Curing, Hydration, and Microstructure of Cement Paste

Abstract

This paper compares hydration characteristics and microstructures of cement pastes with water-cement ratios (w/c) of 0.35 and 0.435, cured under saturated and sealed conditions. Degree of hydration is quantified by loss on ignition (LOI) measurements. The microstructures, and specifically the pore structures, of the hydrated pastes are evaluated using scanning electron microscopy and low temperature calorimetry. The w/c specimens (equal to 0.35) cured under sealed conditions first form a depercolated (disconnected) capillary pore system that later reconnects due to self-desiccation and autogenous shrinkage. Conversely, in the w/c specimens (equal to 0.435), there is some indication that sealed curing actually leads to an earlier depercolation of the remaining capillary pores than saturated curing, but without a subsequent repercolation. The results indicate the criticality of proper curing for both w/c specimens, suggesting that curing for strength and curing for durability may require different practices and may provide the impetus for innovative curing strategies to produce concretes with optimum properties.

A Review on the Use of Self-Curing Agents and Its Mechanism in High-Performance Cementitious Materials

“…Thus, it enhances the strength of internally curing concrete and establishes a well bonding [104] between porous aggregate and cement paste at ITZ. Moreover, some hydrated products that were discovered in pores of porous aggregate contributed to an increase in strength at later ages [42,190,191]. Sun et al [187] applied SEM techniques to compute the ITZ microstructure, founded a 3D digital model of ITZ using 3D image reconstruction techniques, and applied the mesoscale chemo thermal-hydraulic model to simulate the development of ITZ.…”

Relationship between Chloride Migration, Bulk Electrical Conductivity and Formation Factor of Blended Cement Pastes

“…However, a linear relationship with a very good fit (R 2 = 0.99) seems valid for both paste and concrete. According to Bentz and Stutzman [33], sealed curing creates a more disconnected pore network. Hydration products in sealed cured specimens tend to concentrate in the smallest pores between unhydrated cement particles, contrary to saturated curing where hydration products are more evenly distributed.…”

The behavior of reinforced lightweight concrete beams with initial cracks

“…Nonetheless, there are usual difficulties, as shown by shrinking at cracking [23], despite these benefits. While chemical shrinkage occurs in both high and low W/C mixes, low W/C mixes are more prone to self-drying out because of holes and capillary pressure, which produces fractures [23][24][25]. LWC (lightweight concrete) might solve many of these problems.…”