Analysis of Cracking Problems in Self leveling Mortar and Performance Improvement Effect of HPMC

Cracking is a common concern in self-leveling mortar. It can result from excessive water addition, 

rapid moisture loss, poor substrate preparation, unsuitable formulation, excessive layer thickness, or improper curing.

HPMC can help control some of the fresh-mortar properties related to these problems, but it should

not be treated as a standalone solution for cracking.

Common Causes of Cracking in Self-Leveling Mortar

Before changing the HPMC grade, manufacturers should first check the main formulation and application conditions.

Common factors include:

1) Excessive mixing water, which can increase drying shrinkage and affect mortar strength.

2) Rapid moisture loss caused by temperature, air movement, low humidity, or highly absorbent substrates.

3) Poor substrate preparation or insufficient bonding to the base.

4) Unbalanced cement, filler, and additive levels.

5) Excessive application thickness or inconsistent curing conditions.

Cracking is often caused by a combination of these factors rather than by one raw material alone.

How HPMC Affects Self-Leveling Mortar

HPMC is used in construction materials as a thickener, suspending agent, and water retention agent.

In self-leveling mortar, the selection of HPMC should focus on maintaining an appropriate balance

between flow and fresh-mortar stability. Excessive viscosity can affect flow, while insufficient control

of the mortar system may contribute to segregation or inconsistent application.

Water retention is also an important consideration. The selected HPMC can help control water behavior

in the fresh mortar, but the final effect depends on the complete formulation, water level, cement system, fillers, and other additives.

For this reason, HPMC selection should be based on the required performance of the finished self-leveling mortar rather than viscosity alone.

How to Select HPMC for Self-Leveling Mortar

A practical selection process is:

Application requirement → Flow and stability requirements → HPMC grade → Laboratory testing

For self-leveling compounds, a lower-viscosity HPMC can be considered when maintaining suitable flow is an important formulation requirement.

HPMC JINT™ 400 is a low-viscosity HPMC with thickening, suspending, and water-retention functions. Its viscosity

specification is 320–480 mPa·s at 2% solution, and the product page specifically lists self-leveling compounds as a recommended application.

This makes JINT™ 400 the most directly relevant JINTEDIFU HPMC grade to evaluate for the self-leveling mortar application discussed in this article.

Test HPMC in the Complete Formulation

Changing HPMC should be evaluated together with the complete mortar formulation.

For an initial laboratory comparison, keep the cement, fillers, water level, additive dosage, and mixing procedure consistent. Then compare:

1) Flowability

2) Segregation or settlement behavior

3) Fresh-mortar consistency

4) Water retention

5) Surface condition after curing

6) Cracking tendency under the intended curing conditions

If a higher HPMC level improves stability but causes excessive viscosity or loss of flow, adjust the grade or dosage

rather than assuming that more HPMC will provide better performance.

Conclusion

Cracking in self-leveling mortar is usually a formulation and application issue rather than a single additive problem.

HPMC can influence water retention, viscosity, and fresh-mortar stability, so the grade and dosage should be selected

according to the required balance between flow and stability.

For self-leveling compounds, HPMC JINT™ 400 is a practical grade to evaluate because it is a low-viscosity HPMC and

is specifically listed by JINTEDIFU for self-leveling compounds.

The final selection should always be confirmed through testing in the customer's actual formulation and curing conditions.

Name: Molly.Wang

E-Mail:molly.wang@jtdf-rdp.

Mobile:+86 156 5045 0156（Whatsapp）