Gypsum Wallboard Research Articles

Acoustic design for University of Southern California, Annenberg School of Communications, lecture hall remodel

In 1998, the redesign of the 250-seat lecture hall at the USC Annenberg School of Communications was undertaken to update the aesthetics of the 1974 design and meet the modern functional requirements of the University. Primary uses of the hall were to be lectures, audiovisual presentations, and panel discussions. The existing fan-shaped space had a concrete ceiling, plastered concrete side walls, and a concave rear wall with a slatted wood acoustic finish. The existing reverberation time (RT60) was 0.95 s at mid-frequency, but there was a sense of over-reverberance and a lack of speech clarity. This was attributed to focusing by the curved rear wall and to excessive bass reverberation. The acoustic design targets included a modest reduction of the mid-frequency RT60, a significant reduction of the bass reverberation, and mitigation of the effects of focusing, as well as a maximum noise level of NC30 for the new HVAC system. Simple materials, including gypsum board wall linings, fabric wrapped panels, and acoustic foam in inconspicuous areas, were used to achieve cost effectiveness. Acoustics and architecture were fully integrated for efficiency of design. The project, completed in 1999, was an acoustic and architectural success. [Architectural Design by Siegal Diamond Architecture.]

Measurement of Anchor Strength in Non-Rigid Substrates

Abstract This study provides guidelines for measuring anchor strength in non-rigid substrates. ASTM Standard Test Method for Strength of Anchors in Concrete and Masonry Elements (E 48884) was designed to measure the “strength of anchors in concrete and masonry elements” and was never intended for use in flexible substrates. Hence, the load capacity of anchors installed in thin brittle materials like gypsum wallboard may be overestimated when measured in accordance with E 488. This is because ASTM E 488 imposes a reaction load around the anchor and delays the onset of pullout failure related to substrate bending. In contrast, the alternative test does not constrain the front surface of the substrate and can better reproduce the actual mechanisms of anchor failure in flexible materials. The pullout strength of five anchor styles of varying rated strengths was determined following the ASTM E 488 method and by the alternative method. In both cases, the anchors were placed in a wallboard panel attached to a rigid wooden framework by suitable screws and adhesive. With no adhesive cure, the strength by the alternative method was up to 31% less than that obtained by the test following ASTM E 488 guidelines. With full adhesive cure, the strength in the alternative test was still up to 30% less than the ASTM test and up to 45% less than the rated strength. The strength differences can be linked to differences in the flexural stiffness of the test panel, and guidelines are given for determining when the substrate is flexible enough to justify the alternative test. The alternative test requires more setup time than ASTM E 488 but provides a more realistic measure of the ultimate load capacity of relatively strong anchors. In addition, the alternative test makes it possible to relate the effects of factors like screw spacing and bonding efficacy to anchor strength.

Flammability And Dehydration Of Painted Gypsum Wallboard Subjected To Fire Heat Fluxes

The flammability and dehydration of painted gypsum wallboard (GWB) exposed to fire heat fluxes are investigated. Painted GWB samples are subjected to constant incident heat fluxes ranging from 25 to 75 kWlm2 for periods ranging from 5 to 15 minutes in the Cone Calorimeter. A number of coats of latex interior paint, including 0, 2, 4, 6 and 8 coats, are applied over a single coat of latex primer to the exposed surface of 15.9-mm (518-in.) thick type X GWB. A model is used to evaluate the potential for flame spread based on the Cone Calorimeter results. A two-step dehydration model based on a finite difference formulation is described for GWB. Experimental results indicate a distinct dehydration front can be observed by visual inspection; further analysis is needed to determine the composition of the GWB on each side of this front.

Post-fire analysis of construction materials?gypsum wallboard

The objective of this research was to assess scientifically to what extent fire damaged gypsum wallboard (GWB) could be used to identify time, temperature and heat flux exposures of the incipient stages of an uncontrolled fire. Gypsum wallboard is commonly used on vertical and ceiling surfaces that frequently survive a building: fire so permiting samples of the GWB to be removed for post-fire analysis. The gypsum (calcium sulphate dihydrate) is a hydrated cystalline mineral that is chemically very stable and undergoes phase changes at temperatures found in the incipient stages of a building fire. Experiments are described in this paper that support the theory that thermally induced changes in GWB provide a quantitative method for determining time/temperature regimes that have occurred in a building fire.

