Investigation of blended cement hydration by isothermal calorimetry and thermal analysis (original) (raw)
Related papers
Blended cement hydration assessment by thermogravimetric analysis and isothermal calorimetry
MATEC Web of Conferences, 2018
In the present study, the hydration of Portland cement pastes containing 5%, 10%, 15% and 20% tuff, limestone filler and granodiorite was investigated by thermogravimetric analysis coupled with differential scanning calorimetry and microcalorimetry isotherm. The monitoring of the hydration kinetics by thermogravimetric analysis made it possible to quantify the quantity of water combined with the cement (nonevaporable water) and the degree of hydration. By coupling this technique to the differential scanning calorimetry, it was also possible to measure the energy absorbed or released by the material during its decomposition. The results showed that the non-evaporable water content and the degree of hydration of the mixtures containing various mineral admixtures were relatively lower with respect to the reference mixture when as the content of mineral admixture increased. The effect of the evolution of the hydration process on the mechanical properties of mortars was also monitored. The relative variation of the compressive strength to that of the flexural strength was evaluated at 7, 28 and 90 days. Results showed that all the mixtures have a greater contribution in flexion than in compression.
Early hydration of SCM-blended Portland cements: A pore solution and isothermal calorimetry study
Cement and Concrete Research, 2017
In this study the hydration kinetics and the development of concentrations in the pore solution of cement pastes containing different supplementary cementitious materials (blast-furnace slag, Si-rich fly ash, limestone, quartz) at a cement replacement of 50 wt.% were investigated during the first 6 h of hydration. The results indicate that the degree of undersaturation with respect to alite is the primary factor driving the early hydration kinetics. The accelerating effect of the limestone is related to a higher undersaturation. The data reveal also that high aluminium and sulfate concentrations, which depend on the type and chemical composition of the used mineral addition, retard the reaction. High calcium concentrations had no adverse effect on hydration kinetics. The investigations underpin that the mechanisms controlling the early hydration are a complex combination of the filler effect, the pore solution chemistry as well as intrinsic reactivity of the mineral additions and their surface characteristics.
Quantification and analysis of heat hydration of blended cement at different temperature
Journal of Adhesion Science and Technology, 2017
The study of the hydration kinetics appears as a prerequisite for understanding the physical and mechanical phenomena that control the behavior of cementitious materials. This research is based on monitoring the evolution of the degree of hydration for ordinary cement and those containing 10% of limestone powder, 20% of natural pozzolana or 30% of the blast furnace slag under high temperatures. The results provide a better understanding the effect of cure temperature on the hydration kinetics and understand the contribution of mineral additions on improving the cement properties. A new model proposed gives the satisfaction results for predicting in later age the heat of hydration of cements blended kept under constant temperatures. The latter has a wider appreciation of the results, where it gives correlation coefficients very close of unity. This justifies the reliability of this new model proposed.
Journal of Thermal Analysis and Calorimetry, 2019
Present study deals with the influence of metakaolin (MK), silica fume (SF) and ground granulated blast-furnace slag (BFS) on middle hydration of ordinary Portland cement replaced by 45 mass% of particular supplementary cementitious materials (SCMs). Acceleration of cement hydration by SF and MK was proved up to the first 12 h by isothermal calorimetry as well as by thermogravimetric analyses. From the beginning of deceleratory period, when SCMs stopped to act as accelerators, more evident influence of the dilution effect was observed. Nevertheless, the presence of pozzolanic reactions was demonstrated already after 15 h of curing and even when SF and MK were used in the amount equal to 5 mass%. Synergic effect of the used SCMs allowed to increase the quantity of BFS up to 35 mass% without significant changes in their positive action. Keywords Multicomponent cements Á Metakaolin Á Silica fume Á Ground granulated blast-furnace slag Á Isothermal calorimetry Á Thermogravimetric analyses
Heat of hydration of high reactive pozzolans in blended cements: Isothermal conduction calorimetry
Thermochimica Acta, 2005
A study was carried out comparing silica fume (SF) and dealuminated kaolin (DK) as pozzolanic materials in blended cements. Ten, 20 or 30 wt% of SF or DK were substituted for Portland cement. The kinetics of hydration up to 45 h were studied using isothermal conduction calorimetry. Blends containing pozzolanic materials usually have decreased heats of hydration compared to pure cement during the period of C3S hydration, i.e. during the main hydration peak. Depending on the chemical composition and the activity of the pozzolan, the reaction taking place with the lime typically contributes to the heat output after the main hydration peak.The pozzolanic activity of DK is the principal factor and heat evolution increases with respect to pure PC mortar, during the first 15 h. The presence of hydrated silica (silanol groups) in DK increases the pozzolanic activity especially before and during induction period. The acidic silanol sites are capable of a fast acid–base reaction with the alkalis and with any Ca(OH)2 present in cement during the induction period.
