Advanced Process Control and Simulation for Chemical Engineers

186 Advanced Process Control and Simulation for Chemical Engineers

Mix no. Cement Aluminum

powder

Sand Water Silica

fume

Melamine Superplasticizer

0.30 0.015

0.35 0.020

5. Determination of

melamine content

(final mix design)

1.0 0.004 1.4 0.35 0.25 1.0 0.012

1.2 0.011

1.4 0.010

1.6 0.009

1.8 0.008

2.0 0.007

2.2 0.006

13.5 DISCUSSION AND RESULTS

13.5.1 Mix Number 1 (Determination of Melamine Content for the First

Trial Mix Design)

Figure 3 present the variations in the compressive strength and dry density for 7 days

age of mortars as a function of the value of melamine substitutes used. It can ini-

tially be seen, to increased melamine, the compressive strength and dry density of

composites decreased. It was found that the highest compressive strength (3.23 MPa)

was obtained for the ratio of cement, aluminum powder, water, sand, and melamine

of 1.0:0.004:0.35:1.0:1.0. However, the compressive strength for this mix proportion

does not exactly satisfy the standard value. Table 5 shows that the specification of non-

load-bearing lightweight concrete according to [1] Type II.

The reduction in the compressive strength due to the addition of melamine aggre-

gates might be due to either a poor bond between the cement paste and the melamine

aggregates or to the low strength that is characteristic of plastic aggregates. Due to this

reason, the proportion of melamine plastic equal to 1.0 was selected for the next mix

design. After the rest of the composition was determined, the melamine plastic was

tested again to fi nd the suitable proportion.

TABLE 5 Specification of non-load-bearing lightweight concrete [1].

Type Compressive strength (MPa) Density (kg/m3)

Average of three unit Individual unit

II 4.1 3.5 < 1680

TABLE 4 (Continued)