1.Compressive Strength
The incorporation of lightweight aggregates typically reduces the compressive strength of UHPC that from UHPC mortar mixer. For example, when quartz sand is replaced by ceramsite, the compressive strength first increases and then decreases with the increase in ceramsite volumetric replacement. The compressive strength reaches its peak when the ceramsite replacement is 12.5%. Beyond 12.5% replacement, the compressive strength gradually drops.

2.Split Tensile Strength
The influence of lightweight aggregates on split tensile strength is more complex. For ceramsite, when the volumetric replacement reaches 25.0% and the split tensile strength reaches its maximum.

Picture of ceramsite

1.Slump and Flow Spread
The addition of lightweight aggregates typically results in a change in the slump and flow of UHPC. Generally, with an increase in lightweight aggregate content, the slump and flow first increase and then diminish. The maximum slump and flow are observed when the ceramsite volumetric replacement reaches 25.0%.

2.Setting Time
The lightweight aggregates typically absorb a portion of water in the mixture. Therefore, adding lightweight aggregates can shorten the setting time of UHPC (UHPC mortar mixer) when water-to-binder ratio is kept constant.

Therefore, the performance of a UHPC mortar mixer is closely related to the properties of the aggregates used.

1.Autogenous Shrinkage
The use of lightweight aggregates effectively reduces autogenous shrinkage. For fiber-reinforced UHPC made with ceramsite instead of river sand, autogenous shrinkage drops by 41%. When lightweight aggregates are added at 50% by volume, the autogenous shrinkage is reduced to 7.2% of the control mixture.

2.Dry Shrinkage

The addition of lightweight aggregates influences the drying shrinkage of UHPC used in UHPC mortar mixer. Replacing quartz sand with ceramsite results in greater drying shrinkage. However, this trend first decreases and then increases with the rise in presaturation degree of lightweight aggregates.

1.Chloride Ion Penetration Resistance
The porous structure of lightweight aggregates may allow chloride ions to permeate more easily, reducing the chloride penetration resistance of UHPC. Nevertheless, this can be improved to some extent by controlling the presaturation of lightweight aggregates.

2.Salt Spray Resistance
The addition of lightweight aggregates to UHPC, such as in UHPC mortar mixer, can affect its resistance to salt spray attack. For ceramsite-replaced sand, the resistance to salt spray improves, and this improvement becomes more pronounced with higher presaturation of ceramsite.

3.Frost Resistance
The porous structure of lightweight aggregates can absorb freezing expansion stress within the matrix; the lower its water absorption, the greater its ability to absorb freezing stress. Furthermore, the capillary pores within lightweight aggregates can promote secondary hydration of unhydrated cement particles, helping repair microstructural damage and mitigating or even completely compensating freezing damage to the matrix.

Therefore, understanding the relationship between lightweight aggregates and the mixing process is key to optimizing mixture design and performance of UHPC mortar mixer. When using a UHPC mortar mixer, it is essential to consider the various properties of lightweight aggregates.