Proceedings of the International rilem conference Materials, Systems and Structures in Civil Engineering 2016

373

International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

 

 

Figure 5: continued 

 

 

4. Discussion of Test Results 

 

The flexural performances are evaluated in this section by considering mineral admixture 

incorporation compared with control specimens. The cement matrix negatively influences the 

BF fibre-matrix interface after 7 days. Drop rate in averaged flexural strains is evident (28%) 

from 7 days to 28 days [11]. It can be seen in SEM images that the appearance of fibre is no-

longer smooth, and the surface is filled with C-S-H more and more (Fig.6 a,b). Mineral 

admixture replacement retards the C-S-H deposits to 28 days and beyond it. In addition, the 

drop rate of strains in following curing times decreases as well. In all the experiments, both 

BF and GF presented high dimensional stability.  

C-S-H densification accelerates in severe wetting-heating durability cycles (Fig.6 c,d) as a 

result of ongoing hydration in cement particles. Consequently, a sharp brittle failure mode is 

observed even after first cycles. None of BF-NC,S1,S2 series gives rise acceptable 

performance in heat-rain cycles possibly due to the humid/warm conditions supporting 

hydration process.  

In BF-NC,S1, S2 series, it is interesting that remaining strain capacity after 100

th

 freeze-thaw 

cycles is in the range of 0.4-0.6%. Brittle behaviour of BF-specimens in the heat-rain cycles is 

not observed in freeze-thaw cycles (Fig.6 e,f). The structure of matrix and fibre ductility were 

improved with mineral admixtures.  

It is interesting that debonding and degradation in matrix are monitored in GF-S2 series  after 

freeze-thaw cycles, quite smooth surface of fibre and trace of debonding are observed in the 

SEM images (Fig.6 g,h). In heat-rain cycles, 20% increase in strain capacity is under 

consideration, however this enhancement may be a sign of partial debonding as well.  

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374

International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

 

 

 

 

 

 

   

 

(a)

 

                              (b)                                   (c)                                 (d) 

 

 

 

 

 

                (e)                                     (f)                                      (g)                                  (h)

 

Figure 6 : Schematical strain comparisons of BF- cementitious composites under flexure test 

and SEM micrographs from (a) BF, 7 days, 100% cement; (b) BF, 28 days, 100% cement;   

(c),(d) BF after heat-rain 50

th

 cycles, 100% cement; (e),(f) BF surface and cementitious matrix 

in BF-S1 after 100

th

 freeze-thaw cycle; (g),(h) cementitious matrix and trace of fibre 

debonding in GF-S2 after 100

th

 freeze-thaw cycle .  

 

 

5.   Conclusions 

 

 

In this study, the variations of flexural capacities at 3,7,28,56,90 and 120 days as well as at 

durability conditions of basalt fibre cementitious composites are addressed. It is aimed to 

improve BF-matrix interface by mineral additives and to compare GF-ones. The findings 

from this study are given below: 

 100% cement use gives rise to significant reductions in flexural capacity after 7 days in BF-

cementitious composites. Deposition of C-S-H and CH changes and densifies the fibre-matrix 

interface, and the failure mode leads to brittle behaviour due to overbonding. Any sign of 

C S H

Fibre

Trace

of fibre

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375

International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

alkali attack due to CH or lamination due to C-S-H deposits are not observed on the surface of 

basalt fibres. 

 By using sustainable natural or byproduct puzzolanic admixtures as from local sources, e.g 

nano clay and high-volume slag, strength and strain retention were provided up to 56 days, 

afterwards the drop trend especially in strains substantially slow down compared to 100% 

cement case. C-S-H accumulation on fibre surface induced embrittlement decreased 

significantly. 

 15% nano-clay use enhanced 28-day strength over 100% cement ones in BF-specimens, and 

decreased the strain reduction from 7 to 28 days. High slag ratios (50%, 80%) especially 

decreased the flexural strengths and strains of BF-ones higher than GF-ones. However the rate 

in strain reduction at the later curing periods decreased significantly.  

 It is interesting that 80% slag ratio affected fibre-matrix bond mechanism in GF-ones, the 

fibre debonding accompanies to matrix degradation under freeze-thaw conditions. This 

situation is partially observed in heat-rain test. 

 Further research is necessary to solve the brittleness of BF-cementitious composites during 

heat-rain test. Heating and wet conditions accelerate the hydration and lead brittle behaviour. 

Any degradation in matrix or debonding is not under consideration compared to GF-ones. 

New matrix modifications and maybe another surface treatment for basalt fibres may be 

experienced.  

 The freeze-thaw resistance of BRC were enhanced through the mineral admixtures. Flexural 

strains in the range of 0.4-0.6% become possible. Thus, a step to toward ductile failure mode 

was succeeded. This research will proceed with further experiments on this subject. 

 

 

Acknowledgement 

The experiments in this study were carried out in Fibrobeton Inc. Material, employer and 

equipment support of those firm to this experimental research are greatly appreciated. I’m 

also thankful to MSc student Cihan Yolcu for his assistance to compiling of some data and to 

Dr.Ali Can Zaman for his attention in SEM micrographs.   

 

 

References 

 

[1] Morova, N. Investigation of usability of basalt fibres in hot mix asphalt concrete. Constr  

Build Mater 47 (2013), 175-180. 

[2] Fiore V., Scalici T. and Bella G.D., Valenza, A  A review on basalt fibre and its 

composites. Composites Part B: Eng 74 (2015),74-94. 

[3] Sim, J., Park, C., Moon, D.Y. Characteristics of basalt fiber as a strengthening material for 

concrete structures. Composites Part B: Eng 36 (2005), 504–512. 

[4] Lee, J.J., Song, J. and Kim, H. Chemical Stability of Basalt Fiber in Alkaline Solution. 

Fibres and Poly, 15(11) (2014), 2329-2334. 

[5] Campione, G. et al. Behavior in compression of concrete cylinders externally wrapped 

with basalt fibres. Compos Part B, 69 (2015), 576–586. 

[6] Dias, D.P. and Thaumaturgo, C. Fracture toughness of geopolymeric concretes reinforced 

with basalt fibres. Cem Concr Compos 27 (2005), 49–54. 

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