Nghiên cứu nâng cao cường độ chịu kéo khi uốn và khả năng chống mài mòn của bê tông cát mịn đối với mặt đường bê tông xi măng tt tiếng anh

MINISTRY OF EDUCATION AND TRAINING

MINISTRY OF CONSTRUCTION

VIETNAM INSTITUTE OF BUILDING SCIENCE AND TECHONOLOGY
----------------------------------

NGO VAN TOAN

RESEARCH OF IMPROVEMENT OF TENSILE STRENGTH IN BENDING
AND ABRASION RESISTANCE OF FINE SAND CONCRETE FOR
CEMENT CONCRETE PAVEMENT

Specialization: Materials engineering
Code
: 9520309

SUMMARY OF DOCTORAL THESIS

HA NOI-2019


THE DISSERTATION IS COMPLETED AT:
VIETNAM INSTITUTE FOR BUILDING SCIENCE AND TECHONOLOGY

Academic supervisor:
1. Dr. HOANG MINH DUC
INSTITUTE OF CONCRETE TECHONOLOGY - VIETNAM INSTITUTE FOR
BUILDING SCIENCE AND TECHONOLOGY
2. Dr. NGUYEN NAM THANG
VIETNAM INSTITUTE FOR BUILDING SCIENCE AND TECHONOLOGY

Reviewer 1: A/Prof. Dr. Vu Dinh Dau
Reviewer 2: A/Prof. Dr. Nguyen Duy Hieu
Reviewer 3: Dr. Nguyen Duc Thang

This dissertation will be defended by Academy Doctoral Examination Boar at
Institute of Building Science and Techonology, 81 Tran Cung street, Nghia Tan,
Cau Giay District, Ha Noi at …… on the

day of

2019.

The dissertation may be read at:
- National Library of Vietnam
- Library of Vietnam Institute of Building Science and Techonology


LIST OF PUBLISHED SCIENTIFIC WORKS
OF AUTHOR RELATED TO THE DISSERTATION

1. Hoang Minh Duc, Ngo Van Toan "Study the effect of mortar residual coefficient
on the properties of concrete and fine sand concrete mixture using as cement
concrete pavement", Construction Magazine - Ministry of Construction No. 11,
2018.
2. Hoang Minh Duc, Ngo Van Toan "The impact of limestone grit on the abrasion
and shrinkage of fine sand concrete on cement concrete pavement", Journal of
Transport - Ministry of Transport, No. 12, 2018.
3. Hoang Minh Duc, Ngo Van Toan "Study on improving tensile strength in
bending and abrasion resistance of fine sand concrete using to make cement

concrete roads", Transport Magazine - Ministry of Transport, No. 6, 2019.
4.Hoang Minh Duc, Nguyen Nam Thang, Ngo Van Toan "Selecting concrete
components using fine sand according to tensile strength when bending", Journal
of Construction Science and Technology - Institute of Construction Science and
Technology, No. 2, 2019.
5. Ngo VanToan, Hoang Minh Duc "Selection of concrete components using fine
sand and stone grit mixing according to tensile strength when bending for cement
concrete pavement", Transport Magazine - Ministry of Transport, No. 7, 2019.


INTRODUCTION

1. Abstract
The more and more developed the country, the greater the need for travel, that
requires the construction of a higher and higher traffic system, resulting in an
increasing demand for materials used in the concrete industry. This leads to the
current general trend of making the best use of locally available aggregate
materials in concrete production to reduce construction costs. At present, the raw
sand source in the country is increasingly scarce while the fine sand source has
very large reserves distributed in many regions across the country that are less
interested in using in the concrete industry. To meet the needs of materials for
construction works, transportation ... besides the traditional materials such as raw
sand, it is impossible not to mention the fine material used for cement concrete in
general, especially concrete roads. Prior to this fact, the topic "Research of
improvement of tensile strength in bending and abrasion resistance of fine sand
concrete for cement concrete pavement" was conducted, contributing to
demonstrate the ability to use fine sand sources instead of raw sand to make
concrete used for cement concrete pavement and evaluate the feasibility of
applying this type of concrete to transportation and construction works,
construction, irrigation ... in our country.

