1. High Temperature Resistance of Carbonated Concrete Made From Calcium Silicate Cement (CSC)
HyunGu Jeong*, Jan Olek*, Jitendra Jain**, Sadananda Sahu**
*Purdue University at West Lafayette, IN, ** Solidia Technologies at Piscataway, NJ
July. 10th. 2016
Heating and cooling rate
Test Results
Mass loss and compressive strength (concrete)
Change in the appearance
- CSC concrete
- OPC concrete
Test Results
TGA / SEM (Paste)
XRD (Paste)
Calcium Silicate Cement (CSC)
Production
- Composed of low (~1/1.5) Ca/Si compounds so it requires less limestone and has lower (~ 200 to 300°C) burning temperature compared to ordinary portland cement (OPC)
Hardening due to carbonation (CO2 curing) in the presence of moisture
Total (production + application) reduction in CO2 footprint up to 70 % compared to OPC
Applications of calcium-silicate cement concrete
- pre-fabricated products such as blocks, pavers, pervious concrete, hollow-core slabs, pipes and railroad ties
Objectives
Comparison of high temperature resistance of calcium silicate cement and OPC concretes
- Physical degradation: Thermal cracking and spalling leading to loss of stiffness and strength reduction
- Chemical degradation:
Compositional and microstructural changes in the matrix
Chemical Reaction
Experimental Program
Test matrix
- Comparison high temperature behavior of CSC concrete and OPC concrete
1) Visual inspection
2) Loss of compressive strength and mass
3) Change in microstructure
▫ ±1°C/min to minimize the effect of temperature gradient
▫ 2hrs at 105°C to remove free water
Decomposition of CaCO3 Ca CH Ca
CSC
OPC
Hydration
of OPC
Carbonation
of CSC
C3S, C2S
H2O
CS, C3S2
CO2
CaCO3
SiO2
CSH CH
Calcite ( ), Vaterite ( ), Aragonite ( ), Quartz ( ), Lime ( ),
Pseudowollastonite ( ), Rankinite ( ), C2S ( ), Gehlenite ( ),
Wollastonite ( )
Portlandite ( ), C-S-H / tobermorite ( ), ), Lime ( ), Anhydrate CaSO4 ( )
C3S ( ), C2S ( ), Brownmillerite ( )
Conclusions
CSC concrete
- No visible surface cracking below 700°C
- 80% strength drop between 500°C and 700°C
due to decarbonation of CaCO3
OPC concrete
- Visible surface crack past 400°C
- Continuous decrease of strength beyond 200°C
- Complete disintegration of microstructure (loss of binding capability) beyond 800°C.
Before exposure
After 700°C
After 800°C
Test
Type of specimen
Size (in)
Compressive strength
CSC/OPC concretes
3×3×3
TGA, XRD
CSC/OPC pastes
Ground powder
SEM
1×1×1
Small cracks near edge
Small cracks near edge
Future Work
Measurements of changes in porosity with increased temperature by MIP and AFM techniques.
Before exposure
After 400°C
After 800°C
Small cracks near voids
Complete loss of bonding capability