In the production of building materials and ceramics, such as engineered lumber, roofing materials, structural blocks, and decorative ceramics, the control of moisture sorption is important. Whether it is in preparing a surface coating or optimizing a cement formulation, feedback on the effectiveness of the process is critical. Measuring the water sorption of these materials under actual or aggressive (accelerated) conditions can provide the information needed to perfect the process.
Since the absorption of water can compromise the structural integrity, alter the dimensions, or promote the growth of mold, being able to minimize the amount of water adsorbed or absorbed by the material is important to the engineering of these building materials. Both gravimetric (Aquadyne DVS) and volumetric (VSTAR) provide means of measuring the amount of water absorbed by the materials and provide valuable information on the effectiveness of a waterproof coating or a water resistant formulation.
A novel method of determining the age of archaeological fired clay and ceramic artifacts has been developed at the University of Manchester, England. During the manufacturing of ceramics the green pottery is fired at temperatures in excess of 500°C. At these temperatures all water, including chemically bound water, is driven off. When the ceramic cools, it immediately begins absorbing water. Initially the water absorbed is physisorbed onto the surface and into the pores of the ceramic, but after the pores and the surface are saturated, the water begins to chemically bond to the material (hydroxylation). It has been shown that the rate of this hydroxylation process is proportional to the fourth root of the time since firing (t¼). By measuring the amount of water lost when heating the ceramic and the rate at which it is rehydroxilated, it is possible to extrapolate back to t=0 and determine the age of the artifact. The Aquadyne DVS is perfectly suited to these measurements.
Quantachrome Instrument for determining the age of ceramic and fired clay materials is the Aquadyne DVS.
Wilson, M.A., Carter, M.A., Hall, C., Hoff, W.D., Incd, C., Savage, S.D., McKay, B., and Betts, I.M. 2009. “Dating Fired Clay Ceramics Unsing Long-term Power Law Rehydroxylation Kinetics.” Proceedings of the Royal Society A, 465, 2407-2415.
 Wilson, M.A., Hamilton, A., Ince, C., Carter, M.A., and Hall, C. 2012. “Rehydroxylation (RHX) Dating of Archaeological Pottery.” Proceedings of the Royal Society A, 468, 3476-3493. http://dx.doi.org/10.1098/rspa.2012.0109.
Relevant Tech Note:
#57 - Using the Aquadyne DVS to Date Archaeological Material.
Porosity of Bioceramics
For bioceramics, especially implantable devices, porosity is a critical material characteristic. Many times bioceramics are being used to mimic the human bone which is a highly porous, but yet incredibly strong material. The desired physical characteristics such as cell adhesion, bone ingrowth, and vascularization will be heavily influenced by the porosity of the materials. Much research has been conducted not only looking at total porosity but looking at the ideal pore structure for promotion of cell, tissue, and muscle growth and adhesion. Mercury porosimetry is an ideal technology for the measurement of 3 dimensional materials and is sensitive to the arrangement of pores.
"Density Solutions: Ceramics & Structural Materials" (Density Analyzers)
by Martin Thomas, PhD.
True (Skeletal) density is best determined by automatic gas expansion pycnometers;
Tech Note #38 - Pycnometers Aid Osteoporosis Research.
Cement, concrete, mortars and other cementitious materials are used for structural construction, cosmetic finishes, and even forms of artwork. The material properties of these different applications vary, but the methods for measurement are common to all of these
materials and their precursors. Density, surface area, pore volume, porosity, pore size, water content, and affinity to water (hydrophilicity)
of the raw materials, the additives, and the end products are some of the critical properties that affect the structural and textural characteristics of cements and mortars.
Water vapor isotherms provide a wealth of information about the properties of the raw cement and additives as well as the finished product. The water content of the raw ingredients can affect flow and pouring characteristics. Water activity measurements can indicate the amount of loosely and tightly bound water in the cements. Water sorption isotherms can be used in conjunction with nitrogen or argon isotherms to quantify the hydrophilicity1 of the powders.
The Aquadyne™DVS and the VStar™ provide complimentary information on the interaction of water with these materials. The gravimetric method used in the Aquadyne™DVS is ideally suited to measuring water content (see Fiqure1 below, Relative Mass of Water lost on Drying).
1 Matthias Thommes, Sharon Mitchell, and Javier Pérez-Ramírez. “Surface and pore structure assessment of hierarchical MFI zeolites by advanced water and argon sorption studies. ” The Journal of Physical Chemistry C 116.35 (2012): 18816-18823.
The amount of bound water vs. free water can be determined by acquiring two isotherms in a row without degassing in between. The first isotherm deposits both bound water and free water, but only the free water comes off in the desorption step (see Figure 2. above right).
Water sorption measurements of hardened cement products give vital information about the strength, porosity, and physical stability of the product. For example, Powers and Brownyard2 have used water sorption measurements to evaluate several characteristics in hardened Portland cement.
Characteristics ranging from permeability to thermodynamics of adsorption provide useful information on the performance and curing times of cement and can be valuable tools in optimizing their formulations.
2 Powers, T.C., Brownyard, T.L., Studies of the Physical Properties of Hardened Portland Cement Paste, Journal Proceedings, Vol. 43-9, (1946) 249-336.
The true density value of cement materials is routinely needed for determination of their fineness, as with the Standard Blaine method ASTM-C204). Gas pycnometry presents a viable alternative to older, established methods (such as ASTM-C118) which employ difficult to handle liquids, like kerosene or naphtha. Using an inert dry gas, typically helium or nitrogen, as the displacement fluid eliminates any of the safety related challenges related to using liquids like those mentioned above.
This completely non-destructive, operator friendly technique also allows for multiple measurements to be easily performed, increasing the confidence in the results.
The UltraPyc™, and PentaPyc™, utilize gas displacement to measure the true density of a material, which excludes the influence of any pores accessible from the exterior of the sample.
Relevant Tech Note:
#22 -Alternate Method to Determine Density of Cement (Pycnometer)
Pore size distribution is an important factor that affects the moisture diffusion and permeability properties of cement-based materials. Mercury intrusion pore size analyzers are routinely used to assess the pore volume associated with pores sized between 0.003 and 950 µm Mercury intrusion is a simple and quick technique capable of accessing an extremely wide size range of pores difficult to access with other analytical techniques. Because of this, it has long been used to provide pore size and volume information for cement-based materials.
Our PoreMaster™ series of mercury intrusion porosimeters the pore size distribution and pore volume associated with all pores accessible from the exterior of a sample. This is accomplished by measuring the volume of a completely non-wetting liquid, mercury, which is intruded into pores at increasing pressures. The relationship between the size of a pore and the pressure at which mercury is gradually intruded is defined by the Washburn equation.
A typical example of a pore size distribution measured by mercury intrusion.