2. Rationale of the Study
Raw sand reserves are limited, unevenly distributed, while fine sand is available in
many localities across the country that can be used to make cement concrete for
road surface. However, due to the size modulus of the small fine sand, in the past,
standards and technical guidelines used only fine sand for concrete with
compressive strength less than 30MPa and proportional correlation with
compressive strength above tensile strength when bending to reach level 1 (tensile
strength when bending only reaches 4.0MPa), abrasion is only <0.6g/cm2.
Therefore, if there is no improvement, the fine sand concrete is only suitable for
cement concrete pavement of grade IV or lower roads and yards. For I, II, III level
concrete roads, compressive strength over bending strength (Rn/Rku, MPa) requires
higher values, corresponding to not less than 40/5.0 for calves single-layer
pavement or I, II - level road and 35/4.5 pavement pavements for III-level concrete
pavement. The abrasion of concrete to the surface of cement concrete roads of
grades I, II and III also requires less than 0.3g/cm2. Therefore, the study to improve
the tensile strength of bending and abrasion resistance of fine sand concrete
meeting technical requirements for cement concrete pavement to grade I roads is
essential.
3. Research subject and scope
The research objective of the dissertation is to improve tensile strength in bending
and abrasion resistance of fine sand concrete used as cement concrete pavement for
I - level road.
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4. Subjects and research content
4.1. Research subjects:
Concrete uses fine sand and uses fine sand in combination with limestone grit to
make concrete pavement construction according to the normal vibration method,
namely: a) Concrete using fine sand: the tensile strength when bending is greater

than 4.5MPa, the abrasive value is obtained from (0.3÷0.6) g/cm2 for concrete
pavement of IV level road and below and yard; b) Concrete using limestone grit
combined with fine sand in a reasonable proportion: tensile strength when bending
is greater than 5.0MPa, abrasion less than 0.3g/cm2 for concrete pavement to I
level road.
4.2. Research content:
- Research an overview of the research situation and use of fine sand concrete in
the world and in Vietnam to build scientific issues to be solved.
- Researching theoretical basis to improve tensile strength when bending and
abrasion resistance of fine sand concrete for concrete pavement surface.
- Research and choose input materials.
- Research to improve tensile strength when bending and abrasion resistance of
fine sand concrete for cement concrete pavement.
- Research some properties of fine sand concrete for concrete pavement surface.
- Researching practical applications and assessing the economic efficiency of fine
sand concrete for cement concrete pavement.
5. Scientific significance
By theoretical and experimental research, the dissertation has established a number
of influential and dependent correlations in concrete with a small aggregate of fine
sand, fine sand mixture with stone grit, strong water reducing admixture in Rku
tensile strength (4.0÷7.0) MPa, as follows:
- Amount of water used for concrete;
- Correlating compressive strength of concrete with compressive strength of
cement and N/X ratio;
- Correlating tensile strength of concrete with cement tensile strength and N/X
ratio;
- Correlation between compressive strength and tensile strength of concrete;
- The impact of fine aggregate of fine sand, fine sand combined with stone grit on
the abrasion resistance of concrete;
- The effect of fine aggregate of fine sand, fine sand combined with stone cool to

some properties of concrete: soft shrink, dry shrink, strength development, water
resistance, elastic modulus of concrete;
- A number of technological requirements to restrict concrete surface cracking
during construction.
6. Practical significance
Using fine sand combined with stone grit and superplasticizer admixture, cement
(PC40, PCB40) can produce concrete for cement concrete pavement to grade I
2


roads with reduced cost from 10% to 15% compared to when using rough sand
transported remotely.
7. New scientific contributions of the dissertation
Experiments and practical applications have proved that:
- Using fine sand with fineness modulus (Mdl=1.2÷1.9) combined with crushed
stone (Mdl=3.6), cement (PC40, PCB40) and polycarboxylate ether can make
concrete with tensile strength when bending over 5.0MPa, compressive strength
over 40MPa and abrasion < 0.3g/cm2, suitable for making cement concrete
pavement to level I road.
- Using fine sand without crushed stone with cement and additives as above, the
tensile strength of concrete can be enhanced to be equivalent to that of concrete
when there is a combination of crushed stone (tensile strength when bending >
5.0MPa, compressive strength over 40MPa), but does not reduce the abrasion of
concrete to < 0.3g/cm2. Beside, concrete using fine sand is also dehydrated,
splitting mortar, softening stronger than concrete using coarse sand and concrete
using fine sand with crushed stone. Therefore, this type of concrete can only be
used as a concrete pavement of 4 - level roads or yards when appropriate
technological measures are applied to limit cracking of concrete surfaces.
Chapter 1. OVERVIEW OF RESEARCH AND USING OF FINE SAND CONCRETE

1.1. Overview of research situation and using of fine sand concrete
1.1.1. Classification and technical requirements for sand as aggregate for
concrete
In the Russian Federation, according to the GOST 8736-93 standards; GOST
26633-91 and "Instructions for use of fine sand and very fine sand for concrete
pavement and airport". In the United States, applying the AASHTO M6-93
standard; ASTM C33-03. In Vietnam, according to Vietnam standard TCVN 7570:
2006 "Aggregates for concrete and mortar - Technical requirements"; According to
Decision 778/1998/QD-BXD, "Technical instructions for selecting concrete
components of all kinds" and according to TCXD 127:1985 standard, "Fine sand
for making concrete and construction mortar - Instructions for use". Standards of
countries have not agreed on the scope of application of fine sand, generally, all
standards stipulate that sand is considered fine sand when the modulus of
magnitude is less than 2 (Mdl < 2).
1.1.2. The situation of research and use of fine sand concrete in the world
In the world, the study and use of fine sand to make cement concrete mainly in two
main directions: a) Using fine sand as aggregate in the manufacture of smallgrained concrete (also called sand concrete - concrete without large aggregates); b)
Use fine sand instead of all or part of the rough sand (M dl> 2), in ordinary concrete
(with large aggregate).
 Using fine sand as aggregate in manufacturing small-grained concrete, which
has been studied and used by many countries in the world: as in the former Soviet
Union; Russian Federation today; Algieri and France. However, the research
3


