Portable sensor for instant measurement of the w/c ratio and mass fractions of water and cement in fresh concrete

• Grant number: 23/15495-7
• Support Opportunities: Research Grants - Innovative Research in Small Business - PIPE
• Start date: October 01, 2024
• End date: September 30, 2026
• Field of knowledge: Engineering - Electrical Engineering - Electrical, Magnetic and Electronic Measurements, Instrumentation
• Principal Investigator: Marcos Roberto Fortulan
• Grantee: Marcos Roberto Fortulan
• Company: Csense Tecnologia Ltda
• CNAE: Fabricação de aparelhos e equipamentos de medida, teste e controle ; Manutenção e reparação de equipamentos e produtos não especificados anteriormente ; Pesquisa e desenvolvimento experimental em ciências físicas e naturais
• City: São Carlos
• Pesquisadores principais: Oscar Mauricio Hernandez Rodriguez
• Associated researchers: Francisco Júlio do Nascimento
• Associated research grant: 21/11298-7 - Portable and instant sensor for fresh concrete mix ratio measurement, AP.PIPE
• Associated scholarship(s): 24/16697-5 - Portable sensor for instant measurement of the W/C ratio and mass fractions of water and cement in fresh concrete, BP.PIPE; 24/16928-7 - Measurement of the mass fraction of the main components of concrete based on electrical impedance data obtained by testing samples, BP.TT; 24/16584-6 - Measurement of the mass fraction of the main components of concrete using electrical impedance data obtained from sample testing., BP.TT

Abstract

Concrete is one of the main components used in construction today, but its use is not recent. According to Andriolo (1984), there is evidence of the use of cement as an aggregate in Egyptian ruins, and the Greeks and Romans already used calcined limestone and later added lime, water, and aggregates, giving shape to the first concretes in history. However, its use has been intensified by modern society in the last century due to its good compressive strength, ease of molding, on-site molding, and low cost relative to other structural material options.One of the most important parameters for defining the type of concrete is its compressive strength, called fck (NBR 6118). The compressive strength value directly depends on the w/c ratio (mass fraction between water and cement). However, not only the w/c ratio defines the concrete strength, it is a function of the combination of all its components (cement, fine aggregate, coarse aggregate, water, and admixtures) in previously defined quantities called mix. Once the combination patterns and the type of cement are defined, the concrete strength is defined by the w/c ratio.Another important parameter for specifying concrete is its workability. In the structural elements of a work, it is necessary for the concrete to completely encase the reinforcement, eliminating voids, which compromise its strength, and one of the most practical and simple ways to improve workability is by adding water. However, adding water impacts the w/c ratio and, consequently, the concrete strength, creating an antagonistic and difficult-to-control relationship. One of the methods for controlling concrete workability is the Determination of Consistency by the Cone Collapse Test (NBR 16889), known as the Slump Test.Both the compressive strength determination test and the slump test are widely used, but both have limitations. The first requires, according to the standard, 28 days to deliver the final result, although results can be predicted at shorter intervals, such as 24 hours, 3, 7, and 14 days. The slump test has a high dependence on the preparation conditions, the execution location, and the skill of execution and interpretation of the results. In addition, the use of water-reducing admixtures allows the variation of workability without changing the amount of water in the mix, making it impossible to use it as a reference for obtaining the w/c.Therefore, this project proposes to continue the development of a tool to measure the w/c ratio and the mass fractions of water (w) and cement (c) from a fresh concrete sample. Through this tool, it will be possible to provide relevant information for decision-making in the receipt of the material, in addition to allowing a differentiated delivery from concrete companies that want to offer their customers a warranty certification at the time of unloading of their product. (AU)