**1. Introduction**

There are notable differences between lightweight aggregates and normalweight aggregates (NWA), so what are the different effects on different types of concrete?

Lightweight coarse aggregate has a softening effect; does lightweight aggregate concrete have this effect too?

Can the lightweight concrete be used under special environmental conditions such as negative temperature, elevated temperature, and chemical corrosion?

Are there any changes in the mechanical performance of lightweight concrete under complicated stress and in reinforced concrete?

Since 2005, it has been prohibited to mine river sand in most areas of China. The relevant laws, such as the *Water Law of the People's Republic of China* (2002, 2016),

the *Flood Prevention Law of the People's Republic of China* (1997, 2016), the *Mineral Resources Law of the People's Republic of China* (1986, 2009), and the *Regulations of the People's Republic of China on the Administration of River Courses* (1986, 2009), are constantly amended, and thus the prohibition of river sand excavation has been extended throughout the country since 2018. Nowadays, artificial sand is mainly used as normal-weight fine aggregate (NWFA) in normal-weight concrete (NWC) in China. This study mainly discusses artificial sand, and all of the following experiments were carried out strictly according to Chinese national standards.

## **2. Technical requirements of normal-weight sand**

NWFA can be distinguished from lightweight fine aggregate (LWFA) by the apparent density (*ρ*a) and the bulk density (*ρ*b) [1, 2]. If *ρ*<sup>a</sup> ≥ 2500kg/m<sup>3</sup> or *ρ*<sup>b</sup> ≥ 1400kg/m<sup>3</sup> and the void ratio (*e*v) ≤ 44% when calculated by Eq. (1), the sand is NWFA [1]. On the other hand, if *ρ*<sup>b</sup> ≤ 1200kg/m<sup>3</sup> , the sand is LWFA. Also, the LWFA is usually made of lightweight coarse aggregate (LWCA) for producing lightweight aggregate concrete (LWAC) [2]:

$$e\_{\rm v} = \left(\mathbf{1} \frac{\rho\_{\rm b}}{\rho\_{\rm a}}\right) \times \mathbf{100\%} \tag{1}$$

for self-compacting concrete (SCC) production, and the percentage retained on a 315-μm sieve should not be less than 15%. The fineness modulus range of 2.6–3.0 is suitable for high-strength concrete (HSC) production. Moreover, medium sand

Nominal diameter of sand and sieve hole 5 mm 2.5 mm 1.25 mm 630 μm 315 μm 160 μm Mesh size (length of sieve hole) 4.75 mm 2.36 mm 1.18 mm 600μm 300μm 150 μm

> Zone I 10–0 35 5 65–35 85–71 95–80 100–90 Zone II 10–0 25–0 50 – 10 70–41 92–70 100–90 Zone III 10–0 15–0 25–0 40–16 85–55 100–90

Lightweight aggregate (LWA) includes artificial, natural, industrial waste slag, cinder, and spontaneous combustible coal gangue LWA [2]. LWA is called superlightweight coarse aggregate (SLWCA) when *ρ*<sup>b</sup> does not exceed 500 kg/m<sup>3</sup>

tube crushing strengths (TCS) of the different grades of high-strength lightweight coarse aggregates (HSLWCAs) are provided in **Table 3**. The softening coefficient should be equal to or higher than 0.8 and 0.7 for artificial and industrial waste slag LWCA and natural LWCA, respectively. The fineness modulus (*M*x, LA) of LWFA

According to the current LWA production technology and its use in actual

**) Tube crushing strength (MPa) Strength grade of LWAC**

engineering, the particle size distribution of LWA is shown in **Table 4**.

600 4.0 LC25 700 5.0 LC30 800 6.0 LC35 900 6.5 LC40 *Notes: The bulk density grade is a size range, not an exact number. For example, ρ<sup>b</sup> = 600 kg/m<sup>3</sup> means 500*

*Tube crushing strength and strength grade of LWAC for artificial HSLWCA stipulated in [2].*

Continuous grading (5–16 mm) 16.0 mm 9.50 mm 4.75 mm 2.36 mm Cumulative retained percentage (%) 0–10 20–60 90–100 95–100

Continuous grading (5–10mm) 9.50 mm 4.75 mm 2.36 mm Cumulative percentage retained (%) 0 15 90–100 95–100

*Particle size distribution for LWFA and LWCA.*

Mesh size (length of sieve hole) 4.75 mm 2.36 mm 1.18 mm 600μm 300μm 150 μm Cumulative percentage retained (%) 0–10 0–35 20–60 30–80 65–90 75–100

. The

should be used for mass concrete and mortar production [6].

*Particle size distribution for artificial sand stipulated in [1, 3].*

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

**3. Technical requirements of lightweight aggregate**

should be between 2.3 and 4.0.

**Bulk density grade (***ρ***b, kg/m3**

*< ρ<sup>b</sup> 600 kg/m<sup>3</sup> and so on.*

**Table 3.**

**Table 4.**

**83**

Cumulative percentage retained

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

(%)

**Table 2.**

In order to standardise the artificial sand (AS), namely, manufactured sand (MS), the terms, definitions, classifications, specifications, technical requirements, test methods, inspection rules, and so on are stipulated in the Chinese national standards Sand for Construction (GB/T14684-2011) [1], Technical Specification for Application of Manufactured Sand Concrete (JGJ/T241–2011) [3], and Standard for Technical Requirements and Test Method of Sand and Crushed Stone (or Gravel) for Ordinary Concrete (JGJ52–2006) [4].

The MS is made of different parent rocks, whose strength should be in accordance with **Table 1** [3].