orientation of the thesis is to use fine sand instead of all raw sand in manufacturing
and producing ordinary concrete. Therefore, it is necessary to focus on the studies
of countries in the world in the following direction:
 Using fine sand to replace all or part of raw sand (M dl>2), in conventional
concrete, these studies have been researched and used by many countries in the

world: in the Soviet Union (former) Research on fine sand used in concrete has
been carried out quite early, especially for hydraulic concrete. Until the year of
1950s of the twentieth century, fine sand was standardized in "Technical guidelines
for using fine sand in hydraulic concrete". In the year of 1970 of the twentieth
century, Do-nhi-ep fine sand and Bar-khan was applied to concrete in a number of
hydraulic construction projects. A number of research works by Ki-ri-en-co, S.tonnhi-cop and Gu-Ba have also been published. By the year of 1980s of the twentieth
century, it was studied to use sand from the Enisei river to build SayanoShushenskaia hydroelectricity. Also during this period, one of the areas where fine
sand was widely used was in the transport, especially the manufacture of concrete
for roads and airports, which was done in the research of Research on road
construction) is considered as the basis for preparing the "Guidelines for the use of
fine sand in cement concrete for roads and airport pavements" and "Guidance for
the use of low-aggregate concrete of large quantities using fine sand in building
pavement of cars and airports”. In China since the year of 1965 of the twentieth
century, fine sand was also studied and put into use in concrete, this is mentioned
in the BGY Regulation 19-65, allows the use of sand with a module size greater
than 0.7 to make concrete. In 2009, the DuBai City project in the United Arab
Emirates used cement concrete that uses fine sand of (300÷400) kg per cubic meter
of concrete, resulting in compressive strength of the value of 45MPa.
Fine sand may be river sand but fine sand can also be desert sand, so in the Middle
East countries, many studies have been conducted with desert fine sand of high
fineness, moderately fine sand from 0.45 to 0.88. In China, the Tenggeli and
Maowusu desert sands with modules of 0.334 and 0.194 magnitudes have been
studied for use in mortar and concrete. In Australia, research on the use of desert
fine sand is also of interest. During the study of river sand used in concrete, Kim et
al. Studied cracked properties of concrete using crushed sand from limestone in
Korea, the results showed that when used in combination with sand. grinding from
limestone and sand has improved the intensity of concrete. In the study of author
XieZhi-Hua, took advantage of sand and crushed powder from seashells to make
cement concrete, the results showed that strength The degree of concrete is also
improved. In Asia, research by ‟RSNaidu, M Zai University Malaysia, Malaysia

and SE Ang, Open University Kebangsaan Malaysia ” studied the compressive
strength of concrete using fine sand, crushed sand and mineral additives, the results
showed that when replacing 20% of fine sand by sand grinding dust in concrete,
compressive strength of concrete is lower than when using fine sand alone, when
using 10% fly ash to replace adhesives in concrete components, the compressive
4


strength of concrete is increased. Concrete using dust grit sand combined with 10%
silica fume instead of the binder component shows that the strength of concrete
reaches the highest value.
1.1.3. The situation of research and use of fine sand concrete in Vietnam
The use of fine sand for concrete in Vietnam has been studied for a long time, such
as the topic ‟Using black sand of the Red River to produce concrete (CCA)" – Doc
Nguyen Van and Lan Hoang Phu chaired and reported the Conference of Concrete
throughout the North - 1967 ”. By the 70s of the twentieth century, the Institute of
Water Science Research and the Institute of Construction Science and Technology
had studied and applied fine sand concrete with the compressive strength  30 MPa
for a number of hydraulic works and civil construction. The study on “using fine
sand for concrete and construction mortar” - Nguyen Manh Kiem and Duong Duc
Tin, has been conducted with a number of different fine sand types in the Northern
region (Cao Lang, Vinh Phu, Ha Nam Ninh, Thai Binh, Hanoi). Types of sand
used in the study (Mdl=0.47÷1.97), compared with concrete using rough sand (Mdl=
2.20÷2.26) with the same compressive strength and tensile strength, prismatic
strength, elastic modulus, bonding strength between concrete and reinforcement,
water absorption, softening coefficient and contraction of concrete using fine fine
sand equivalent to raw sand. The abrasion resistance of concrete using fine sand is
inferior to that of concrete using raw sand. The topic also mentioned the use of
plasticizers as a cement saving measure. However, these are just initial studies, the
role of plasticizers when using fine sand has not been clearly defined. By the 90s of

