Pozzolanic Effects of Meta-Halloysite and Micro-Silica on Mechanical Strength and Durability of Concrete

Document Type : پژوهشی

Authors

• Abolfazl Soltani
• Amir Tarighat
• Mohammad Byezidi

Shahid Rajaee Teacher Training University

10.22067/civil.v32i1.68650

Abstract

To determine the effects of meta-halloysite and micro-silica pozzolans on mechanical strength and durability of concrete, 8 mix designs with two water/cementitious (W/C) ratios of 0.40 and 0.45 were performed. The ordinary Portland cement (OPC) was replaced by incorporations of 10 and 20% of meta-halloysite, and 7% of micro-silica. Samples were cured until the ages of 14, 28 and 90 days. Results imply that the combination of meta-halloysite and micro-silica for both W/C ratios particularly in the case of the lower ratio (0.40) when the sample contains 10% meta-halloysite, leads to a significant increase (89%) in the compressive strength of mixes (from 25.3 to 47.7 MPa). Also, the highest flextural strength (6.18 MPa) resulted in the lower W/C ratio (0.40). It is noteworthy that increases in W/C ratios for all mixes don’t lead to remarkable decreases in flextural strengths. Notably, the ultrasonic velocity (UV) for all mixes in the lower W/C ratio (0.40) shows a considerable increase particularly in 10% meta-halloysite compared with control samples. The findings above are all indications of better improvement of concrete strengths by natural pozzolan (meta-halloysite).
 

Keywords

• concrete
• Meta-halloysite
• Silica-fume
• Mechanical Strength
• durability

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Standards:

ASTM: C311–05, Standard Test Methods for Sampling and Testing Fly Ash or Natural Pozzolans for Use in Portland-Cement Concrete.

ASTM: C78-02, Standard Test Method for Flexural Strength of Concrete (Using Simple - Beam with Third –Point Loading).

ASTM: C618–78, Standard Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete.