Olive pomace based lightweight concrete, an experimental approach and contribution

Due to conventional aggregates resources depletion, material recycling has become an economic and ecologic alternative. In this paper, locally available natural residues such as olive pomace were investigated, when partially incorporated in the concrete formulation, since the mechanical characteristics of lightweight aggregate concrete strongly depend on its properties and proportions. Lightweight aggregates are more deformable than the cement matrix because of their high porosity, and their influence on the concrete strength remains complex. The purpose of this paper is to investigate the aggregates properties on lightweight concrete mechanical behaviour through an experimental approach. In addition, the different substitution sequences and the W/C ratio on lightweight concrete behaviour were evaluated, in order to determine the W/C ratio influence on the improvement of the lightweight concrete mechanical properties while knowing that the mixing water quantity gives the cement paste manoeuvrability and mechanical strength effects. The last part of this paper, therefore, was to provide statistical survey for estimating strength and weight reduction through the different natural aggregate substitutions to improve the lightweight concrete properties. The results achieved in a significant olive-pomace lower adhesion with the matrix after the cement setting, making the lightweight concrete mechanical strength weak. However, this work can open several perspectives: Results modeling and correlation with an experimental approach, the evolution and determination of lightweight concrete characteristics when exposed to high temperatures and thermohydric properties.


Introduction
In this article, we wish to show that the building sector, being so polluting, can now become an ecological lung in terms of recycling waste to obtain ecological concrete. Moreover, in the construction of a certain number of structures, weight reducing lead to general cost-savings, concrete density may vary between 0.5 to 2 when using lightweight aggregates, but because the concrete has less density, then its compressive strength is lower [1]. Conventional aggregate resources are becoming increasingly depleted over the years, especially in the Saharan areas. These materials are expensive to store and storage sites are also scarce, environmental standards restrict the use of toxic materials. In addition, more processing is required for materials originating from natural environment involving treatment and crushing stations, and therefore, the cost of natural aggregate manufacture is high. That's why part of material recycling remains the best and effective option. [2].
Because the Algerian industry produces huge quantities of olive-pomace every year, lightweight concrete was composed with a variety of olive-pomace aggregates mixtures (731.332t) [3]. The objective of this experimental approach is to demonstrate that the lightweight concrete mechanical behaviour is affected by the aggregate porous properties when inserted in the cement formulation, making it more complex in terms of maneuverability and strength.

Experimental materials and procedures
Conventional concrete can be chosen via many methods, in our study case, the method of [4] was applied, which consists of making mixtures with different aggregates. The objective here is to produce an insulating concrete [1]. The S / C ratio remains constant, for all tests we use moulds Ø 16cm x 32cm, filled almost equally in three layers, this is to determine the lightweight aggregates influence on the lightweight concrete mechanical behaviour, 16x32 cm test tubes were made with a variable matrix and a different aggregates percentage. During material mixing, the subsidence of Abrams cone and density were determined for each batch, density is used to possibly correct the mixtures proportions [5].

CMSS-2017
-The matrix is made of CPJ-CEM II / A 42.5 cement mortar and non-core sand [6].

Sand of Sidi Bel Abbès area(Algeria)
The report covers the majority of analysis results led by the Laboratory of the engineering department on the sand quarry of Sidi Bel Abbes area.

Fig1. Aggregates granulometric analysis.
By curve analysis, we found out that the gravel granulometry and alluvial sand has a continuous shape which will affect the concrete quality, durability and strength.

Physical properties
Alluvial sand from the area of Sidi Bel Abbes (North West Algeria). The equivalent of sand [7] shows that it is clean, and good for a quality concrete. The characteristics are reported in table.1 below. Minor constituents (0 to 5% Calcium sulphate is added as a setting regulator).

Aggregates choice
The choice fell on the olive-pomace based lightweight concrete " fig. 2" from the area of Sig (Wilaya of Mascara -Algeria) , due its abundance and important natural features [9]. Knowing that the mechanical properties of lightweight concrete strongly depend on its aggregates proportions present in the concrete formulation, in particular due to their high porosity, lightweight aggregates are more deformable than the cement matrix and have a complex influence on the concrete strength.
As part of the previous research carried out on lightweight concretes, this one aims to understand the behaviour of light aggregates, an experimental part was carried out where the olive pomace was pre-wetted before being introduced into the mixtures, the absorption rate reached 35% during the first days, followed by a longterm stabilization. sand Gravel1 Gravel2 Table 4.Olive-pomace physical properties

Adjuvant
The adjuvant is a plasticizer that helps to decrease the water quantity in the cement matrix and to increase the mechanical strength. These additives W / C ratio.