the twentieth century, there were studies using fine sand of the Red River
(Mdl=1.1÷1.72) in intermittent concrete mixtures with intermittent levels of sand
loam different from (19÷40)%, the ratio of N/X from (0.40÷0.55), the amount of
cement used (233 ÷ 526) kg/m3, indicating that the slump of concrete mixes may
vary from (0 ÷ 18) cm, the intensity reaches from (28÷50)MPa. In 2005, studies
using fine sand to manufacture high-strength concrete at Hanoi University of
Construction were conducted with an additive system including mineral
admixtures and superplasticisers and fine sand (Mdl=1.08) used in research;
compressive strength of concrete to achieve values up to 98MPa (sample
10x10x10cm). In 2006, Vung Tau and Binh Thuan sands with modules of 0.95 and
1.31 respectively and NaCl content of about 0.06% are studied to make cement
concrete for highways construction. The research results show that the fine sand in
the sea can be used to make cement concrete for the construction of high-grade
pavement, the surface of low-grade automobile pavement and the pavement of
rural roads in suburban sea provinces. In 2006, a study on using Red river black
sand made low strength concrete, proposed fine sand (M dl=1.1) used to make
concrete with required strength over 10MPa, the authors also propose to use roller
compaction method for low strength concrete construction using fine sand. By
2010, there was a study on the use of fine sand and the mixture of rice husk ashslag ash additives to produce high strength concrete, resulting in the compressive
5


strength of concrete at the age of 28 days gained from (67÷80) MPa, chloride ion
permeability level is very low. In 2012, there was a study on the use of Song Hong
black sand (Mdl=1.0;1.5;2.0) and the workability of D3, D4 to produce 40MPa
concrete for local constructions in Hanoi. In 2013, fine sand in the Mekong Delta
(Mdl=1.21) was studied in concrete fabrication with a ratio of sand to the aggregate
of 0.34 to 0.40. The results show that when using fine sand, the decrease is about
(23÷25)% but the decrease level over time is less, compressive strength decreases
from (9÷15)%. The elasticity of the modulus is reduced (5÷7)% compared to when

using raw sand (Mdl=2.71). Fine sand concrete has a higher shrinkage than raw
sand concrete at age 60 days. Fine sand concrete has higher water absorption and
chloride permeability than raw sand concrete, but the waterproofing is equivalent
(declining at a high N/X ratio). In 2010, there was a study of mechanical properties
and applicability of sand concrete for building roads, the author used sand
(Mdl=1.73) used for sand concrete, achieving the value of the intensity of
compressive strength of concrete at the age of 28 days from (30÷40) MPa. In the
field of manufacturing concrete products, fine sand is also commonly used. At
Song Day Construction Material Joint Stock Company, Hong river sand
(Mdl=1.2÷1.5) has been used to produce culverts, manholes, box culverts ... At
Song Day Joint Stock Company - Hong Ha Petroleum also used fine Hong River
fine sand (Mdl=1,5) to produce autoclaved aerated concrete block (AAC) of
compressive strength 3 and 4.
 Regarding research on improving tensile strength in bending and abrasion
resistance for fine sand concrete, there have been some research works. The
outstanding contents and rules can be drawn from these studies: fine sand concrete
follows the general rules with cement concrete. The influence of fine sand on the
properties of concrete and concrete mixtures is reflected in changing the amount of
water used, the workability and the strength of concrete. However, the
characteristics and the degree of influence depend on the characteristics of the sand
as well as the use of concrete. On the other hand, in the standards and technical
guidelines of some countries around the world, the use of fine sand is still in the
open trend, so if appropriate and optimal technology measures are used component
of concrete, concrete can be made using fine sand to meet the technical
requirements and the amount of cement equivalent to the concrete using coarse.
 Summary of studies in the world and in Vietnam, it can be seen that fine sand
was initially used to make cement concrete roads at all levels. In order to develop
and expand these applications in practice, especially in the context of Vietnam,
more in-depth studies are needed as well as further clarification of one of the points
of particular interest, when using fine sand, there are some disadvantages such as

bending strength in bending and abrasion resistance of concrete using fine sand
lower than coarse sand. Therefore, the study to improve the tensile strength of
bending and abrasion resistance of concrete using fine sand equivalent to coarse
sand, meeting technical requirements for cement concrete pavement for roads at all
6