The fineness module (*M*x, calculated by Eq. 2) should be *M*x, c = 3.7–3.1, *M*x, m = 3.0–2.3, *M*x, f = 2.2–1.6, and *M*x, e = 1.5–0.7 for coarse, medium, fine, and extrafine sand, respectively. The detailed particle size distribution sieved with a square hole mesh sieve is provided in **Table 2**:

$$M\_{\rm x} = \frac{(A\_2 + A\_3 + A\_4 + A\_5 + A\_6) \cdot 5A\_1}{100 \cdot A\_1} \tag{2}$$

where *A*1, *A*2, *A*3, *A*4, *A*<sup>5</sup> and *A*<sup>6</sup> are the cumulative percentages retained in 4.75, 2.36, 1.18, 600, 300 and 150 μm sieves, respectively.

For concrete production, it is recommended that sand from Zone II be used. The sand ratio (sand-to-sand and coarse aggregate weight ratio, *S*p, %) should be improved properly when selecting sand from Zone I to keep a sufficient cement content to satisfy the workability requirement of concrete. When selecting sand from Zone III, *S*<sup>p</sup> should be reduced properly. Also, medium sand should be selected


#### **Table 1.**

*Strength of parent rock made of artificial sand (unit, MPa).*

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


#### **Table 2.**

the *Flood Prevention Law of the People's Republic of China* (1997, 2016), the *Mineral Resources Law of the People's Republic of China* (1986, 2009), and the *Regulations of the People's Republic of China on the Administration of River Courses* (1986, 2009), are constantly amended, and thus the prohibition of river sand excavation has been extended throughout the country since 2018. Nowadays, artificial sand is mainly used as normal-weight fine aggregate (NWFA) in normal-weight concrete (NWC) in China. This study mainly discusses artificial sand, and all of the following exper-

NWFA can be distinguished from lightweight fine aggregate (LWFA) by the

*ρ*<sup>b</sup> ≥ 1400kg/m<sup>3</sup> and the void ratio (*e*v) ≤ 44% when calculated by Eq. (1), the sand

, the sand is LWFA. Also, the

(2)

� 100% (1)

apparent density (*ρ*a) and the bulk density (*ρ*b) [1, 2]. If *ρ*<sup>a</sup> ≥ 2500kg/m<sup>3</sup> or

LWFA is usually made of lightweight coarse aggregate (LWCA) for producing

*ρ*b *ρ*a 

In order to standardise the artificial sand (AS), namely, manufactured sand (MS), the terms, definitions, classifications, specifications, technical requirements, test methods, inspection rules, and so on are stipulated in the Chinese national standards Sand for Construction (GB/T14684-2011) [1], Technical Specification for Application of Manufactured Sand Concrete (JGJ/T241–2011) [3], and Standard for Technical Requirements and Test Method of Sand and Crushed Stone (or Gravel)

The MS is made of different parent rocks, whose strength should be in accor-

The fineness module (*M*x, calculated by Eq. 2) should be *M*x, c = 3.7–3.1, *M*x, m = 3.0–2.3, *M*x, f = 2.2–1.6, and *M*x, e = 1.5–0.7 for coarse, medium, fine, and extrafine sand, respectively. The detailed particle size distribution sieved with a square

> *<sup>M</sup>*<sup>x</sup> <sup>¼</sup> ð Þ *<sup>A</sup>*<sup>2</sup> <sup>þ</sup> *<sup>A</sup>*<sup>3</sup> <sup>þ</sup> *<sup>A</sup>*<sup>4</sup> <sup>þ</sup> *<sup>A</sup>*<sup>5</sup> <sup>þ</sup> *<sup>A</sup>*<sup>6</sup> ‐5*A*<sup>1</sup> <sup>100</sup>‐*A*<sup>1</sup>

where *A*1, *A*2, *A*3, *A*4, *A*<sup>5</sup> and *A*<sup>6</sup> are the cumulative percentages retained in 4.75,

For concrete production, it is recommended that sand from Zone II be used. The

sand ratio (sand-to-sand and coarse aggregate weight ratio, *S*p, %) should be improved properly when selecting sand from Zone I to keep a sufficient cement content to satisfy the workability requirement of concrete. When selecting sand from Zone III, *S*<sup>p</sup> should be reduced properly. Also, medium sand should be selected

**Igneous rock Metamorphic rock Sedimentary rock** ≥100 ≥80 ≥60

*Notes: The test method of compressive strength of parent rock refers to GB/T50266–2013 [5].*

*<sup>e</sup>*<sup>v</sup> <sup>¼</sup> <sup>1</sup>‐

iments were carried out strictly according to Chinese national standards.

**2. Technical requirements of normal-weight sand**

*Sandy Materials in Civil Engineering - Usage and Management*

is NWFA [1]. On the other hand, if *ρ*<sup>b</sup> ≤ 1200kg/m<sup>3</sup>

lightweight aggregate concrete (LWAC) [2]:

for Ordinary Concrete (JGJ52–2006) [4].

hole mesh sieve is provided in **Table 2**:

2.36, 1.18, 600, 300 and 150 μm sieves, respectively.

*Strength of parent rock made of artificial sand (unit, MPa).*

dance with **Table 1** [3].

**Table 1.**

**82**

*Particle size distribution for artificial sand stipulated in [1, 3].*

for self-compacting concrete (SCC) production, and the percentage retained on a 315-μm sieve should not be less than 15%. The fineness modulus range of 2.6–3.0 is suitable for high-strength concrete (HSC) production. Moreover, medium sand should be used for mass concrete and mortar production [6].
