ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 59, (1) 17 - 23 (2015)


HYDRATION CHARACTERISTICS OF PROMPT CEMENT IN THE PRESENCE CITRIC ACID AS RETARDER
 
Heikal Mohamed 1,2, El-Didamony H. 3, Kishar E.A. 4, Negeada M.A. 5
 
1 Chemistry Department, College of Science, Al Imam Mohammad Ibn Saud, Islamic University (IMSIU),P.O Box 90950, Riyadh 11623, Saudi Arabia
2 Chemistry Department, Faculty of Science, Benha University, Benha, Egypt
3 Chemistry Department, Faculty of Science, Zagazig University, Zagazig, Egypt
4 Chemistry Department, Women's College, Ain Shams University, Egypt
5 Preparatory year university College of Dhiba, Tabuk University, Dhiba, Saudi Arabia

Keywords: Prompt cement, Citric acid, Hydration characteristics, Retarder
 

The aim of the present work is to study the influence of citric acid (CA) as retarder on the properties of prompt cement pastes. The dosages of CA were 0.50, and 0.75, 1.00 and 1.25 mass % of prompt cement. The initial and final setting times, bulk density, compressive strength, total porosity, and hydration kinetics such as free lime, combined water contents and XRD for selected sample were investigated. The results obtained in this study showed that the addition of CA elongates the initial and final setting times and decreases the compressive strength and combined water contents, whereas, it increases the total porosity at all ages of hydration. CA retards the liberation of Ca(OH)₂ of prompt pastes. The free lime contents of prompt cement pastes are slightly increased up to 28 days then sharply increased up to 90 days. Thus, it is suggested that citrate sorbed onto the clinker surface and formed a protective layer around the clinker grains retarding their dissolution. The sharp increase of compressive strength at later ages after 28 days up to 90 days. The presence of 0.75 mass % citric acid achieves the initial and final setting time of the prompt cement according to the ASTM specification.


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