Physical and mechanical properties of cement mortar made with brick waste

The development of new building materials is a current problem where researchers are trying to find the right materials for each region and returning cheapest countries. Recycling and recovery of waste are now considered as a promising solution to meet the deficit between production and consumption and protecting the environment. This work focused on the study of the effect of brick waste in the production of cement mortar with substitution rates ranging from 5-30% by weight of cement and to compare its performance with fresh and hardened state with ordinary mortar considered as control mortar. Compressive and tensile strengths up to 28 days of age were compared with those of controlled mortar. Water absorption was also measured at 28 days of age. The test results indicate the beneficial effect of brick waste powder on performance of cement mortar with an optimum of 15% of cement weight substitution.


Introduction
The manufacturing of cement, mortar and concrete, as is the case with many industrial materials, consumes a considerable amount of energy, generates large quantities of greenhouse gases (estimated today to 1 tone of CO 2 per 1 tone of cement produced in the world), contributes to the gradual depletion of natural resources and leads to the production of certain residues which must be eliminated.
In order to ensure the growth of these indispensable building materials, the sustainable development approach must be integrated into their production, thus achieving a balance between environmental protection constraints and economic and social considerations [1][2][3][4][5].Therefore, in view of the increasing need for materials resources and the need to preserve the environment in a sustainable development vision, it has become necessary and relevant to explore all possibilities for reuse and recovery of waste and -industrial products, particularly in the field of civil engineering.However the waste storage disposals are becoming also a serious environmental problem, especially for main cities where disposal sites are lacking.Wastes from construction materials, materials factories, demolition sites, earthquakes and natural disasters are until now rarely used in Algeria: there is hence a need for recycling more and more waste materials.
The need to find new and cheaper binders has led manufacturers to produce various cements containing in addition to clinker, secondary additions with varying proportions.In Algeria, blast furnace slag and pozzolana are used as an additive to cement.Other local materials can also be used and valorized.And it is in this context that our study takes place.It aims to develop new composite cement based on brick waste and having a strength class of 42.5MPa.These by-products of the red products industry, which remain little used or recycled so far, are relatively abundant in Algeria because of the high number of brickyards and the discharge rates (noncompliant or broken bricks) They generate and account for 10 to 15% of their productions [6,7].
The terracotta products are really very durable and their resistance to the test proves it.Moreover, studies carried out by several researchers have shown the beneficial effect of the use of this type of waste [8][9][10][11] in addition to the pozzolanic character of the latter [8, [12][13][14][15][16].
The objective of this work is to study the effect on physical and mechanical properties of mortar made with fine crushed brick waste powder.Cement is substituted by weight by bricks waste powder at rates varying from 0, 5, 10, 15, 20, 25 and 30%.Compressive and tensile strengths are evaluated and compared up to 28 days of age.Capillary water absorption is also measured at 28 days of age

CMSS-2017
The powder used in the manufacturing of cement mortar derives from the brick waste from the brickworks of Draa Smar in Médéa.Once the waste was received, it was crushed by a laboratory jaw crusher which allowed us to obtain a material whose grain size is 0-5 mm.After they are placed in a disk mill to convert them into fine powder, with fineness comparable to that of the cement used (3500 cm 2 /g).Its absolute density has a value of 2.66 g/cm 3 .
For the fineness modulus of sand used is about 2.50, we combined two sands: 0/3 roller siliceous sand (S1) from the region of Hassi Bahbah (28%) and 0/4 crushed limestone sand (S2) from the quarry of Mont Guorno (72%).The grain size distribution of roller and crushed sand is presented in "figure 1" and their physical properties are summarized in Table 1.To ensure satisfactory workability of the brick waste-based mortars, a water-reducing plasticizer adjuvant manufactured by the company Granitex-NP and marketed under the name "MEDAFLOW 145" was used in this study which does not exhibit a retarding effect.Its normal range of use is fixed by the data sheet of 0.3 to 2% of cement weight, and its specific gravity is of 1.06 g/cm 3 .Fig. 1.Particle size distribution of used sand and coffee waste.

Mix design
For the purpose of this study, a reference mortar is made from 100% cement named MT.And seven (07) other mixtures are prepared by replacing the cement by different % of brick waste (5, 10, 15, 20, 25 and 30%).
In order to determine the quantities of The different materials: sand, cement, water and plasticizer of this mortar, we based on the standard formulation method for normal mortar (S/C = 3 et W/C = 0.5) [21], with some modifications made in the determination of water to cement ratio (W/C = 0.54) in order to adapt the requirements of local materials, taking into account their absorption rate and to get a good plasticity of mortar in fresh state.
The composition adopted for the control mortar and the mortars based on brick waste is that corresponding to the composition which gave satisfactory workability and comparable to that for a normal sand-based mortar (Flow time in LCPC maneabilimeter is close to 10 seconds) [22].The optimum compositions of the various mixtures are shown in Table 2.

Characterization of mortar mixes in fresh state
Preliminary tests on non-adjuvant brick waste mortars have shown that this waste adversely affects the workability of mortar in LCPC maniabilimeter [22], which confirms the results found by several researchers [23][24][25]12].This decrease in workability appears due to the high rate of absorption of brick waste in addition to the irregular shape of its grains [26].
In order to be able to compare the different types of brick waste mortar with the control mortar, the mixtures must have the same workability.This requires the reformulation of the mortars with brick waste.For this, we used a plasticizer admixture to keep the same flow time of the brick mortars with the control mortar.
The admixture need for the different mortars is shown in "figure 2".It can be seen that the demand of plasticizer in brick waste mortars increases with the increase in the percentage of waste in the mortar.

Mechanical strength
In order to better understand the relative evolution of compressive and tensile strength of the different mortars with age and in function of the rate of substitution of brick waste and to allow comparison with the control mortar, we present this evolution under histogram form given in "figure 3" and "figure 4".respectively.
The first point to be emphasized in these figures is that, at a young age, the resistance of mortars based on brick waste decreases with the increase in the rate of substitution in waste.It is also noted that mechanical performance develops in the early days of hydration.Figure 3 also shows that the resistances of all mortars increase steadily with age and show no fall.It is also observed that the initial resistances of the various mortars (at 3 days) reach 50% compared to that of the 28 days.At the age of 28 days, the strength of mortars MBr 5%, MBr 10% and MBr 15% exceed that of the reference mortar which is probably due to the pozzolanic activity of this material according other researchers [12][13][14][15][16].

Water absorption
The results of capillary water absorption test for mortars mixes carried out are summarized in "figure 5".This figure shows that the mortar based on the brick waste absorbs less water than the control concrete.This it may be due to the pozzolanic reactions of brick waste which have improved the compactness of mortar structure.

Table 1 .
Physical properties of sand used.

Table 2 .
Mix proportion of mortar mixes