Application of HPMC in mix proportion design of common plastering mortar

Shandong chuangyao biotechnology explains the mix proportion design of common plastering mortar

1. The mix proportion design of plastering mortar shall be carried out before construction, and the compressive strength of mortar shall be calculated according to the following formula:

fm,0 = k f2

In the formula: FM, 0 -- Trial mixing strength of mortar (MPA), which should be accurate to 0.1MPa;

F2 -- mortar strength grade (MPA), accurate to 0.1MPa;

K -- quality level coefficient of mortar production (mixing), 1.15-1.25.

Note: when the quality level of mortar production (mixing) is excellent, general and poor, K values are taken as 1.15, 1.20 and 1.25 respectively.

2. Hydroxypropyl methyl fiber can be added into plastering mortar, and the content should be determined by test.

3. The mix proportion of plastering mortar shall be measured by quality.

4. The consistency of plastering mortar should be 90mm ~ 100mm.

5. The frost resistance of plastering mortar for external wall shall meet the design requirements.

Cement fly ash plastering mortar shall meet the following requirements:

1) The amount of fly ash instead of cement should not exceed 30%.

2) The strength grade shall be M5, M15 and M15.

3) Masonry cement should not be used in preparation of cement fly ash plastering mortar.

4) The apparent density of the mixture should not be less than 1900kg / m3.

5) When used for external wall, the cement dosage should not be less than 250kg / m3.

6) The material consumption of mix proportion can be selected according to table 4-4.

7) The water retention rate of HPMC should not be less than 88%, and the tensile bond strength should not be less than 0.15Mpa.

Mix proportion test, adjustment and determination

1) After selecting the material amount of plastering mortar mix proportion according to the table, trial mixing shall be carried out first, and the consistency and layering degree (or water retention rate) of the mixture shall be measured. When the requirements cannot be met, the material dosage shall be adjusted until the requirements are met.

2) During the trial mixing of plastering mortar, the actual needs of the project shall be considered. The mixing shall comply with the provisions of the current industry standard "code for design of masonry mortar mix proportion" (jgj98). The determination method of trial mixing strength is the same as that of masonry mortar.

3) The test consistency of plastering mortar shall meet the construction requirements, and the compressive strength, water retention rate and tensile bond strength of mortar with different mix proportions shall be measured according to the current industry standard "standard for test methods of basic performance of building mortar" (JGJ / T70). The mix proportion that meets the requirements and has the lowest amount of cement is used as the mix proportion of plastering mortar.

4) During the trial mixing of plastering mortar, at least three different mix proportions shall be adopted, one of which shall be the reference mix proportion obtained according to this regulation, and the cement consumption of the other two mix proportions shall be increased and decreased by 10% respectively according to the reference mix proportion. When hydroxypropyl methylcellulose is added, the water consumption or the amount of mineral admixtures such as lime paste and fly ash can be adjusted accordingly under the condition that the consistency and stratification degree (or water retention rate) meet the requirements.

5) The mix proportion of plastering mortar shall be corrected according to the following steps:

A the theoretical apparent density value of plastering mortar shall be calculated as follows: ρ t = ∑ Qi

Where: ρ T -- Theoretical apparent density of mortar (kg / m3)

Qi -- the amount of various materials in each cubic meter of mortar (kg).

B the mortar mix proportion correction factor (δ) shall be calculated according to the following formula:

δ=ρc/ρt

Where: ρ C is the measured apparent density of mortar (kg / m3).

C when the absolute value of the difference between the measured apparent density value and the theoretical apparent density value of mortar does not exceed 2% of the theoretical apparent density value, it can be determined as the mix proportion of plastering mortar; when the absolute value is more than 2%, the amount of each material in the mix proportion shall be multiplied by the correction coefficient δ to determine the mix proportion of plastering mortar.

8 performance index of ready mixed mortar and matters needing attention in mix proportion design

According to the new industry standard of ready mixed mortar issued in 2007, the mix proportion should be trial mixed, adjusted and determined before mortar production. The consistency and performance of trial mixing should be carried out according to the current industry standard "ready mixed mortar" JG / j230.

The application of HPMC in the mix proportion design of common plastering mortar is very important! The quality of mortar is of great importance. The construction party must strictly control the quality of mortar and conduct regular inspection.

The above information is edited by mortar Laboratory of Shandong chuangyao Biotechnology Co., Ltd www.cyhuagong.com