiti Teknologi MARA 40450 Shah Alam
Puan
TAJUK PROJEK: RICE HUSK-DERIVED S i0 2 AEROGELS AND THE EFFECTS ON PROPERTIES OF PORTLAND CEMENT
Dengan hormatnya perkara tersebut di atas dirujuk.
Sukacita dimaklumkan bahawa Mesyuarat Jawatankuasa Mengendalikan Penyelidikan ke-65 pada 27 Februari 2003 telah membuat keputusan:
i. Bersetuju meluluskan cadangan penyelidikan yang telah dikemukakan oleh puan dan Dr Hamidah Mohd Saman.
ii. Tempoh projek penyelidikan ini ialah 12 bulan, iaitu mulai 15 Mac 2003 hingga 14 Mac 2004.
iiii. Kos yang diluluskan ialah sebanyak RM 20,000.00 sahaja.
IV.
v.
VI.
Penggunaan geran yang diluluskan hanya akan diproses setelah perjanjian ditandatangani.
Semua pembelian peralatan yang kosnya melebihi RM 500.00 satu item perlu menggunakan Pesanan Jabatan Universiti Teknologi MARA (LO). Pihak puan juga dikehendaki mematuhi peraturan penerimaan peralatan. Panduan penerimaan peralatan baru dan pengurusannya, dilampirkan.
Semua peralatan/kelengkapan penyelidikan yang dibeli adalah menjadi hak milik fakulti. Semua peralatan/kelengkapan hendaklah diserahkan kepada pihak fakulti setelah tamat penyelidikan untuk kegunaan bersama.
COPYRIGHT UiTM
vii. Kertaskerja boleh dibentangkan dalam seminar setelah 75% deraf awal laporan akhir penyelidikan dihantar ke Biro untuk semakan. Walau bagaimanapun, puan perlu membuat permohonan kepada Biro Penyelidikan dan Perundingan.
viii. Pihak puan dikehendaki mengemukakan Laporan Kemajuan Projek Penyelidikan bagi tempoh 6 bulan pertama penyelidikan dijalankan. Laporan Akhir perlu dihantar selewat-lewatnya 3 bulan selepas penyelidikan disiapkan. Format menulis laporan akhir boleh diperolehi di Biro Penyelidikan dan Perundingan atau di fakulti.
Bersama-sama ini disertakan dokumen perjanjian untuk ditandatangani oleh pihak puan. Sila penuhkan perjanjian berkenaan dengan menggunakan pen berdakwat hitam dan kembalikan ke pejabat ini untuk tindakan selanjutnya. Sekian, terimakasih.
"SELAMAT MENJALANKAN PENYELIDIKAN"
Yang benar
PROI R DR AZNIZAIN AHMED Penolong JNaib Canselor (Penyelidikan)
1. Timbalan Naib Canselor (Pembangunan dan Penyelidikan) Universiti Teknologi MARA
2. Dekan Fakulti Sains Gunaan Universiti Teknologi MARA Shah Alam
3. Dekan Fakulti Kejuruteraan Awam Universiti Teknologi MARA Shah Alam
4. Penolong Akauntan Unit Kewangan Zon 17 Biro Penyelidikan dan Perundingan
COPYRIGHT UiTM
Tarikh : 20 Januari 2006 No. Fail Projek : 600-BRC/ST.5/3/545
Penolong Naib Canselor (Penyelidikan) Institut Penyelidikan, Pembangunan dan Pengkomersilan Universiti Teknologi MARA 40450 Shah Alam
Ybhg. Prof.,
LAPORAN AKHIR PENYELD3IKAN "RICE HUSK-DERIVED SI02 AEROGEL AND THE EFFECTS ON THE STRENGTH AND THERMAL PROPERTY OF ORDINARY PORTLAND CEMENT"
Memjuk kepada perkara di atas, bersama-sama ini disertakan 2 (dua) naskah Laporan Akhir Penyelidikan bertajuk "Rice Husk-Derived Sio2 Aerogel And The Effects On The Strength And Thermal Property Of Ordinary Portland Cement"
Sekian, terima kasih.
Yang benar. benar,
PROF. MADVADRUMI SARAH JAIS Ketua Projek Penyelidikan
COPYRIGHT UiTM
PROJECT TEAM MEMBERS
ASSOCIATE PROFESSOR DR UMI SARAH JAIS Project Leader
toU V Tandat&Igan
*->
ASSOCIATE PROFESSOR DR HAMIDAH MOHD. SAMAN
Project Member
kx Tandatangan
ii
COPYRIGHT UiTM
PENGHARGAAN
Setinggi-tinggi penghargaan dan ribuan terima kasih diucapkan kepada semua pihak yang terlibat secara langsung dan tidak langsung bagi membolehkan penyelidikan ini disiapkan dengan sempurna.
Diantaranya:
Prof. Madya Dr. Mohd Kamal Harun (Dekan Fakulti Sains Gunaan)
Prof. Madya Dr. Muhamad Rosli Sulaiman (Fakulti Kejuruteran Kimia)
Staf Bahagian Seramik Teknologi (AMREC, SIRIMBHD, Shah Alam)
dan
Semua pembantu makmal yang telah memberikan kerjasama dan sokongan di dalam menjayakan penyelidikan ini
iv
COPYRIGHT UiTM
TABLE OF CONTENTS
TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES ABSTRACT
CHAPTER
1 INTRODUCTION 1.1 What are aerogels 1.2 History about the creation and evolution of aerog 1.3 Applications of aerogels 1.4 Research background and the problem
1.4.1 Ordinary Portland cement 1.4.2 Pozzolonic admixture
1.5 Obj ectives of study
2 LITERATURE REVIEW 2.1 Synthesis of silica aerogels
2.1.1 Properties of silica aerogel 2.1.2 The Surface Chemistry of silica aerogel 2.1.3 Drying of silica aerogel 2.1.4 Applications of silica aerogel
2.3.4.1 Thermal insulators 2.3.4.2 Particle detection and counters
2.2 Cement hydration
3 MATERIALS AND METHODS
iv
COPYRIGHT UiTM
3.1 Rice husk sample preparation 17 3.2 Synthesis of rice-husk derived silica aerogel 17 3.3 Characterisation of rice husk-derived silica aerogel 20
3.3.1 Density 20 3.3.2 Porosity 20 3.3.3 Surface area 20 3.3.4 Fourier Transform Infrared Spectroscopy (FTIR) 20 3.3.5 Thermal Gravimetric Analysis (TGA) 20 3.3.6 X-Ray Diffraction (XRD) 21 3.3.7 Scanning Electron Microscopy (SEM) 21 3.3.8 Thermal conductivity 21
RESULTS AND DISCUSSION 22 4.1 Characterisation of rice husk and rice husk-derived aerogel 22
4.1.1 Rice husk 22 4.1.2 Rice husk derived silica aerogel (RH-aerogel) 23
4.1.2.1 Physical properties 23 4.1.3 Hydroxyl content 24 4.1.4 Thermal properties 26
4.2 Effect of RH-aerogel on strength and thermal property of ordinary Portland cement 27
4.2.1 Effect on compressive strength 27 4.2.1.1 Phase evolution during strengthening 30
4.2.1.1.1 XRD 30 4.2.1.1.2 SEM 32
4.2.2 Effect on thermal conductivity. 33
REFERENCES 35 APPENDIX: Paper presented at Regeonal Coference
v
COPYRIGHT UiTM
List of Tables Page
Table 1.1 Cost involved in commercial production of aerogel 4 Table 1.2 Composition of ordinary Portland cement 5 Table 4.2 Properties of rice-husk aerogel 24 Table 4.3 Thermal conductivities of cement compositions with
7% of different pozzolans as cement replacement 34
vi
COPYRIGHT UiTM
List of Figures
Figure 1.1 Schematic diagram showing thermal insulating 5 property of aerogel-OPC composite
Figure 2.2 Schematic illustration of the different stages 14 of cement hydration
Figure 3.1 Process of obtaining rice husk ash from local rice husk 18 Figure 3.2 Schematic diagram showing the synthesis and 19
characterisation of rice husk=derived aerogel Figure 4.1 Pictures of a) Rice husks and b) Ash obtained after 22
heating rice husk at 1000C for lh Figure 4.2 Pictures of a) Water glass b) Rice husk aerogel 23 Figure 4.3 FTIR spectra of AO Rice husk ash and B) RH-aerogel 25
showing the strong hydroxyl absorption band Figure 4.4 TGA profile of RH-aerogel heated to 1000C at arate of 26
10C/min Figure 4.5a Effect of increasing amounts of RH-ash on strength of 29
OPC composite with varying days of hydration Figure 4.5b Effect of increasing amounts of RH-aerogel on strength 29
