SU34371A1 - The method of acceleration in the first stages of the process of hardening of pozzolanic, slag, etc. portland cement - Google Patents

Description

It is known that pozzolanic and slag portland cements are characterized by the fact that they harden somewhat slower than portland cement. As a consequence, in the early stages (4 and 7 days) they give lower numbers of mechanical strength.

The speed with which the mechanical strength of the pozzolanic Portland cements depends on strongly depends on the activity of acidic hydraulic additives, namely, the higher the activity of the acidic hydraulic additive, the faster the pozzolanic Portland cement hardens and the earlier it reaches the mechanical strength that Portland cement has without additives. The speed of increase in the mechanical strength of slag portland cements depends on the chemical composition of the slag and FROM how much., The granulation process was completely carried out.

Described event is slow

The belief that pozzolanic and slag portland cements in the first periods should be considered as a negative property that prevents their use in structures subject to rapid commissioning. From what has been said, it becomes clear in one way or another to achieve the correction of pozzolanic and slag portland

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cement in the direction of increasing their mechanical strength in the first periods of hardening.

However, so far, as far as we know, no significant progress has been achieved in this direction. In 1929, a competition was even announced for the acceleration of the hardening of pozzolanic Portland cement, produced by the cement plant named. Vorovskogo (b. Maltsevsky), but he did not give any positive results.

In 1932 in the laboratory of L, VNIC, the authors decided to re-deliver the work on obtaining quick-hardening pozzolanic and slag portland cements. At the same time, by the way, it was observed to study how the chemical composition of clinker used for its manufacture is affected on the properties of pozzolanic and slag portland-cement. In particular, the authors investigated the question of the effect of saturation coefficient of the original clinker on the rate of hardening of pozzolanic and Portland cement slag. For preliminary experiments, two different Portland cement with different saturation coefficients were used: one of Plant A and the second of Plant B. Chemical analyzes of the two specified Portland cements are given in

tab. 1, it also gives the values of the moduli and saturation coefficients.

Those b and l tsa 1.

Portland cement of the Leningrad plant A shows a higher content of calcium oxide with a lower content of acid oxides, as a result of which the saturation coefficient reaches 0.96.

When testing for uniformity of change in the volume of these cements, it was found that Portland cement plant B maintains all three standards established by the standard. Portland cement plant A gave satisfactory results only when storing the input at room temperature, and when tested by a scientific research institute with hot samples, the lepets completely disintegrated.

In view of the assumption that the uneven change in volume was due in this case to the lack of clinker storage and the presence of free lime in the latter, a test for the uniformity of volume change. See Prof. V.L., Kinda-Chimicheka characteristic of Portland cement, in Li 9 Building materials for 1932

The emulsion was repeated 3 months after the first one, and during these three months the clinker was kept above the pools with water in a thin layer scattered on iron sheets. Repeated trials gave the same result as in the first case.

Portland cement plant tb shows a normal build-up of mechanical strength; . Portland cement plant L, on the contrary, shows a decrease in mechanical strength already by 7 days of storage. Samples prepared from this cement and intended to be tested for 3 months, 6 months and 1 year, completely collapsed after a month and a half of their storage in water.

Mixtures with a number of hydraulics were prepared on these two cements. chesky additives, namely: 1) from 50% of the Karadag highway,

2) from 3095 brillian thistle,

3) with 40% brine thistle,

4) with 30% sishtoff,

5) with 20% sishtoff,

6) with 75% of Kerch granulated primary blast furnace slag.

The mixture was prepared by mixing powdered Portland-centrifugal and hydraulic additives, within an hour, in a laboratory ball mill.

Adding acidic hydraulic additives such as the Karadag highway, the throne of Cyprus and Sishtoff, as a percentage, when preparing pozzolan polypropylene cementoons, gives cements that are uniform in terms of volume change, even in cases where the original clinker shows sharp volume inconsistency . The same is observed when adding slag in an amount of 75%.

This fact is extremely important because it allows you to correct and quickly put into operation Portland cement with a clear uneven change in volume, adding to it one or another hydraulic additive in the appropriate percentage.

The results of the mechanical tests are given in table. 2

As can be seen from the experiments, hydraulic additives and mixtures with Portland cement plant I show the picture, usually

x; 4 (ffWP

month s of these ls over m / s,

Provision of 7 days small for the gaps and without field; were

favly

for pozzolanic and slag portland cements. All the mixtures in the first periods — 1, 4, and 7 days — are in almost all cases inferior in mechanical strength to pure Portland cement.

By the 28-day period, the mechanical strength of pure Portland cement is exceeded only by mixtures with the most active hydraulic additives, such as sishtoff and tripilla. The track, as a relatively inactive hydraulic additive, and by the 28-day period gives lower results than pure Portland cement. These results completely coincide with the previously obtained results of numerous tests of pozzolanic and slag portland cements.

A completely different picture shows Portland Cement Plant A. Adding

) After 3 days.

to it, the Karadag highway, the brilliant tripoli, the sishtoff and the Kerch slag does not entail a decrease in mechanical strength in the first periods of hardening, as is usually observed for pozzolanic and slag portland cements. Mixed cements should be considered as rapidly hardening cements.

It is also very important that while for pure Portland cement a sharp decrease in mechanical strength is observed on the 28th day (caused by uneven volume change), pozzolanic and slag-and-portland-cemeite G1Okaz1,1 continuous and extremely intensive increase in mechanical strength up to b months

Comparison of mechanical strength of pozzolan and slag portland cement with the requirements of technical