Dry mixed mortar is a kind of granular and powdery mixture of fine aggregate and inorganic cementing material, water-retaining thickening material, water-reducing agent, anti-cracking agent, defoaming agent and other additives mixed evenly in a certain proportion. It is transported to the site site by special tank truck or sealed waterproof paper bag, and mixed with water. Now in addition to cement and sand in a large number of dry mixed mortar, the amount of more is redispersible redispersible polymer powder RDP. Because of its high price and great influence on mortar properties, it is the focus of people’s attention. The influence of redispersible polymer powder RDP on the properties of mortar was discussed in this paper.
1 Test Method
In order to determine the influence of redispersible polymer powder RDP content on polymer mortar properties, Several groups of formulations were designed by orthogonal test method and tested according to dbjoi-63-2002, the quality Inspection Standard of polymer Mortar for External insulation of exterior wall, to determine the influence of polymer mortar on the tensile bond strength, compressive shear bond strength and the compressive strength, flexural strength and flexural ratio of polymer mortar on concrete base.
The main raw material is P-04 2.5-pu silicon cement; RE5044 and R1551Z can be re-dispersed and re-dispersed emulsion powder; 70-140 mesh quartz sand; Other additives.
2 Influence of redispersible polymer powder RDP on properties of polymer mortar
2.1 Tensile bond and compression shear bond properties
With the increase of redispersible polymer powder RDP content, the tensile bond strength and compressive shear bond strength of polymer mortar and cement mortar also increase, and the five curves move up parallel with the increase of cement content. All relevant points weighted average, but quantitative analysis can be dispersed emulsion powder content on the degree of the influence of the cement mortar performance can see that with the increase of reusable dispersed emulsion powder content on bonding strength of cement mortar, polymer mortar compressive shear strength linear growth trend, the overall trend for a 1% increase to disperse polymer powder RDP, the bonding strength increased by 0.2 MPa, Compression shear bond strength increased by 0.45MPA.
2.2 Compressive/bending properties of mortar itself
With the increase of the content of redispersible polymer powder RDP, the compressive strength and flexural strength of polymer mortar decrease, indicating that the polymer has a hindering effect on the hydration of cement. FIG. 4 shows the influence of redispersible polymer powder RDP content on the compression and folding ratio of polymer mortar. , with the increase of the content of redispersible polymer powder RDP, the self-compression ratio of polymer mortar decreases, indicating that polymer improves the toughness of mortar. The influence of the content of redispersible polymer powder RDP on the performance of polymer mortar can be quantitatively analyzed by weighted average of each correlation point. With the increase of the content of redispersible polymer powder RDP, the compressive strength, flexural strength and flexural ratio of polymer mortar show a linear decreasing trend. The compressive strength, flexural strength and flexural ratio of redispersible polymer powder RDP decreased by 1.21 MPa, 0.14MPa and 0.18 per 1%. It can also be seen that due to the increase of the amount of redispersible polymer powder RDP, the flexibility of mortar has been improved.
2.3 Quantitative analysis of influence of cement-sand ratio on properties of polymer mortar
In polymer mortar, the cement-sand ratio and redispersible polymer powder RDP content interact directly with each other, so it is necessary to discuss the influence of cement-sand ratio separately. According to orthogonal experiment data processing method will be different contrast as variables, scatter can be associated with the polymer powder RDP content as a constant factor draw contrast on the impact of change on mortar quantitative figure, can see that with the increase of contrast on the performance of the cement mortar polymer mortar and polymer mortar performance itself are linearly decreasing trend, The general trend is that the tensile bond strength of polymer mortar to cement mortar decreases by 0.12MPa, the compressive shear bond strength decreases by 0.37MPa, the compressive strength of polymer mortar decreases by 4.14MPa, the flexural strength decreases by 0.72MPa, and the flexural ratio decreases by 0.270 with each increase of cement-sand ratio
3 Influence of redispersible polymer powder RDP on tensile bonding between polymer mortar and EPS foam polystyrene board DB JoI-63-2002 standard proposes that the bonding of polymer mortar to cement mortar and EPS board is contradictory.
The former requires polymer mortar to be rigid, while the latter requires its flexibility to be high, but considering the external insulation engineering both to stick rigid wall and flexible EPS board, at the same time to ensure that the cost is not too high. Therefore, the influence of the content of redispersible polymer powder RDP on the flexible bonding property of polymer mortar is listed separately to emphasize its importance.
4 Influence of types of redispersible polymer powder RDP on bonding strength of EPS board
R5,C1,P23 kinds of redispersible polymer powder RDP were selected from abroad. Taiwan D2,D4 2 kinds; Domestic S1, S2 2 species 7 species; Polystyrene board made in Beijing 18kg/ lined EPS board. According to dbJ01-63-2002 standard, the stretch bond redispersible polymer powder RDP of EPS board can meet the rigid and flexible tensile bond performance requirements of polymer mortar at the same time.