This chapter is concerned with the details of the properties of the materials used, the method followed to design the experiment and the test procedures followed. The theory is supplemented with a number of pictures to have a clear idea of the methods.

The materials used to design the mix for C30, C40, grade of concrete is cement, fly ash grade II, sand, coarse aggregate, water, Carbon Nanotube (CNT). The properties of these materials are presented below.

Ordinary Portland cement (Chinese Standard GB 8076-2008) Classified as 42.5R was applied in This Study. Chemical Composition, Mineral Composition, as well as Physical Performance of the cement, are shown in Table 1. The contents of oxides were measured Through X-Ray Fluorescence. The Content of F-Cao was analyzed by the Franke Method. The mineral phases were calculated by The Bogue Method.

The disposal of Fly ash poses increasingly difficult problems for many urbanized regions. A viable solution to the problem is reclamation of Fly ash for Civil Engineering applications. Previous researchers shown that fly ash is a potential source of construction material and soil stabilizer. Although it is one of the lowest cost and most widely used materials in the world, cement raises many concerns for the environment and human health. Many studies have been conducted with the aim of reducing the cost of cement for soil stabilization; one option is to partially replace cement with waste materials such as fly ash. This study we used Fly ash grade II.

The China ISO Standard Sand Compiling with GB/T 17671-2005 was used to prepare cement Mortar. For coarse aggregate, the parent concrete is crushed through mini jaw crusher. During crushing it is tried to maintain to produce the maximum size of aggregate in between 20 mm to 4.75 mm. The coarse aggregate particle size distribution curve is presented in Figure 1.

Tap water was used in this experiment. The properties are assumed to be same as that of normal water. Specific gravity is taken as 1.00. Pure water (deionized water) was used to make mortar specimen and cement paste.

Table 2 showed the properties of the Carbon nanotube.

Specification for mix proportion design of ordinary concrete. The mix design for C30, C40 grade of concrete is described below in accordance with Chinese Standard Code IS JGJ552011 and JGJ /T55-96.

➢ Target strength for C30 Mix Proportioning:

f c u , o ≥ f c u , k + 1.645 σ

Characteristic compressive strength at 28 days: f c u , k = 30   MPa

Assumed standard deviation (Table 4.0.2 of JGJ552011): σ = 5   MPa

Target average compressive strength at 28 days: f c u , o = f c u , k + 1.645 σ = 38.225 MPa

➢ Target strength for C40 Mix Proportioning

Characteristic compressive strength at 28 days: f c u , k = 40   MPa

Assumed standard deviation (Table 4.0.2 of JGJ552011): σ = 5   MPa

Target average compressive strength at 28 days: f c u , o = f c u , k + 1.645 σ = 48.225 MPa

➢ Selection of water Cement ratio:

Maximum water content per cubic meter of concrete (refer Tables 1-17 of JGJ/T55-96): Wmax = 175L (for 40 mm slump).

Since the slump was less than 40 mm, no adjustment was required. To start with let us assume a water-cement ratio of 0.42.

➢ Calculation of cement content:

Mass of water selected per cubic meter of concrete = 175 kg.

Mass of cement per cubic metre of concrete = 175/0.35 = 500 kg.

Minimum cement content = 260 kg/m³ (for moderate exposure condition, Cl 1.7 of JGJ/T55-96). Maximum cement content = 550 kg/m³ (Cl. 1.7 of JGJ/T55-96)

So, the selected cement content is alright.

➢ Proportion of volume of coarse Aggregate and Fine Aggregate content:

Volume of coarse aggregate per unit volume of total aggregate (Tables 1-17 of JGJ/T55-96) = 1278 kg

(This is corresponding to 20 mm size aggregate and Zone III fine aggregate for water-cement ratio of 0.35)

Mix calculations for cement paste

The design of each mix began with a constant paste content (water + cement + supplementary cementitious materials) of 0.32 by weight of the total mix. The weight of cement and water were adjusted based on the specified water to binder ratio. The remainder of the mixture consisted of an equal weight of fine and course aggregate. Superplasticizer and air entraining agent were added based on experience and trial mixing prior to beginning the test program. The below tables detail the actual weights of the mixture components.

The mix proportion for concrete grade C30 and C40 are resumed in the following Tables 3-7.