levels. is very necessary and has a scientific basis. The current surface of cement
concrete roads is usually constructed using roller-compacted and vibratory
technology, in the conditions in Vietnam, especially in remote areas, Northwest
areas with complex terrain, the work vibratory technology can be considered more
reasonable. Therefore, the thesis focuses on construction methods based on normal
vibration technology.
1.2. Characteristics and properties of cement concrete for road construction
Technological characteristics of cement-concrete for road construction are cast in
situ place concrete without cased beam and solidified in natural conditions.
Concrete cast, compaction and finishing are carried out by means of a specialized
apparatus which are suitable for the construction of relatively dry concrete
mixtures. Strength is the most important characteristic of cement concrete for road
construction, evaluated by two criteria: tensile strength during bending and
compressive strength in which tensile strength when bending is the main criterion.
The compressive strength used to evaluate the wear resistance of surface concrete.
Abrasion is also a major indicator of concrete for roads. Stability and deformation
properties are also an important characteristic of concrete for roads. Elastic
modulus of concrete characterizes the ability of concrete to deform under the effect
of a load. Shrinkage of concrete is an important property of concrete for making
roads.
1.3. Characteristics, properties and technical requirements for concrete
pavement surface
1.3.1. Characteristics and properties for cement concrete pavement

Cement concrete pavement is a high-grade hard pavement. The surface layer is a
cement concrete with very high stiffness, the computational model is on the elastic
floor (soil and road foundations). The main strength reinforcement of the sheet is
tensile strength during bending.
1.3.2. Technical requirements for cement concrete pavement
According to standard 22TCN 223-95; According to Article 5.2.a, Circular
No.12/2013/TT-BGTVT; According to the Minister of Transport's Decision No.
1951/QD-BGTVT of August 17, 2012: a) Tensile strength in bending: with cement
concrete surface of highways, grades I and II less than 5.0MPa, with pavements of
cement concrete grade III or lower not less than 4.5MPa. b) Abrasion: with the
cement-concrete pavement of expressways, I,II,III lever not bigger than 0.3g/cm2,
with pavements of cement concrete IV lever or lower not exceeding 0.6g/cm2.
1.4. The scientific basis of the dissertation
As analyzed above, the disadvantage of fine sand concrete is that it has
compressive strength, tensile strength when bending lower than coarse sand
concrete (10÷15)% when using the same amount of cement. and have the same
construction slump. In addition, fine sand concrete has low abrasion resistance, the
abrasion is usually from (0.3÷0.6) g/cm2 compared to the value (<0.3 g/cm2) in
rough sand concrete. Therefore, in order to use fine sand for road concrete,
7


improving the tensile strength of bending and the abrasion resistance of concrete
plays an important role.
1.4.1. Improvement of tensile strength when bending of concrete
The compressive strength (Rn) is closely related to the tensile strength of concrete
(Rku). The ratio between them commonly used in the concrete road design standard
is: Rn/Rku=30/4.0; 35/4.5; 40/5.0; 50/5.5. According to the relationship Rn (Rku) and
the ratio of water / cement (N/X), in order to improve Rn (or Rku), it is necessary to
improve the cement strength, reduce N/X and improve the quality of aggregate. In

specific field conditions, when the commonly used cement is PC40 (or PCB40),
aggregate is mined on site, the most feasible solution is to reduce N/X. For road
concrete (usually using stone with D max=40 mm, the slump of 2 ÷ 3 cm), the use of
water reducing admixture can compensate for the increase of water due to fine
sand without increasing cement. Water reducing admixture for road concrete is
rarely used due to the fear that they may reduce Rku of concrete due to the
smoothing effect of cement stone structure. However, in the case of using strong
water-reducing additives (polycarboxylate-based additives), it can be expected that
Rns will increase sharply (30 ÷ 40)% and lead to it Rk also increase, although the
increase is not expected as increase Rn (can be 20÷25% or higher if the additive
increases the uniformity of the structure of concrete). In addition, when choosing
concrete components, the application of mortar data higher than conventional
compressive concrete approximately (0.10÷0.20) also increases (5÷8)% Rku.
1.4.2. Improvement of the abrasion resistance of concrete.
According to the studies in the overview, fine sand concrete has poor abrasion
resistance because fine sand usually contains fine particles (≤ 0.14 mm) to 35%
compared to no more than 10% in standard sand of TCVN 7570:2006. For abrasive
concrete ASTM C33-03, also specify the amount of grain (≤ 0.075 mm) must not
exceed 3%. This fine-grained sand often flakes off the surface when rubbing or
grinding from the outside. To improve the abrasion resistance, it is possible to mix
more grit to reduce the percentage of fine particles in the small aggregate, while
creating a solid aggregate frame in the concrete mortar to keep the remaining fine
particles, increasing area of aggregate directly subjected to grinding. In addition,
the abrasion resistance of fine sand concrete can be enhanced by the use of large
aggregates with good abrasive resistance such as basalt, granite, high strength
limestone and when increasing their density in the concrete. cardboard. In the
context of the priority to use large amounts of locally exploited aggregate, the
increase in their density (reduction of mortar residue coefficient) leads to the
reduction of Rku so solution to use a part of stone grit from the mines themselves
will be the most feasible and practically feasible solution.

