During the period March through October 2016, research was conducted at the U.S. Army Engineer Research and Development Center in Vicksburg, MS, to develop alternative backfill materials for rapid airfield damage repairs using a variety of commercially available products. The performance of a variety of additives, including 15 traditional and nontraditional materials, and a control comprised the test matrix of stabilization additives. The types of additives included cement, polymer, polyurethane, petroleum emulsion, and silicates. This report presents the technical evaluation of the laboratory and field performance of alternative backfill materials used in the subgrade of concrete repairs using Rapid Set Concrete Mix ® . The additive performance criteria focused on bearing capacity, unconfined compressive strength at 2 hr and at 7 days, and durability of the specimen when partially submerged in water. Laboratory testing included mixing silty, clayey sand soil with each of the additives at specified application rates; compacting; curing; and conducting unconfined compressive strength and California Bearing Ratio testing. For the field evaluation, a repair consisted of preparing the subgrade with a selected additive and overlaying it with Rapid Set Concrete Mix ® . Passesto-failure rates for each repair were determined by using an F-15E load cart at a maximum of 3,500 passes.
Alkali-silica reaction (ASR) is a deleterious chemical reaction that can lead to expansion and cracking of concrete structures. The reaction occurs between alkali hydroxides in the pore solution and reactive forms of silica present in some aggregates. To successfully mitigate ASR in new structures, the potential alkali reactivity of the aggregates must be known. Standardized test methods for this purpose are sometimes too time-consuming for rapid military construction operations. To assess the viability of a five-hour autoclaved mortar bar test method for ultra-rapid identification of aggregate reactivity, researchers in five laboratories participated in a multi-laboratory study led by the U.S. Army Engineer Research and Development Center (ERDC). The test method uses fine aggregate in mortar bars like those used in ASTM C1260, Standard Test Method for Potential Alkali Reactivity of Aggregates (Mortar-Bar Method), but the equivalent alkali content of the mortar is boosted to 3.5 % by mass of cement. Mortar bars are cured for 48 hours prior to autoclaving at 130°C for five hours at peak temperature. This paper details the test procedure, expansions, comparisons with the accelerated mortar bar test and the concrete prism test, within- and multi-laboratory precisions, and investigation into the amount of alkali leaching during the test. For 85 % of the 20 aggregates tested, there was agreement between the autoclave test and ASTM C1260 in determining whether or not an aggregate was reactive to some degree. The agreement between the autoclave test and ASTM C1293, Standard Test Method for Determination of Length Change of Concrete Due to Alkali-Silica Reaction, was 100 % for ten of the aggregates for which ASTM C1293 data were available. The average within- and multi-laboratory coefficients of variation were 5.9 and 20.0 %, respectively. Results showed alkali leaching to be between 6 and 9 % per mortar bar. This study demonstrated the viability of the five-hour autoclave test for rapidly assessing aggregate reactivity in military construction operations.
The U.S. Army Engineer Research and Development Center (ERDC) solves the nation's toughest engineering and environmental challenges. ERDC develops innovative solutions in civil and military engineering, geospatial sciences, water resources, and environmental sciences for the Army, the Department of Defense, civilian agencies, and our nation's public good. Find out more at www.erdc.usace.army.mil. To search for other technical reports published by ERDC, visit the ERDC online library at http://acwc.sdp.sirsi.net/client/default.
In support of the U.S. Army Corps of Engineers (USACE) Nashville District, a preliminary investigation of concrete materials was conducted pursuant to reconstruction at the Chickamauga Lock and Dam located near Chattanooga, TN. Local materials provided to the U.S. Army Engineer Research Development Center (ERDC) for testing included three different coarse aggregate gradations, two fine aggregate sources, two type I/II cements, a fly ash sources, a slag cement, a silica fume, and a limestone powder. Aggregate tests consisted of sieve analysis, specific gravity, absorption, materials finer than No. 200, organic impurities, soundness, LA abrasion, clay lumps and friable particles, flat and elongated particles, lightweight particles, petrography, and freezing and thawing. All cementitious and admixture materials were tested for chemical and physical properties based on appropriate specifications. This report presents the material characteristic results determined by laboratory testing in accordance with American Society for Testing Materials (ASTM) procedures or regulating specification criteria. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.
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