The mind-set in the early days of stabilization was to use a mortar that would last for a very long time, but nobody really gave any thought to the combined physical properties of the materials or the dynamics, so the result is a system that when it fails, it is usually catastrophic in that it involves major loss of stone and/or wall collapse. Most of Gran Quivira was stabilized with this exceptionally hard soil-cement, which we are now slowly reversing.
Today, we believe that the mortar should be very close to the original, but not so close that it cannot be distinguished from original fabric. Replacement materials are typically 'marked' in some fashion to avoid confusion. We want the reconstruction to be authentic, but not false. Obviously, we are not introducing animal bone and potsherds to the mix, but we do try to use soil very similar in color and texture (sand and silt mixture) to that used by the original builders. As an amender, we are using Type S masonry cement. Type S still contains Portland cement, but has a higher lime content, greatly reducing the strength. Because we cannot perform wholesale removal of the previous Portland mortars without damaging the stone, we have to gradually 'step down' the mortar strength until the balance of the hard mortar is gone. As the years go by, replacement mortars can gradually evolve to something more ideal.
The Stabilization of Kiva F
Kiva F has been showing the signs of stone deterioration brought on by the harder mortars. Some of the original stone in the kiva––an igneous dike material––is very soft and vulnerable to moisture and the migration of salts. As the stone deteriorates, mortar then falls out. Kiva F had reached a point where intervention was required. We removed all of the loose old mortar and replaced it with the newly formulated soil-cement. When Kiva F was originally excavated in 1923 by Edgar Lee Hewitt, the original adobe covering on the bench was still in place. So, to bring the kiva back to more closely match its appearance as excavated by Hewitt, we re-covered the bench with true adobe installed as it was originally. More importantly, the adobe bench itself is a preservation technique designed to protect the kiva from erosion and to protect the soft igneous stone, most of which can be found along the base of the kiva walls (the igneous stone is actually bedrock to which the kiva pit was excavated).The Learning Process
While we always keep an eye out for artifacts and architectural details that may have migrated or been previously missed, we did not learn anything new about the kiva. We did learn a lot about recreating a lost technology, re: formulating, preparing, and applying adobe surfaces, which can be far more complex than meets the eye. The original stabilization dates to Hewitt, and all subsequent stabilzations at Gran Quivira until recently followed his example with the excavation of Mound 7 being the last major archaeological project within Salinas Pueblo Missions National Monument. The Mound 7 excavation was directed by NPS archaeologist Alden Hayes from 1965-1970, and even then the portland soil-cement was used to stabilize the structure. Much of what remains in place in Mound 7 is still the Hayes-period mortar. Research and experimentation regarding stabilization mortars for archaeological ruins remains a highly active and viable topic amoung scholars.The Salinas Pueblo Missions National Monument is open to the public year round daily. Summer hours (Memorial Day - Labor Day) are 9:00 a.m.-6:00 p.m. Winter hours (rest of the year): 9:00 a.m.-5:00 p.m. Gran Quivira is located twenty-six miles south of the park's headquarters at Mountainair, New Mexico.
