**2. Literature review**

Waste foundry sand is generated by industries that use sands, binders and additives to form moulds and cores for castings. Sands are chosen for several reasons; they are readily available everywhere, inexpensive, highly refractory and readily bonded by clays or other inorganic and organic materials [8, 9, 14]. The mould forms the outside of the castings; the core forms the internal shape. When the part to be made has deep recesses or hollow portions, sand cores must be provided in the mould [3]. The material to be used to form moulds and cores in a foundry should have cohesiveness and porosity properties at the same time. Adding binder (bentonite, resins, cement, sodium silicate and oils) will improve the cohesiveness of the sand grains but will tend to reduce porosity. Additives are those materials which are added to the bonded sands to improve properties, either during the moulding process or during the casting process or both [8]. The moulding processes which involve sand are (1) green sand moulding (or clay-bonded sand, [12]), (2) chemically bonded process and (3) shell moulding process [3, 5, 8, 9]. The most commonly used process is green sand moulding [15]. Green sand is composed of four major materials. Sand comprises 85–95% of the green sand mixture. Most often the sand is inert silica, but olivine and zircon sand are also used [8, 15–17]. Approximately, 4–10% of the mixture is made of some form of clay, e.g. bentonite. The clay acts as a binder for the green sand and provides strength and plasticity. Combustible additives like sea coal, cereal, fuel oil and wood flour typically make up from 2 to 10% of the green sand mixture. The final additive of green sand is water which is usually added in small percentages (2–5% by weight) [5, 8]. Chemically bonded sands are those that use furan, phenolic urethane and acid cured no-bake systems, as well as alkyd and phenolic urethane cold box processes. Shell moulding uses a mixture of sand and thermosetting resin (usually phenol formaldehyde) to form the mould [8, 17].

The physical, chemical and mechanical characteristics of virgin sand make it a popular material for construction engineering, but after several reuses in moulds and cores, it becomes WFS [7]. The grain size distribution of WFS is quite uniform, with a majority of the sizes (85–95%) falling within a narrow range between 0.6 and 0.15 mm, and 5–12% is smaller than 0.075 mm [5, 8, 10] or between 1 and 16.5% [14]. According to Tikalsky et al. [17], more than 80% of the particles by mass are concentrated by size between 0.15 and 0.70 mm, compared to 0.30–4.75 mm for conventional fine aggregate. Most of the WFS materials reported are found to be

**51**

*Use of Waste Foundry Sand (WFS) as Filler in Hot-Mixed Asphalt Concrete*

been reported to vary between 0.3 and 6.2% [3, 8, 17].

then it will have an increase in its strength [19, 20, 27].

properties of material and increase of surface area [10, 32].

saturation greatly influenced the indirect tension values.

ture's rutting potential but do improve fatigue performance [17].

asphalt mixtures [3, 7, 16, 25, 26], etc.

medium to fine sand. WFS have been found to be too fine to satisfy the specifications for general fine aggregate [8, 10, 12]. WFS has uniform equidimensional subangular to rounded grains, and a few has rounded grains [8, 10, 17, 18].

For density and unit weight, the values found for the WFS were very close to conventional aggregate [13]. The bulk specific gravities reported in the literature on WFS ranged from 1.985 to 2.722 [8, 17]. In most of the cases WFS have been reported to be almost dry. The moisture content as received for WFS were reported to be in the range of 0.0–4.85% [8, 17, 18]. Concerning absorption, the values are relatively higher than those obtained for the natural aggregate, due to the presence of organic matter [6, 8]. The percentage absorption values on WFS samples have

Over the past three decades, there have been several studies around the world on the use of WFS in engineering works, in different areas: base and subbase layers of highway construction [19–21], embankments [22, 23], hydraulic barriers [24],

Highway subbase layers using WFS have been shown to resist winter conditions (freeze–thaw cycles) better than specimens of reference materials [5, 17, 19]. If a subbase layer stabilised with WFS is compacted in field at dry of optimum content