=> Thus, improving the tensile strength of bending (R ku) and abrasion resistance of
fine sand concrete to make cement concrete pavement in this topic is based on the
main scientific hypothesis:
8


- Use strong water reducing admixture (polycarboxylate based superplasticiser) to
simultaneously increase the tensile strength of bending and compressive strength
of concrete;
- Use a part of grit combined with fine sand to improve abrasion resistance and
tensile strength when bending for concrete.
1.5. Objectives of the research
Improvement of bending tensile strength and abrasion resistance of fine sand
concrete used as cement concrete pavement for I level road construction.
1.6. Subjects and research content
1.6.1. Research subjects
Concrete using fine sand and fine sand combined with limestone grit to make
concrete pavement construction by normal vibration method, namely: a) Concrete
using fine sand: tensile strength when bending greater than 4.5MPa, the value of
abrasion is obtained from (0.3÷0.6) g/cm2 used for concrete pavement of IV level
roads or lower and yards; b) Concrete using limestone grit combined with fine sand
in a reasonable proportion: tensile strength when bending is greater than 5.0MPa,
abrasion less than 0.3g/cm2 for concrete pavement to I level road.
1.6.2. Research content:
- Research an overview of the research situation and use of fine sand concrete in
the world and in Vietnam to build scientific issues to be solved.
- Research the theoretical basis to improve tensile strength when bending and
abrasion resistance of fine sand concrete for cement concrete pavement.
- Research and choose input materials.
- Research to improve tensile strength when bending and abrasion resistance of

fine sand concrete for cement concrete pavement.
- Research some properties of fine sand concrete for cement concrete pavement
- Researching practical applications and assessing the economic efficiency of fine
sand concrete for cement concrete pavement.
Chapter 2: MATERIALS AND RESEARCH METHODS
2.1. Materials used in the study
+ Cement: PCB40 Nghi Son; (PC40 But Son used to test the water reduction
efficiency of superplasticizer according to TCVN 8826:2011);
+ Coarse aggregates: Stone (Dmax=20mm) - Dong Ao - Ha Nam;
+ Crushed sand: M (<5mm) - Ha Nam;
+ Fine aggregate: Fine sand: C1 (Mdl=1.2); C2 (Mdl=1.6); C3 (Mdl=1.9) - Red
River; Raw sand: CV (Mdl=2.5) - Lo River;
+ Additive: Daltonmat-RDHP of Vietnam Spemat;
+ Mixture water: Hanoi.
2.2. Research Methods
2.2.1. Standard test methods
TCVN 6017:2015 (ISO 9597:2008); TCVN 6016:2011 (ISO 679:2009); TCVN
4030:2003; TCVN 7572-2:2006; TCVN 4506:2012; TCVN 7572-4:2006, ASTM
9


C469-10; TCVN 3016:1993; TCVN 3015:1993; TCVN 3108:1993; TCVN
3109:1993; ASTM C231-10; TCVN 3114:1993; TCVN 3116:1993; TCVN
3118:1993; TCVN 3119:1993; TCVN 3120:1993; TCVN 8864:2011; TCVN
8867:2011; TCVN 8866:2011.
2.2.2. Non-standard test methods
- Determination of dehydration and elasticity of concrete mixture is determined
based on TCVN 9204:2012, with some modified.
- Determine the shrinkage of concrete based on ASTM C157/157M-08, with some
modified.

Chapter 3: IMPROVEMENT OF TENSILE STRENGTH IN BENDING AND
ABRASION RESISTANCE OF FINE SAND CONCRETE FOR CEMENT
CONCRETE PAVEMENT

Tensile strength when bending is an important property for cement concrete
pavement. In Vietnam today, the selection of concrete components that meet the
requirements on tensile strength when bending is done under Decision No.
778/1998/QD-BXD. Accordingly, concrete gradation is still selected in accordance
with the compressive strength based on the Bolomey-Skramtaev formula (1):
Rb = A. Rx . ( + B)
(1)
Where: Rb, Rx - Concrete and cement intensity; X, N - Amount of cement and
water used; A - Material quality coefficient; B - Equation factor.
When designing components according to compressive strength, the value of R b,
Rx is the compressive strength of concrete and cement, the coefficient B is taken by
± 0.5 depending on the X/N ratio, coefficient A is determined according to the
investigation table depending on the quality of materials used.
According to Y.M.Bazenov, formula (1) can also be used to select concrete
components according to tensile strength in bending. Then Rb, Rx is the tensile
strength when bending of concrete and cement, coefficient B is taken by -0.2,
coefficient A is taken from the lookup table. However, the values shown in (1) are
based on cement test data using the method of plastic mortar and the use of
materials in the former Soviet Union. Therefore, these coefficients are likely not
suitable for the current situation in Vietnam. Besides, when designing concrete
components according to tensile strength in bending, attention should be paid to
mortar residuals (reasonable mortar residuals should increase by about 0.15÷0.20
compared to when designed according to compressive strength). When increasing
the mortar balance calculation, the work of concrete mixture will be reduced, so it
is recommended to select the appropriate initial amount of water to ensure
workability. On the other hand, using fine sand in concrete, the tensile strength of

