Development of Blended Pozzolans Using Natural Pozzolan and Ground Glass Through Reactivity and Durability Investigations

Abstract

Abstract This study emphasizes the reactivity evaluation of pozzolans and the durability performance of blended cements containing pozzolans. A ground glass, three raw natural pozzolans, and two blended pozzolans of ground glass and raw natural pozzolan were examined for reactivity using the modified lime-reactivity test, the strength-activity index (SAI) (ASTM C311, Standard Test Methods for Sampling and Testing Fly Ash or Natural Pozzolans for Use in Portland-Cement Concrete/ASTM C618, Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete), the bound water test (ASTM C1897, Standard Test Methods for Measuring the Reactivity of Supplementary Cementitious Materials by Isothermal Calorimetry and Bound Water Measurements), and an electrical resistivity index (ERI) from tests conducted on the mortar cubes produced for the SAI. The pozzolans, including the blends, were combined with a high-alkali portland cement and investigated for their efficacy in mitigating alkali-silica reaction (ASR) in the Pyrex mortar bar test (ASTM C441, Standard Test Method for Effectiveness of Pozzolans or Ground Blast-Furnace Slag in Preventing Excessive Expansion of Concrete due to the Alkali-Silica Reaction) and the accelerated mortar bar test (ASTM C1567, Standard Test Method for Determining the Potential Alkali-Silica Reactivity of Combinations of Cementitious Materials and Aggregate (Accelerated Mortar-Bar Method)). Mortar bars with the control mix and two blended pozzolans were prepared to determine sulfate resistance in a 5 % sodium sulfate solution. In addition, three concrete mixes were developed to determine air void parameters, compressive strength, and resistance to chloride ion penetration. The pozzolans demonstrate a range in reactivity in all tests except the ASTM C1897 bound water test. The natural pozzolans have high water demand but meet the water demand limit and both the 7-day and 28-day SAI requirements of ASTM C618-19, whereas the ground glass does not meet one of the requirements of ASTM C1866, Standard Specification for Ground-Glass Pozzolan for Use in Concrete—the 28-day SAI. Blended pozzolans improve the resistance of blended cements against sulfate attack and chloride-ion penetration at 28 days or later. The reactivity results indicate that resistivity or ERI is effective in estimating the pozzolanic reactivity of materials tested. ASR mitigation caused by pozzolans in one test is in good agreement with that found in another. However, a disparity between the outcomes of the ASR tests (ASTM C441 and ASTM C1567) is present.