**3. Investigation of cement matrix compressive strength development under various temperature conditions**

Different concrete types are made and cured for compressive strength test. For each grout, 15 ASTM verified cubes are cured based on the material plan summarized in **Table 1**. The compressive behavior is evaluated with compressive test machine shown in **Figure 3** at each time interval of 1, 3, 7, 14, and 28. For each time interval, the average of three compressive values is selected for accuracy of the results. It is noted that the rate of the compressive loading based on the ASTM manuals [14–16] should be consistent for all the specimens, since the loading rate has a significant effect on the ultimate compressive strength. **Figure 3** shows the compressive test machine and cube samples for use in compressive test experiment.

The general behavior of the concrete under different environmental conditions is summarized in **Figure 4**. Based on the results, it is concluded that the concrete would develop desirable compressive strength at room temperature (23°C) and 100% humidity rate. The hydration process in which the cement matrix develops bonds between aggregates is highest before 14 days of curing. It is concluded that the temperature before 14 days of curing is highly important factor in general strength development compared to other factors (e.g., humidity index rate).

The strength behavior is highly affected by the temperature of curing as compared to humidity rate index value. The temperature of curing plays an undeniable role specifically at early stages of curing process. The temperature reduction of 15° generally ends up in more than 20% drop in ultimate strength regardless of the

**95**

and higher humidity condition.

**with maturity method**

*Compressive Behavior of Concrete under Environmental Effects*

cement types. While, decreasing 50% of humidity rate leads to about 10% drop in ultimate strength values. Therefore, to reach to the specific ultimate compressive strength, the temperature should be controlled and monitored at different stages of curing. In addition, more than 75% of the total strength compressive strength development, for all the specimens, is occurred within the first 14 days of curing. The least compressive strength is associated with lower temperature and drier condition, while the most strength development is related to milder temperature

*The effect of temperature and humidity on various cement types. (a) BASF. (b) Five star. (c) Quickrete.* 

**4. Investigation of curing process and strength development of concrete** 

In-place concrete strength evaluation is an important step in achieving the reliable performance of structures and construction scheduling [18, 19]. The level of maturity is in need of evaluation for deciding the forms' striping time, posttesting, protection

*DOI: http://dx.doi.org/10.5772/intechopen.85675*

*(a) Compressive test machinery. (b) Cube concrete samples.*

**Figure 3.**

**Figure 4.**

*(d) Dayton.*

*Compressive Behavior of Concrete under Environmental Effects DOI: http://dx.doi.org/10.5772/intechopen.85675*

#### **Figure 3.**

*Compressive Strength of Concrete*

**Relative humidity during the first 7 days (%)**

**Temperature after 7 days (°C)**

*Testing plane for evaluating the effect of temperature and humidity index.*

**Temperature during the first 7 days (°C)**

23 23

10 5

**Table 1.**

mild, and moderate temperature conditions.

**under various temperature conditions**

made for compressive strength development investigations.

All the samples were prepared in molds accordingly and consolidated with tamping rods. Roding is done for each layer uniformly on the cross-sectional area with rounded end. The number of strokes varies depending on the type of molds used, which is based on ASTM standards [14]. The samples are subsequently covered with burlaps to effectively initiate the hydration process for 24 h. Subsequently, the samples are demolded after being cured for 24 h, and the compressive strength is monitored for 1, 3, 7, 14, and 28 days curing time based on the ASTM recommended procedure [14–16]. It is noted that the mixing procedure is based on the ASTM manuals [14–16] for simulating the actual behavior of the concrete under cold,

**Relative humidity after 7 days (%)**

**Number of cubes (2 × 2 × 2 in.)**

100 23 100 15 2 2 50 50 15 2 2

**Number of cylinders (maturity)**

15 2 2 15 2 2

**Number of rectangular cubes (Freeze-thaw)**

It is noted that samples are remained in temperatures shown in **Table 1** for a week and then moved to room temperature area with the same humidity afterward. In general, for each grout type at each time interval, three cubic and two cylinders as well as two large rectangular samples for freeze-thaw durability index test are

**3. Investigation of cement matrix compressive strength development** 

each grout, 15 ASTM verified cubes are cured based on the material plan summarized in **Table 1**. The compressive behavior is evaluated with compressive test machine shown in **Figure 3** at each time interval of 1, 3, 7, 14, and 28. For each time interval, the average of three compressive values is selected for accuracy of the results. It is noted that the rate of the compressive loading based on the ASTM manuals [14–16] should be consistent for all the specimens, since the loading rate has a significant effect on the ultimate compressive strength. **Figure 3** shows the compressive test machine and cube samples for use in compressive test experiment. The general behavior of the concrete under different environmental conditions is summarized in **Figure 4**. Based on the results, it is concluded that the concrete would develop desirable compressive strength at room temperature (23°C) and 100% humidity rate. The hydration process in which the cement matrix develops bonds between aggregates is highest before 14 days of curing. It is concluded that the temperature before 14 days of curing is highly important factor in general strength development compared to other factors (e.g., humidity index rate).

Different concrete types are made and cured for compressive strength test. For

The strength behavior is highly affected by the temperature of curing as compared to humidity rate index value. The temperature of curing plays an undeniable role specifically at early stages of curing process. The temperature reduction of 15° generally ends up in more than 20% drop in ultimate strength regardless of the

**94**

*(a) Compressive test machinery. (b) Cube concrete samples.*

#### **Figure 4.**

*The effect of temperature and humidity on various cement types. (a) BASF. (b) Five star. (c) Quickrete. (d) Dayton.*

cement types. While, decreasing 50% of humidity rate leads to about 10% drop in ultimate strength values. Therefore, to reach to the specific ultimate compressive strength, the temperature should be controlled and monitored at different stages of curing. In addition, more than 75% of the total strength compressive strength development, for all the specimens, is occurred within the first 14 days of curing. The least compressive strength is associated with lower temperature and drier condition, while the most strength development is related to milder temperature and higher humidity condition.
