P N OJHA, SURESH KUMAR, ABHISHEK SINGH, BRIJESH SINGH & B N MOHAPATRA
C 1567, and has the potential to resolve uncertainties about results obtained with C 289, C 1260 and C 1567 when no additional alkalis are expected to become available to the system.
(v) Accelerated Mortar-Bar Test (ASTM C 1567)[14]
ASTM C 1567, a test method for determining the potential alkali-silica reactivity of combinations of cementitious materials and aggregate (Accelerated Mortar-Bar Method), assesses the expansion of specimens made with the aggregate in question and blended cement, or cement plus pozzolan or slag under the same accelerated test conditions as ASTM C 1260. It tests the effectiveness of cement-pozzolan-aggregate combinations. It may be required to test different levels of pozzolan and ground granulated blast-furnace slag to determine the amount required to reduce expansion to an acceptable level. Pozzolans and ground granulated blast-furnace slag may be tested separately or in combination. It is recommended to test the same aggregate and hydraulic cement (without pozzolans and slag) using Test Method C 1260 for a comparative control. Due to the long duration of time (1 year) required to run a concrete prism test (CPT), as per ASTM C 1293, in this study the ASTM C-1260 standard test method for potential alkali reactivity of aggregates (accelerated mortar bar method) was used to determine the potential alkali reactivity of aggregates collected from six different sources across India.
2. Experimental Program
In this study, coarse aggregates CA-1, CA-2, CA-3, CA-4, CA-5 and CA-6 from six different sources across India were evaluated. These aggregates were proposed to be used in different
concrete dams in India with Ordinary Portland Cements having Na2Oeq in excess of 0.60%, which is high from an alkalinity point-of-view, and may lead to alkali-aggregate reactions if the aggregates are reactive in nature. All six coarse aggregates samples were evaluated for their different physical parameters such as specific gravity, water absorption, deleterious material, soundness, abrasion value, crushing value, impact value, flakiness and elongation index as per relevant Indian Standards. These aggregates were also subjected to petrographic and mineralogical examinations as per IS 2386 Part VIII -1963[15]. Evaluation of the expansion potential of aggregates due to alkali-silica reaction was conducted using an accelerated mortar bar test, as per ASTM C-1260.
3. Materials
Apart from coarse aggregate samples, one brand of Ordinary Portland Cement (OPC 43 Grade) and water has been used to prepare the mortar bars for the accelerated mortar bar test. Water complying with the requirements of IS: 456-2000[16] for construction purpose was used. The physical and chemical characteristics of OPC 43 used in this study has been tabulated in Table 1. The physical and chemical properties of OPC 43 meet the various requirements suggested by IS: 269-2015[17].
170 DAM ENGINEERING Vol XXXI Issue 3
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