How to determine whether the workability of dry-mix mortar is good or not?
Release Time:
2015-09-30
Source:
How to determine whether the workability of dry-mix mortar is good or not?
The workability of mortar also refers to its workability or ease of placement. It refers to the fresh mix Mortar It is easy to handle during construction—mixing, transporting, placing, and vibrating—and can achieve uniform quality and dense compaction. Workability is a comprehensive technical property that typically encompasses three aspects: 1) flowability; 2) water retention; and 3) cohesiveness. These characteristics are reflected in the corresponding physical index values.
1. Fluidity (Consistency)
It refers to the ease with which mortar flows under its own weight or external forces. Its magnitude is expressed as the slump (or consistency value) in millimeters, which is the depth, in millimeters, to which the cone of the mortar consistency tester sinks into the mortar.
2. Water retention
The ability of fresh mortar to retain water is known as water retention, which also refers to the property that the constituent materials of the mortar do not easily separate from one another. Water retention is commonly expressed in terms of the segregation degree (in millimeters). To determine the segregation degree, first measure the slump of a uniformly mixed mortar sample; then place the sample into a segregation-degree testing apparatus and allow it to stand for 30 minutes. After this period, take the bottom one-third of the mortar and measure its slump again. The difference between the two slump measurements is defined as the segregation degree.
3. Cohesiveness
The cohesive properties of fresh concrete refer to the internal bond among its constituent materials, which prevents segregation and layering during placement. Cohesion reflects the homogeneity of the concrete mix; poor cohesion can lead to separation of aggregates from the cement paste, resulting in an uneven concrete mass and, upon vibration, the formation of honeycombing and voids. The primary factor influencing cohesion is the water-to-cement ratio.
The workability of concrete mix is a comprehensive concept that cannot be fully and appropriately characterized by a single, simple evaluation method. Typically, the slump test is used to measure the flowability of the concrete mix, supplemented by visual, empirical assessments of cohesion and water retention to arrive at a comprehensive evaluation.
