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USE OF CONSTRUCTION WASTE GENERATED IN THE CITY OF ALMERÍA IN THE MANUFACTURE

OF BASES AND SUB-BASES OF RURAL ROADS AND CONCRETE OF LOW STRENGTH

E. Garzón*, S. Martínez-Martínez**, L. Pérez-Villarejo** and P. J. Sánchez-Soto***

* Department of Engineering, University of Almería, Almería, Spain

** Department of Chemical, Environmental and Materials Engineering, University of Jaén, Jaén, Spain

*** Institute of Materials Science of Sevilla, CSIC – University of Sevilla, Sevilla, Spain

e-mail: egarzon@ual.es

Introduction

❑ At the Andalusian level, three million tons were generated in 2015

and the percentage that is recycled is similar to that registered at

the national level, however there is 44% of construction waste that

goes to uncontrolled landfills (Moreno and Bueno, 2020). Although

there is a Territorial Master Plan for Urban Waste Management in

Andalusia, where there is talk of an annual production of

12.200.000 tons, which means 5 Kg./hab./day. In this plan, Almería

was assigned 862.588 tons/year, most of this rubble corresponding

to municipalities with more than 5.000 inhabitants, where the

construction index registered the highest values in the years of the

construction boom (Decreto 218, 1999).

❑ On this point Aguilar (1997) indicates that the factors that influence

the volume and composition of the RCDs are: type of activity, either

construction or demolition, type of construction, age of the building,

volume of activity in the sector and policies in force in housing

matter. Regarding the importance, wood is more relevant in the

demolition of old houses, metals in the demolition of industrial

buildings, bituminous products are limited to repair works and road

expansion and plastics appear in recent construction works. Based

on the above, this research work has been carried out in the

municipality of Almería, in order to take advantage of construction

waste in earthworks and in the manufacture of concrete.

Experimental

❑ Aliquots of this material have been studied by different experimental techniques

such as: X-ray diffraction, X-ray fluorescence, scanning electron microscopy on

a sample previously metallized with gold, chemical analysis by dispersive

energies X-ray analysis and oven test up to 1000 ºC .

❑ On the other hand, its mechanical behavior has been determined by carrying

out the following tests:

▪ Texture according to UNE 103101 (1995) and Atterberg limits according to

UNE 103103 (1994) and UNE 103104 (1993).

▪ The material has been subjected to different degrees of compaction with a

normal proctor “1/2PN” (PN13 blows), “PN” (PN26 blows), “2PN” (PN52

blows) following the UNE 103500 (1994) standard.

▪ California Bearing Ratio (CBR) on the original material samples following

the UNE 103502 (1995) standard.

❑ With another part, HA-25/B/20/L type concretes were made with gravel,

standardized sand (100%), cement (CEM V/A SPV 32.5N) (UNE-EN 197-1,

2000), water and Sikament 390 additive (concrete 1), concrete 2 where 48%

recycled sand and 52% normalized sand were introduced and concrete 3 with

100% recycled sand. The dosage for this type of concrete was as follows:

gravel (1000 Kg/m3), sand (820 Kg/m3), cement (320 Kg/m3), additive at 1% of

the weight of cement and water (160 l). And its consistency (UNE 80303, 1990)

and compressive strength at 7 and 28 days were determined (UNE-EN 12390-

2, 2001, UNE-EN 12390-3, 2001, UNE-EN 12390-4, 2001).

Conclusions

❑ Construction waste generated in the metropolitan area of Almería can be reused as esplanades or sub-bases of roads

and highways, since it is a granular material with a very high CBR (36). However, its granulometry is not adequate and

the sulfur level is above 1%. These restrictions can be overcome by acting on the crushing machine, so that a larger

recycled aggregate is generated. And on the selective waste process, eliminating the gypsum responsible for the high

relative levels of sulfur.

❑ However, its use as a substitute for sand, for the manufacture of concrete, can only be used in percentages lower than

10% by weight of recycled aggregate, since higher percentages give very low compressive strength values, which

make its use unfeasible use in this application.

The authors would like to express appreciation for the support of Reciclados Almerienses 2005

Results and discussions

b) Application on rural roads:

The size of the aggregates leaving the crusher is between 0,08 mm - 25 mm. However, the characteristics of the

aggregates of this plant do not comply with the General Technical Conditions of Roads and Bridges (PG3) and Technical

prescriptions required in the Spanish standard UNE 146131 (2003), in its annex of “recycled aggregates” (Fig. 4), since its

granulometry is not included within the Spindle intervals (dashed lines). These deficiencies can be corrected by mixing

this material with another larger aggregate or by acting on the crushing machine in such a way as to increase the size of

the aggregate that comes out of the machine. It has also been observed that the dominant fractions are sand (56.9%) and

gravel with 38.4%, the rest is silt (4.7%). In addition, it has been impossible to determine the liquid and plastic limits

following the standards, since it is a material that does not present plasticity. All this allows this material to be classified as

GW (Well-graded gravel, sand-gravel mix, little or no fine grains), GP (Poorly graded gravel, sand-gravel mix, little or no

fine particles) or GM (Silty gravel, Gravel mix- sand, silt) according to the unified classification of Casagrande.

