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Soft Clay Treatment Using Geo-Foam
Beads and Bypass Cement Dust
Mahmoud Samir El-kady1,2* and Essam Farouk Badrawi1,3
1Faculty of Engineering, Department of Structural Engineering, Zagazig University, Egypt
2Department of Civil Engineering, Jouf University, Kingdom of Saudi Arabia
3 Department of Civil Engineering Department, University of Business and Technology, Kingdom of Saudi Arabia
Submission: October 01, 2018; Published: December 12, 2018
*Corresponding Author:Mahmoud Samir El-kady, Department of Civil Engineering Jouf University, Kingdom of Saudi Arabia.
How to cite this article:Mahmoud Samir El-kady, Essam Farouk Badrawi. Soft Clay Treatment Using Geo-Foam Beads and Bypass Cement Dust.
Civil Eng Res J. 2018; 7(1): 555701. DOI: 10.19080/CERJ.2018.07.555701
Soft clays are usually classified according to their undrained shear strength, Cu. Values of Cu less than 12.5kPa are associated with very soft clays, whereas, soft clays possess undrained shear strength ranging between 12.5kPa and 25kPa. In addition to the low shear strength of soft clays, they experience high compressibility upon loading. This is why soft clays are considered as problematic for foundation purposes. Also, Geo-foam is an industrial material, characterized by a very low unit weight (average of 20kg/m3) compared to that of the soil. Having a density ranging from 1.0% to 2.5% of that of soil EPS possesses a compressive strength ranging between 70kPa and 140kPa and an elastic modulus ranging between 5MPa and 12MPa, According to Horvath (1997). EPS Geo-foam blocks are used in a wide range of geotechnical applications as a light weight fill.
So, the main objective of this study is to investigate the geotechnical properties of soft clay with Geo-foam beads and bypass cement dust. Also, investigate the possibility of preparing low strength excavatable fill mixtures. For studying the effect of (Geo-foam beads + CBPD) / soft clay on fluid-state and hardened properties of new fill, experimental work was carried out on two groups of mixture (A&B). Different ratios of (Geo-foam beads + CBPD) were added to the mixture to study its effect on flow consistency, dry unit weight, unconfined compressive strength, and shear strength. The results of test conducted on the materials illustrated that, cement bypass dust and excess foundry sand can be successfully used to procedure self-compaction, self-leveling excavatable flowable fill material. The unconfined compressive strength of the studied mixtures without Geo-foam ranged between 271.8kPa and 1405.14kPa at CBPD between 3.88% and 18.63%. The Cohesion values for group with Geo-foam with ranged between 50kPa and 20kPa at Geo-foam between 0.32% and 1.35%. The friction angle of group with Geo-foam with ranged between 10 and 22kPa at CBPD between 0.32% and 1.35%.
EPS Geo-foam blocks are used in a wide range of geotechnical applications as a light weight fill. The primary function of Geo-foam is to provide a lightweight void fill below a highway, bridge approach, embankment or parking lot . EPS Geo-foam minimizes settlement on underground utilities. Geo-foam is also used in much broader applications, the major ones being as lightweight fill, green roof fill, compressible inclusions, thermal insulation, and (when appropriately formed) drainage. Expanded polystyrene (EPS) Geo-foam has been used as a geotechnical material since the 1960s. EPS Geo-foam is approximately 1% the weight of soil and less than 10% the weight of other lightweight fill alternatives. As lightweight fill, EPS Geo-foam reduces the loads imposed on adjacent and underlying soils and structures .
