Elsevier

Construction and Building Materials

Volume 105, 15 February 2016, Pages 69-81
Construction and Building Materials

Mechanical and durability properties of mortars prepared with untreated sugarcane bagasse ash and untreated fly ash

https://doi.org/10.1016/j.conbuildmat.2015.12.047Get rights and content

Highlights

  • Untreated sugarcane bagasse ash and untreated fly ash were added to mortars.

  • Compressive strength and UPV test of those mortars are discussed.

  • Electrical resistivity and rapid chloride permeability tests are also highlighted.

  • Correlations between mechanical and durability tests are established.

  • More reliable predictions of the properties of cementitious materials are needed.

Abstract

Mechanical and durability properties of mortars containing mineral admixtures were analysed. Mortar mixtures were prepared with a water-to-cementitious materials ratio of 0.60 and a cementitious/sand ratio of 1:3.5. A partial replacement of Ordinary Portland Cement (OPC) by 10% and 20% of untreated sugarcane bagasse ash (UtSCBA), and by 10% and 20% of untreated fly ash (UtFA) was used practically “as received”. The only post-treatment was to sieve SCBA and FA through No. 200 and No. 100 sieves, respectively. Compressive Strength (CS), Ultrasonic Pulse Velocity (UPV), Electrical Resistivity (ER) and the Rapid Chloride Permeability (RCPT) tests were carried out on cylindrical specimens. The addition of 10% and 20% of UtSCBA and 10% and 20% UtFA to the mortars had the following effects: the CS decreased generally for all the mortars at early ages but after 90 days was similar or surpassed the level of the control; the UPV decreased generally for all the mortars, except for the 10% UtFA mortar which surpassed the control at 180 days; the ER increased generally for all the mortars after only 14 days, especially when UtSCBA was used; the level of permeability decreased generally in all the mortars, but was especially true for the 20% UtSCBA mortar. Correlations between the results of the different tests evidence the need for further investigation of the influence of additives in mortar mixtures in order to develop more reliable predictions on the behaviour of the properties of cementitious materials.

Introduction

The use of pozzolanic materials in concrete or mortar mixtures as partial replacement of cement provides a satisfactory solution to environmental concerns and to the loss of durability that some reinforced concrete structures have. Studies have shown that pozzolanic materials have a significant amount of amorphous silica in their chemical composition. When pozzolanic materials are added to the cement, this silica (SiO2) reacts with the free lime from the hydration of the cement and new silicate hydrate products are formed, thus improving the mechanical and durability properties of the concrete [1].

The use of industrial waste as pozzolanic additions in concrete or mortar mixtures, and in particular the use of fly ash (FA), has been studied extensively. FA is a by-product of the combustion of pulverized coal in thermal power plants and is gathered by electrostatic precipitators from the combustion gases before they are discharged into the atmosphere. Only flying particles produced from the burning of the coal are attracted to the precipitators. Consequently, most of the FA is formed by silica and alumina rich particles with only a small amount of unburnt coal particles. As a result, FA reacts effectively with hydration products to form more dense and resistant cementitious products, improving in this manner the long-term mechanical and durability properties of concrete.

Research on FA shows that its presence improves the workability of mortars and concretes in their fresh state. In a their hardened state, the presence of FA also improves structural properties; however, this improvement occurs at later ages than in the mortars and concretes which have no FA [2].

FA improves the impermeability and durability of concrete. Some researchers have found that the replacement of 20% of cement with FA in concrete mixtures improved compressive strength and significantly delayed the corrosion initiation period due to the decreased permeability to chloride ions [3], [4].

As a result of the variability of both the coal composition and the burning conditions, the chemical properties of FA vary greatly and this variability has a significant impact on the properties of the cementitious materials where FA is used.

