Complex Maturity Method for Estimating the Concrete Strength Based on Curing Temperature, Ambient Temperature and Relative Humidity

The maturity method is deservedly considered one of the reliable indirect methods for determining the strength at the early stages of concrete curing. The main parameter in the calculation is the internal temperature of concrete that accumulates during the chemical reaction of concrete curing, while external factors such as ambient temperature and relative humidity are fallaciously omitted. In this work, the complex maturity method was developed based on ASTM C1074, accounting for the influence of ambient temperature and relative humidity and coefficients indicating their influence weight. The laboratory testing to measure the concrete strength by compression method and non-destructive sclerometer method were performed on concrete samples according to ASTM C109, GOST 22690, and GOST 10180. According to the calibration dependence of the existing and proposed methods results in comparison with the strength of cubic samples, the highest coefficient of determination R2 = 0.976 was revealed for the complex method of maturity, which indicates its reliability in contrast with sclerometer and traditional maturity methods. The determination of complex maturity allows for an evaluation of the current state of concrete strength, but also reduces the waiting time for concrete curing and increases the economic effect during construction.

Application of the maturity method in slipforming operations

The main objective of this thesis is to study the application of the maturity method in slipforming operations so as to provide more efficient means of the construction planning of a project. The main target of this research is to use the maturity method to establish the initial setting times and then apply those times to estimate the slipform mockup time and speed. In this research various maturity functions are compared and the most efficient one is used. The apparent activation energy (E) and the temperature sensitivity factor (B) are, examined so as to understand their effect on the maturity function and also to establish a relationship between them and the retarder dosage. Furthermore, the "FHP Strength Model (SFHP)" and the "Rate Constant Model (SkY' are used to evaluate their competence in representing the strength development of a concrete mixture in the laboratory and in the field. Also, the maturity method is used to estimate the times of mockup and then compared with the "Penetration Resistance", "2°C Temperature Increase", "Rod", and "Conductivity" methods. Furthermore, an example is presented and the mock-up times are established based on various initial concrete temperatures and slipform layer arrangements. Finally a computer program is developed to establish the mockup times, time of concrete placement, and the slipform speed during the removal process. The results of this research showed that the Carino and Tank maturity function is preferred for the calculation of the maturity indexes. Also, it is found that a linear relationship between the retarder dosage and E or B can be established. Moreover, it is shown that E or B can be estimated by the method suggested by Pinto and Hover. In addition, a new strength-maturity model is suggested. Finally, it is found that the maturity method can be used with efficiency to establish the slipform mockup times, the time of the concrete layer, and the slipform speed.

Application of the maturity method in slipforming operations

The main objective of this thesis is to study the application of the maturity method in slipforming operations so as to provide more efficient means of the construction planning of a project. The main target of this research is to use the maturity method to establish the initial setting times and then apply those times to estimate the slipform mockup time and speed. In this research various maturity functions are compared and the most efficient one is used. The apparent activation energy (E) and the temperature sensitivity factor (B) are, examined so as to understand their effect on the maturity function and also to establish a relationship between them and the retarder dosage. Furthermore, the "FHP Strength Model (SFHP)" and the "Rate Constant Model (SkY' are used to evaluate their competence in representing the strength development of a concrete mixture in the laboratory and in the field. Also, the maturity method is used to estimate the times of mockup and then compared with the "Penetration Resistance", "2°C Temperature Increase", "Rod", and "Conductivity" methods. Furthermore, an example is presented and the mock-up times are established based on various initial concrete temperatures and slipform layer arrangements. Finally a computer program is developed to establish the mockup times, time of concrete placement, and the slipform speed during the removal process. The results of this research showed that the Carino and Tank maturity function is preferred for the calculation of the maturity indexes. Also, it is found that a linear relationship between the retarder dosage and E or B can be established. Moreover, it is shown that E or B can be estimated by the method suggested by Pinto and Hover. In addition, a new strength-maturity model is suggested. Finally, it is found that the maturity method can be used with efficiency to establish the slipform mockup times, the time of the concrete layer, and the slipform speed.

