**7. Properties of lightweight sand mortar**

#### **7.1 General performance of mortar**

Because of the rough surface and higher porosity, SP can absorb cement particles and water, which leads to poor mixture workability, so an admixture of cellulose ether, emulsion powder, and so on must be added to meet the code requirements for the mortar consistency and delamination degree of mortar [18–20]. The mix proportions for different strength grades and the test results are shown in **Table 26**.

Compared with the code [18, 19], the dry apparent density of lightweight sand mortar is smaller than 1900 kg/m<sup>3</sup> , and the heat conduction coefficient is smaller than 0.8–1.0 W/(mK). Because of the porosity of SP, the dry apparent density and heat conduction coefficient are smaller than those of normal-weight sand mortar, so SP has better thermal insulation performance.

*The Influence of Hybrid Aggregates on Different Types of Concrete DOI: http://dx.doi.org/10.5772/intechopen.88254*

**Figure 6.** *Test curves for load deflection. (a) Bending beam, (b) Shear beam, and (c) Shear beam.*

#### **7.2 Durability of mortar**

Taking carbonisation, chloride iron penetration, and sulphate attack, for example, the test results are shown in **Table 27**.

The durability of mortar is enhanced with increases in the strength grade. Especially until 30 cycles, the mass increases. Analogously, the sulphate resistance coefficient is also enhanced until 15 cycles. The reason for this is the porosity and water absorption capacity of SP, which can strengthen the internal curing capacity and thus promote the hydration reaction.

#### **7.3 Fire-resistant performance of mortar**

The test results for cubic compressive strength, tensile bond strength, and heat conduction coefficient after elevation of the temperature are shown in **Table 28**, where the average values of mass loss are 9, 19, 39, 53, and 65 g after 100, 200, 300, 400, and 500°C, respectively.

The behaviour of the mortar is similar to that of concrete after the elevation of temperature, and the residual strengths after high-temperature treatment are almost 75% at 500 °C and can therefore meet the fire protection design requirements. Below 300°C, the strength and heat conduction coefficient increase; however, at temperatures above 300°C, the strength and heat conduction coefficient decrease, and all of the parameters increase with increases in the strength grade.

**7. Properties of lightweight sand mortar**

*beam, and (b) Sketch of reinforcement for shear beam.*

Because of the rough surface and higher porosity, SP can absorb cement particles and water, which leads to poor mixture workability, so an admixture of cellulose ether, emulsion powder, and so on must be added to meet the code requirements for the mortar consistency and delamination degree of mortar [18–20]. The mix proportions for different strength grades and the test results are shown in **Table 26**. Compared with the code [18, 19], the dry apparent density of lightweight sand

*Sketch of reinforcement for bending and shear beams, respectively. (a) Sketch of reinforcement for bending*

S4 1.56 316 100.5 2 267 150 91.81 93.55 1.02 S5 1.50 316 100.5 2 270 150 91.62 92.65 1.01 S6 1.59 316 100.5 2 265 150 91.71 94.83 1.03 S7 1.64 316 100.5 0.95 267 150 111.09 103.75 0.93 S8 1.53 316 100.5 1.5 267 150 97.33 97.05 1.00 S9 1.58 316 100.5 3.05 267 150 84.00 85.35 1.02 S10 1.62 316 100.5 2 267 150 93.01 99.30 1.07 S11 1.54 316 100.5 2 267 150 115.63 118.75 1.03 S12 1.57 316 100.5 2 267 150 78.55 82.3 1.05 *Notes: (1) ft stands for axial tensile strength obtained by the test or calculated directly by splitting tensile strength or bending strength; (2)*

*Sandy Materials in Civil Engineering - Usage and Management*

*stand for the ultimate bending moment of the normal section calculated by the code and the test values, respectively; (3) Vcs*

*stand for the ultimate shear strength of the diagonal section calculated by the code and the test values, respectively.*

*Theoretical and test values of ultimate strength for normal and diagonal sections, respectively.*

*c*

than 0.8–1.0 W/(mK). Because of the porosity of SP, the dry apparent density and heat conduction coefficient are smaller than those of normal-weight sand mortar, so

, and the heat conduction coefficient is smaller

**7.1 General performance of mortar**

*Mu <sup>c</sup> and Mu t*

*and Vcs t*

**Table 25.**

**Figure 5.**

**100**

mortar is smaller than 1900 kg/m<sup>3</sup>

SP has better thermal insulation performance.


