Cement hydration with ultrasound treated clinoptilolite
There are many cement replacement materials and one of them is zeolites. Zeolites are crystalline solids structures made of silicon, aluminum and oxygen that form a framework with cavities and channels inside where cations, water and/or small molecules may reside. In this study natural zeolite clinoptilolite was used. Clinoptilolite is the most popular natural zeolite mineral with the chemical formula (Na, K, Ca)23Al3(Al,Si)2Si13O3612H2O. The present paper shows the results of using ultrasound treated clinoptilolite as Portland cement replacement material. The duration of ultrasound treatment was 5 min, 10 min, and 20 min. Results showed that the XRD of ultrasound-treated clinoptilolite slightly differs in comparison to conventional clinoptilolite. The cement samples with 5% and 10% clinoptilolite substitute provide the strength increase, 30% significantly reduces the strength compared to control samples. The heat measurements of Portland cement paste hydration, containing clinoptilolite, showed that the clinoptilolite slightly increases the duration of hydration, but hydration temperature is lower than in the controls samples. The experimental results suggest that ultrasound-treated clinoptilolite positively influence cement hydration processes, consolidation kinetics, CSH formation; the mechanical strength of the samples is increased. Typical content of Portland cement substituting does not exceed 20% of mass of Portland cement in samples. Reducing the consumption of Portland cement with substituting it with ultrasound treated clinoptilolite is preferred for reasons of environmental protection.