Grinding the FA and high-temperature curing have shown to reduce the variability and to improve the mechanical properties of mortars [5]. Recalcination can also be used to improve its pozzolanic activity. Finally, the addition of Calcium Hydroxide and Sodium Silicate to accelerate the cement early hydration and promote setting and hardening of mortars has been investigated [6]. There is an extensive developing body of knowledge on the effects of post-treated FA on alkali-silica reaction resistance, permeability modification, and corrosion resistance of Portland cement based concretes.

Recently, attention has been placed on the study of agricultural waste materials whose use has been shown to improve the mechanical and durability properties of reinforced concrete and mortar.

Some authors have reported that Sugar Cane Bagasse Ash (SCBA) has substantial amounts of Silica (SiO2), Alumina (Al2O3) and Ferric Oxide (Fe2O3) [1], [7], [8] and that these account for over 70% of the constituents of SCBA, indicating that SCBA can also be used as a mineral admixture.

According to Frias et al. [9], the method of capturing the SCBA and the conditions under which it is calcinated influence the chemical and mineralogical composition and pozzolanic material properties.

Cordeiro et al. [10] found that at 800 °C Cristobalite and Calcium were formed. The production of SCBA under controlled conditions helps to prevent the formation of crystalline phases and in this way increases its pozzolanic activity.

Some researchers have shown that a high percentage of the loss on ignition (LOI) of the SCBA has a negative effect on its pozzolanic activity. For example, the development of the compressive strength of mortars with an addition of SCBA with a high LOI value was less than for SCBA mortars with low LOI values [11].

Cordeiro et al. [12] analysed the influence of the particle size of the SCBA on the density and compressive strength and found that the reduction in the particle size of the SCBA resulted in an improvement in the pozzolanic activity.

It has been reported an increase in the compressive strength of concrete and mortar mixtures with an addition of SCBA and it has been also demonstrated that the optimal percentage of cement replacement is 20% [1]. On the other hand, Hernandez et al. [8] observed that a poor curing time of mortar specimens with an addition of SCBA had a negative effect on the compressive strength.

The effect of the addition of SCBA on the properties that determine the durability of mortar and concrete mixtures has received attention in recent research. Ganesan et al. [1] found that the replacement of 20% of cement with SCBA decreased permeability and penetration of chloride ions. Meanwhile, Hernandez et al. [8] found that the higher the content of the SCBA, the higher the content of chlorides in surface layers of mortar specimens, which led them to conclude that the addition of 10% and 20% of SCBA reduced the diffusion coefficient by about 50%.

The results obtained by different researchers show that when post-treated, SCBA and FA have significant pozzolanic activity and can be used as additives in concrete and mortar mixes, because they help to improve mechanical and durability properties.

Unfortunately, all the methods used to activate FA and SCBA demand a lot of energy, making it necessary to investigate whether or not the impairment of the properties of mortars or concretes caused by the use of untreated, “practically as received” ashes, is tolerable.

Therefore, this research proposes to evaluate the mechanical and durability properties of minimally treated SCBA and FA as a partial replacement for cement in mortar mixtures. Compressive Strength (CS), Ultrasonic Pulse Velocity (UPV), Electrical Resistivity (ER) and Rapid Chloride Permeability (RCPT) tests were carried out. The correlations between mechanical and durability testing results were analysed as well.

Section snippets

Experimental design

To evaluate the effects of untreated sugarcane bagasse ash (UtSCBA) and untreated fly ash (UtFA) mortars were prepared containing these materials at three levels. Tests of these mortars in fresh and hardened states were carried out. Details of the experimental design and experimental procedures for results in the hardened state are summarized in Table 1.

Materials

The materials used in this research consisted of Ordinary Portland Cement R-40 (OPC) according with the NMX-C-414-ONNCCE Mexican Standard. The

Chemical analysis

Table 3 presents the major oxides for OPC, UtSCBA and UtFA. The ASTM 618 establishes that for Class N and F pozzolans, the minimum value of the sum of SiO2 + Al2O3 + Fe2O3 should be higher than 70% and for pozzolans Class C higher than 50%.

