Rainwater could be used for concrete mixtures
Making concrete mixtures with rainwater does not impact quality, resistance or other cement properties.Medellín, 29 de agosto de 2014 — Agencia de Noticias UN-
Use of rainwater for concrete making in building projects was a concern that stemmed from this master’s thesis project. Photo: http://dc250.4shared.com
Surface topography and microstructure of concrete made with drinking water as seen under a microscope. Photos: Courtesy of Carlos Alberto Medina.
Biological and chemical analysis performed as part of a master’s thesis project of Carlos Andrés Medina, Civil Engineer and Specialist in Sustainable Building, indicate that besides using drinking water, rainwater is also viable for making simple concrete mixtures.
The proposal was tendered by UNal-Medellín Construction master’s holder is an option to reduce costs in concrete fabrication and environmental impact, as currently concrete manufacturing requires use of drinking water due to the required quality standards.
This is common practice used without prior verification. This supposes that all drinking water is also appropriate for making concrete.
“However, there are occasions in which this not fulfilled because some drinking water forms have small amounts of sugars which do not impact its potability, but make it inadequate for concrete fabrication,” he said.
The quality of this type of water is directly related to the quality of the air. Therefore it is necessary to carry out an analysis to establish the minimal requirements included in the NTC 3459 (2001) standards, which regulate water issues for concrete mixing. However these parameters are not always fulfilled.
The standard says that the liquid destined for this purpose can be obtained from other sources, but also be clear, clean in appearance and without damaging amounts of oil, acid, salt, organic material and other substances that may impact the resistance of the concrete.
For this research project, Medina designed a mixture using Portland type 1 cement, gravel and sand to perform tests with drinking water and rainwater obtained by a collection system.
After the materials were classified, cylinders were emptied to continue the curing process, which consisted of submerging or spraying the parts to control temperature changes and moisture towards the inside and outside of the concrete cylinders.
The researcher said that the purpose is to maintain it saturated until the fresh cement spaces, originally filled with water are replaced with hydration products of the same.
They also carried out physical-chemical analysis such as the amount of sulphides, chlorides, total solids, dissolved solids, pH and liquid turbidity. Data was compared to NTC 3459 standard reference values and determined that rainwater use was justified.
Once the cylinders were ready they performed other analysis using X-Ray diffraction, which showed the surface topography and microstructure of the concrete of each sample. They also performed scanning electron microscope imagery to complete the analysis.
The concrete compressive tests established that 1-day cylinder average resistance in megapascals (MPa) (concrete compression resistance) was 7.62 for rainwater and 7.24 for drinking water, while for 28 days the index 27.51 and 27.24 respectively, with the rainwater mixture showing greater resistance.
Finally he said that this proposal could mean a significant reduction of water use in building projects and therefore contribute to taking care of the environment and lowering costs.(Por: Fin/ME/DMH