#### **Table 26.**

*Reference mixes (1 m3) and test results of lightweight sand mortar.*

**8. Summary**

**Table 28.**

**103**

*<sup>λ</sup>* (w<sup>m</sup><sup>1</sup> <sup>k</sup><sup>1</sup>

**Strength grade** *h***<sup>c</sup>**

**Table 27.**

**28 d (mm)** *Q***<sup>e</sup>**

*DOI: http://dx.doi.org/10.5772/intechopen.88254*

*The Influence of Hybrid Aggregates on Different Types of Concrete*

*Test results for durability of lightweight sand mortar.*

**56 d (C) Mass loss (g) Corrosion resistance coefficient (%)**

**<sup>15</sup>** *K***<sup>f</sup>**

**<sup>30</sup>** *K***<sup>f</sup>**

**60**

**Δ***m***<sup>15</sup> Δ***m***<sup>30</sup> Δ***m***<sup>60</sup>** *K***<sup>f</sup>**

*T* **(°C) LM 5.0 LM 7.5 LM 10 LM 15 LM 20**

 7.1 9.2 13.8 18.7 24.1 7.8 10.3 14.9 18.9 24.7 5.7 7.6 11.2 16.0 20.4 4.7 6.3 9.2 14.3 18.7

 0.114 0.160 0.420 0.468 0.510 0.123 0.175 0.430 0.504 0.532 400 0.090 0.117 0.308 0.328 0.348 0.083 0.106 0.170 0.214 0.239

 0.211 0.239 0.248 0.259 0.277 0.220 0.241 0.253 0.263 0.281 0.205 0.226 0.230 0.241 0.259 0.204 0.218 0.222 0.236 0.254

) 100 0.231 0.253 0.260 0.275 0.299

LM 5.0 19.42 1042.3 18.1 20.2 12.1 130 78.4 40.8 LM 7.5 18.32 902.4 16.3 19.6 10.9 128 79.8 55.7 LM 10 18.01 858.4 16.5 17.7 9.4 125 83.9 68.4 LM 15 17.65 743.8 15.5 16.9 8.5 120 85.3 71.1 LM 20 15.13 701.2 13.8 15.1 7.7 119 91.4 75.6

*f*cu (MPa) 100 6.5 8.3 12.9 18.0 23.4

*η*cu*<sup>T</sup>* (%) 500 78.3 79.7 74.2 83.1 83.1 *f*tb (MPa) 100 0.100 0.146 0.349 0.366 0.397

the strength and durability.

ALWC has a number of advantages and disadvantages. Using NS (or MS) and crushing stone to replace a part of LWAs alone or at the same time in equal volume ratio, the new concrete types can be called semi-lightweight concrete (semi-LWC), which includes SLWC, GLWC, HALWC, and so on. Semi-LWC can not only reduce the cost of ALWC but also increase the properties of ALWC, such as workability, strength, durability, anti-deformation, fire resistance, and so on. Especially, moderate amounts of mineral powder and limestone powder can significantly increase

*Strength and heat conduction coefficient of lightweight sand mortar after elevated temperature treatment.*

All types of the concrete can meet the Chinese National Code requirements as well as have a smaller heat conduction coefficient and higher ratio of cubic compressive strength to dry apparent density than NWC. However, the effect of NWAs on semi-LWC is different. Gravel aggregates are bigger than sand aggregates, so the

multiaxial strength increases with increasing lateral pressure, and the ratio of biaxial

effect is more complex when added simultaneously. At the same time, the


### *The Influence of Hybrid Aggregates on Different Types of Concrete DOI: http://dx.doi.org/10.5772/intechopen.88254*

**Table 27.**

*Test results for durability of lightweight sand mortar.*


**Table 28.**

*Strength and heat conduction coefficient of lightweight sand mortar after elevated temperature treatment.*