For the UtSCBA and UtFA under study the sums are 88.27% and 93.95%, respectively, which are higher than the value recommended by the Standard to consider the materials as pozzolans. The results are consistent with those from the literature which have been

Conclusions and recommendations

Based on the results of the tests the following conclusions can be drawn:

  • 1.

    The addition of 10% untreated SCBA had the following effects on the properties of the mortars: a decrease in the Compressive Strength at early ages but an increase in strength at later ages to a level similar or higher than the control; a decrease in the Ultrasonic Pulse Velocity at each of the ages studied; an increase in the Electrical Resistivity at all ages, but especially at 90 days, when the increase was 2.4 times

Acknowledgments

The authors are grateful for the financial support of the Consejo Nacional de Ciencia y Tecnología of Mexico (CONACyT), the Instituto Politécnico Nacional of Mexico (IPN), COFAA-IPN, PIFI-COFAA-IPN Program, CIIDIR-IPN-Oaxaca. The authors also thank the Universidad Autónoma de Nuevo León (UANL), the Faculty of Civil Engineering of the UANL (FIC-UANL) and the Institute of Civil Engineering of the UANL (IIC-FIC-UANL), as most of the testing was carried out in these institutions.

References (51)

  • N. Chusilp et al.

    Utilization of bagasse ash as a pozzolanic material in concrete

    Constr. Build. Mater.

    (2009)
  • E.V. Morales et al.

    Effects of calcining conditions on the microstructure of sugar cane waste ashes (SCWA): influence in the pozzolanic activation

    Cem. Concr. Compos.

    (2009)
  • S.A. Abo-Qudais

    Effect of concrete mixing parameters on propagation of ultrasonic waves

    Constr. Build. Mater.

    (2005)
  • R. Hamid et al.

    A combined ultrasound method applied to high performance concrete with silica fume

    Constr. Build. Mater.

    (2010)
  • D. Breysse

    Non-destructive evaluation of concrete strength: an historical review and a new perspective by combining NDT methods

    Constr. Build. Mater.

    (2012)
  • R. Demirboga et al.

    Relationship between ultrasonic velocity and compressive strength for high-volume mineral-admixtured concrete

    Cem. Concr. Res.

    (2004)
  • J.M.R. Dotto et al.

    Influence of silica fume addition on concretes physical properties and on corrosion behaviour of reinforcement bars

    Cem. Concr. Compos.

    (2004)
  • A.A. Ramezanianpour et al.

    Influence of metakaolin as supplementary cementing material on strength and durability of concretes

    Constr. Build. Mater.

    (2012)
  • G. Fajardo et al.

    Corrosion of steel rebar embedded in natural pozzolan based mortars exposed to chlorides

    Constr. Build. Mater.

    (2009)
  • A. Lubeck et al.

    Compressive strength and electrical properties of concrete with White Portland cement and blast-furnace slag

    Cem. Concr. Compos.

    (2012)
  • V. Baroghel-Bouny et al.

    Easy assessment of durability indicators for service life prediction or quality control of concretes with high volumes of supplementary cementitious materials

    Cem. Concr. Compos.

    (2011)
  • C. Shi

    Effect of mixing proportions of concrete on its electrical conductivity and the rapid chloride permeability test (ASTM C1202 or ASSHTO T277) results

    Cem. Concr. Res.

    (2004)
  • A.A. Ramezanianpour et al.

    Practical evaluation of relationship between concrete resistivity, water penetration, rapid chloride penetration and compressive strength

    Constr. Build. Mater.

    (2011)
  • D.A. Koleva et al.

    Correlation of microstructure, electrical properties and electrical phenomena in reinforced mortar

    Mater. Charact.

    (2008)
  • W.J. Mc. Carter et al.

    Electrical conductivity, diffusion, and permeability of Portland cement-based mortars

    Cem. Concr. Res.

    (2000)
  • Cited by (105)

    View all citing articles on Scopus
    View full text