FURTHER DISCUSSION ABOUT THE USE OF PERVIOUS CONCRETE
These days water represents the major problem for our cities. The use of water is taken from the subsoil, or brought from remote rivers, lakes or dams.
The water from the subsoil is found in deposits called aquifers. The best of these deposits is formed over time with the filtration of rainwater. The exploitation of these aquifers creates the necessity of a cycle, with the water that is taken needing to be returned. The aquifers are exhausted. Now we know that our reserves of water are limited.
This exploitation creates additional problems like the creation of caverns, instability of the strata and collapsing ground on the surface, which has very dangerous results in our country (Mexico) because we have enormous seismic zones.
In Mexico City, the problem of sinking becomes worse because a very important part of it is built in aquifer areas, formed with mud, which contains liquid that is extracted for use in a variety of construction. This liquid is never returned to the aquifer, which accentuates the sinking ground, which in some places is several centimeters per year. The drainage system suffers from the effects of the sinking, and the stability of this drainage system is in danger.
As we have mentioned before, the rain is the way to refill the aquifers. But as the cities become urbanized this is prevented from happening.
The water from the rain normally is channeled into the drainage system, becoming contaminated, and through there reaches rivers, and from there to the sea. This process, in fact, has modified the ecosystems of the cities, which are losing their water slowly.
Certainly, in most cases, the intensive rain causes very severe damage, and usually the damage is caused by the incapacity of the drainage system.
Now concerned government officials are attempting very complicated works to make the water potable in the drainage system, which represents a very high cost. The rainwater is free and easy to purify.
PORTLAND CEMENT PERVIOUS CONCRETE:
With the purpose of normalizing the cycles of the water, it becomes indispensable for recapturing water to make the surfaces of the cities permeable.
Currently it is necessary to continue to build streets, sidewalks, parking lots, etc. The surfaces made with pervious concrete permit these structures to function for the purposes for which they were built, with the advantage that because they are made with a permeable material (15 25% void in the integral structure, layed on a bed of permeable crushed stone, gravel and sand), they allow the infiltration of water. These can be used even in very heavy traffic (Please refer to sections 5, 6, 8, 9 & 10 of this folder for guide design, strength, etc).
Pervious Concrete permits the fabrication of totally permeable concrete with a high resistance to compression, which, through a system that has been developed by a multidisciplinary group of researchers and scientists, allows a solution to all the problems described above, as well as others.
The surfaces of pervious concrete also can be used like a conduction system of water, which can travel through them, to water storage tanks for irrigation, artificial lakes, shafts for faster infiltration into the aquifer, etc.
In some cases, it is necessary to conduct a study of permeability. In the case of surfaces with little permeability, very small tubes can be used, whose basic purpose is to work as pumps, using hydrostatic pressure generated the surface to push water down.
ADVANTAGES OF THE SURFACES MADE WITH PORTLAND CEMENT PERVIOUS CONCRETE:
The first advantage is to allow infiltration of water to the aquifer, or like a conductor of water without the use of tubes. Because its characteristics, it eliminates puddles and standing water in the streets, improving traffic in the street, consequently reducing atmospheric contamination.
In areas of new developments, it allows the streets, alleyways, and parking areas to comply with established regulations that may impact the environment, which require local authorities to grant permitting, licensing, and construction. This will allow an increase in the sellable area. Also, the water collection system will be reduced, and it will be more cost effective for residents, which will directly impact their property value.
In the streets and parking lots it can reduce and eliminate drainage with the consequence of saving in cost of building. In the highways it can prevent hydroplaning.
To channel the rain water to the subsoil or storage tanks reduces substantially passage of water through the drainage system, eliminating the problems that can be caused by the saturation of these systems. Part of the pluvial water stays inside the floors made with pervious concrete. This water is going to evaporate, maintaining the higher humidity level in these places. This benefits the recuperation of microclimates.
Another advantage of the floors made with pervious concrete is that they can be poured on the site or made in factory, precast. Additionally, it is clear that surfaces made with pervious concrete can be constructed with any kind of stones added, permitting the use of regional materials, increasing jobs available and keeping our economy strong.
Maybe the best advantage of pervious concrete is that it is made with Portland cement, which permits exploiting a large variety of colorings and finishes, or with resins, permit maintaining the natural color of the aggregate. Surface made with pervious concrete are ideal for wharves and marinas. With pervious concrete, retaining walls can be built that, because its permeability, it eliminates hydrostatic pressure, which is the principal enemy of these kind of walls.
THE COST OF SURFACES MADE WITH PORTLAND CEMENT PERVIOUS CONCRETE: