Proceedings of the 7th World Congress on Mechanical, Chemical, and Material Engineering (MCM'21)
Prague, Czech Republic Virtual Conference – August, 2021
Paper No. MMME 119
DOI: 10.11159/mmme21.119

Synthesis and Mechanical Evaluation of Portland Cement Mortars
Reinforced With Silicon Carbide Powder
J.F. Gamarra-Delgado1, M.L. Benavides-Salinas, V.C. Bringas-Rodríguez1, C.K. Palomino-Naupa, D.L.
Mayta-Ponce1, G.P. Rodríguez-Guillén1, R.M. 1Zapana-Vilcapaza1
and F.A. Huamán-Mamani
Grupo de Investigación en Ciencia y Tecnología de Materiales, Departamento de Ciencias Naturales, UniversidadCatólica San Pablo, Arequipa, PerúUrb. Campiña Paisajista, Quinta Vivanco s/n, Arequipa 04001, Perúfrank.gamarra23@gmail.com; mirandabenavides7@gmail.com; veronicawnh@gmail.com; cpalominon@unsa.edu.pe;
dlmayta@ucsp.edu.pe; gprodriguez@ucsp.edu.pe; mzapana@gmail.com; fhuaman@ucsp.edu.pe
1

Abstract – Portland cement mortars reinforced with silicon carbide (SiC) powder were manufactured in this study. The volume of SiC
powder added to the mixtures ranged from 0 to 8 vol.% of the total volume of the mixtures studied, in addition the volume of SiC powder
added replaced equivalent volumes of fine sand, within a standard mix of Portland cement mortars. (75 vol.% of fine sand and 25 vol.%of Portland cement). SiC powder used was manufactured in the laboratory from the reuse of wood waste following wood pyrolysis
processes to obtain carbon powder, followed by thermodiffusion of metallic silicon into pyrolyzed carbon powder.
All manufactured mortars were studied physical, microestructural and mechanically by helium pycnometry tests, optical microscopy anduniaxial compression, respectively. The average real density found for all mortars was 2.1 g/cm3. The microstructure observed in mortars
suggests the presence of three well-differentiated phases (Portland cement, fine sand and SiC particles), while the mechanical data foundshows higher values of maximum resistance in mortars with 4 vol% SiC added, which would appear to be the most suitable amount of
SiC powder to be added to the Portland cement mortar mixture.
Keywords: silicon carbide, mechanical resistance, wood, powder, fine sand, reinforced agent

1. Introduction

Fabrication of biomorphic silicon carbide is made from wood precursors through pyrolysis process followed by silicon
infiltration.
The compressive strength of these biomorphic composites was found to be strongly dependent on their bulk density anddecreased as the test temperature increased [1,2]. Currently the wood industry in Peru generate large amounts of waste suchas shavings, sawdust and large and small cuts of wood. Many times, these wastes are reused in certain types of industries ascomponents or basic additives. It is starting to consider such waste as possible precursors for the manufacture of advanced
materials [3,4].
Silicon carbide manufactured from wood precursors (biomorphic SiC or bioSiC) has advantages due to its low
production cost, the diversity of microstructures, as well as being able to generate elements with complex shapes. Biomorphic
SiC is a material of proven potential in applications as structural reinforcers [5].
Biomorphic Silicon Carbide (SiC) has been widely used in industries due to its unique biological structure produced bynatural wood. SiC exhibits excellent low density strength. The importance of the fabrication of SiC using wood precursor
powders is based on the fact that the SiC ceramic produced is denser and the SiC is more homogeneous [6]. The demand for
repair and strengthening of concrete structures is a current issue in civil construction [7]. The selection of an applicablestrengthening material and method is essential in strengthening operations [8].
Deng [8] indicated that applying Highly ductile fiber-reinforced concrete (HDC) to strengthen the compression zone ofan over-reinforced concrete beam is a highly effective method to change its brittle failure and improve the ductility showing
an increase in flexural capacity and deformation.
A number of studies have been reported that the use of high ductile and high-performance cementitious fiber-reinforced
composites mortar such as Engineered Cementitious Composites (ECC) mortar can significantly enhance the brittleness ofconcrete [9]. Fischer and Li [10,11] applied Engineered Cementitious Composites (ECC) mortar to improve the seismic
performance of reinforced concrete columns and the effect of ductile deformation behavior of ECC. Resulting that theapplication of ECC to reinforced concrete members improves the deformation and load-carrying capacities.
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2. Materials and methods

Temperature (ºC)

Portland cement mortars reinforced with SiC powder were manufactured in two stages: (i) first, silicon carbide
powder was manufactured from wood residues, through consecutive processes of pyrolysis of wood residues (in an inert
atmosphere, 850 °C , 1 hour isotherm), thermodiffusion of metallic silicon into pyrolyzed carbon powder (in vacuum,1450 °C, 1 hour isotherm) and oxidative pyrolysis (500 °C, in air, 1 hour isotherm) and (ii) then Portland cement mortars
reinforced with SiC powder were manufactured, according to the volumetric compositions of table 1. The mortar
manufacturing process began with the dry mixing of the three components (table 1), then water was added in a water:
cement ratio of 0.5 and mixing was continued until a plastic and workable paste was obtained. The plastic mortar mixture
was pressed at 10 MPa in a 20 mm diameter metal mold, then allowed to set in water for 28 days.
1600
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
20010001450 ºC, 1 h.