Journal of Thermal Analysis and Calorimetry, 2020
Two Portland cement (PC) replacement levels (35, 45 mass%) and three locally available supplementary cementitious materials (SCMs; metakaolin (MK, 5-15 mass%), silica fume (SF, 5, 10 mass%), ground granulated blast-furnace slag (BFS, 10-35 mass%)) in different ratios were used for the preparation of multicomponent binders, the hydration of which was studied up to 365 days by means of thermal analysis. The suitable compositions were found for both PC replacement levels. In the case of the lower one as well as in the compositions prepared with higher SF amount, 20 mass% of BFS appeared as beneficial. When lower amounts of SF and cement were used, samples with larger quantity of BFS reached better results. Concerning compressive strength (CS), synergic influence of SCMs overcame the dilution effect already after 28 days of curing and no significant dependence on the PC content was determined. Later, the majority of the blended samples reached higher CSs than the corresponding referential ones. With respect to the coefficient of pozzolanic activity, the combination of higher SF level (10 mass%) mainly with higher amount of BFS seemed to be more desirable in general.
Materials Research, 2015
Water/cement (w/c) ratios equal to 0.5, 0.6 and 0.66 were used to prepare the pastes. The hydration of these two types of cement was monitored on real time by NCDTA curves, through the thermal effects of the hydration reactions, from which cumulative evolved energy curves were obtained. These techniques allow one to analyse the influence of each type of cement on the main stages that occur during the hydration process. Thermogravimetric analysis were also performed at 4 and 24h of hydration for both cements, to analyse the influence of each kind of cement on the amount of the main formed hydrated products. The results showed that with 4h of hydration, the total combined water amount released from the hydrated products was higher for the PC II pastes than for the HIS SR PC pastes. Otherwise, with 24h of hydration, the amount of the total combined water released from the hydrated products was higher for the HIS SR PC pastes than for the PC II pastes.
The chemical composition and microstructure of hydration products in blended cements
Cement & Concrete Composites, 2004
Pastes of neat and blended Portland cement (incorporating either 60% ground granulated blast furnace slag, or 30% pulverised fuel ash, or 22% volcanic ash) were cured for one year at temperatures ranging from 10 to 60 OC. The hydration products were characterised by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The apparent porosity of the pastes increased with increasing curing temperature. Chemical analysis data for the hydration products are presented in ternary composition diagrams, where it is noted that in the presence of the replacement materials the composition of the C-S-H shifted towards higher Si and Al contents, whereas that of Ca was lower.
Hydration of a Portland cement blended with calcium carbonate
Thermochimica Acta, 2000
The hydration of a commercial Portland cement blended with calcium carbonate was studied by thermal analysis. TG, DTA and DTG analyses were performed on pastes prepared with a water to cement weight ratio of 0.5, after different setting times during the ®rst 28 days of hydration. The analyses were run from 288C to 10008C with a 108C/min heating rate and 100 ml/ min of air as the purge gas. All the analyses were performed after a drying step at 288C in the equipment itself, using the purge gas as the drying agent, resulting in a more effective and less time-consuming method than other conventional drying procedures. The original cement contains a partially decomposed dihydrated calcium sulfate, which is regenerated after 1 h of hydration and is consumed in about 16 h of setting. The results indicate that TG and DTG curves are faster and more precise tools than DTA curves to identify and to quantify all the main hydrated and carbonated phases which are present in the pastes, especially in the case of this cement blended with calcium carbonate, the total content of which cannot be estimated correctly by DTA as hydration proceeds.
Hydration and Properties of Blended Cement Systems Incorporating Industrial Wastes
Ceramics Silikaty
This paper aims to study the characteristics of ternary blended system, namely granulated blast-furnace slag (WCS), from iron steel company and Homra (GCB) from Misr Brick (Helwan, Egypt) and silica fume (SF) at 30 mass % pozzolanas and 70 mass % OPC. The required water of standard consistency and setting times were measured as well as physico-chemical and mechanical characteristics of the hardened cement pastes were investigated. Some selected cement pastes were tested by TGA, DTA and FT-IR techniques to investigate the variation of hydrated products of blended cements. The pozzolanic activity of SF is higher than GCB and WCS. The higher activity of SF is mainly due to its higher surface area than the other two pozzolanic materials. On the other side, GCB is more pozzolanic than WCS due to GCB containing crystalline silica quartz in addition to an amorphous phase. The silica quartz acts as nucleating agents which accelerate the rate of hydration in addition to its amorphous phase, ...