**5.7 Shrinkage**

Generally, we note that the flexural tensile strengths of the mortars with marble waste sand, at all the ages (7, 28 and 90 days) are better than that of control mortar. The most significant value is achieved with the 20% mixture of marble waste sand, which presents a gains of 13.29, 22, 58 and 28% compared to the control mortar on the ages 2, 7, 28 and 90 days respectively. Two factors can explain these notations. Mortars based on marble waste sand contain quantities of fine particles, which favor granular stacking during mixing and thus causes an increase in flexural strength. However, the marble waste sand is characterized by more acute and porous grains, so that the bond with the cement paste of the mixture is better [7].

The absorption of water by immersion is a property related to the durability of mortar, it allows estimating the volume of open pores of specimens by the penetra-

When the ratio of replacement of marble waste sand in mortar increased (**Figure 12**), there was an increase in water absorption, especially for the 20% of

**5.5 Absorption by immersion**

**Figure 11.**

**Figure 12.**

**42**

tion of water through the structure of these pores.

*Absorption of water by immersion as a function of substitution rate.*

*Effect of the substitution rate on the flexural tensile strength.*

*Sandy Materials in Civil Engineering - Usage and Management*

The shrinkage test is carried out according to standard NF P 18-433, test is mentioned in **Figure 14**.

**Figure 14.** *Shrinkage measurement on prismatic test piece.*

Shrinkage results of various mortars are presented in **Figure 15**.

**Figure 15** shows that the incorporation of marble waste sand has a considerable impact on the shrinkage of mortars stored in the laboratory room with a relative humidity of 80%. The mean values recorded are higher than that displayed for the control mortar, except for the mortar of 5% marble waste sand from 2 days until 21 days, where the mortar has a similar shrinkage to the mortar witness.

The highest value is found in the mortar with 20% marble waste sand on all ages. These expected shrinkage values are due to the evaporation of the free water contained in the test specimens.

It can be observed that all specimens had a weight loss, through the reaction between the calcium hydroxide Ca(OH)2 and the chlorine, the reaction was

salt increases the porosity because it is very soluble in water.

*Weight loss of specimens after 1–7–14–21–28–56–90 days of immersion in 5% HCl.*

*Introduction of Marble Waste Sand in the Composition of Mortar*

*DOI: http://dx.doi.org/10.5772/intechopen.91254*

Calcium chloride (CaCl2) causes dissolution of cement, the production of CaCl2

It can be also noted that in all ages the loss weight increased proportionally with marble waste sand substitution, and the control mortar presented the lowest weight loss at all ages. It can be concluded that a high calcium carbonate (CaCO3) content in marble waste sand increases the capacity of mortars to react with aggressions

A sudden loss of weight was noticed during 1–90 days (**Figure 18**). It can be also

noted that in early age all weight loss is close, the highest value of weight loss

*Weight loss of specimens after 1–7–14–21–28–56–90 days of immersion in 5% H2SO4.*

CaðOHÞ2 þ 2HC ! CaCl2 þ 2H2O (1)

CaCO3 þ 2HCl ! CaCl2 þ H2O þ CO2 (2)

expressed in Eq. (1).

**Figure 17.**

**Figure 18.**

**45**

according the reaction Eq. (2)

**Figure 15.** *Shrinkage results of various mortars.*

### **5.8 Acid attack**

After 28 days of water curing, the 5 <sup>5</sup> 5 cm3 specimens were immersed in two solutions, HCl and H2SO4 acid with the same concentration 5% (**Figure 16**). The aggressive solutions were renewed every 14 days. After 1, 7, 14, 21, 28, 56 and 90 days, they were used to estimate the weight loss according to the standard ASTMC267-96.

Results of the weight changes for the different mortars preserved in HCl and H2SO4 solution are presented in **Figures 17** and **18**.

The curves, presented by **Figure 17**, show the weight loss in % measured at the end of each aging of mortars stored in HCl solution (after 28 days of cure in water).

**Figure 16.** *Specimens immersed in acid solution.*

*Introduction of Marble Waste Sand in the Composition of Mortar DOI: http://dx.doi.org/10.5772/intechopen.91254*

Shrinkage results of various mortars are presented in **Figure 15**.

*Sandy Materials in Civil Engineering - Usage and Management*

21 days, where the mortar has a similar shrinkage to the mortar witness.

contained in the test specimens.

**5.8 Acid attack**

*Shrinkage results of various mortars.*

**Figure 15.**

ASTMC267-96.

**Figure 16.**

**44**

*Specimens immersed in acid solution.*

These expected shrinkage values are due to the evaporation of the free water

**Figure 15** shows that the incorporation of marble waste sand has a considerable impact on the shrinkage of mortars stored in the laboratory room with a relative humidity of 80%. The mean values recorded are higher than that displayed for the control mortar, except for the mortar of 5% marble waste sand from 2 days until

The highest value is found in the mortar with 20% marble waste sand on all ages.

After 28 days of water curing, the 5 <sup>5</sup> 5 cm3 specimens were immersed in two solutions, HCl and H2SO4 acid with the same concentration 5% (**Figure 16**). The aggressive solutions were renewed every 14 days. After 1, 7, 14, 21, 28, 56 and 90 days, they were used to estimate the weight loss according to the standard

Results of the weight changes for the different mortars preserved in HCl and

The curves, presented by **Figure 17**, show the weight loss in % measured at the end of each aging of mortars stored in HCl solution (after 28 days of cure in water).

H2SO4 solution are presented in **Figures 17** and **18**.

**Figure 17.** *Weight loss of specimens after 1–7–14–21–28–56–90 days of immersion in 5% HCl.*

It can be observed that all specimens had a weight loss, through the reaction between the calcium hydroxide Ca(OH)2 and the chlorine, the reaction was expressed in Eq. (1).

$$\text{Ca(OH)}\\2 + 2\text{HC} \rightarrow \text{CaCl}\_2 + 2\text{H}\_2\text{O} \tag{1}$$

Calcium chloride (CaCl2) causes dissolution of cement, the production of CaCl2 salt increases the porosity because it is very soluble in water.

It can be also noted that in all ages the loss weight increased proportionally with marble waste sand substitution, and the control mortar presented the lowest weight loss at all ages. It can be concluded that a high calcium carbonate (CaCO3) content in marble waste sand increases the capacity of mortars to react with aggressions according the reaction Eq. (2)

$$\text{CaCO}\_3 + 2\text{HCl} \rightarrow \text{CaCl}\_2 + \text{H}\_2\text{O} + \text{CO}\_2 \tag{2}$$

A sudden loss of weight was noticed during 1–90 days (**Figure 18**). It can be also noted that in early age all weight loss is close, the highest value of weight loss

**Figure 18.** *Weight loss of specimens after 1–7–14–21–28–56–90 days of immersion in 5% H2SO4.*

corresponds to control mortar, when the mortars are attacked by sulfuric acid H2SO4, they react with the Portlandite Ca(OH)2 resulting from the hydration of the cement [15], which causes the of gypsum. The process is described by the following chemical reaction:

$$\text{Ca(OH)}2 + \text{H}\_2\text{SO}\_4 \rightarrow \text{CaSO}\_4.2\text{H}\_2\text{O} \tag{3}$$

The low percentage of alumina Al2O3 in marble waste sand decreases the formation of C3A, which reacts with gypsum to produce ettringite (Eq. 4), that is why the increase in marble waste sand percentage decreases the weight loss of mortars.

3CaSO4 þ 3CaO*:*Al2O3*:*6H2O þ 26H2O ! 3CaO*:* Al2O3*:* 3CaSO4*:*32H2O (4)
