An Integral Materials and Logistical Approach to Increasing the Shelf Life of Rapid Setting Cements

Abstract- The objective of this Phase I project is to explore a multi-thronged, integral approach to increasing the shelf life of rapid-setting cements. Rapid-setting cements are a special class of cements developed for their early strength and fast-setting characteristics. They are important materials in the context of military and civilian applications that require fast rehabilitation of concrete infrastructure such as runways, taxiways, airports or highways. The rapid-setting concrete must exhibit sufficient versatility to repair potholes, full-size craters or pavement for aprons or taxiways. It may also be used in adverse climatic environments. However, heat and humidity can adversely affect the stability of the cementitious powder.Typically, rapid-setting cements are not silicate-based cements, which are relatively slowly hydraulic. They are either calcium aluminates or calcium sulfoaluminates that hydrate more rapidly than silicate-based Portland cements, which explains their rapid strength development. They hydrate in a matter of minutes or hours, not days. As a result of this enhanced reactivity with water, they can also react with ambient moisture, especially in hot and humid climates. This can result in a reduced shelf life. Generally, the shelf life of packaged aluminates or sulfoaluminates cement is limited to a couple of years or so under optimum ambient conditions. This can be shortened drastically under adverse storage or shipping conditions. A compromised shelf life can lead to decreased performance, such as delayed setting, reduced strength, or loss of hydraulic reactivity. Therefore, improving and maintaining the shelf life of rapid strength cements is crucial for product consistency, performance reliability, cost efficiency and waste minimization.In this proposal we explore the physical, chemical, and logistical strategies that can be employed to enhance the shelf life of rapid-setting concrete mixtures we take a top-down approach involving clinker and cement materials chemistry, microstructure of the clinker, fineness of the cement, the use of anti-caking or dessicating additives, or time-delay coatings. Packaging improvements are also considered.