Fuzzy Logic-Based and Nondestructive Concrete Strength Evaluation Using Modified Carbon Nanotubes as a Hybrid PZT–CNT Sensor

Concrete strength and factors affecting its development during early concrete curing are important research topics. Avoiding uncertain incidents during construction and in service life of structures requires an appropriate monitoring system. Therefore, numerous techniques are used to monitor the health of a structure. This paper presents a nondestructive testing technique for monitoring the strength development of concrete at early curing ages. Dispersed carbon nanotubes (CNTs) were used with cementitious materials and piezoelectric (PZT) material, a PZT ceramic, owing to their properties of intra electromechanical effects and sensitivity to measure the electromechanical impedance (EMI) signatures and relevant properties related to concrete strength, such as the elastic modulus, displacement, acceleration, strength, and loading effects. Concrete compressive strength, hydration temperature, mixture ratio, and variation in data obtained from the impedance signatures using fuzzy logic were utilized in the comparative result prediction method for concrete strength. These results were calculated using a fuzzy logic-based model considering the maturity method, universal testing machine (UTM) data, and analyzed EMI data. In the study, for data acquisition, a hybrid PZT–CNT sensor and a temperature sensor (Smart Rock) were embedded in the concrete to obtain the hydration temperature history to utilize the concrete maturity method and provide data on the EMI signatures. The dynamic changes in the medium caused during the phase in the concrete strengthening process were analyzed to predict the strength development process of concrete at early curing ages. Because different parameters are considered while calculating the concrete strength, which is related to its mechanical properties, the proposed novel method considers that changes in the boundary condition occurring in the concrete paste modify the resonant frequency response of the structure. Thus, relating and analyzing this feature can help predict the concrete strength. A comprehensive comparison of the results calculated using the proposed module, maturity method, and cylindrical specimens tested using the UTM proved that it is a cost-effective and fast technique to estimate concrete strength to ensure a safe construction of reinforced cement concrete infrastructures.

An IoT device for striking of vertical concrete formwork

PurposeTimely removal of formwork is one of the crucial aspects of construction management that directly influences the safety and quality of the structure as well as the economy of the project. Code recommendations in this regard are not widely practiced because of the difficulties in their implementations. Also, such code recommendations are not robust for all the possible construction conditions. The present paper proposes an IoT-enabled system that notifies the minimum striking time of vertical formwork based on a specified target compressive strength.Design/methodology/approachAn IoT device is proposed for the timely removal of vertical formwork by monitoring of early age concrete compressive strength in real-time. The maturity method is utilized for this purpose. The implementation of the proposed system is demonstrated on three concrete columns. The proposed system is found to be suitable for any construction condition.FindingsThe proposed system is a novel, cost-effective, IoT-enabled real-time monitoring system which includes features like cloud connectivity and remote monitoring. This system can be easily implemented at the site without any human intervention.Practical implicationsThe study explores the development of an IoT device for the timely removal of vertical formwork which will ensure quality, safety and productivity in concrete construction.Originality/valueThis paper is the first attempt to determine the minimum striking time of vertical formwork using IoT-based technology.

Application of the maturity method to reinforced concrete roof slabs

ABSTRACT The maturity method is a procedure that associates the evolution of the temperature of concrete cast to the structure and the evolution of its hardened state properties like compressive strength, usually at early ages. Its use is justified when safety and agility are required for activities like prestressing, shoring removal, demolding and low temperature concrete curing analysis. Temperate regions are known for having lower temperatures during the winter, which can delay concrete strength gains. The aim of this study was to apply the maturity method to a reinforced concrete structure located in Southern Brazil in industrial construction. It was noted that the concrete, despite being expected to reach 30 MPa at 28 days, managed to reach 70% of the strength at 8.5 days for slab 1. Slab 2, whose function was to support garners 4, 5 and 6, presented the data at 4.4 days, it being possible to measure such property using the maturity method.