Modern Masonry Using Pre-blended Mortar
Specifying Pre-Blended Mortar
In general, it should be clear by now that mortar is critical to a masonry wall’s structural integrity and aesthetic value. Therefore, specifications for it must be based on good information, and quality assurance tests must be applied correctly. Architects writing specifications for mortar need to be aware of the differences and specific capabilities of the different mortar types, making good spec writing critically important. Under the MasterFormat specification standard, masonry mortar is normally including in Section 04 05 13 or related sections.
Under Part 1: General of a standard three-part specification, the performance standards should be listed, including ASTM C270 and ASTM C1714, for the mortar and whether property specifications need to be followed or if proportion specifications will be acceptable. Also list the relevant standards for each ingredient and any relevant details related to them. This is a case where it makes sense to always request a complete submittal package so the materials, colors, and any admixtures can be fully inspected and confirmed. It also makes sense to request that a sample or test panel be constructed to see the product on the site before it is incorporated fully into the project. Be sure to call for it to be washed and cured for seven days on-site before being evaluated. As part of the quality assurance of the mortar, distinguish between on-site testing and material testing in a laboratory and request laboratory-certified test results. Verify that the same materials used in the test panel are the ones that were specified and tested.
Under Part 2: Products, there should be reference to a masonry schedule or other information on the drawings if multiple types of masonry construction and mortar are being used so the locations are clear. The specification should then go on to provide the details of each of the scheduled or identified products. If pre-blended mortar is being specified, then it should be clearly stated along with any restrictions against site-mixed mortar. Either way, identify each type of mortar needed (M, S, N, O) and where each is called for. If colored mortars are being used, then the specific colors need to be identified. Overall, specify consistent mortar materials, pigments, and mixing procedures.
In terms of Part 3: Installation Requirements, proper handling of all mortar materials on-site, whether pre-blended or otherwise, needs to be emphasized. If the mortar is pre-blended, then no instructions need to be given related to mixing other than the means of adding water. Final placing, protecting, and cleaning in a manner consistent with PCA and other approved standards or methodology will round out the specification.
The back side of CMU and mortar treated with an admixture to improve water repellency is shown on the left compared to CMU and mortar without the admixture on the right. Both were sprayed with water on the front side, and after a short time, the difference in water repellency was clearly evident.
Conclusion
With an understanding of the importance of masonry mortar and the clear advantages of pre-blended mortar, the final question isn’t why would you use it on your projects, but rather, why wouldn’t you specify pre-blended mortar? The structural integrity of the mortar is easier to assure, and the aesthetic values are more controllable. Pre-blending provides better quality control and consistency with full technical support available from manufacturers. Further, it produces less waste and can improve job-site safety for workers.
HOME OF THE SAN FRANCISCO 49ERS BUILT WITH PRE-BLENDED MORTAR
Project: Levi’s Stadium
Location: Santa Clara, California
Levi’s Stadium, located in Santa Clara, California, is the home of the San Francisco 49ers, host to Super Bowl 50 in 2016, and widely considered the “next generation” of stadium design. When it came to the construction of this new stadium, concrete masonry was chosen for its versatility, durability, and structural qualities. CMU pre-blended mortars were used very successfully throughout this project. Type S mortar was used underneath the stadium for corridors, locker rooms, storage and mechanical rooms, and even a detention area for rowdy fans. Water-repellent mortar (WRM) was selected for use in the architectural ground face blocks for the exterior walls.
The WRM was used as part of a total system where the CMUs also contained water repellents to create a wall system with superior moisture resistance. Seen as a revolution in the industry, water-repellent additives were factory blended in the mortar. This way, the water-repellent agent is traceable and measurable in the hardened mortar, verifying that the exact proportions for optimal water resistance are included in every bag. WRM has also been proven to maintain the normal bond strength and board life of the mortar.
“The masons preferred the pre-blended mortar because it was not as coarse as other mortars and had longer board life,” says Chuck Wood, estimator and project manager with Bratton Masonry of Fresno, California, for Levi Stadium. The selected pre-blended mortar was submitted as preferable over other pre-blended brands by the contractor due to the qualities noted by Wood, who has a long history using these products.
Just as Levi’s Stadium is redefining what a stadium can be with solar panels and a green roof, pre-blended mortar with integral water resistance is redefining what is possible in modern masonry construction. It only makes sense that a next-generation sporting arena would be constructed using mortars that have been engineered to withstand the test of time and the elements, remaining strong for years to come.
PRE-BLENDED MORTAR PLAYS ROLE INCONSTRUCTION OF ICONIC NEW STADIUM AT BAYLOR UNIVERSITY
Project: McClaine Stadium
Location: Baylor University, Waco, Texas
With Baylor’s football program on the upswing, the university invested in a new state-of-the-art stadium that was completed in time to begin the 2014 season. Located on the Brazos River and directly adjacent to the I-35 Corridor, McLane Stadium serves not only as the front door to Baylor University but also as the east anchor of downtown Waco. The $266-million stadium is a multifunctional facility that hosts world-class music, family, and sporting events throughout the year in addition to Baylor University football.
The mortar for the entire project was pre-blended and comprised 1.045 super sacks, or more than 3 million pounds. “This was a very high-profile project on a facility that was not only important to Baylor University but also to the entire city of Waco since it’s essentially part of the city’s downtown,” says Quality Brick Works Owner James Traylor. “One of the reasons why pre-blended mortar was such a good fit was the high quality of the product combined with the ability to consistently match the mortar color across the entire project.”
A special, high-polished block was specified by the architect along with a distinct red brick. Since the mortar was pre-blended, it eliminated any room for human error and provided a consistent product that looked the same and performed the same throughout the project. The mason was also pleased to work with one supplier to provide all of the mortar, which enhanced logistics and project flow and offered a single source to guarantee the quality of the product.
“When you work on an extremely high-profile project like McLane Stadium you are center stage, and if something’s not right, you know about it very quickly,” Traylor says. “Pre-blended mortar is a quality product that gives us the confidence to do our work and not have to think twice about the mortar.”
As with most stadium projects, there was a finite deadline due to the impending first game of the season. The supplier of the pre-blended mortar helped the construction team easily meet its deadline so the capacity crowd could enjoy the Bears’ history-making opening game on August 31, 2014.
Peter J. Arsenault, FAIA, NCARB, LEED AP, is a practicing architect, green building consultant, continuing education presenter, and prolific author engaged nationwide in advancing building performance through better design. www.linkedin.com/in/pjaarch
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