Table 1: volumetric composition of the mortar mixtures
studied_________ Pyrolysis (inert atmosphere)_________ Thermodiffusion (vacuum atmosphere)_________ Oxidative pyrolysis (air atmosphere)

850 ºC, 1 h.

samplefine sand(vol.%)

portlandcement(vol.%)

SiC powder(vol.%)

AB
CDE

75737169672525252525

02468500 ºC, 1 h.

01234Time (h)5678Fig. 1: Thermal profiles for inert pyrolysis (blue line),
thermodiffusion (red line) and oxidative pyrolysis (greenline) processes

All manufactured mortars were physically, microstructurally and mechanically characterized. The physicalcharacterization consisted in the determination of real density by the technique of pycnometry, in this work a calibrated
glass pycnometer and distilled water were used. The microstructural characterization was carried out on polishedsurfaces of the manufactured mortars. The preparation of the samples for microscopy began with a fine grinding of thesurfaces, using SiC abrasive paper of # 600, # 800 and # 1200 grain, then the surfaces were polished using diamondpaste (6, 3 and 1 micron) and lubricating liquid. The polished surfaces were cleaned with plenty of distilled water andallowed to air dry, no grain development technique was used. Microstructural observations were made in an AMSCOPE
brand light microscope (50X - 500X), model ME320B-PZ (USA).
The mechanical tests consisted of uniaxial compression tests at a constant compression speed of 0.05 mm/min, in
an air atmosphere and were executed in a universal testing machine, MICROTEST brand, model EM1/50/FR, (Spain).
Samples for compression tests consisted of 10x5x5 mm3 parallelepipeds and were obtained from cylindrical samples ofhardened mortars. Force and displacement data were obtained from the mechanical tests, which were then converted
into stress vs. strain.

3. Results and Discussion

3.1. Physical and Microstructural Characterization
The real average density for all the materials studied was 2.1 g/cm3. Fig. 2 shows optical microscopy micrographsof the five types of mortars studied, two well differentiated phases could be appreciated, on one hand, a continuous
phase in dark gray contrast that corresponds to the agglomerating phase of Portland cement, and on the other hand,
individual particles dispersed within the continuous phase are seen, corresponding to fine sand particles (light grayphase) and SiC particles (bright white phase). In the micrograph of the mortar with 8 Vol% SiC powder, the identified
phases are indicated (FS: fine sand, PC: Portland cement and SiC: silicon carbide powder)

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0% SiC powder

2% SiC powder

4% SiC powder

6% SiC powder

8% SiC powder

PCFSSiCFig. 2: Optical microscopy micrographs of cement Portland mortars with various percentages of SiC powder added.

3.2. Mechanical Characterization
Fig. 3 (a) presents stress vs. average strain for the five types of mortars studied, from these curves a slight increase in
the deformation of mortars with added silicon carbide powder was observed, compared to mortars without the addition ofSiC powder (curve in blue). It was also possible to observe a systematic increase in the average maximum resistance, as thepercentage of SiC powder added to the Portland cement mortar mixtures increased, up to 4 Vol.% of SiC powder added. OnMMME 119-3

the other hand, Fig. 3 (b) shows the relationship between the average maximum resistance and the percentage of SiCpowder added, a maximum value of increase in mechanical resistance could be clearly appreciated (in comparison withmortar without SiC powder added) in mortars with 4 vol%. of SiC powder added, however, increases greater than 4Vol.% SiC powder added led to a reduction in average maximum strength.
120

150

110
90
80
7060
50
4030
20130
120
110
100
90
80

83.4

78.6

71.9

70

79.3
69.6

60
50100(b)140Maximum stress (MPa)100

STRESS (MPa)(a)

0% SiC powder
2% SiC powder
4% SiC powder
6% SiC powder
8% SiC powder

40
00.5

11.5
STRAIN (%)

22.5

30% SiC

2% SiC

4% SiC

6% SiC

8% SiC% SiC powder added

Fig. 3: (a) Stress vs. strain curves for the five types of mortars studied, (b) relationship between the maximum stress andthe percentage of SiC powder added.

4. Conclusions

Portland cement mortars reinforced with silicon carbide powder, in various percentages, were successfullymanufactured.
The average density found for all the mortars studied was 2.1 g/cm3, which indicated that the addition of SiC
particles to a mixture of conventional Portland cement mortar does not lead to increasing or reducing the density of thematerial after setting.
The microstructural evaluation revealed the presence of two well differentiated phases, on one hand, a continuous
phase that corresponded to the agglomerating phase of Portland cement and, on the other hand, individual particles
dispersed within the continuous phase, corresponding to the sand particles. fine and SiC powder.
The systematic increase of the average maximum resistance was evidenced, by increasing the percentage of SiC
powder added to the Portland cement mortar mixtures, up to a value of 4 Vol.% of SiC powder added, from which themaximum resistance decreases.

Acknowledgements

This work was financed by CONCYTEC - FONDECYT within the framework of call E041-01 with contract N°362018-FONDECYT-BM-IADT-AV and was executed in the laboratories of the Universidad Católica San Pablo.

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