SU1249460A1 - Method of determining contraction value of cement stone - Google Patents

Abstract

The invention relates to building materials and can be used to determine the contraction of cement stone in assessing the durability of products and structures made of minerals in the course of their curing. A sample of the hardened cement mixture (stone) with a known ratio (W / C) and specific volume (Uz) is crushed, evacuated and saturated with water under vacuum. The mass of the water-saturated sample (fflg) is determined, then dried and calcined, after which the mass of the calcined sample (w) is determined. The amount of contraction () is calculated using the formula UKONGR, -m „/ m JV6- (B / C + V) 100%, where Vg is the specific volume of water (). with (Lgo 42; O 4 O

Description

The invention relates to construction materials and can be used to determine the contraction of cement stone, as well as assess the durability of products and structures made of minerals that are in the process of hardening.

The aim of the invention is to improve the accuracy of determining the magnitude of contraction and the expansion of the scope.

The method is carried out as follows.

A sample is taken of the hardened cement mixture (stone) with a known water-cement ratio (W / C) and specific volume (, 322).

Next, the product is crushed to SOCHKOV with a size of 0.5.0.0 mm, vacuum to 0.5– 20.0 mm Hg. and saturate with water under vacuum, determine the mass of water-saturated sample (ffig ,, g), then dry and calcine at 950-1000 0, determine the mass of calcined sample (t, g), and the contraction value () is calculated by the formula

V.OH ,, t () v. (BM

(one)

+ V.). 100%,

where Vj is the specific volume of water, cm / g.

Example. Samples are taken from laboratory samples of a 28-day hardened cement stone made from cement grade 400 with the addition of 0.5% superplasticizer at, 28. These samples, in the form of pieces of 0.51 cm, vacuum up to 0.5–20.0 mm Hg, pour water in a vacuum, after removing extra vacuum from a vacuum, scrape a piece of tracing paper, then immediately place the sample in a pre-calcined and weighted porcelain the crucible and, together with the crucible, into a dry, pre-weighed weighing bottle, then weighed to determine the mass of water-saturated sample taken from the sample (t). BsiJeuietuiyra sample is slightly dried, calcined at 950-1000 ° C and weighed again, determines the mass of the calcined sample (nf) - According to

the obtained data is calculated the magnitude of contraction by the formula (1).

For comparison, the amount of contraction of cement stone is determined by a known method.

Comparison of the obtained results give a difference of 30%.

The difference is due to the neglect of the influence of changes in the composition and manufacturing technology of the cement

stones for empirical coefficients used in calculating the magnitude of contraction for the limestone method.

Claims (1)

Invention Formula The method of determining the amount of cement stone contraction, including grinding the selected sample of cement stone, calcining it at 9501000 ° C, determining the mass of the calcined sample and determining the size of contraction, according to the formula, in order to improve the accuracy of determining the contraction value and expand , before calcining, the cement stone sample is evacuated and pressed into water in a vacuum, the weight of the accumulated water sample is determined, and the contraction amount (V) is determined by the formula V COITR  (.) V (B / C-e W, R + V) - 100% where Shz - the mass of water-saturated samples cement stone, g t - mass of calcined sample cement stone, g; V is the specific volume of water CMVr, B / C is the water-cement ratio of the cement mixture taken during manufacture; Vy is the specific volume of the initial cement, cm / g.