This effect is encountered particularly in massive concrete castings, due to the limited heat dispersion, leading the behavior closer to adiabatic conditions.

The isothermal and semi-adiabatic testing methods are consequently less representative and most commonly used for mortars and cement pastes, basically to compare the behavior of different types of cements.

The adiabatic method is the only method allowing correct evaluation of the heating process inside massive concrete works.

When concrete is curing and hardening, the hydration reaction of cement develops a large amount of heat with an increase in temperature. The temperature rise accelerates hardening of cement however, if it is not properly dissipated, it can cause the arise of tensile stresses inside the concrete structure with the consequent appearance of cracks and reduction of mechanical properties.

Working principle

A fresh sample is positioned in a calorimeter cell ensuring adiabatic conditions by avoiding heat exchange with the environment. Since this condition cannot be obtained in practice in a passive system (no insulating material is infinitely non-conductive) the temperature of the room sorrounding the specimen is forced to be equal (or slightly lower by max 0.5°C) to the temperature of the sample during all the test.

Two PT 100 temperature sensors are used, one positioned in the sample and one in the calorimeter cell. The temperature measurements are used by a PID closed loop control system to ensure a stable sample conditioning according to the Standard requirements.

The equipment consists of:

Calorimeter cell 

Calorimeter cell conditioning system controlled by a PID closed loop system

External insulating enclosure 

Two platinum PT 100 temperature sensors measuring sample and cell temperatures

150mm polystyrene cubic mould

PC software.

Technical Specifications:

Up to 6 calorimter cells can be managed by the same PC software

Adiabatism error: less than 0.05°C/h

Max concrete temperature: 80°C

Platinum PT 100 having 0.01°C resolution and 0.1°C accuracy 

PC connection via LAN cable

Internal SD memory for test data backup in case of temporary loss of communication with PC

PC software for acquisition, elaboration and printout of test data including: 

Concrete temperature vs time graph

Cumulative heat development

Cell temperature vs time graph

Intrinsic of temperature rise.