Evaluation some properties of nanometakaolin or rice husk ash cement mortar and its resistance to elevated temperature

الملخص EN

The objective of this research is to find the optimum value of some properties like compressive, flexural strength of blended cement mortar by nanometakaolin ( NMK) or rice husk ash (RHA) and to evaluate the effect of high temperature on these properties.

The ordinary Portland cement(OPC) of mortar was partially substituted by NMK or RHA of 5,10,15 and 20% by weight of cement.

(108) control and blended specimens were casted and tested at ambient temperature (33 ºC) for compressive and flexural strength for 28 and 90 days.

Another (270) of the control and blended specimens were casted and cured for 90 days and exposed to elevated temperature of a gradual increase in temperature up to 200 ºC,300 ºC, 400 ºC,600 ºC and 800 ºC for two hours in an electrical furnace and they were under the same previous tests.

The test results at ambient temperature indicate that the optimum compressive and flexural strength was with ratio of 15% NMK cement replacement in mortar for 28 and 90 days but for RHA was ratio of 10% for 28 days and 15% of cement weight in mortar for 90 days compared to control specimens.

The results of exposing control and blended specimens of (90) days to elevated temperature showed that the optimum strength for control and the best MK replacement ratio were found at 200 ºC, and the best RHA replacement ratio specimens was found at 300 ºC.

It is also found that exposing the mortar to more than these temperatures destroyed its strength and it was detrimental to its properties.