HIGH PERFORMANCE AEROGEL CONCRETE

HIGH-PERFORMANCE
AEROGEL CONCRETE
Guided By:
Dr. Anupama Krishna D
Assistant Professor,
Department of Civil Engineering,
MBCET, Trivandrum
Presented By:
Savinaj V Santhosh
Roll Number: 53
CE – 2 ; Semester – 7
MBCET, Trivandrum
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OVERVIEW
➢ INTRODUCTION
➢ OBJECTIVES
➢ WHAT IS HPAC
➢ MATERIALS USED IN HPAC
➢ MIXTURES FOR HPAC
➢ PROPERTIES OF HPAC
➢ ADVANCEMENTS IN HPAC
➢ CASE STUDY
➢ ADVANTAGES AND LIMITATIONS OF HPAC
➢ CONCLUSION
➢ REFERENCES
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HIGH-PERFORMANCE AEROGEL CONCRETE

➢ Requirements for the thermal insulation of residential and non-
residential buildings have led to a number of developments in the field
of building materials for massive outer walls.
➢ For thermal insulation it requires building materials with low thermal
conductivity and high compressive strength.
➢ Most of the masonry blocks or concrete show either a low thermal
conductivity with low compression strength or vice versa.
➢ Preferred Lightweight Aggregate Concrete (LWAC) over all other building
materials for insulation.
INTRODUCTION
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INTRODUCTION (Contd..)
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Materials ρ (kg/m³) fk / fck (MPa) λ (W/(mK))
Light-weight Concrete Block 315-335 0.8 0.06
Aerated Cement Block 250 0.8 0.07
Proton Brick 810-900 4.2 0.09
Aerated Cement Block 400 1.8 0.10
Light-weight Concrete Block 600 2.5 0.14
Proton Plane Brick 710-800 4.7 0.16
Sand-lime Brick Silica 1210-1400 5.6 0.56-0.70
Light-weight Aggregate Concrete 1500-1600 35.0 0.89-1.00
Sand-lime Brick Silk 1810-2000 10.5 0.99-1.10
Normal weight Concrete 2200-2400 12.0 1.65-2.0
Reinforced Concrete 2300-2400 30.0 2.3-2.5
Table 1: Bulk Density, Compressive Strength and Thermal Conductivity of selected Wall Building materials. [1]

INTRODUCTION
➢ Still LWAC had low thermal conductivity and comparatively low
compressive strength.
➢ High-performance concrete (HPC) is concrete are stronger than LWAC. It
has high compressive strength of above 80 MPa.
➢ But one of the major demerit of these concrete is its high thermal
conductivity.
➢ The thermal conductivity can be reduced by introducing silica aerogels into
high performance concrete mix instead of aggregates known as High-
Performance Aerogel Concrete (HPAC) and thereby increasing its
compressive strength.
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INTRODUCTION (Contd..)

