Mechanical behavior of cement mortar with different polymer type

lectron micrographs of ordinary cement mortar in 28 days. It can be seen
that there are both more gel pores and capillary pores in the ordinary cement stones,
so it performs worse compactness.
FIG.9 shows micrographs of PVAc modified cement mortar in 28 days. As a kind
of high molecular material, PVAc almost combines with cement paste by physical
function, while enrichment area of PVAc are appearance during the polymer content
being added and overtaking the level. It may be caused by the different density of
polymer, cement and sand, and it also can be explained through the assumption of
Grosskurth that the polymer is pushed and concentrated by cement stone during
hydration process. With water evaporating and observed by other base materials, the
polymer particles interweaves with cement and hydration products through a
condensation reaction. This conclusion can be proved by the result of FIG. 9. It can be
seen that the presence of PVAc can reduce pores and increase the compactness of
mortar. Crosslinking network structure of polymer with other materials can improve
adhesion property of cement with sand, and toughness also can be increased.

Figure 8. Scanning electron micrographs of ordinary cement mortar.

Figure 9. Scanning electron micrographs of PVAC modified cement mortar.
CONCLUSIONS
Based on the laboratory test results and analysis of the modified mechanism, the
following conclusions were drawn.
a. Four types of polymer emulsion can improve mechanical properties of cement
mortar in a degree.
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b. The SBR and PVAc latex can effectively increase the flexural strength of
cement mortar.
c. The PVAc latex modified cement mortar. The tensile strength of all modified
cement mortar were increased.

d. PVAc can interweave with cement and hydration products, and form
crosslinking network structure, which is useful to improve toughness of mortar.
ACKNOWLEDGEMENTS
The corresponding author of this paper is Huaxin Chen. The authors gratefully
acknowledge the Special Fund for Excellent Doctoral Dissertation Research of
Central Colleges, Chang’an University (NO. 310831150022) for financial support to
this work.
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