Pore structure of mortars containing limestone powder and natural pozzolan assessed through mercury intrusion porosimetry and dynamic vapour sorption

Natalia Alderete,Yury Villagrán,Nele De Belie,Didier Snoeck,Arn Mignon

doi:10.1051/matecconf/201819902020

Natalia Alderete, Yury Villagrán + Show 3 more

Open Access

https://doi.org/10.1051/matecconf/201819902020

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Abstract

Pore structure characterization is a key aspect when studying the durability of cementitious materials. When supplementary cementitious materials (SCMs) are used changes in pore structure are expected, and the complexity of its analysis is increased. The purpose of this paper is to describe the pore structure variation of mortars with two types of SCMs: natural pozzolan from volcanic origin (NP), and limestone powder (LP). We tested mixes with cement replacements (in weight) of 20 % and 40% by NP, and 10 % and 20% by LP. To analyse the pore structure, two widely accepted and complementary techniques were applied: dynamic water vapour sorption (DVS) and mercury intrusion porosimetry (MIP). With the DVS data, the Barret-Joyner-Halenda (BJH) model was used for pore size distribution assessment. Calculations with the Dubinin-Radushkevich (DR) model were also made for the smallest pore size range. Tests were performed at 28 and 90 days. MIP and DVS allowed evaluating the effect of the studied SCMs on different pore size ranges. Both techniques provided comprehensive information over a wide range of pore sizes. The mix with 40 % of NP had the best evolution, showing a significant volume decrease in the mesopore range.

Highlights

The pore structure of cementitious materials generally changes when supplementary cementitious materials (SCMs) are used
The purpose of this paper is to describe the pore structure of mortars with cement replacements of 20 %, and 40% by natural pozzolan of volcanic origin (NP), and 10 %, and 20 % by limestone powder (LP)
When comparing pore size distribution over time, the NP40 mix had the best evolution, showing a significant volume decrease especially in the mesopore range. This was detected by the decrease in the dtg and ɸin values, from the mercury intrusion porosimetry (MIP) results

Summary

Introduction

The pore structure of cementitious materials generally changes when supplementary cementitious materials (SCMs) are used. Those changes will influence directly the physical, mechanical and durability performance of the cementitious matrix. When using natural SCMs, such as pozzolans, there is normally an improvement in durability-related properties [2] mainly because of the delayed formation of C-S-H, which usually leads to pore refinement with time. The pore structure of cementitious materials has been widely investigated [3]–[7], no unique model or method provides a complete description and characterization. Limitations include critical assumptions made for each method; it is important to characterize the pore structure with different methods and compare the results to obtain a comprehensive description

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