of OPC with increasing days of hydration Figure 4.6 XRD profile of A) 7 wt%RH-ash-OPC composite and 31
B) 7 wt% RH-aerogel-OPC composite Figure 4.7 SEM micrographs showing the microstructure of a) OPC 32
and b) RH-ash-OPC composite after 3 days of hydration Figure 4.8 SEM micrographs showing a) CSH fibres in RH-ash- 33
OPC and b) the microstructure of RH-aerogel -OPC after 7 days of hydration
vii
COPYRIGHT UiTM
ABSTRACT
Silica aerogel is a highly porous material and is the lightest material known to date. In this study silica aerogel was synthesised from local rice husk ash using sol-gel process. The effects of adding various quantities ranging from 3 to 7 weight percent of the rice husk-derived silica aerogel on the strength and thermal conductivity of ordinary Portland cement were studied. The strength was measured using ELE compressive strength machine while the thermal conductivity was determined using Lee's disc method. The results indicate that while there was no significant improvement in terms of strength, there was a marked drop in the thermal conductivity of the resultant cement composite. The significant drop in the thermal conductivity indicates that the rice husk-derived silica aerogel is highly potential as a thermally insulating cement replacement material suitable for a hot country like Malaysia.
viii
COPYRIGHT UiTM
CHAPTER 1
INTRODUCTION
1.1 What are aerogels?
Aerogels are the lightest and lowest-density solids known to exist. Aerogels consist
of a fine network of bubbles, with cell walls just a few atoms thick. Inside these cells, typically 50-99.5 %, is simply air, or whatever gas the designer wishes to
include. Due to their high porosity (up to 99%) and nano-structured nature, they
have low density (
or by accident, Kistler found a way to remove the fluid from a wet silica gel, leaving
behind its solid structure.
In the early 1930s, Kistler continued his experiments with aerogels, studying some
of their thermal and catalytic properties. The first commercial aerogels were
produced in 1942 by the Mosanto Corporation, under the trade name Santocel. The
process involved soaking a sodium silicate solution in sulfuric acid, then repeatedly
washing it in alcohol before drying it at high pressure. Mosanto described the
product as "a light, friable, slightly opalescent solid containing as much as 95
percent air volume. It is a very effective heat insulating material." [24] Mosanto
claimed to have produced aerogels with densities of 1.8 pounds per cubic foot (29
kg/m3), but their regular output was between three and five pounds per cubic foot
(48to80kg/m3)[19].
Mosanto marketed Santocel mainly as a flatting agent for paints and varnishes. Its
applications, though not numerous, were as varied as thermal insulation in
household freezers and an ingredient in Napalm. Because of its high manufacturing
cost, however, Mosanto discontinued aerogel production in 1970. Interest in
aerogels, and their very low thermal conductivity, increased in the 1980s as energy
conservation became increasingly important. However, high production costs still
prevent their widespread use [19].
2
COPYRIGHT UiTM
1.3 Applications of aerogels
According to their physical parameters (density, index of reflection, etc.) aerogels
occupy an intermediate position between solid and gas. For example, the density of
aerogel might be a hundred times less than the density of substances it is synthesized
from and, sometimes, heavier than air. Besides being the best thermal, electrical and
acoustic insulators known, aerogels find application as filters for seawater
desalination, micrometeoroid collectors, and subatomic particle detectors.