It has been mentioned in the literature that the fines of WFS affect the properties of asphalt concrete negatively [7, 28]. The amount of WFS used in an asphalt mixture depends largely on the amount of fines in the WFS [5, 12, 14, 29]. Studies have recommended that WFS should replace successfully as much as 15% (in mass) of the conventional sand (fine) content in asphalt concrete [3, 9]; 8–10, 10–20 and 10%, respectively, in engineering practice in Pennsylvania, Michigan and Tennessee States [5]; 35% [30]; 15% [26]; 10% [7, 13]; 15% [10, 31]; 35% [27, 32]; and 15–30% [14]. Concerning physical characteristics, the densities of the mixtures decreased as the percentage of WFS in the asphalt concrete increased [7, 9, 10, 12, 13, 17, 32]. Percentage of air voids and voids in the mineral aggregate (VMA) were found to increase with blending of increased quantities of WFS [8, 9]. The optimum asphalt content (4.9–6.8%) for HMA mixtures containing various amounts of foundry sand is comparable to the content of mixes not containing foundry sand [14, 17]. The OAC increases with increase in the WFS percentage [13], although Miller et al. [14] found lower values for mixtures containing WFS, in relation to control ones. According to this author, the mixtures obtain the higher percentage of OAC with the WFS with the higher amount of particles passing the #200 sieve. This happens due to the fineness

Regarding the mechanical characteristics, the Marshall stability of the asphalt concrete samples containing WFS decreases as the quantity of WFS is increased [3, 6–8, 10, 12, 29, 32]. The flow values of mixtures decreased with increasing percentage of WFS in the asphalt concrete mixtures [7,–10, 13]. The indirect tensile strengths of the asphalt cement mixtures decreased as the percentage of WFS material was increased [7–10, 12, 13, 32]. However, Abdulsattar and Mohammed [25] found that all the WFS mixtures that they analysed showed higher tensile strength than the control mixture. According to Tikalsky et al. [17], the level of air voids and

In relation to moisture susceptibility, WFS has little effect on top-down fatigue cracking resistance and moisture susceptibility of the mixtures [32]. When WFS replacement is higher than 15%, asphalt mix may become more sensitive to moisture damage (i.e. stripping) due to the presence of silica [10, 27]. WFS, on average, decreases the unconditioned tensile strength and thus the durability of asphalt mixtures; on the other hand, WFS do not necessarily increase or decrease a mix-

*DOI: http://dx.doi.org/10.5772/intechopen.89715*

#### *Use of Waste Foundry Sand (WFS) as Filler in Hot-Mixed Asphalt Concrete DOI: http://dx.doi.org/10.5772/intechopen.89715*

*Sandy Materials in Civil Engineering - Usage and Management*

increasing of the lifespan of landfills [13].

adequate performance of the mixtures.

formaldehyde) to form the mould [8, 17].

**2. Literature review**

settlement [7–10].

landfills [6]. The major portion of the WFS is considered as non-hazardous waste and is currently deposited in a special WFS landfill that is remote from areas of

The metal casting industry annually discards about 10% of foundry sand for production, i.e. approximately an estimated 9–10 million tons of WFS each year, in the USA [5, 10, 11]. Generally speaking, approximately 1 ton of foundry sand is needed to produce 1 ton of metal casting [8, 12]. WFS can be used as an alternative material (fine aggregate in asphalt mixtures) in highway constructions allowing the

This work analyses the physical and mechanical behaviour of asphalt mixtures, using the WFS as a mineral filler in asphalt concrete, in 5% (in mass) of maximum replacement to conventional Portland cement (CP). The waste was obtained from an industry located in the free-trade zone of Manaus city, Amazon State, Brazil. The results showed that the addition of industrial WFS in asphalt mixture resulted in

Waste foundry sand is generated by industries that use sands, binders and additives to form moulds and cores for castings. Sands are chosen for several reasons; they are readily available everywhere, inexpensive, highly refractory and readily bonded by clays or other inorganic and organic materials [8, 9, 14]. The mould forms the outside of the castings; the core forms the internal shape. When the part to be made has deep recesses or hollow portions, sand cores must be provided in the mould [3]. The material to be used to form moulds and cores in a foundry should have cohesiveness and porosity properties at the same time. Adding binder (bentonite, resins, cement, sodium silicate and oils) will improve the cohesiveness of the sand grains but will tend to reduce porosity. Additives are those materials which are added to the bonded sands to improve properties, either during the moulding process or during the casting process or both [8]. The moulding processes which

involve sand are (1) green sand moulding (or clay-bonded sand, [12]),

(2) chemically bonded process and (3) shell moulding process [3, 5, 8, 9]. The most commonly used process is green sand moulding [15]. Green sand is composed of four major materials. Sand comprises 85–95% of the green sand mixture. Most often the sand is inert silica, but olivine and zircon sand are also used [8, 15–17]. Approximately, 4–10% of the mixture is made of some form of clay, e.g. bentonite. The clay acts as a binder for the green sand and provides strength and plasticity. Combustible additives like sea coal, cereal, fuel oil and wood flour typically make up from 2 to 10% of the green sand mixture. The final additive of green sand is water which is usually added in small percentages (2–5% by weight) [5, 8]. Chemically bonded sands are those that use furan, phenolic urethane and acid cured no-bake systems, as well as alkyd and phenolic urethane cold box processes. Shell moulding uses a mixture of sand and thermosetting resin (usually phenol