OBJECTIVES
➢ By the development of High-Performance Aerogel Concrete the aim is to
develop a building material, which has low bulk density, low thermal
conductivity and higher compressive strength compared to LWAC.
➢ HPAC makes it suitable for the construction of single-leaf exterior walls of
multi-storey buildings without any further thermal insulation.
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WHAT IS HPAC ?
➢ Prepared by embedding silica aerogel granules
in a high strength cement matrix.
➢ HPAC is extremely water repellent and protects from moisture damage
corrosion.
➢ HPAC is a High Thermal Insulating material with
High Compressive Strength.
➢ HPAC retains its shape in high-temperature
exposure and does not crack, clump, or sag like other insulating materials.
➢ The thermal conductivities are in the range 0.16 ≤ λ ≤ 0.37 W/(mK).
➢ The compressive strength is about 60 MPa, further could be increased by
providing reinforcement for about 80 MPa or greater.
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Fig 1: Microstructure of HPAC. [1]
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MATERIALS USED IN HPAC
1.SILICA AEROGEL
2.HIGH PERFORMANCE CONCRETE
1. SILICA AEROGEL
➢ Created by SAMUEL STEPHENS KISTLER.
➢ Also called blue or frozen smoke.
➢ Traditional thermal insulating building material.
➢ Nano-porous material with remarkable properties:
1. High specific surface area (500–1200 m2/g).
2. High porosity (80–99.8%).
3. Low density (0.003 g/cm3).
4. Ultra-low dielectric constant (k = 1.0–2.0).
5. High thermal insulation value (0.005 W/(mK)).
6. Low index of refraction (1.05).
Fig 2: Silica Aerogel.
(Source: www.googleimage.com)
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MATERIALS USED IN HPAC (Contd..)
Synthesis of Silica Aerogel
The synthesis of silica aerogels can be
divided into 3 general steps:
a. Gel Preparation
b. Aging of Gel
c. Drying of Gel
Fig 3: Synthesis of Silica Aerogel.[3]
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2. HIGH PERFORMANCE CONCRETE
➢ HPC possesses high workability, high strength and high durability.
➢ Gives excellent performance in the structure in which it will be placed.
➢ Compressive strength > 80 MPa.
➢ Main characteristic properties are:
1. Low porosity.
2. It has very low permeability.
3. High resistance to chemical attack.
4. Low heat of hydration.
5. High early strength.
6. Low Bleeding.
MATERIALS USED IN HPAC (Contd..)
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MIXTURES FOR HPAC
➢ Silica Aerogel granules used :
- amount varies from 45 to 70 %.
- particle size from 0.01 mm to 4.0 mm.
- a thermal conductivity of ≤0.02 W/(mK).
- porosity > 90%.
➢ Flow behaviour is adjusted by the amount
of superplasticizers used (e.g., sulphonated
melamine formaldehyde (SMF), sulphonated
naphthalene formaldehyde (SNF) etc.)
Portland Cement kg/m3 541.0
Silica Aerogel Granule vol% 61.4
Silica Suspension wt% * 13.0
Superplasticizer wt%* 3.6
Organic Stabilizer wt%* 0.5
w/c based on the amount of - -
the cement used.
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Table 2: Reference mixture of HPAC. [4]
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01
02
03
04
Add water-silica mixture,
water-plasticizer mixture
and the stabilizer
After restarting the mixing,
add the remaining water
and continuing to mix
Add the inorganic
binder during a
suspension of mixing
Mixing aerogel and
any lightweight
aggregates
MIXTURES FOR HPAC (Contd..)
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Fig 4: Preparation of HPAC.

PROPERTIES OF HPAC
1. Dry Bulk Density
▪ Due to the absence of sand and coarse aggregate the solid content
of HPAC is reduced resulting in lower dry bulk density.
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Fig 5: Relation between the Aerogel amount and the Dry Bulk Density of
High-Performance Aerogel Concrete compared to Aerogel Concrete. [4]
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2. Compressive Strength
▪ Performed using Universal Testing Machine
with constant load speed set to 9 kN/s.
▪ Compressive strength of HPAC was higher
than 600 kg/m3, which is equal to 60 MPa.
▪ Compressive strength of HPAC is higher
than that of the Aerogel Concrete.
PROPERTIES OF HPAC (Contd..)
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Fig 6: Relation between Dry Bulk Density and
Compressive Strength of HPAC
compared to Aerogel Concrete. [4]
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3. Flexural Tensile Strength
▪ Flexural tensile strength of HPAC was determined for
eight mixtures with an amount of aerogel granule
between 45% to 70% volume.
▪ Four-point bending tests performed on the samples
with dimensions: 700mm x 150 mmx150 mm.
▪ Flexural tensile strength of HPAC is slightly lower
than that of LWAC.
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Fig 7: Four-point bending test
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3. Flexural Tensile Strength (Contd..)
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Fig 8: Relation between Compressive Strength and Tensile Strength
of HPAC in comparison to Lightweight Aggregate Concrete.[4]
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4. Young’s Modulus
▪ Standard cylinders with dimensions of
150mm x 300mm are used to determine
the Young’s Modulus of the mixtures.
▪ Young’s modulus of HPAC is slightly
lower than that of LWAC.
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Fig 9: Relation between the Compression Strength and
Young’s Modulus in comparison to Lightweight
Aggregate Concrete.[4]
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5. Thermal Conductivity
▪ Thermal conductivity is determined using the
Heat Flow Meter Method.
▪ 14 days after concreting cubes with an edge
length of 150 mm were cut into slices of
30 mm thickness and stored in a drying
cabinet at 100°C for 24 hrs before testing.
▪ Thermal conductivity of HPAC is very much
lower compared to Aerogel concrete.
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Fig 10: Heat Flow Meter Method

