NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC A MACRO-MODEL FOR SELF-DESICCATION IN HIGH PERFORMANCE CONCRETE Lars-Olof Nilsson Div. of Building Materials Lund Institute of Technology Lund University Kristina Mjörnell Dept. of Building Physics Swedish National Testing and Research Institute, Borås

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Outline 1. Introduction 2. The model for self-desiccation 3. Physical binding of water 4. Chemical binding of water 5. Internal curing 6. Predictions with the model 7. Conclusion

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC HPC in Sweden 1.A few important marine concrete structures where a service-life of some 100 years is required in harsh marine environments (a SRPC/silica fume HPC) ’s of concrete floor slabs where a moisture sensitive flooring is to be used (OPC HPC; w/C  0.40: Main reason for using HPC is the controlled and rapid drying by self-desiccation.

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Drying of HPC HPC NC

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Dominating mix parameters for self- desiccation cement type and w/c Really true?

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Self-desiccation in the sorption isotherm

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC The model for self-desiccation where

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Physical binding of water w e /C wewe S cap Alkali effect

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Desorption isotherms for HPC f(w/B, Si)

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC The model for self-desiccation  the desorption isotherm at different ages

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Desorption isotherms for HPC at early ages (room temperature)

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC The model for self-desiccation where = chemical binding of water at different T & RH(t)

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Chemical binding of water

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Chemical binding of water lack of space  w/c cc

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Chemical binding of water moisture effects carbonation?  RH w n /C(RH, t 1 )

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC TGA-studies on reactivity at shortage of water Norling-Mjörnell (1997) SRPC, w/C=0.3, 5% Si-fume

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Chemical binding of water moisture effects OPC Mjörnell (1997)  RH w n /C(RH, t 1 )

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Chemical binding of water moisture effects OPC Si-fume Mjörnell (1997)  RH w n (RH, t 1 )

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Chemical binding of water moisture effects  RH w n (RH, t 1 ) f(  ) alkali effect?

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Chemical binding of water moisture effects cc  ,w cf. Snyder & Bentz(2004)

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Chemical binding of water temperature effects

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Predictions with the model - cement hydration cc w/c 0.4 OPC

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Predictions with the model - self-desiccation, room temperature

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Predictions with the model - cement hydration, curing effects cc SRPC with w/c 0.4

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Predictions with the model - self-desiccation, low temperature But later findings indicate quite another low-temperature curing effect! cf. Persson (2005) SRPC with w/c 0.4

NIST self-desiccation seminar June 20, 2005 L-O Nilsson A MACRO-MODEL FOR SELF-DESICCATION IN HPC Conclusions The model for self-desiccation seems very promising and potentially useful for many applications of HPC The model is especially designed for concrete floor slabs, where self-desiccation is beneficial. Could very well be applied to concrete structures of HPC were the main concern of self-desiccation is shrinkage and early age cracking, and including internal curing. The model can easily be integrated into a model that includes moisture transport (has been done!) The most uncertain part of the model is the moisture effect on rate of reaction, where more research is needed, especially at very early ages. The effect of early curing at low temperature may require special attention!