bending and the abrasion resistance of concrete are reduced compared to when
using coarse sand. In order to improve the tensile strength of bending and abrasion
resistance of fine sand concrete equivalent to coarse sand, meeting the technical
requirements for concrete pavement to grade I, the use of water-reducing
10


admixture, increasing mortar residues and adding grit combined with fine sand is
really necessary.
3.1. Properties of concrete mixtures
3.1.1. Selecting concrete components for research
The dissertation has used the same type of PCB40 Nghi Son cement, stone (D max =
20mm), superplasticizer Daltonmat-RDHP, fine sand (C1,C2,C3), coarse sand
(CV), dust limestone (M) combines fine sand with the rate of replacing 40% of fine
sand with crushed stone. workability of concrete, Rku, amount of cement and N/X
ratio as recommended by Decision No.1951/QD-BGTVT. To ensure appropriate
construction conditions, the workability in the study is not immediately after
mixing but takes into account the loss of slump depending on the actual conditions
and weather of the construction. The use is higher than that required for cement
concrete pavement. Therefore, the amount of cement selected is 350 kg/m3, the rate
of additives according to the manufacturer's recommendations is 1% of the weight
of cement, the ratio of X/N=1.80; 2.00 and 2.30. Given an X/N ratio and sand
magnitude module, the experimental gradients are designed with two different
reasonable mortar residues for Rn and Rku according to Decision No.778/1998/QDBXD and TCXD 127:1985. In particular, the reasonable mortar residual coefficient
according to Rku was chosen higher than Rn from 0.15 to 0.20, Based on batches
and volume of concrete mixture using fine sand and concrete using fine sand
combined with crushed stone, calculated the actual concrete composition and
research results are presented in Table (3.1, 3.2).
3.1.1.1. Selection of concrete components using fine sand
No

1
2
3
4
5
6
7
8
9
10
11
12

Table 3.1. Studied components of concrete used (fine sand, rough sand)
Material quantity, kg/m3
Distribution parameters
Symbol
Cement
Water
Sand
Stone
PG
Mdl
Kd
X/N
CP1
349
193
642
1217

3.49
1.6
1.37
1.80
CP2
347
193
707
1143
3.47
1.6
1.53
1.80
CP3
347
174
613
1291
3.47
1.6
1.23
2.00
CP4
345
173
685
1205
3.45
1.6
1.39

2.00
CP5
347
151
672
1288
3.47
1.6
1.23
2.30
CP6
344
149
742
1199
3.44
1.6
1.41
2.30
CP7
346
173
564
1332
3.46
1.2
1.16
2.00
CP8
344

172
647
1237
3.44
1.2
1.33
2.00
CP9
346
173
692
1208
3.46
1.9
1.39
2.00
CP10
344
172
754
1130
3.44
1.9
1.56
2.00
CP11
347
174
697
1212

3.47
2.5
1.38
2.00
CP12
345
172
759
1134
3.45
2.5
1.55
2.00

3.1.1.2 Selection of concrete components using fine sand and limestone grits
No

Table 3.2. Components of concrete used (fine sand combined with grit, coarse sand)
Material quantity, kg/m3
Distribution parameters
Symbol
Cement Water M Sand Stone PG Mdl Mdlhh M/CLN Kd X/N

11


1
2
3
4

5
6
7
8

CPM1
CPM2
CPM3
CPM4
CPM5
CPM6
CP11
CP12

348
347
349
348
349
349
347
345

174
173
174
174
174
174
174

172

280
307
282
309
283
311
---

420
460
423
463
425
466
697
759

1214
1141
1217
1145
1217
1147
1212
1134

3.48
3.47

3.49
3.48
3.49
3.49
3.47
3.45

1.2
1.2
1.6
1.6
1.9
1.9
2.5
2.5

2.2
2.2
2.4
2.4
2.6
2.6
---

0.40
0.40
0.40
0.40
0.40
0.40

---

1.38
1.54
1.37
1.53
1.37
1.52
1.38
1.55

3.1.2. The relationship between the used amount of water and the workability
of the concrete mixture
3.1.2.1 Relationship between the used amount of water and the performance of
the concrete mixture using fine sand
Research results show that the slump of concrete mixture tends to decrease with
increasing mortar residual coefficient. The volumetric mass of a concrete mixture
is less affected by the sand category but only depends on the sand magnitude
module. The air bubbles content of the concrete mixture using different types of
sand in the study is not much different. The sand modulus has a significant effect
on the correlation between water use and the slump of the concrete mixture. When
using finer sand, the ratio of surface area increases the level of water absorption, so
the amount of water mixed to reach the same slump tends to increase with
decreasing sand modulus. Based on the above test results, combined with the
recommendations of Decision No.778/1998/QĐ-BXD, it is possible to create Table
3.6 to reference the initial preliminary water required for 1m3 of concrete using
fine sand. When using polycarboxylate-based superplasticizers for concrete
components to make cement concrete roads (priority for tensile strength in
bending) as follows:
Table 3.6. The initial amount of mixing water required for 1 m3 of concrete, liters

