Calcium chloride acceleration in ordinary Portland cement

Abstract

Early-age hydration of ordinary Portland cement is now acknowledged to originate from nucleation and crystal growth of calcium–silicate–hydrates. The acceleration mechanism of water-soluble inorganic substances, such as calcium chloride, is still unclear. In the present study, the acceleration mechanism was approached in two independent ways. First, the acceleration effect of filler materials (limestone and quartz powder) and calcium chloride (CaCl2) were studied experimentally with a conduction calorimeter. Second, the calcium chloride effect was studied with thermodynamic modelling. The experimental test results showed that the filler materials accelerated the acceleration period of ordinary Portland cement hydration, whereas calcium chloride accelerated hydration throughout the 24 h measuring period. A synergistic effect was observed with fillers and calcium chloride. Thermodynamic modelling indicated that calcium chloride provides a supersaturation with respect to pure calcium–silicate–hydrate. It was concluded that the supersaturation provides a qualitative explanation for both calcium chloride-induced acceleration and the synergistic effect observed with fillers.

Development of a Novel Methodology to Assess the Corrosion Threshold in Concrete Based on Simultaneous Monitoring of pH and Free Chloride Concentration

“…These results are in agreement with the data reported by Liu et al [ 42 ], where it was shown that after one year of accelerated carbonation exposure (20% CO 2 , 70% RH, 20 °C), the carbonation depth was reduced by approximately 20–50% for concrete samples containing admixed chlorides (0.076% by concrete weight, or ≈0.5% by cement weight), compared to chloride-free samples. According to literature in References [ 42 , 45 , 46 , 47 , 48 ], it would thus be generally expected that a higher amount of admixed chlorides translates into a higher carbonation resistance. A reason for this may be that admixed chlorides accelerate cement hydration [ 45 , 46 ] and may lead to a denser pore structure of the cement paste [ 42 , 47 ], which generally increases the carbonation resistance [ 42 ].…”

“…According to literature in References [ 42 , 45 , 46 , 47 , 48 ], it would thus be generally expected that a higher amount of admixed chlorides translates into a higher carbonation resistance. A reason for this may be that admixed chlorides accelerate cement hydration [ 45 , 46 ] and may lead to a denser pore structure of the cement paste [ 42 , 47 ], which generally increases the carbonation resistance [ 42 ]. Another aspect to consider, however, is that the presence of chlorides in concrete promotes moisture retention, retarding the drying process [ 48 ], which decelerates the carbonation process under some exposure conditions.…”

The Hydration and Volume Expansion Mechanisms of Modified Expansive Cements for Sustainable In-Situ Rock Fragmentation: A Review

“…Other cations of a similar size and charge, that are is a similar charge density, would also show an accelerated reaction mechanism [107]. Thus, the effectiveness of cations as a chemical accelerator is as follows [108,109]: Ca 2+ > Sr 2+ > Ba 2+ > Li + > K + > Na + ≈ Cs + > Rb + The counter ion which would maintain the electroneutrality of the sample, should not bind to either CSH or alite during the hydration process, by replacing the silicates.…”

Reducing the Waiting-On-Cement Time of Geopolymer Well Cement using Calcium Chloride (CaCl2) as the Accelerator: Analysis of the Compressive Strength and Acoustic Impedance for Well Logging

“…However, at Days 28 and 90, the cement samples gained the highest compressive strength at a CaCl 2 concentration of 1.5%, and the compressive strength decreased as the concentration of CaCl 2 increased to 2%. The increase in compressive strength of the OPC with the addition of CaCl 2 is discussed thoroughly by another study [15] through a calorimetric study and thermodynamic modelling, and it was revealed that the CaCl 2 resulted in a higher supersaturation of C-S-H, which reduced the free energy barrier and consequently enhanced the nuclei formation on the cement surface.…”

“…There is a lack of studies that have investigated the influence of CaCl 2 in cement under exposure to HPHT conditions. Previous studies were conducted at ambient conditions, which is at atmospheric pressure and temperature and hence different to the downhole HPHT conditions [15][16][17]. Furthermore, previous studies predominantly focused on concrete, where the composition of concrete is different to well cement [17,18].…”