5. Thermal Conductivity (Contd..)
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Fig 11: Relation between Compressive Strength and Thermal
Conductivity of HPAC compared to Aerogel concrete. [4]
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ADVANCEMENTS IN HPAC
➢REINFORCED HPAC
▪ The comparatively low flexural tensile strength of
HPAC result in the need for reinforcement if HPAC
is intended to use for construction members
subjected to bending.
▪ GFRP reinforcement bars were used in order to
avoid negative effects on the thermal conductivity
of HPAC and problems resulting from different
thermal expansion coefficients which may be
caused by steel reinforcement. Fig 12: Test Set Up for the Pull-Out tests.[6]
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➢GRADED HPAC
▪ Thermal insulating properties of HPAC is achieved by
the realization of graded HPAC members.
▪ It consists of:
i) load carrying layer with a high compression strength.
ii) an insulating layer with a low thermal conductivity
▪ The bond strength or shear strength, respectively, and
the adhesive tensile strength is very much higher.
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ADVANCEMENTS IN HPAC (Contd..)
Fig 13: Graded HPAC.
Above: heat-insulating layer,
Below: load carrying layer.[6]
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➢3D PRINTABLE AEREOGEL CONCRETE
▪ Aerogel incorporated concrete is suitable for 3D printing.
▪ The optimal replacement range for sand by silica aerogel
in a cementitious mixture was about 0% – 20% by volume.
▪ The thermal conductivity of the cast and printed
specimens decreased gradually with an increase in the
aerogel content.
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ADVANCEMENTS IN HPAC (Contd..)
Fig 14: 3D Printed Aerogel Concrete.[6]
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CASE STUDY
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CASE STUDY 1
STUDY OF PHYSICAL PROPERTIES AND MICROSTRUCTURE OF AEROGEL-
CEMENT MORTARS FOR IMPROVING THE FIRE SAFETY OF HIGH-
PERFORMANCE CONCRETE LININGS IN TUNNELS.
▪ The St. Gotthard Tunnel in Switzerland.
▪ The Mont-Blanc Tunnel in France-Italy.
(Authors: Pinghua Zhu, Samuel Brunner, Shanyu Zhao and Michele Griffa)
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INTRODUCTION
➢ Tunnel fire that occurred during the past decades increased the interest in
structural fire safety of large underground facilities and have highlighted
the importance of increasing the fire resistance in materials and structural
design of tunnels.
➢ During tunnel fires HPC results in explosive spalling, causing devastating
damage of the tunnel structure, which threatens both, civilians and
emergency response units.
➢ Solution to this problem is to make use of a highly-insulating layer.
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OBJECTIVE OF THE STUDY
➢ Aim of making use of highly-insulating layer to delay the heating of the
HPC and extending the performance of the main concrete structure of the
tunnel under fire.
➢ Uses silica aerogel in the protection of concrete linings by coating with a
layer of High-Performance Aerogel Concrete.
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EXPERIMENTAL INVESTIGATION
➢THERMAL CONDUCTIVITY
▪ Small cylindrical aerogel-cement mortar samples
(ϕ 60 mm × 15 mm) were measured on a
custom-built guarded hot plate device with
guarded zone: 50 × 50 mm2, measuring zone:
25 × 25 mm2 having a 15°C temperature
difference, which was originally designed for
small samples of low thermal conductivity
materials.
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Fig 15: Guarded Hot Plate Device