Lightweight concrete formulation
Through this experimental work, the lightweight concrete is formulated of olive pomace Dreux formulation methods, to determine the substitution rate, rheology and compactness of light concretes.

3.2
Lightweight aggregates effects on mechanical properties.
On the basis of elementary formulations, the W / C ratio as well as olive pomace substitution in the concrete preparation, then correcting the 1.20, in a way to introduce this ratio in our final composition, in order to achieve objectives.

CMSS-2017 physical properties.
The adjuvant is a plasticizer that helps to decrease the water quantity in the cement matrix and to increase additives help reduce the

Lightweight concrete formulation
experimental work, the lightweight olive pomace aggregates, using Dreux formulation methods, to determine the substitution rate, rheology and compactness of light concretes.

Lightweight aggregates effects on
formulations, by varying substitution in the correcting the G / S ratio to ratio in our final to achieve objectives.

Fig.3. Concrete compressive strength
It can be seen from " fig. 3" that the olive concrete has low compressive strength (light) concretes, the compressive strength decreased increasing the olive pomace dosage. The decreasing resistance throughout 28 days the nature and the substitution rate of the natural aggregates as well as the cement dosage.
The lightweight aggregates concrete determined by the concrete composition, through the W / C ratio " fig. 3", the Aggregate/ Cement content. The concrete strength is higher if the W / C ratio is lower [10]. However, too little water may not be able to completely hydrate the cement and may lead to a concrete strength drop and may limit the variations in the W / C ratio during the concrete manufacture due to high aggregates absorbency, whic drained [5].

Olive-pomace rate in lightweight concrete
Concrete compressive strength that the olive-pomace-based has low compressive strength than conventional compressive strength decreased by pomace dosage. The decreasing resistance throughout 28 days depends on the nature and the substitution rate of the natural aggregates as well as the cement dosage.
aggregates concrete strength is determined by the concrete composition, through the W / , the Aggregate/Sand volume ratio and the Cement content. The concrete strength is higher if the W However, too little water may not be able to completely hydrate the cement and may lead to and may limit the variations in concrete manufacture due to , which must be saturated and Test tube crack line subjected to the compression fracture lines corresponding to the by [5]. It demonstrates the the maximum stress of the lightweigh concrete is along Oz and picture 4", however, the maximum 60% pomace rate in lightweight concrete EG1 EG2 EG3 stress of the conventional concrete is along Ox axis, according to [5].

Void volume variation based on W / C ratio
The notion of compactness, being an intrinsic characteristic of the mixture had to be well defined during the solid suspension elaboration. I were random mixtures, so the aim was with granular materials of different densit purpose, the relationship between minimal porosity and granular extent was investigated. In order to improve the processing and and to reduce the concrete porosity, many carried out on the water content measurement of lightweight concrete by making hydrostatic weighing tests on olive pomace-based lightweight C, the results shown in " Fig. 5" show temperature affects the material characteristics, the pre wetting of the lightweight aggregates prove essential part in the manufacture of lightweight concrete by granting it a long-term fundamental kin the hydration of the cement. There is a good correlation between the void volume and the W / C ratio, demonstrated by [10].

CMSS-2017
stress of the conventional concrete is along Ox axis,

Void volume variation based on W / C ratio
, being an intrinsic had to be well defined during the solid suspension elaboration. In practice, they was to fill the space with granular materials of different densities. For this purpose, the relationship between minimal porosity and Void volume variation based on W/C ratio at 60° C.
processing and the compaction, many tests have been carried out on the water content measurement of hydrostatic weighing weight concrete at 60 ° " show that the drying temperature affects the material characteristics, the prewetting of the lightweight aggregates proved to be an essential part in the manufacture of lightweight concrete term fundamental kinetics affecting the hydration of the cement. There is a good correlation between the void volume and the W / C ratio, as -the concrete composition, through the W/C ratio " Fig. 6". -the Aggregate/Sand volume ratio.

compressive strength evolution based on
-the cement content. The compressive strength of the the W/C ratio, that is to say [11]. However, too little water may not be able to fully hydrate the cement, and may lead to a concrete strength drop, and possibly limit the variations of the during the concrete manufacture absorbency, which must be saturated and drained Compressive strength evolution based on W/C ratio.
lightweight aggregate concrete resistance is the following elements: the concrete composition, through the W/C ratio Sand volume ratio.
strength of the concrete is higher than the water quantity is low However, too little water may not be able to fully hydrate the cement, and may lead to a concrete strength limit the variations of the W/C ratio rete manufacture high aggregates , which must be saturated and drained [5]. and the substitution rate of the natural aggregates as well as the cement dosage.