Land application of crushed gypsum wallboard waste for alfalfa

Three seasons of research that evaluated the effect of the land application of crushed gypsum wallboard waste (CW) for alfalfa were conducted at four Wisconsin locations having differing soil types and climatic conditions. Material was applied at rates up to 36.0 Mg ha‐1 preplant and 2.2 Mg ha‐1 topdress. The highest application of CW pre‐plant showed a positive trend for increased yield of alfalfa at three of the four locations, although this response was not statistically significant. Stand density was not affected with the exception of one year at one location for which the stand was lower where the highest rate Of CW was applied. The soil pH decreased slightly where high rates of CW were applied, presumably caused by an increase in soil solution hydrogen ions which were displaced from exchange sites. Soil calcium (Ca) and sulfur (S) usually increased, and soil test magnesium (Mg) usually decreased where the highest rate of CW was applied. There was no consistent effect of CW application on the soil test levels of other nutrients. Application of CW generally increased the Ca and S, and reduced the Mg concentrations in the harvested forage. Crushed wallboard appears to be as effective as commercial gypsum fertilizer, although this study did not compare equivalent rates of the two materials. No phytotoxic effects from the direct application of CW were noted. The land application of wallboard was found to have no substantial positive or negative agronomic effect on alfalfa production. This practice provides a reasonable alternative to land filling.

Sanitation of wallboard colonized with Stachybotrys chartarum.

Sections (8 cm2) of unused, nonsterile gypsum wallboard (dry wall) were inoculated with varying densities (10(4) to approximately 10(8)/ml) of conidia from 14- to 21-day cultures of Stachybotrys chartarum grown on cellulose agar. The sections were permitted to air dry and were placed into vessels with 86% or 92% RH and incubated at 22-25 degrees C for up to 12 weeks. The moisture content of the dryboard increased from near 10% to over 35%. Selected sections with confluent surface growth, mainly of S. chartarum, were obtained within 3 weeks. Sections were cleaned with a quaternary or quaternary and chlorine dioxide or a concentrated oxygen-saline solution and treated, in some cases, with a preservative system and returned to humidity vessels. Reemergence of S. chartarum from inoculated and treated surfaces occurred within 5 weeks only with sections treated with the quaternary alone. Other fungi, mostly species of Aspergillus, Chaetomium and Penicillium, slowly colonized (between 9-12 weeks) at least some areas of most treated surfaces and most uninoculated control surfaces. Stachybotrys chartarum was also found on several sections of uninoculated controls. Sections treated with a quaternary/acrylic and placed in a dynamic challenging chamber remained visually free of colonized fungi for over 90 days. These studies indicate that control samples of uninstalled wallboard, available from local distributors, can contain a baseline bioburden, including S. chartarum, that will colonize surfaces under high humidity conditions. Sanitation and preservation treatment of the wallboard can markedly delay regrowth of these fungi, particularly of S. chartarum.

Background noise levels in classrooms

Field measurements of background noise levels produced by air-conditioning systems were taken in a sample of 47 elementary school classrooms. Noise levels were grouped by air-conditioning system type and resulting noise criterion (NC) levels. Eight computer models of classrooms were constructed with varying combinations of absorbent materials on the surfaces of the rooms. A sound source was configured to approximate the normal speaking voice of a teacher in the room. RASTI measures were estimated for six seating locations in each room for background noise levels from 0 dB to NC- 55 in 5-NC point increments. RASTI values remained above 0.8 in seven of the eight rooms at NC levels of 32 and below. RASTI levels decreased to 0.50 and less in all eight rooms at levels of NC- 45. The one exception to this was the room constructed with a gypsum board ceiling, vinyl tile floor, and gypsum board walls. Even with no background noise, RASTI values in this room never exceeded 0.60. Background noise levels of NC 32 or less appear to be necessary in most typical classrooms to maintain reasonable RASTI values. Very few of the actual classrooms visited achieved these noise levels.

Evaluation of thermal storage as latent heat in phase change material wallboard by differential scanning calorimetry and large scale thermal testing

Differential scanning calorimetry and large scale thermal testing were conducted to determine the latent heat storage in a thermal storage wallboard. Thermal storage wallboard was developed at School for Building, Concordia University, by incorporating about 20% by weight of a phase change material in gypsum wallboard. It was determined that differential scanning calorimetry can adequately predict the performance of a full-scale installation of thermal storage wallboard. Consequently, the expensive large scale tests need only be performed when the development of thermal storage wallboard is well advanced.

Energy-Storing Wallboard: Flammability Tests

Flammability tests were conducted on energy-storing wallboard—ordinary gypsum wallboard impregnated with approximately 24% organic phase change material (PCM). Such wallboard is able to store or release a significant amount of thermal energy. The major energy storage factor is the latent heat of the PCM, which is endothermic as PCM melts and exothermic as it crystallizes. A short presentation of the results obtained in the evaluation of such wallboard points out that flammability tests represent almost the last stage in this evaluation. The flammability tests evaluated the surface burning characteristics: flame spread and smoke development classifications determined in a Steiner tunnel, as well as heat and smoke release rates determined by cone calorimeter. The tests indicated that the energy-storing wallboard does not meet all requirements in the National Building Code regarding fire characteristics for building materials. Therefore, the possibility of reducing its flammability is discussed. Comparison o...