INFERENCE:
For avoiding or delaying the explosive spalling of HPC tunnel linings, the
thermal conductivity of the aerogel mortars used is the essential parameter
to be controlled..
● without aerogels-thermal conductivity 1.7 W/(mK),
● With the addition 33% in volume of silica aerogels, thermal conductivity
was about 0.4 W/(mK)
With increasing amounts of aerogels in the mortar, proportionally smaller
decrease of thermal conductivity is observed.
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EXPERIMENTAL INVESTIGATION (Contd..)
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➢EVALUATION OF EXPLOSIVE SPALLING
▪ Thermal loading was performed from one side of the specimens
(corresponding to the side coated with aerogel mortar and uncoated HPC)
using a heating plate.
▪ The heating process started from room temperature and the temperature
of the plate was increased uniformly up to a maximum temperature of
600 °C within about 40 min.
▪ The maximum temperature was kept for 2h, followed by free cooling down
on the heating plate in ambient air.
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Fig 16: Modelling method of Tunnel and Lining.[7] Fig 17: Design method of Silica Aerogel Coating.[7]
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INFERENCE:
● The HPC cube without aerogel protection spalled after 25 min of thermal
loading, confirming the susceptibility of HPC to explosive spalling when
exposed to high temperatures .
● In the case of the HPC samples protected by a aerogel layer, explosive
spalling occurred later on samples with thinner mortar layer at 68 and 148
min after the start of loading.
● On samples with thicker layers, spalling did not occur during the testing
period.
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CONCLUSION OF THE STUDY
➢ In this study, a strategy for protecting tunnel shield high performance
concrete (HPC) from explosive spalling was suggested, consisting in coating
the surface with High-Performance Aerogel Concrete of low thermal
conductivity.
➢ In a series of preliminary tests, layers of 40–50 mm of such aerogel
mortars were able to prevent fire spalling of high-performance concrete
cubes.
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CASE STUDY 2
10/30/2022
STUDY ON THE THERMAL PERFORMANCE OF EXTERIOR WALLS COVERED
WITH SILICA-AEROGEL-BASED INSULATING COATING.
▪ Domestic Buildings in Switzerland.
▪ Buildings in cities of Basel and Zurich.
(Authors: Mohamad Ibrahim, Pascal Henry Biwole and Etienne Wurtz)
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INTRODUCTION
➢ The building's external fabric is in continuous interaction with the outside
environment.
➢ The outside surface temperature of the walls/roof is greatly affected by
the outer air temperature and solar radiation leading to fluctuations in the
heat flux passing through them to the inside.
➢ The lower the energy consumption, the better is the wall.
➢ Solution to this problem is make use of an insulating layer with low
thermal conductivity.
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OBJECTIVE OF THE STUDY
➢ Aims at examining the energy behaviour of the buildings multi-layer
exterior wall structures.
➢ To find the best wall structure and best position of insulation layers within
exterior walls for continuous heating, intermittent heating, and no heating
operation modes using HPAC.
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Fig 18: Silica-Aerogel-Based Coating.[9]
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EXPERIMENTAL INVESTIGATION
➢ Done on test-cell of a small-scale building
composed of three cells (current test cell,
adjacent cell, and acquisition cell).
➢ The test-cell is composed of two external walls
having orientations south and east, and two
internal walls (partitions with the other cells).
➢ The volume of the test cell is 30 m3.
➢ The south wall is taken as the test wall, composed
of concrete (external layer), glass wool & plaster.
➢ Then, added a 4 cm layer of the HPAC coating on
its external surface.
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Fig 19: Test Cell (and Adjacent Cells) [9]
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Material Thickness
(cm)
Thermal
conductivity
(W/(mK))
Specific heat
(J/(kg.K))
Density (kg/m3)
Plaster (inside layer) 1.3 0.32 800 790
Glass wool 16 0.041 840 12
Concrete 5 2.1 800 2400
Aerogel coating 4 0.027 1100 200
Table 3: Thermo-Physical properties for South Wall construction materials in the Test Cell. [9]
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➢ Temperatures are measured using K-type Thermo-couples
with a precision of ±0.3 C.
➢ They are placed:
i) at the exterior surface of the coating,
ii) at the interface between the coating and the concrete,
iii) at the interface between concrete and internal insulation
(glass wool), and
iv) at the interior surface of the plaster layer.
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Fig 20: Temperature Sensors
