For a complete report on the laboratory tests completed at Georgia Tech submitted to ACI, please click this link: Georgia Tech Comparison Study.
Significant increases in compressive and flexural strength, especially in early stages
Increased Compressive Strength
KAOROCK™ increases strength in all stages of the curing process. It reacts with the free calcium hydroxide (lime) produced during the cement hydration process to form additional cementitious materials.
Both KAOROCK™ and silica fume showed increased strength in this laboratory test. Preliminary data on silica fume indicated a decrease at 1-day strength. As a result a new silica fume sample (SF Redo) was acquired and the test repeated.
Increased Flexural Strength
KAOROCK™ increases flexural strength during the curing process, especially at early stages. During testing, concrete prisms were subjected to four-point bending with a water to cement ratio of 0.4.
Metakaolin and silica fume reached 600 psi in one day indicating relevance to pavements. Metakaolin could be used to shorten the time needed before newly paved roads may be opened to traffic.
Enhanced Concrete Durability
Reduction or elimination of Alkali-Silica Reaction (ASR)
Silica is present in concrete due to the cement hydration process, and will react with the different aggregates found in concrete. As a result, this silica can dissolve and produce a gel. When moisture is present, the gel expands and results in stresses on the structure which can lead to cracks in the concrete. KAOROCK™, with its structure and reactivity, greatly reduces ASR. Since it reacts with lime, KAOROCK™ lowers the alkalinity of concrete, decreasing the reactivity of the silica. The graph shows expansion due to alkali-silica reaction at a water to cementitious materials ratio of 0.47 (ASTM C 1260, accelerated mortar bar test). This method has proven reliable for evaluating the effectiveness of SCM’s in suppressing ASR. KAOROCK passed while the control and silica fume failed.
Reduction of elimination of efflorescence
Water enters the masonry structure through absorption and through cracks and joints. This water dissolves the available calcium hydroxide (lime) that is produced during cement hydration. This water migrates to the surface and evaporates leaving behind the lime, which can show up as a crystalline or powdery, unattractive deposit. KAOROCK™ helps to eliminate this effect by reacting with the free lime to form additional cement and by lowering the permeability of the structure; thereby, making it more difficult for water to move to the surface.
Due to its particle shape and size, KAOROCK™ can greatly reduce the permeability of a concrete mix. It is very effective in reducing chloride ion ingress, with values in the low or very low (below 2000 Coulombs) range. The graph shows experimental test data on rapid chloride permeability showing KAOROCK™ with a remarkably lower permeability than the control and silica fume.
Improved Handling and Color Matching
KAOROCK™ is processed under strict controlled conditions; thereby the consistency of color is very good. KAOROCK™ is not a by-product as other pozzolans such as silica fume and fly ash; therefore, the color is not strictly defined by the original raw materials that make the product.
Since it is white, it will not darken the appearance of concrete. Therefore, it is a perfect choice in architectural applications such as countertops, block or pavers. Furthermore, the water demand is not as great as with silica fume, and hence, fresh concrete becomes easier to work with by not being so “sticky”.