A research program was developed to investigate relative properties of three mortars containing lime-replacement additives compared to the properties of four traditional portland cement-lime mortars used in masonry construction. Plastic and hardened properties were determined using standard ASTM test methods. The test program indicates that, although the three lime-replacement mortars have comparable compressive strengths to portland cement-lime mortars, they have significantly different water retention and air content percentages and, as tested, the lime-replacement mortars do not meet specification requirements of either ASTM or ICBO. In addition, masonry walls constructed with the three lime-replacement mortars studied in this program were less resistant to water penetration than walls constructed with portland cement-lime mortars. It is suggested that ASTM specifications and test methods currently under development consider the essential properties of water retention, air content, and water penetration resistance in addition to compressive strength for acceptance of lime-replacement materials.
Injection of grout into cracks may be used as a form of repair following a damaging event or as a means to strengthen multi-wythe masonry, enhancing composite action between the wythes. An experimental program has been conducted to evaluate grouting procedures, the suitability of different types of cementitious grouts for injection, and the effect of grout injection on structural behavior.
Over 30 separate mixes utilizing various cementitious components, aggregates, admixtures and different water/cement ratios have been evaluated. A standardized series of evaluation tests have been used to compare injectability, mix stability, and grout properties for each of the mixes. These grouts possess properties similar to the masonry being repaired, and would be available for widespread use as a material for masonry repair. An additional contribution of this research has been the application of nondestructive techniques as a means of measuring quality of the injection process.
An investigation of parameters which affect the strength of lap splices within reinforced masonry is currently being conducted as part of the U.S. Army Corps of Engineers program for Construction Productivity Advancement Research (CPAR). Results from the first phase of the investigation complement existing data regarding lap splices in reinforced masonry and provide a comprehensive review of the effects of masonry unit width, masonry unit type, reinforcing bar diameter, and lap length on both the strength and monotonic behavior of lap splices in masonry.
Results of the experimental investigation have shown that the linear relationship used by current working stress masonry design standards does not accurately describe ultimate splice capacity in some cases. An alternate model, adopted for use in the proposed Masonry Limit States Design Standard, provides a more rational approach to the determination of lap splice lengths in masonry. This method considers reinforcing bar diameter and yield strength, grout tensile strength, and masonry wall thickness when determining splice length. Experimental results are in good agreement with values provided by this analysis and have been used to further verify the applicability of the model.
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