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Heat of Hardening

It should be underlined that in case of cement we can measure the heat of hardening the heat of hydration relates to the situation when the phase composition of hydration products is known. For example, as a result of CaO reaction with water the calcium l droxide is formed and the heat evolved dining this hydration process is 1168 J/g CaO. However, even in this case Lea [83] reports that depending on the physical properties of CaO used and the product obtained, the heat can evolve in the range from 1110 to 1168 J/g. However, in this case it is possible to determine precisely the heat of hydration. [Pg.192]

There is quite another problem for example in the case of C3A. As it is commonly known this phase reacts with a solution and the trisulphoaluminate or mono-sulphoaluminate is produced, depending on the gypsum content  [Pg.192]

The hydration, or rather hydrolysis, of orthosilicates is more complex. The C-S-H phase is poorly crystallized and reveals variable C/S ratio this is not a ciystalhne phase but rather a gel. The heat of adsorption of water on the C-S-H gel interferes with the heat of reaction. Nowadays, it is assumed that the hydration of orthosilicate phases are linked with the following heat of reaction  [Pg.192]

According to Lerch and Bogue According to Woods, Starke [Pg.193]

In this heat value, apart from the heat of hydration, the heat of water adsorption on a gel product is included. If this heat, evaluated as 84-168 J/g of anhydrous phase, is subtracted, the following values are obtained for C3S—404.0 6.3 J/g C3S and for 38 102.6 14.7 J/g C2S [83]. This problem was discussed with details by Branauer and Kantro [155]. For the practical purpose the aforementioned total heat of the process is important. Taking into account all the cireumstances, apart from some cases dealing with the known crystalline hydration products, we should rather use the term heat of hardening . [Pg.193]


The resin is too brittle to give a tme meaning to mechanical properties. The thermal properties are interesting in that there appears to be a transition point at 46°C. Above this temperature, specific heat and temperature coefficient of expansion are much greater than below it. The specific heat of hardened shellac at 50°C is lower than that of unhardened material, this no doubt reflecting the disappearance, or at least the elevation, of the transition temperature. [Pg.869]

Type II. Moderate-heat-of-hardening and sulfate-resisting portland cements are for use where moderate heat of hydration is required or for general concrete construction exposed to moderate sulfate action. [Pg.156]

Table 3.4 Heat of hardening of clinker phases (J/g of anhydrous phase) [158]... Table 3.4 Heat of hardening of clinker phases (J/g of anhydrous phase) [158]...
Cement heat of hardening is affected primarily by the phase composition of the clinker. This heat is an additive value and therefore it can be evaluated based on the known composition of Portland cement clinker and the heat of hardening for particular phases, given in Table 3.4. [Pg.193]

Table 3.5 Heat of hardening values (J/g) evaluated per 1 % of clinker phases which content was calculated from Hogue s equations (temp. 23 2°C, w/c = 0.45, Blaine s surface area 3100 200 cm /g)... Table 3.5 Heat of hardening values (J/g) evaluated per 1 % of clinker phases which content was calculated from Hogue s equations (temp. 23 2°C, w/c = 0.45, Blaine s surface area 3100 200 cm /g)...
Taking into account all these factors the heat of hardening can be evaluated based on the values given in Table 3.5. A little higher values are given by Kuhl [158], according to the measurements by Woods, Steinour and Starke. These data are given in Table 3.6. [Pg.194]

Finally, it is necessaiy to discuss the heat of hardening as a source of cracks in the massive concrete stractures, resulting fiom the stresses dealing with the temperature gradient [162], This problem has been reported with details by Kiemozycki [162] and Neville [163]. [Pg.198]

From the data given in Table 3.5 it can be concluded also that the heat of hardening can be lowered by the CjA and CjS content decrease in the latter case it means the reduction of the lime saturation factor. Unfortunately, this is simultaneously linked with the lowered strength development and reduced class of cement. [Pg.199]

The heat of hardening can be determined not only by a simplified ealculation, but by direct calorimetric measurements, or indirectly applying the Hess rule. According to this rule, the heat of reaction depends only on the initial and final state and this is the basis of the dissolution method. In this dissolution procedure, the heat of hardening is determined as a difference between the heat of neat cement dissolution and heat of hydration products (cement paste) dissolution. The mixture of nitric and fluoric acids is used for this purpose. Only the dissolution method is applied in the case of the longer hydration time. The most accurate, differential calorimetric method has been developed by Zielenkiewicz [164]. The completely hydrated mortar is placed in one container of calorimeter and in the second one— the fiesh mortar. [Pg.199]

Kaminski and Zielenkiewicz [165] investigated the heat of hardening of cement phases and cements and found a good correlation of calculated heat and experimental data, when the following heat values for particular cement phases (in J/g) are applied ... [Pg.199]

The concretes produced from cements with natural pozzolana addition are particularly resistant to the chemical corrosion, but the resistance to physical factors is only slightly changed. However, they should be cured for a longer time in humid condition than the concrete produced from Portland cement without mineral additions. They are useful in these conditions where a low heat of hardening and high resistance to chemical corrosion is required [5]. [Pg.536]

The usage of slag cements is partieirlarly favourable in the ease of massive concrete straetures, dams and barrages [1, 36], because of the low heat of hardening. However, slag cement concrete shoitld be ctued in moist condition at early age in order to prevent scaling [1]. [Pg.553]

Clinkers with increased C2S and reduced C3S contents are employed in the production of cements with reduced hydration heat evolution (see section 19), such as moderate heat of hardening cement (corresponding to ASTM Type II cement) and low-heat cement (corresponding to ASTM Type IV cement). To slow down the rate of heat evolution, cements employed for this purpose are usually ground to a relatively low specific surface area. Cements of this type are used in applications in which a reduced release of hydration heat is required, as in the constraction of dams and other bulk concrete structures (Kelham and Moir, 1992 Sone et al, 1992). High-C2S cUnkers, especially those with a reduced C3A content, are also constituents of some oil well cements (see section 27). L0W-C3S clinkers are less suitable for the production of blended cements, owing to the reduced amount of free calcium hydroxide produced in the hydration of such clinkers. [Pg.16]


See other pages where Heat of Hardening is mentioned: [Pg.3]    [Pg.66]    [Pg.192]    [Pg.193]    [Pg.193]    [Pg.194]    [Pg.195]    [Pg.195]    [Pg.195]    [Pg.195]    [Pg.196]    [Pg.197]    [Pg.199]    [Pg.199]    [Pg.266]    [Pg.279]    [Pg.335]    [Pg.335]    [Pg.567]    [Pg.571]    [Pg.603]    [Pg.611]   


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