In future, aerogels could be used in windows, building insulation, automobile
catalyst converters, and high-efficiency battery electrodes. Also, Stardust spacecraft
will use aerogel to capture particles from comet Wild 2 in 2004 [20].
One of the first developments of aerogels was most strongly promoted by their
utility in detectors of Cerenkov radiation [20]. The speed of light in a given medium
is determined by the medium's index of refraction, and the index of refraction for
aerogels happens to be in a range that can be covered neither by compressed gases
nor by liquids. Aerogels have already been incorporated in several Cerenkov
detectors worldwide. Indeed, this is currently the widest practical application of the
material [20].
NASA used aerogel for thermal insulation on the Mars Exploration Rover, and it
may assist in a proposed fundamental-physics-testing mission and the Mars Scout
Program.
3
COPYRIGHT UiTM
1.4 Research background and the problem
Although the potential applications for aerogels are wide ranging and virtually
unlimited, they have to be cheaply manufactured in order to have an impact in the
commercial marketplace. As such, researchers have now turned their attention to
achieving these goals. Some groups have sought ways to eliminate the supercritical
drying process and the high capital cost associated with it, while others have sought
to make it more efficient.
The results of the above studies have shown that the cost of starting materials,
alkoxides, have been identified as the major contributor in the high overall cost of aerogel production. The costs of the two most common alkoxides being used
currently as the raw materias are listed in Table 1.1
Table 1.1: Cost involved in the synthesis of aerogel Alkoxide
Tetramethoxyorthosilane (99%)
Tetraehoxyorthosilane (99%)
Cost per liter (RM
1150.00
550.00
Aerogel produced perlitre of alkoxide (g)
100
100
The current study would try to synthesise silica aerogel from local rice husks which
as has been well known to contain silica and indirectly overcome the disposal
problem of an otherwise waste material
In the current study, the potential use of the developed aerogel as insulating material
is explored for walls of buildings in hot countries like Malaysia by adding varying
amounts of the aerogel to Ordinary Portland cement (OPC)
4
COPYRIGHT UiTM
1.4.1 Ordinary Portland cement
There are several types of cements for special purposes, but this project only concerns ordinary portland cement. OPC consists of five major compounds and a few minor compounds. The composition of a typical portland cement is listed by
weight percentage in Table 1.2.
Figure 1.1: Thermal insulating property of the aerogel-OPC composite
Table 1.2: Composition of ordinary Portland cement
Cement Compound
Tricalcium silicate
Dicalcium silicate
Tricalcium aluminate
Tetracalcium aluminoferrite
Gypsum
Weight Percentage
50%
25% 10%
10%
5%
Chemical Formula
Ca3Si05 or 3Ca0.SiO2
Ca2Si04 or 2CaO.Si02 Ca3Al206 or 3CaO .Al203 Ca4A12Fel0or 4CaO.Al203.Fe203
CaS04.2H20
5
COPYRIGHT UiTM
1.4.2 Pozzolanic admixture
Pozzolanic admixtures or "pozzolans" contain reactive silica (Si02) and sometimes
also reactive alumina (AI2O3) which in the presence of water react with lime to give
a gel of calcium silicate hydrate (SCH gel).
In the hydration of Portland cement, a considerable amount of calcium hydroxide is
produced. Hence, in mixtures made of pozzolan and Portland cement, a pozzolonic
reaction will take place due to the availability of lime. This availability of lime
facilitates the replacement of Portland cement by pozzolans and explains why such
an admixture can be used to produce pozzolan-based blended cements. The most
common materials are pulverised fly ash (PFA) and rice husk ash (RHA). The very
high surface area, combined with the high silica content, accelerate the pozzolanic
reactions, and thereby accelerate strength development. The very snail silica
particles, however, readily fill the spaces between the much coarser cement grains
and thereby, reduce the spacing between the solids. Hence, on subsequent
hydration, the resulting capillary pores in the silica aerogel containing paste are
much finer than the pores in the neat cement paste. The refinement in the pore
system has important particle implications. It will be seen later that the lower
permeability of silica aerogel containing cement and its associated improved
durability (10)
6
COPYRIGHT UiTM
1.5 Objectives The objectives of this study are:
1. To synthesis silica aerogel from rice husk ash by sol-gel process
2. To study the effect of the aerogel on the strength and thermal insulating
property of OPC.