Finish Ratings of Gypsum Wallboards

The term “finish rating” is used in NFPA 70, National Electrical Code (NEC)1 to describe the required performance of finish materials installed as thermal barriers for electrical nonmetallic tubing. Finish rating data is most commonly associated with assemblies containing combustible wood framing, although the definition has also been extended to assemblies with noncombustible metal framing. To date, however, very little finish rating data has been available for common finish materials installed over metal framing. To supplement the available information, finish rating tests were conducted on identical wall sections finished with standard 1/2″ gypsum wallboard from five different manufacturers, constructed with metal and wood stud framing. All 10 assemblies tested demonstrated finish ratings of 15 minutes or more.

Static Racking Behavior of Plywood, OSB, Gypsum, and FiberBond Walls with Metal Framing

Recent results from full-scale static racking tests and small-scale lateral shear tests on plywood, oriented strand board (OSB), gypsum wallboard (GWB), and FiberBond wallboard (FB) attached to light gauge steel studs are presented and discussed in this paper. The objectives of the tests were to investigate the performance of sheathed light gauge steel framed shear walls and determine whether simple static lateral shear values for the panel connection can provide a useful correlation with full-scale test values. The full-scale tests were conducted in accordance with the basic test criteria defined in ASTM E 72-80. A procedure similar to that described in ASTM D 1761-88 was used for the small-scale tests. Panels used in the tests included 11.9 mm APA rated four-ply plywood sheathing, 11.1 mm APA rated OSB sheathing, 12.7 mm gypsum wallboard (ASTM C 36), and 12.7 mm FiberBond wallboard. Results obtained from tests showed that failure of the walls resulted from rotation (tilting) of the fasteners about the p...

Revisiting the Component Additive Method for light-frame walls protected by gypsum board

The National Building Code of Canada provides architects, engineers and builders with a simple, practical calculation method for assigning fire-resistance ratings to wood-frame and steel-frame wall, floor and roof-ceiling assemblies. It was originally devised in the early 1960s and is commonly known as the Component Additive Method (CAM). A collaborative industry–government research program was carried out recently at the National Research Council Canada to develop new fire-resistance ratings for gypsum-board protected walls. Forintek Canada Corp. and the Canadian Wood Council participated in that program on behalf of Canada's wood industry. As part of the research program, a number of full-size fire-endurance tests were carried out on wood-frame and steel-frame walls. The results of those fire tests have allowed us to revisit those sections of the Component Additive Method which are applicable to light-frame walls lined with gypsum board. © 1997 John Wiley & Sons, Ltd.

A Methodology for Quantifying the Volume of Construction Waste

Estimates for construction waste generation are often based on per capita multipliers in much the same way as municipal solid waste estimates. This has lead to estimation rates with more than 10-fold variation and little confidence in the resulting estimates. A methodology is offered in this paper that bases construction waste estimates on the financial value of building permits for a variety of types of construction projects. In this way, estimates reflect actual construction activity more closely and are based on a detailed and widely available database from the U.S. Census Bureau. A case study estimating gypsum wallboard waste generation for a region of the United States is described. The case study results were used in the decision-making process by a wallboard manufacturing plant interested in the development of a regional gypsum wallboard recycling programme. © 1996 ISWA

Fire-resistance and Sound-transmission-class Ratings for Wood-frame Walls

A collaborative industry-government research program was carried out at the National Research Council Canada (NRC) to develop new sound-transmission-class and fire-resistance ratings for gypsum-board protected walls. Forintek Canada Corp. and the Canadian Wood Council participated in the program on behalf of Canada's wood industry. As a result of that NRC research program, sound-transmission-class (STC) and fire-resistance (FR) ratings were formulated for approximately 140 gypsum-protected wood-frame walls. Fire-resistance ratings for the walls range from 30 minutes to 2 hours. Sound-transmission-class ratings range from 30 to 65. Sound-transmission-class and fire-resistance ratings for approximately 90 of the wall designs appear in tbe 1995 edition of the National Building Code of Canada (NBCC). This paper highlights some of those STC and FR ratings and describes how they were derived from the data obtained through the research program.