Within the South Wall.[9]
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INFERENCE
➢ Placing the insulation at the middle of the wall and at the interior surface
provides the best performance.
➢ Placing the insulation at the interior wall surface is the best solution when
considering the discomfort hours during the occupied period.
➢ Exterior insulation is the worst of all cases when considering the
discomfort hours during the occupied period.
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CONCLUSION OF THE STUDY
In this study, a strategy for understanding which layer of the wall would
provide better insulation while coating with High-Performance Aerogel
Concrete was undertaken. Results revealed that placing the insulation at the
interior wall surface is the best solution.
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ADVANTAGES OF HPAC
➢ Low Thermal Conductivity.
➢ High Stability of Aerogel in Concrete.
➢ Highly Durable.
➢ Low Density.
➢ Light Weight.
➢ High Frost Resistance.
➢ Energy Efficient.
ADVANTAGES AND LIMITATIONS OF HPAC
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LIMITATIONS OF HPAC
➢ Highly Expensive
➢ Low Modulus of Elasticity
➢ High Tendency to Shrink.
➢ Low Bond Stress compared to HPC.
➢ Requirement of reinforcement.
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CONCLUSION
➢ HPAC shows an improved correlation between dry bulk density and
compressive strength as well as compressive strength and thermal
conductivity.
➢ HPAC shows an improved performance over the full spectrum of
investigated compressive strength in the range 25MPa ≤ fcm ≤ 60MPa.
➢ Due to low flexural and tensile strength of HPAC, reinforcement is required
if HPAC is intended to be use for construction members subjected to
bending.
➢ HPAC can be used to avoid exposure spalling during tunnel fires.
➢ Layer of 40-50 mm of silica aerogel were able to prevent fire spalling.
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➢ Lower thermal conductivity, high sound absorption and high fire
resistance of HPAC allows the production of load-carrying, single-leaf
exterior walls without any further thermal insulation.
➢ HPAC with 50 vol% aerogel content showed the sound absorption capacity
of µ = 0.309, which was about 38 % better than normal-weight concrete.
➢ The HPAC achieved a thermal conductivity of λ = 0.26 that is approx. 25.7
% lower as the LWAC’s thermal conductivity by the same density.
➢ The modulus of elasticity of HPAC with 50 vol% aerogel content was about
8000-10,000 MPa and is comparable to LWAC with the same bulk density.
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CONCLUSION (Contd..)
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REFERENCES
[1] Fickler, S., Milow, B., Ratke, L., Schnellenbach-Held, M. and Welsch, T.
(2015), “Development of High-Performance Aerogel Concrete”, Energy
Procedia 78, 406-411.
[2] Shah, S. N., Mo, H. K., Yap, S.P. and Radwan, M., K.H. (2021), “Towards an
Energy Efficient Cement Composite Incorporating Silica Aerogel: A State-of-
the-Art Review”, Journal of Building Engineering 44, 103227.
[3] Lamy-Mendes, A., Pontinha, A. D. R., Alves, P., Santos, P. and Duraes, L.
(2021), “Progress in Silica Aerogel-Containing Materials for Building’s
Thermal Insulation”, Construction and Building Materials 286, 122815.
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[4] Welsch, T. and Schnellenbach-Held, M. (2018), “High Performance
Aerogel Concrete”, High Tech Concrete: Where Technology and Engineering
Meet, 117-124.
[5] Wang, Y., Huang, J., Wang, D., Liu, Y., Zhao, Z. and Liu, J. (2019),
“Experimental Investigation on Thermal Conductivity of Aerogel
Incorporated Concrete Under Various Hygrothermal Environment”, Energy
Procedia 188, 115999.
[6] Schnellenbach-Held, M. and Welsch, T. (2016), “Advancements in High
Performance Aerogel Concrete”, Structural Engineering, Mechanics and
Computation, 1577-1582.
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REFERENCES (Contd..)

[7] Liu, S., Zhu, P. and Li, X. (2020), “Design Approach for Improving Fire-
Resistance Performance of Tunnel Lining Based on SiO2 Aerogel Coating”,
Journal of Performance of Constructed Facilities 34 (3), 0402003.
[8] Zhu, P., Brunner, S., Zhao, S., Griffa, M., Leemann, A., Toropovs, N., Lura,
P., Malekos, A. and Koebel, M. M. (2019), “Study of Physical Properties and
Microstructure of Aerogel Cement Mortars for Improving the Fire Safety of
High-Performance Concrete Linings in Tunnels”, Cement and Concrete
Composites 104, 103414.
[9] Ibrahim, M., Biwole, H. P., Wurtz, E. and Achard, P. (2014), “A Study on the
Thermal Performance of Exterior Walla Covered with Silica-Aerogel-Based
Insulating Coating”, Building and Environment 81, 112-122.
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REFERENCES (Contd..)

THANK YOU
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HIGH PERFORMANCE AEROGEL CONCRETE

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