7
COPYRIGHT UiTM
CHAPTER 2
LITERATURE REVIEW
2.1 Synthesis of silica aerogel
Silica aerogel could be derived by sol gel process. The process involved:
i) reacting silica precursor such as silicon aikoxide with sodium hydroxide
to form sodium silicate solution and precipitating it as water glass by
acidifying with acid such as hydrochloric or sulphuric acid,
ii) Drying the gel under supercritical conditions.
I Hj#slysis SiOR + HOH -, : - * SiOH + ROH Equation 2.2
Water | I Ces&nsitlan I I
SiOH + -SiOH ^ - ^ ^ * ^ 0^| + HO] Equation 2.3
-inn + -4 -OR ^ " ^ V -k -HH- l i - + I j ""* I I I Akoto^sis I
R: alkyl (example: CH3, C2H5, etc)
Figure 2.1 Sol gel process
Equation 2.4
8
COPYRIGHT UiTM
2.1.1 Properties of silica aerogel
Silica aerogel is one of the best candidates for transparent insulating materials [12].
It has very low thermal conductivity and good transparency because of its extremely
large porosity and small pore size [12]. At ambient temperature, the conductivity
value of silica aerogel is less than one half of that of usual insulating materials like
glass wool [12]. But silica aerogel is transparent, and radiative heat transfer
increases with the increase of temperature. The authors expected that the thermal
conductivity of silica aerogel is more affected by the temperature than that of usual
insulating materials.
Silica aerogels contain primary particles of 2-5 nm in diameter [13]. Silica particles
of such a small size have an extraordinarily large surface-to-volume ratio (~2 x 109
m") and a corresponding high specific surface area (-900 m7g) [13]. It is not
surprising, therefore, that the chemistry of the interior surface of an aerogel plays a
dominant role in its chemical and physical behavior. It is this property that makes
aerogels attractive materials for use as catalysts, catalyst substrates, and adsorbents
[13].
2.1.2 The surface chemistry of silica aerogel
The nature of the surface groups of a silica aerogel is strongly dependent on the
conditions used in its preparation. For example, if an aerogel is prepared using the
supercritical alcohol drying process, its surface may consist primarily of alkoxy (-
OR where R in alkyl group) groups. On the other hand, with the carbon dioxide
drying process the surface is almost exclusively covered with hydroxyl (-OH)
9
COPYRIGHT UiTM
groups. The extent of hydroxyl coverage is ~5 -OH/nm2, a value consistent with
other forms of silica. This value, combined with their high specific surface area,
means that silica aerogels present an extremely large number of accessible hydroxyl
groups. Silica aerogels are therefore a somewhat acidic material. A more striking
effect of the hydroxyl surface is seen in the physical behavior of silica aerogels [13].
As with most hydroxyl surfaces, the surface of silica aerogels can show strong
hydrogen-bonding effects. Because of this, silica aerogels with hydroxyl surface are
extremely hygroscopic. Dry silica aerogels will absorb water directly from moist air,
with mass increases of up to 20%. This absorption has no visible effect on the
aerogel, and is completely reversible. Simply heating the material to 100-120
degrees C will completely dry the material in about an hour (or longer, depending on
thickness).
As the sample cools, water will readsorb quickly (mass increases can be seen almost
immediately) [13]. While the adsorption of water vapor does not harm silica
aerogels, contact with liquid water has disastrous results. The strong attractive forces
that the hydroxyl surface exerts on water vapor also attract liquid water. However,
when liquid water enters a nanometer-scale pore, the surface tension of water exerts
capillary forces strong enough to fracture the solid silica backbone. The net effect is
a complete collapse of the aerogel monolith. The material changes from a
transparent solid with a definite shape to a fine white powder. The powder has the
same mass and total surface area as the original aerogel, but has lost its solid
10
COPYRIGHT UiTM
integrity. Silica aerogels with fully hydroxylated surfaces are, therefore, classified as
"hydrophilic" [13].
