Masons can enhance construction quality and speed using a hand-held moisture measurement device to prevent errors due to seasonal or environmental variability
Words: Del Williams
Photos Kett
For hundreds of years masons have been the craftsmen responsible for creating strong, beautiful structures from homes to cathedrals using mortar with brick, marble, granite, limestone, cast stone, concrete block, glass block, and adobe. Quality work can last for centuries and become part of a nation’s historic architectural heritage.
As the concrete masonry industry evolves popular new styles have emerged such as stone masonry, gabion masonry, veneer masonry, and reinforced masonry.
No matter the materials used, however, the quality of the mortar and workmanship as well as the pattern in which the units are assembled can significantly affect the structure’s overall durability and appearance. Because water is such an essential element of both mortar (water, aggregate, binding material) and concrete (water, aggregate, cement) it must be measured accurately.
Unfortunately, at the jobsite everything from seasonal temperature, rain, humidity, and groundwater to circulating air can greatly affect the moisture content in mortar and concrete. This can impact setting and drying time. Even more importantly, incorporating the wrong moisture levels in mortar and concrete can be potentially devastating to quality, finish, longevity, and even safety.
On top of this, with global warming causing ever greater fluctuations of temperature, rainfall, and weather, instantly measuring the actual moisture level in mortar and concrete will become more important at all stages of the construction project to achieve enduring quality.
While masons have access to moisture meters, to some extent, these tools typically require calibration, sampling and time. In addition, they are not always portable or durable enough to be used on job sites.
Today, however, masons are updating their craft and competitiveness by using hand-held, instant moisture measurement devices on the job. These devices allow anyone without special training to spot check mortar and concrete moisture level at the jobsite to assure that it is properly mixed, set, and dry. In many cases, such pre-calibrated systems allow non-destructive, non-invasive testing on digital displays with no pin holes or discoloration. This approach facilitates masonry construction work as soon as feasible, speeds project completion, and improves quality.
Beat the Heat and Cold
Binding material-water ratios can make a big difference in the permeability of mortar, but air humidity and summer heat and winter cold also can affect the rate at which moisture migrates through drying mortar or concrete.
“Higher relative humidity during winter can increase the risk of fractures and other structural issues. Mortar and concrete can also gradually change from ductile to brittle if relative humidity decreases during summer. Either way seasonal variability will affect drying and evaporation time,” says John Bogart, Managing Director of Kett US, a manufacturer of a full range of moisture and organic composition analyzers.
Mortar and concrete usually cure best between 70-80°F, so if temperatures rise above that and climb towards 90°F, the materials can be affected and cause surface problems as well as reduced strength.
Hot weather, wind and dry conditions can increase mortar’s rate of evaporation, which can threaten the integrity of a wall or building. Water quickly evaporates from the surface layer, which can cause the mix to be drier and susceptible to surface cracking and shrinkage.
Reduced strength can also become an issue with hot, dry weather, which can shorten the hydration portion of the curing process (when water is absorbed and crystals form in the material). Then the mortar mixture has less time to hydrate these forming crystals and create compressive strength. So, mortar or concrete curing in hot weather can suffer from limited strength and durability.
On the other hand, in wetter seasons, excess moisture can do a great deal of damage to mortar as well as affect binding material-water ratios. Because mortar is porous, issues arise when water is trapped within the material.
When it comes to structural mortar or concrete, including walls, buildings, or foundational slabs, masons do not want to “guestimate” moisture levels, which can potentially jeopardize the whole project.
The Benefits of Simplified Moisture Measurement
Although traditional laboratory and online-based moisture measurement techniques are useful in the right settings, they have lacked the simplicity and flexibility required for frequent spot checks on construction sites. Because such moisture tests are too slow, laborious, and alter or destroy the sample, they are not practical for the jobsite, where mortar or concrete must stay in place. Instead, what is needed is a fast, easy method to determine moisture content.
So, industry innovators have developed a simplified approach with testing equipment that allows anyone in the field to get laboratory-quality measurements in any environment.
As an example, using a hand-held device such as the HI520-2 mortar and concrete moisture meter by Kett, the worker would select the calibration (i.e.- mortar or concrete), press it against the sample, and moisture is immediately displayed with accuracy of +/-0.5% (0-15% for mortar/0-12% for concrete). Automatic temperature compensation enhances measurement accuracy, and two “raw” modes allow the user to calibrate for deep or shallow samples. Up to 1,000 measurements can be stored in memory and downloaded to a PC for analysis.
The device utilizes high-frequency capacitance, comparing the di-electric constant of the solid with water. A direct relationship exists between this and moisture content.
For masons who need more specialized applications of measuring moisture, such as for “wet” mortar or concrete, this is also available with other units. For instance, with such units, the sample moisture of slurry and aggregate can be instantly measured, allowing masons to optimize batch mixing anytime, anywhere.
While masons have inherited a classic craft, the bottom line for those working with mortar or concrete is that using modern hand-held devices that provide instant moisture measurement helps to ensure that quality work is done as soon as it is feasible, without excess or insufficient moisture, setting, or drying times. In the end, this facilitates project profitability.
For more info, contact Kett: call 800-438-5388; email support@kett.com; or visit www.kett.com.