1) Mixing Sequence

Before concrete mixing could begin, the concrete mix ingredients had to be weighed and placed in containers so that the ingredients could be placed into a mixer with little loss of time. Each ingredient was weighed and placed carefully into the mixer. The mixing drum had to be prepared. The purpose of this mix is to wet the mixing drum so that no water is lost during the preparation of the actual mix. The concrete ingredients were placed into the rotating drum following the order. The dry constituents of each mixture were mixed for 15 min using the mixer. Then, 75% of the water was added and mixing continued for 10 min. Next, the remaining 25% of the water was added and mixing continued for another 15 min.

2) Curing Regimens

The specimens remained in their molds for 24 hours at room temperature, 25˚C. The Specimens tested were generally curing with air cured at 25˚C and RH 92|% for 3days, 7 days and 28 days.

3) Preparation of Test Specimen

For conducting compressive strength test on concrete cubes of size 100 × 100 × 100 mm are cast. A rotary mixture is used for thorough mixing and a vibrator is used for good compaction. After successful casting, the concrete specimens are demolded after 24 hours and put in curing room for 3 days, 7 days and 28 days maintaining 25˚C.

1) Testing to evaluate the durability factor

➢ Freezing and Thawing

Prismatic specimens with dimensions of 100 mm × 100 mm × 400 mm were tested for resistance to freezing and thawing according to GB/T50082-2009. In accordance with this testing method, a 5 hours-cycle was selected. One full cycle of freezing and thawing consisted of a rapid temperature decrease from 8˚C to −18˚C in approximately 2 h 20 min. The temperature was then held constant for 8 min before raising the temperature back to 3˚C in 53 min. The temperature was then held constant at 3˚C for 10 min. Testing was conducted during this 10 min window.

The specimens were subjected to 300 cycles of freezing and thawing (or less if the RDM of a specimen dropped below 60). Length, mass, and fundamental frequency (to compute dynamic elastic modulus) measurements were taken at intervals no greater than 25 cycles. Distilled water was used in the conditioning water bath and for immersion of the specimens during freezing and thawing cycles.

➢ Dynamic Elastic Modulus

Testing procedures for determining dynamic elastic modulus are specified in ASTM C 215. To determine the dynamic elastic modulus, concrete prisms are excited over a wide range of frequencies using an impact hammer or a transducer to identify the frequency at which the maximum amplitude occurs. The frequency at which the maximum amplitude occurs is the resonant frequency. The concrete specimen is generally assumed to be a single degree of freedom system, for which the resonant frequency is referred to as the fundamental frequency. The fundamental frequency is used to compute dynamic elastic modulus, E_d, with the following equation:

E D = C m ω r 2 (1)

where C is a constant that accounts for Poisson’s ratio and the geometry of the specimen, m is the mass of the specimen, and ω r is the measured fundamental frequency.

When ASTM C 215 is used to monitor deteriorating concrete, it is common to present results in terms of the relative dynamic modulus, computed as follows:

R D M = E n E o ( 100 ) (2)

where RDM is the relative dynamic modulus after n cycles of freezing and thawing, En is the dynamic elastic modulus after n cycles, and Eo is the dynamic elastic modulus at zero cycles of freezing and thawing. After completion of freezing and thawing cycles, a durability factor, DF, can be computed as:

D F = R D M ⋅ N M (3)

where N is the number of cycles imposed and M is the specified number of cycles (usually 300).

2) Testing procedures used to evaluate compressive strength and flexural strength are presented in this section.

➢ Flexural Strength Test

Flexural testing machine Reference number YAW-300 was used. Flexural strength was evaluated according to Chinese standard with the software Super Test version 8 and the load rate was 50 N/s. Prismatic specimens with dimensions of 40 mm × 40 mm × 160 mm were loaded using a third point loading setup across their strong axis. Three specimens from each batch were tested at an age of 3, 7, and 28 days and the mean Flexural strength of three specimens is considered as the Flexural strength of the specified category.

➢ Compressive Strength Test

Compressive testing machine Reference number YAW-300 was used after 3, 7, and 28 days of curing with surface dried condition as per Chinese Standard. The compressive strength of specimens is determined with the software Super Test version 8 and the load rate was 2.4 KN/s. Three specimens are tested for typical category and the mean compressive strength of three specimens is considered as the compressive strength of the specified category.