Figure 5 shows the evolution of density with increasing humidity when normal proctor energy is applied. Subsequently,

this curve is compared with those obtained at ½ PN and 2PN (Fig. 5). It can be observed that by increasing the

compaction energy applied to the rubble, there is an increase in the dry density. The decrease in required humidity is only

recorded when going from ½ PN to PN. However, going from PN to 2PN results in an increase in optimal humidity.

Observing that the differences between PN and 2PN are very small, this is associated with the fact that the efficiency in

the compaction energy applied to the soil decreases as the void index decreases and these decreases are high at the

beginning to decrease later.

In figure 6 is observed that the CBR is 36 to 100% of the PN, which makes it a selected soil (CBR≥20) for the formation of

esplanades (Art. 330 PG3). In addition, the swelling registered has been zero. This value is related to the majority

granulometric composition, formed by gravel and sand.

Figure 6: CBR of construction waste.

c) Application in the manufacture of concrete:

The results for the shape coefficient of the recycled aggregates do not meet the specifications of the EHE instruction for

structural concretes, since the percentage retained in the 8 mm and 16 mm aperture sieves is less than 0,2 (Table 2). In

the same way, with the dosage used it has been verified that the decrease in the Abrams Cone for the three concretes

has been between 0-1 cm. Which allows classifying these concretes in the group of dry consistency. Likewise, the

compressive strength at 7 days has been much higher in conventional concrete compared to concretes that incorporate

recycled sand, being concrete with 100% recycled sand the one that has registered the lowest levels of resistance to

compression. These differences have remained after 28 days. In Figure 7 it can be seen that by incorporating less than

10% of the plant's construction waste, the drops in compressive strength are not very high both at 7 and 28 days,

although the slope is greater at 28 days.

With these values of compressive strength so low, it is impossible to use it as sand to make concrete (Castilla, 2004).

These results confirm the need for a selection of the material that reaches the plant, so that it is used for the manufacture

of recycled aggregates: mortars, concrete, ceramic products. Eliminating debris with the presence of gypsum or wood that

generate very low compressive strength values.

Figure 1: Recycled plant details.

Figure 2: Sample of

recycled aggregate.

a) Physical and chemical characterization of the sample:

X-ray diffraction analysis of the crystalline phases present in the sample revealed the presence of quartz and

calcite as the major components, in addition to an average content of dolomite and albite, while illite,

chlorite/kaolinite, gypsum and iron oxides among other minor components. This composition reveals the majority

presence in the recycled material of lime mortar with quartz and limestone aggregates.

The iron oxide content of around 4,58% and of sulfur (1,23%) stand out, the latter related to the presence of

gypsum. This sulfur content is above the technical specifications (<1%) of the recycled aggregates standard

(Anexo PNE de norma UNE 146131, 2003). To avoid this problem, it will be necessary to carry out a selective

demolition, so that the construction elements where there is presence of gypsum are separated (Table 1).

The weight loss due to calcination at 1000 ºC is 15,30%, which is attributed to the presence of calcite and

dolomite. Subsequently, a study by electron microscopy was carried out, which facilitated the observation of a

very heterogeneous structure formed by particles of different sizes (Figure 3) and the presence of quartz crystals,

with their characteristic morphology.

Figure 4: Granulometric curve of recycled

Aggregate.

Figure 5: Evolution of humidity and dry density with

the compaction Energy of construction waste.

Figure 3: Scanning electron

microscopy (sample extracted

from an oriented aggregate

made from a mixture of

construction waste and distilled

water, left to stand (24 hours).

SiO2 (%) Al2O3 (%) Fe2O3 (%) K2O (%) CaO (%) MgO (%) Na2O (%)

39.13 9.55 4.58 1.62 21.42 3.50 0.68

TiO2 (%) P2O5 (%) S (%) Cl (%) Sr (%) Ba (%) Zn (%)

0.68 0.12 1.23 0.09 0.26 0.02 0.01

CBR index Value

100% compactation 36

95% compactation 27

Swelling Null

Shape coefficient (UNE

7238:1971)Retained on 4 mm

sieve0.237

Retained on 8 mm

sieve0.086

Retained on 16 mm

sieve0.015

Table 1: Elemental chemical composition of the construction waste sample.Table 2: Shape coefficient.

Figure 7: Compressive strength according to the

percentage of incorporation of recycled aggregate.