We have made a set of concrete specimens for predicting their early-age strength. Before demoulding, the fresh concrete is in the plastic status, then its strength can not be determined by using testing machine. Do you know any method to determine the early-age strength of the fresh concrete before demoulding?
The paper mentioned below may be of help to you.
Venkiteela, G., Sun, Z., and Najm, H. (2013). ”Prediction of Early Age Normal Concrete Compressive Strength Based on Dynamic Shear Modulus Measurements.” J. Mater. Civ. Eng., 25(1), 30–38.
ABSTRACT:
In this research, the relationship between the compressive strength, fc, and the dynamic shear modulus, Gd, of normal concrete at an early age was studied. To investigate the correlation between fc and Gd at an early age, different types of mixtures, including mortar and concrete, were prepared, and the corresponding fc and Gd values were measured every 12 h after initial mixing up to 72 h after casting. The influences of hydration age, water-to-cement (w/c) ratio, curing temperature, aggregate volume content, and maximum aggregate size on the Gd−fc relationship of concrete were studied. The Gd−fc relationship was then mathematically modeled by using multivariable power laws. The developed model is reasonably accurate to predict the early age compressive strength of concrete with variations in hydration age, aggregate content, and sizes. This type of model can be used directly in the field for the estimation of concrete strength when nondestructive testing (NDT) techniques are employed.
The paper mentioned below may be of help to you.
Venkiteela, G., Sun, Z., and Najm, H. (2013). ”Prediction of Early Age Normal Concrete Compressive Strength Based on Dynamic Shear Modulus Measurements.” J. Mater. Civ. Eng., 25(1), 30–38.
ABSTRACT:
In this research, the relationship between the compressive strength, fc, and the dynamic shear modulus, Gd, of normal concrete at an early age was studied. To investigate the correlation between fc and Gd at an early age, different types of mixtures, including mortar and concrete, were prepared, and the corresponding fc and Gd values were measured every 12 h after initial mixing up to 72 h after casting. The influences of hydration age, water-to-cement (w/c) ratio, curing temperature, aggregate volume content, and maximum aggregate size on the Gd−fc relationship of concrete were studied. The Gd−fc relationship was then mathematically modeled by using multivariable power laws. The developed model is reasonably accurate to predict the early age compressive strength of concrete with variations in hydration age, aggregate content, and sizes. This type of model can be used directly in the field for the estimation of concrete strength when nondestructive testing (NDT) techniques are employed.
fib Model Code 2010 proposes models for determining strength and Young Modulus of concrete as a function of time. So you can estimate early-age strength of your concrete. More refined models are based on hydration reaction properties. You can read some papers I've written.
Another alternative is to weigh a sample of fresh concrete yet, subjecting the sample to washing with water, separating the gravel and sand, and weigh each. The difference between the weights of gravel and sand and the total weight is the weight of water with cement and thus can have a close idea of its ultimate strength.
Another alternative is to weigh a sample of fresh concrete yet, subjecting the sample to washing with water, separating the gravel and sand, and weigh each. The difference between the weights of gravel and sand and the total weight is the weight of water with cement and thus can have a close idea of its ultimate strength.
you can use some Non- destructive tests like Schmit hammer, ultrasound ....
But you need to have a benchmark from previous studies or some information about density of materials and wave propagation in the solid and liquid materials
The most commonly used methods for estimating the in-situ strength of concrete for optimizing the formwork removal time, are either cast-in-place cylinders (that you need to crush at various intervals) or maturity-based strength estimation in real-time. You can learn more about the latter from the attached link.
http://www.giatecscientific.com/knowledge-center/concrete-maturity-in-situ-compressive-strength/
I think there is an ultrasonic test to obtain concrete strength at any age of the concrete.
As per my knowledge there is no direct method prescribed by any of the organisations to determine strength of green concrete just before its laying
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