This would appear to pose a significant problem to using silica aerogels in exposed
environments. Fortunately, this problem can be easily circumvented by converting
the surface hydroxyl (-OH) groups to a non-polar (-OR) group. This is effective
when R is one of many possible aliphatic groups, although trimethylsilyl- groups are
the most common.
The derivitization can be performed before (on the wet gel) or after (on the aerogel)
supercritical drying. This completely protects the aerogel from damage by liquid
water by eliminating the attractive forces between water and the silica surface.
In fact, silica aerogels treated in this way can not be wet by water, and will float on
its surface indefinitely. Silica aerogels that have been derivitized in this way are
classified as "hydrophobic" [13].
2.1.3 Drying of silica aerogel
Aerogel properties are greatly influenced by the drying media used in supercritical
drying (SCD). Alcohol [14] and carbon dioxide (CO2) [15] are the two major types of SCD fluid used to prepare silica aerogel. Aerogel is made from an alcohol-based
gel containing silica particles, and in its raw form resembles a cube of DunsenDe
dessert [16]. This gel had to be dried without allowing it to collapse in on it, which
was done by soaking the gel in liquid carbon dioxide and then evaporating the
11
COPYRIGHT UiTM
alcohol and carbon dioxide at high pressure [16]. This left a structure of silica
particles with air between them. These pores, or spaces between the particles, made
the material both light-weight and a good insulator [16].
2.1.4 Applications of silica aerogel
Research on silica aerogels has focused on its use as a transparent thermal insulator
[17] and in Cherenkov detectors in high-energy physics [18].
2.1.4.1 Thermal insulators
Aerogel materials exhibit the lowest thermal conductivities of any of the solid or
porous materials. This key property of the material leads to many applications
including insulation for architectural purposes [17], piping, heat and cold storage
appliances and devices [17], automotive exhaust pipes, transport vehicles and
vessels. An advantage of silica aerogels for insulation applications is their visible
transparency (which will allow their use in windows and skylights) [17].
2.1.4.2 Particle detectors and counters
Earliest recorded use of aerogels was as particle detectors using the Cherenkov
effect in the early 1980s. High energy physics studies relied on aerogels having
specific refractive indexes for threshold detectors. Solid aerogels, though fragile,
were much easier and safer to apply than high pressure gas alternatives. Aerogel use
for particle detectors and counters continues in space, at accelerators around the
world, and in upper atmosphere balloon borne experiments [18].
12
COPYRIGHT UiTM
2.2 Cement hydration
Concrete is prepared by mixing cement, water, and aggregate together to make a
workable paste. It is molded or placed as desired, consolidated, and then left to
harden. Concrete does not need to dry out in order to harden as commonly thought.
The concrete (or specifically, the cement in it) needs moisture to hydrate and cure
(harden). When concrete dries, it actually stops getting stronger. Concrete with too
little water may be dry but is not fully reacted. The properties of such a concrete
would be less than that of a wet concrete. The reaction of water with the cement in
concrete is extremely important to its properties and reactions may continue for
many years. This very important reaction will be discussed in detail in this section.
When water is added to cement, each of the compounds undergoes hydration and
contributes to the final concrete product. Only the calcium silicates contribute to
strength. Tricalcium silicate is responsible for most of the early strength (first 7
days). Dicalcium silicate, which reacts more slowly, contributes only to the strength
at later times. Tricalcium silicate will be discussed in the greatest detail.
The equation for the hydration of tricalcium silicate is given by:
Tricalcium silicate + Water>Calcium silicate hydrate+Calcium hydroxide + heat
1 Ca3Si05 + 7 H20 > 3 Ca0.2Si02.4H20 + 3 Ca(OH)2 + 173.6kJ Eqn. 2.5
13
COPYRIGHT UiTM
Top Related