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 The platy crystal formation of the calcium hydroxide system (CONEX) has a greater surface area than the needle-like surfaces of an ettringite system such as that developed with a Type-K cement and/or a CSA (calcium sulfoaluminate) ettringite system. The bond to steel of the component calcium hydroxide platelet system (CONEX) tends to be greater, and thus less material is necessary to obtain the same RE (Restrained Expansion) than with a component ettringite system when tested in accordance with ASTM C-878. The addition of CONEX to a concrete mix provides a predetermined percentage of CALCIUM OXIDE and ALUMINUM DIOXIDE, plus certain other chemical compounds that will react with specific elements found in the concrete to form CALCIUM HYDROXIDE PLATELETS. The amount of platelets produced, thus the percentage of restrained expansion (RE), is regulated by the amount of CONEX introduced into the mix. There have been certain misconceptions relative to the amount of expansion that occurs during the early time of setting and strength gain (i.e.: the first 24 hours). Some engineers have been of the opinion that if the rate of expansion is “too fast”, there is a loss of RE (restrained expansion) in the concrete, and therefore, the rate of expansion should occur over several days of wet curing, (which is necessary in an ettringite system, but not in a calcium hydroxide platelet system). This hypothesis is correct, but only to a degree. If the initial set time of the concrete is slow (retarded greater than 8-10 hours), the amount of loss of RE during this period of extended set time should be considered. This can be done by increasing the dosage of the component CONEX. The increased dosage will produce a greater RE that will allow (compensate) for the possible loss during the early stage of extended setting. CONEX has its RE achieved during the first 24 to 48 hours, depending upon the cement in use. CONEX is compatible with virtually all cements meeting ASTM C-150, including, but not limited to Types I, II, III, IV, V, LA, IP, IA, & slag cement. CONEX can also be used with fly ash, silica fume, and most other concrete additives. It is recommended that IAI’s Superplast-1000 be used in order to provide a good workable mix. | What is CONEX | Chemistry | Concrete Characteristics | Facts about SCC | CONEX & Floor Slabs | Pre-Stressed | Links | | Return Home | CONEX | Projects | What's New | Our Services | Contact Us | |
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