What is internally cured concrete?
Internally-cured concrete is defined as a concrete that utilizes absorptive materials that contain absorbed moisture. The absorbed moisture is released as the internal humidity of concrete drops below 100% to enhance and maximize the hydration of cement. Internal curing is defined as supplying water throughout a freshly placed cementitious mixture using reservoirs that readily release water as needed for hydration or to replace moisture lost through evaporation or self-desiccation.
Why is internal curing recommended?
Concrete curing technology has been challenged by the advent of modern concrete mixes. This includes high performance concrete (HPC), decorative concrete, pervious concrete, and shotcrete, among others. Both low w/cm and SCM present new challenges to conventional curing. Concrete with a water-cementitious materials ratio (w /cm ) below 0.42 does not contain enough batch water to fully hydrate all of the cement (Neville 1996).
The characteristics of concrete that may be improved by increased hydration from internal absorbed moisture include resistance to early-age cracking, higher strength, decreased permeability, decreased warping, dimensional stability, resistance to freezing and thawing damage, resistance to deicing chemicals, resistance to chemical attacks, and creep.
Neville, A. M., Properties of Concrete , 1996, fourth edition, John Wiley & Sons, New York, July, 844 pp.
HydroMax®
How does HydroMax® work?
HydroMax® internal curing admixture provides an internal source of water necessary to replace that consumed by chemical shrinkage during hydration. As the cement hydrates, this water is drawn from the pores in the admixture’s water reservoirs and absorbed into the pores of the cement paste. This process assists traditional curing techniques and can minimize the development of autogenous shrinkage, help in avoiding early-age cracking, and improve strength.
Will HydroMax® “swell” my mix or create “blobs”?
No. HydroMax® does not “swell” inside a mix. Most concrete mixes contain mix water that is not used for cement hydration. This is evidenced by bleed water from traditional mixes or evaporated moisture from pervious concrete and shotcrete. Have you ever seen condensation under a plastic curing sheet? That is mix water evaporating from the mix before cement hydration can take place.
HydroMax® retains the free water that is available in a concrete mix. Typically, this amounts to 1-3 gals of water/CY. The free water is suspended in the mix instead of bleeding or evaporating. This available water increases cement hydration and paste density contributing to improved durability and chemical resistance.Will HydroMax® make my pervious concrete feel "spongy"?
No. In fact just the opposite. HydroMax® increases the workability and decreases the effort of compaction required for pervious concrete. Pervious concrete that feels “spongy” is typically a result of very low w/cm mixes with excessive paste or fines. More information on pervious concrete mix design can be found here.