The physical, chemical and mechanical characteristics of virgin sand make it a popular material for construction engineering, but after several reuses in moulds and cores, it becomes WFS [7]. The grain size distribution of WFS is quite uniform, with a majority of the sizes (85–95%) falling within a narrow range between 0.6 and 0.15 mm, and 5–12% is smaller than 0.075 mm [5, 8, 10] or between 1 and 16.5% [14]. According to Tikalsky et al. [17], more than 80% of the particles by mass are concentrated by size between 0.15 and 0.70 mm, compared to 0.30–4.75 mm for conventional fine aggregate. Most of the WFS materials reported are found to be

**50**

medium to fine sand. WFS have been found to be too fine to satisfy the specifications for general fine aggregate [8, 10, 12]. WFS has uniform equidimensional subangular to rounded grains, and a few has rounded grains [8, 10, 17, 18].

For density and unit weight, the values found for the WFS were very close to conventional aggregate [13]. The bulk specific gravities reported in the literature on WFS ranged from 1.985 to 2.722 [8, 17]. In most of the cases WFS have been reported to be almost dry. The moisture content as received for WFS were reported to be in the range of 0.0–4.85% [8, 17, 18]. Concerning absorption, the values are relatively higher than those obtained for the natural aggregate, due to the presence of organic matter [6, 8]. The percentage absorption values on WFS samples have been reported to vary between 0.3 and 6.2% [3, 8, 17].

Over the past three decades, there have been several studies around the world on the use of WFS in engineering works, in different areas: base and subbase layers of highway construction [19–21], embankments [22, 23], hydraulic barriers [24], asphalt mixtures [3, 7, 16, 25, 26], etc.

Highway subbase layers using WFS have been shown to resist winter conditions (freeze–thaw cycles) better than specimens of reference materials [5, 17, 19]. If a subbase layer stabilised with WFS is compacted in field at dry of optimum content then it will have an increase in its strength [19, 20, 27].

It has been mentioned in the literature that the fines of WFS affect the properties of asphalt concrete negatively [7, 28]. The amount of WFS used in an asphalt mixture depends largely on the amount of fines in the WFS [5, 12, 14, 29]. Studies have recommended that WFS should replace successfully as much as 15% (in mass) of the conventional sand (fine) content in asphalt concrete [3, 9]; 8–10, 10–20 and 10%, respectively, in engineering practice in Pennsylvania, Michigan and Tennessee States [5]; 35% [30]; 15% [26]; 10% [7, 13]; 15% [10, 31]; 35% [27, 32]; and 15–30% [14].

Concerning physical characteristics, the densities of the mixtures decreased as the percentage of WFS in the asphalt concrete increased [7, 9, 10, 12, 13, 17, 32]. Percentage of air voids and voids in the mineral aggregate (VMA) were found to increase with blending of increased quantities of WFS [8, 9]. The optimum asphalt content (4.9–6.8%) for HMA mixtures containing various amounts of foundry sand is comparable to the content of mixes not containing foundry sand [14, 17]. The OAC increases with increase in the WFS percentage [13], although Miller et al. [14] found lower values for mixtures containing WFS, in relation to control ones. According to this author, the mixtures obtain the higher percentage of OAC with the WFS with the higher amount of particles passing the #200 sieve. This happens due to the fineness properties of material and increase of surface area [10, 32].

Regarding the mechanical characteristics, the Marshall stability of the asphalt concrete samples containing WFS decreases as the quantity of WFS is increased [3, 6–8, 10, 12, 29, 32]. The flow values of mixtures decreased with increasing percentage of WFS in the asphalt concrete mixtures [7,–10, 13]. The indirect tensile strengths of the asphalt cement mixtures decreased as the percentage of WFS material was increased [7–10, 12, 13, 32]. However, Abdulsattar and Mohammed [25] found that all the WFS mixtures that they analysed showed higher tensile strength than the control mixture. According to Tikalsky et al. [17], the level of air voids and saturation greatly influenced the indirect tension values.

In relation to moisture susceptibility, WFS has little effect on top-down fatigue cracking resistance and moisture susceptibility of the mixtures [32]. When WFS replacement is higher than 15%, asphalt mix may become more sensitive to moisture damage (i.e. stripping) due to the presence of silica [10, 27]. WFS, on average, decreases the unconditioned tensile strength and thus the durability of asphalt mixtures; on the other hand, WFS do not necessarily increase or decrease a mixture's rutting potential but do improve fatigue performance [17].