Water quantity influence on the concrete compressive strength
The water quantity is a major factor that impact lightweight concrete strength, since lightweight aggregates undergo pre-wetting before they are introduced into the mixture, the amount of water added will be directly related to the effective W Fig. 8. Compressive strength and the mixing water relation.
" Fig. 8" represents the concrete mixtures with a variation in the W/C ratio, the quantity actually used (mixing water) to increase subsidence in accordance with natural aggregate substitution rate.
" Fig. 8" shows that the evolution according to the quantity of water added to the olive concrete and the conventional lightweight concrete similar behaviour, this leaves us to conclude that the cement hydration is normal. Finally, the substitution rate of natural aggregate concrete does not ex have an acceptable long-term resistance. the strength drop rises slightly in the course of time for each lightweight concrete composition.

Elastic properties of lightweight aggregates
It is hard to describe the grain strength aggregates; it has more elastic properties [12].
It can also be seen that their high porosity reduces the wall effect, and the transition zone are normal aggregates. The thin interfacial zone is characterized by mechanical and chemical

Water quantity influence on the concrete
is a major factor that impacts on the strength, since lightweight wetting before they are introduced into the mixture, the amount of water added W/C ratio.
. Compressive strength and the mixing water " Fig. 8" represents the concrete mixtures with a variation in the W/C ratio, the quantity actually used (mixing water) to increase subsidence in accordance with natural shows that the evolution according to the ity of water added to the olive-pomace-based conventional lightweight concrete have this leaves us to conclude that the the substitution rate concrete does not exceeding 35%, term resistance. As a conclusion, rises slightly in the course of time for rties of lightweight aggregates the grain strength in lightweight elastic properties [12].
It can also be seen that their high porosity reduces the are different to the interfacial zone is racterized by mechanical and chemical linkage between the paste and the facial aggregates different authors [13,14].

Concrete test tubes subjected to compression
A group of test tubes subjected to the same test should appear more or less identical to the naked eye, however, these test tubes contain structural defects of various sizes, up to the microscopic scale purpose, Weibull distribution uniaxial stress, using it to test material resistance simple sollicitations. The ability to resist undoubtedly one of the most important and most studied characteristics of materials. A separation into two or more pieces under stress [15] In many areas such as building, this ability to resist breakage is considered as safety feature. What is the maximum stress the probability of fracture is less than 1%. A statistical survey will be applied on to reduce the maximum stress that the probability of rupture is less than 1% [15]. It is clearly seen on the obtained curve Weibull distribution was used: Where m: Weibull modulus.

a-The assumptions
The weibull distribution is assumptions, which we present here: 1-The fracture strength of each volume element is modelled by independent variables. The randomness aspect makes allows taking into account the dispersion; Independent sub-volumes imply that there is interaction between infinitesimal volumes, which means that the fracture is a purely punctual phenomenon [16]. 2 -The fracture of the infinitesimal volume containing the first activated fault brings about the ruin of the inspected structure: in other w fracture occurs, the mechanical functions of the whole piece are lost [16]. Water quantity -L between the paste and the facial aggregates as defined by he cement matrix.

Concrete test tubes subjected to
of test tubes subjected to the same test appear more or less identical to the naked eye, contain structural defects of es, up to the microscopic scale. For this distribution is presented in case of ing it to test material resistance under The ability to resist fractures is undoubtedly one of the most important and most studied characteristics of materials. A fracture of a material is the separation into two or more pieces under stress [15].
In many areas such as building, this ability to resist safety feature. Question is: maximum stress that can be applied so that is less than 1%. survey will be applied on these data in order to reduce the maximum stress on lightweight concrete so that the probability of rupture is less than 1% [15]. n on the obtained curve the fact that : : The probability of survival.
is based on two simple assumptions, which we present here: he fracture strength of each volume element is modelled by independent variables. The randomness aspect makes allows taking into account the dispersion; volumes imply that there is no interaction between infinitesimal volumes, which means that the fracture is a purely punctual phenomenon [16].
of the infinitesimal volume containing the first activated fault brings about the ruin of the structure: in other words: as soon as the occurs, the mechanical functions of the whole