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