EPS Geo-foam is not a general soil fill replacement material but is intended to solve engineering challenges. The use of EPS typically translates into benefits to construction schedules and lowers the overall cost of construction because it is easy to handle during construction, often without the need for special equipment, and is unaffected by occurring weather conditions . EPS Geo-foam can be used to replace compressible soils or in place of heavy fill materials to prevent unacceptable loading on underlying soils and adjacent structures. The high compressive resistance of EPS Geo-foam makes it able to adequately support traffic loadings associated with secondary and interstate highways . Also, using EPS Geo-foam eliminates the need for compaction and fill testing, reduces the construction time and minimizes impact to the existing roadway and adjacent structures and/or buried utilities . Experimental work was
carried out on two groups of mixture (A&B) and different ratios
of (Geo-foam beads + CBPD) were added to the mixture to study
its effect on the geotechnical properties.
The experimental work was divided into two groups, each
with the same size of 600cm3. Group A was divided into five subsamples
without the use of Geo-foam and mixed with increasing
percentages of CBPD (50g) for each sample and different
percentages of water. In addition, the B group was divided into
five sub-samples and mixed with increasing percentages of
Geo-foam (5g) for each sample as well as different percentages
of water with stable weight of CBPD as shown in the following
Samples were mixed for groups A-B for different percentages
of water as shown in Figure 1b. The consistency flow of the
samples was measured for each sample. It is found that the
flow consistency increased slightly for group B than for group
A. So, the flow consistency was measured in laboratory as listed
in (Tables 6-7 ) for the two groups. Although the percentage of
water present in the B samples, the effect of the presence of Geofoam
beads than bypass cement dust on soil was clear as shown
in Figure 2.
The studied mixtures for each group were molded and
hardened. Unconfined compressive strength was obtained by
the Triaxial test for the studied mixtures as shown in Figures
3. It was found that with the increase of cement bypass dust,
the unconfined compressive strength increased significantly
and especially for the samples (A4 - A5) compared to a slight
increase in the values of the strain% as shown in Figure 4. Also,
compressive strength values are also stabilized with increasing
mixing rates in cement bypass dust from approximately 14
to18% as shown in Figure 5. This shows the significant effect of
cement bypass dust on compressive strength of studied samples.
Shear box test was carried out on the studied samples. The
samples were loaded with increasing stresses (50-100-150kPa)and the shear stresses were calculated versus horizontal
displacement (mm). We took samples (A4-B4) for examples as
shown in Figures 6-7. Shear strength parameters were obtained
from direct shear test and it is concluded that CBPD affected in
the cohesion of the group A samples as shown in Figure 8. On the
contrary, angle of internal friction was increased significantly
when increasing the ratio of Geo-foam beads for group B samples
as shown in Figure 9 [6-10].
This paper presented an experimental study of various
samples of soft clay mixed with different percentages of Geofoam
beads and cement bypass dust. The following conclusions
may be drawn:
A. The results of test conducted on the materials
illustrated that, cement bypass dust and excess foundry sand
can be successfully used to procedure self-compaction, selfleveling
excavatable flowable fill material.
B. The dry unit weight of the studied mixtures for group
without Geo-foam ranged between 1.40 and 1.6 gm/cm3 at
CBPD between 3.88% and 18.63%.
C. The dry unit weight of the studied mixtures for group
with Geo-foam ranged between 0.65 and 1.20 gm/cm3 at
Geo-foam between 0.32% and 1.35%.
D. The unconfined compressive strength of the studied
mixtures without Geo-foam ranged between 271.8kPa and
1405.14kPa at CBPD between 3.88% and 18.63%.
E. The unconfined compressive strength of the studied
mixtures with Geo-foam ranged between 230kPa and
120kPa at Geo-foam between 0.32% and 1.35%.
F. The Cohesion values for group without Geo-foam with
ranged between 62kPa and 105kPa at CBPD between 3.88%
G. The Cohesion values for group with Geo-foam with
ranged between 50kPa and 20kPa at Geo-foam between
0.32% and 1.35%.
H. The friction angle of group without Geo-foam with
ranged between 3 and 11° at CBPD between 3.88% and
I. The friction angle of group with Geo-foam with ranged
between 10° and 22° at CBPD between 0.32% and 1.35%.