Page 24 - RoadCem Manual - PCT BV

RoadCem enhances and increases the strength and flexibility of stabilized road layers and improves the overall performance of cement bound materials used in road construction. RoadCem modifies and extends the chemistry of the cement hydration process and extends the crystallization process by forming long needle crystalline structure. It is able to delay or to speed up the hydration process of cement and can thus be used as a tool to custom designs the mixes of required performance. Any type of material that can be bound with RoadCem and gives strength to the construction can be used in a road pavement. This eliminates the need for material import and export and in so doing significantly reduces the cost of road construction and the environmental impacts thereof. Its unique characteristics enable cost effective and rapid construction of high quality roads of different categories and rapid and effective stabilization of soil for different purposes (embankments, dikes, supporting structures etc.).
RoadCem is a product that is always used in combination with cement and/or other pozzolanic materials. In order to understand how RoadCem works we first have to briefly explain how Cement and pozzolanic materials act as binders of different materials.
2.2 Portland Cement
Cement needs moisture to hydrate and cure (harden) and become an effective binder of other materials such as aggregate, sand etc. When the binder (Cement) dries, it actually stops getting stronger. Cement with too little water may be dry and it will not fully react. The properties of such paste would be inferior to those of a wet paste. The reaction of water with the cement is extremely important to cement proporties as a binder and these reactions may continue for many years.
Portland cement consists of five major compounds and a few minor compounds. The composition of a typical Portland cement is listed by weight percentage in Table 2.1.
Table 2.1 Composition of Portland cement with chemical composition and weight percent.
Cement Compound
Weight Percentage
Chemical Formula
Tricalcium silicate Dicalcium silicate Tricalcium aluminate
Tetracalcium aluminoferrite Gypsum
50 % 25 % 10 %
10 % 5 %
Ca3SiO5 or 3CaO.SiO2
Ca2SiO4 or 2CaO.SiO2 Ca3Al2O6 or 3CaO .Al2O3
Ca4Al2Fe2O10 or 4CaO.Al2O3.Fe2O3
CaSO4.2H2O
When water is added to cement, each of the compounds undergoes hydration and contributes to the final product. Only the calcium silicates contribute to strength. Tricalcium silicate is responsible for most of the early strength (first 7 days). Dicalcium silicate, which reacts more slowly, contributes only to the strength at later times.
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