Method for predicting plastic shrinkage cracking of cement mortar material
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A shrinkage cracking, cement-based material technology, applied in the field of materials science and engineering, can solve the problem of not being able to give a multivariate constitutive equation for plastic shrinkage cracking
Inactive Publication Date: 2011-09-14
TONGJI UNIV
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Problems solved by technology
However, so far, a multi-component constitutive equation for plastic shrinkage cracking including cement-based material composition, environmental conditions, initial structural parameters and constraints has not been given, so it is expected to be used for early prediction of plastic shrinkage cracking of mortar
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Embodiment 1
[0031] The water-cement ratio Wc of a certain cement mortar is 0.45, the lime-sand ratio is 1, and the fiber content Fc is 0.9kg / m 3 , fiber length F 1 It is 12mm, and the moisture evaporation rate of the mortar under certain environmental conditions is measured to be 0.250Kg / (m 2 h), the degree of delamination is 0.1cm, the degree of constraint is 0.66, the calculated K=1.60, which is greater than 1.41, and it is predicted that the mortar will not crack under this environmental condition.
[0032] The actual measured K value is 1.82, the relative error is 12.1%, and the mortar does not crack.
Embodiment 2
[0034] The water-cement ratio Wc of a certain cement mortar is 0.40, the lime-sand ratio is 0.67, the fiber content Fc is 0, and the fiber length F 1 is 0, and the water evaporation rate of the mortar under certain environmental conditions is measured to be 0.296Kg / (m 2 h), the degree of delamination is 0.1cm, and the degree of constraint is 0.83. K = 2.11 is calculated by bringing it into the constitutive equation, which is greater than 1.41. It is predicted that the mortar will not crack under this environmental condition.
[0035] The actual measured K value is 2.33, the relative error is 9.44%, and the mortar does not crack.
Embodiment 3
[0037] The water-cement ratio Wc of a certain cement mortar is 0.45, the lime-sand ratio is 1, and the fiber content Fc is 0.9kg / m 3 , fiber length F 1 The water evaporation rate of the mortar under certain environmental conditions is 0.30Kg / (m2h), the degree of stratification is 0.4cm, and the degree of constraint is 0.83. K = 0.97, which is less than 0.99, is calculated by bringing it into the constitutive equation. The mortar is predicted to crack under these environmental conditions.
[0038] The actual measured K value is 1.07, the relative error is 9.34%, and the mortar cracks.
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Abstract
The invention relates to a method for predicting plastic shrinkage cracking of a cement mortar material. The method comprises the following step of: substituting four cement-based material composition parameters comprising water cement ratio (Wc), cement sand ratio (Cs), fiber content (Fc) and fiber length (F1), water evaporation speed (Er) and demixing degree (Dd) and restraint degree (Rd) of the cement-based material into the following formula: K = 13.8822 - 14.0949Wc - 2.8247Cs + 0.5293Fc + 0.0022F1 - 17.0650Er + 0.2582Dd + 0.9436Rd, wherein the K is anti-cracking index. When the K value is more than 1.41, the cement-based material test piece is not cracked; when the K value is less than 0.99, the test piece is cracked; and when the K value is between 0.99 and 1.41, the test piece is cracked in certain probability. A multiplex constitutive equation of plastic shrinkage cracking of the mortar is constructed by using the parameters with great influence on the cement-based plastic shrinkage cracking, the tendency of early plastic shrinkage cracking of the cement-based material can be accurately predicted, and the method can be widely applied to early prediction of the plastic shrinkage cracking of the mortar.
Description
technical field [0001] The invention relates to a method for plastic shrinkage cracking of cement-based materials. It can be used for early qualitative prediction of plastic shrinkage cracking tendency of cement mortar materials. It belongs to the subject field of material science and engineering. technical background [0002] Cement concrete is one of the most widely used building materials in the world. Because cement concrete has the advantages of wide application range, cheap price, easy pouring, relatively durable, and can effectively use some industrial solid waste to make energy-saving and environmentally friendly building materials, it will still be irreplaceable in modern engineering construction in our country in the 21st century. main building material. [0003] However, it is undeniable that cement concrete has shortcomings such as heavy weight, low tensile strength, small ultimate tensile strain, poor impact strength, and easy plastic dehydration shrinkage an...
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