Shear Resistance of Gypsum-Sheathed Light-Gauge Steel Stud Walls

This paper presents detailed results on the shear behavior of 2.44 m by 2.44 m light-gauge steel stud walls for three different shear resisting systems: framed walls with 20 gauge flat strap X-bracing on the face—type A; framed walls with 12.5 mm (1/2 in.) single-ply gypsum wallboard on the back and 12.5 mm (1/2 in.) single-ply gypsum sheathing board on the face—type B; and framed walls with 12.5 mm (1/2 in.) single-ply gypsum wallboard on the back, 12.5 mm (1/2 in.) gypsum sheathing board on the face, and 20 gauge flat strap X-bracing on face—type C. The steel framing used in these tests is typical of framing used in residential construction. The behavior of the type A walls was governed by the yield strength of the straps with practically no resistance provided by flexure in the studs. In the type B and type C tests, the measured maximum load was controlled by the breaking of the wallboard along its edges. The failure mechanism was initiated by a rotation of the screws at the edges. This was followed by the partial pull-through of the screws at the edges of the gypsum board and simultaneous breaking of the board at the edges. Each 1.22 m by 2.44 m (4 ft by 8 ft) gypsum panel was observed to behave independently during loading. A comparison of the results from the type B and type C tests showed that the use of 50.8 mm, 20 gauge tension bracing prevented cracking of the boards at the perimeter, reduced the lateral displacement, and increased the maximum load capacity of the wall by as much as 28%.

DSC analysis for the evaluation of an energy storing wallboard

Sensible heat storage in building materials has been practiced for thousands of years. Recent work at the Centre for Building Studies of Concordia University on the incorporation of various phase change materials (PCMs) in gypsum wallboard has resulted in the addition of their latent heat values to the sensible heat storage value of wallboard. In this way its heat storage capacity can be increased by at least eightfold. PCM-wallboard development tests were conducted on a small scale using DSC analysis for selecting the PCMs; evaluating PCM-wallboard prototypes; to ascertain the reproducibility of PCM thermal characteristics in wallboard, to verify the spatial uniformity of PCM and to ascertain the effects of temperature cycling on the thermal characteristics of PCM-wallboard.

A model for predicting heat transfer through noninsulated unloaded steel-stud gypsum board wall assemblies exposed to fire

With the advent of performance-based codes and performance-based fire safety design options, validated fire-resistance models have become essential. In this paper, a one-dimensional heat transfer model for steel-stud, noninsulated, unloaded gypsum board protected wall assemblies is presented. Also presented are a comparison between temperature predictions and measured temperatures at different locations in gypsum board wall assemblies as well as a comparison between the predicted and measured fire-resistance ratings. The model, which predicts slightly conservative fire-resistance ratings compared to the experimental measurements, is appropriate for most fire safety engineering applications. Considerations for further model development are identified.

Water vapour absorption and desorption by carpets, spruce lumber, and painted gypsum board

Abstract Tests were conducted to determine the moisture absorption/desorption characteristics of representative indoor building materials and furnishings. The experiments consisted of weighing several iteras while they were being subjected to humidity step changes. The quantities of moisture absorbed and released and the associated time constants were noted. The results showed that for a step change in humidity ratio, common indoor materials exhibited significant moisture uptake (release) relative to the change in moisture content of the air space. Of the materials tested, carpet was the most reactive, followed by unpainted spruce lumber, and then by latex‐painted gypsum wallboard.

Development and application of organic phase change mixtures in thermal storage gypsum wallboard

A latent heat storage material which would be useful in hot climate is proposed. It is a mixture of 93–95 wt% commercial Methyl Palmitate (MeP) with 7-5 wt% commercial Methyl Stearate (MeS), having a melting-freezing interval of approximately 23–26.5°C and a latent heat of transition of at least 180 kJ/kg. Normal wallboard may be impregnated with up to 25 wt% of one of these mixtures. Air passing over such an impregnated wallboard would be cooled down due to the heat absorption taking place between 23–26.5°C when the mixture melts. Recharging the wallboard will occur at 22–23°C during freezing, when the latent stored heat is released to the cool night air. The total storage capacity of such an impregnated wallboard, in a 3.5°C temperature interval, is at least twelve times higher than the storage capacity of wallboard alone over this range.

Attenuation properties of diagnostic x‐ray shielding materials

Single- and three-phase broad-beam x-ray attenuation data have been obtained using lead, steel, plate glass, gypsum wallboard, lead acrylic, and wood. Tube voltages of 50, 70, 100, 125, and 150 kVp were employed and the resulting curves were compared to transmission data found in the literature. To simplify computation of barrier requirements, all data sets were parametrized by nonlinear least-squares fit to a previously described mathematical model. High attenuation half value layers and the lead equivalence of the alternate materials were also determined.