Henderson Thomas » England » Structural Investigations

HAC Investigations

Our HAC Investigational approach has been adopted by Network Rail & Engineering Consultants

HTA’s investigation proposals / approach  to HAC Investigations has been adopted by Network Rail and other large civil engineering consultants to ensure a correct diagnosis of the HAC condition is achieved.

Experience includes the 30 year monitoring a single structure

HTA have been involved with a number of projects investigating the presence and conversion of HAC and its effects on strength. Numerous technologies can be used such as the PUNDIT (Portable Ultrasonic Non Destructive Tester) is a proven NDT technique to determine strengths of materials.

HTA in one instance has been monitoring and testing a structure over a 30 year period.

Understanding HAC to ensure a correct diagnosis

HAC concrete can be unaffected by any strength reductions for a number of years. However changing exposure conditions many years after construction (eg, leaking waterproofing systems) can activate the conversion process and dramatically reduce the strength of the concrete.

High Alumina Cement (HAC) was first used in 1925, and more commonly used in the 50’s, 60’s and 70’s. The HAC concrete gained strength rapidly and meant fast manufacture became possible.

The material was widely used in the construction of precast beams, which were then used to construct buildings and bridges.

In certain instances a crystalline re-arrangement (conversion) to the HAC concrete could take place, which could result in a reduction of concrete strength, and in the most extreme case, failure of element, which could lead to collapse of build / bridges.