Maximum particle size of large aggregate Dmax=20mm
No
Slump, cm
Modulus of magnitude of sand, Mdl
1.2
1.6
1.9
1
1÷2
157
152
148
2
3÷4
163
158
154

3.1.2.2. The relationship between the used amount of water and the performance of the
concrete mixture using fine sand and crushed lime stone
Research results show that the slump of concrete mixture tends to decrease with
increasing mortar residual coefficient. The volumetric mass of a concrete mixture
is less affected by the sand category but only depends on the magnitude modulus of
the fine sand mixture with crushed stone. The air content of the concrete mixture
using fine sand and crushed stone in the study is not much different. The fineness
modulus of fine sand mixed with crushed stone has a significant effect on the
correlation between the amount of water used and the slump of the concrete
12

2.00

2.00
2.00
2.00
2.00
2.00
2.00
2.00


mixture. The amount of mixing water to achieve the same slump tends to increase
gradually in the direction of decreasing the modulus of the magnitude of the fine
sand mixture with crushed stone.
3.1.3. Ability to maintain the working properties of the concrete mixture
3.1.3.1. The ability to maintain the workability of concrete mixtures using fine sand
The study results showed that after 60 minutes, the slump of the concrete mixture
using fine sand decreased over time about 3cm, using coarse sand decreased by
about 2cm.
3.1.3.2. The ability to maintain the workability of a concrete mixture using fine
sand and limestone grit
The results of the study showed that after 60 minutes the slump of the concrete
mixture using fine sand and stone grout decreases over about 2cm equivalent to the
use of coarse sand and magnitude modulus.
3.1.4. Stratification of concrete mixture
3.1.4.1 Stratification of concrete mixture using fine sand
The research results show that with the same X/N ratio, the level of mortar
separation tends to increase gradually with the decrease of the sand bulk module,
the increase of mortar residual coefficient, the level of mortar separation for fine
sand. value of (1.8÷2.8)%, coarse sand is equal to 0% and all meet technical
requirements within the allowable limits according to TCVN 9340:2012. Mortar
separation for concrete using fine sand is of great value when the mortar residual

coefficient is high.
3.1.4.2. Stratification of the concrete mixture using fine sand combined with
limestone grit
Research results show that the use of grit combined with fine sand has limited the
splitting of mortar of concrete mixture compared to when using fine sand alone,
which means that the ability to improve the resistance abrasion of concrete to
cement concrete pavement.
3.2. Properties of concrete
3.2.1. Relationship compressive strength of concrete with compressive strength of
cement and X/N ratio
Analysis of experiment results in the former Soviet Union recommends that the value of
B coefficient be equal to -0.5 when the ratio of X/N <2.5 and equal to +0.5 when the ratio
of X/N>2.5. Then, formula (1) has the form:
Rbn = An . Rxn . ( + 0.5)
(2)
n
n
In which: Rb , Rx - Compressive strength of concrete and cement, MPa; An- Material
quality coefficient according to compressive strength; X, N- Amount of cement and water
in 1 m3 of concrete, kg. The study also showed that the An factor depends on the
proposed material quality of 0.55; 0.60; 0.65 (when X/N <2.5) and equals 0.37; 0.40; 0.43
(when X/N> 2.5), suitable for concrete with poor, medium and good quality materials.
Using materials in Vietnam, the An coefficient (when X/N <2.5) has been
determined to be valued at 0.50; 0.55; 0.60 and (when X/N> 2.5) has a value of
13


0.32; 0.35; 0.38 corresponds to concrete using poor, medium and good quality
materials. Several other studies have suggested that the value of An coefficient
(when X/N <2.5) is equal to 0.45; 0.50; 0.54 and (when X/N> 2.5) equals 0.29;

0.32; 0.34, corresponding to concrete using poor, medium and good quality
materials. Previous studies with fine sand in Vietnam were used as a basis to
recommend taking the value of B=0.5, and the An coefficient corresponds to the
poor, average and good material quality equal to 0.46; 0.52; 0.60 with sand of
modulus of magnitude (0.7÷1.1) and equal to 0.49; 0.55; 0.62 with sand with
modulus of magnitude (1.2÷2.0).
3.2.1.1. Relationship compressive strength of concrete using fine sand with compressive
strength of cement and X/N ratio
It can be seen that, although the studies use formula (2) as a basis for the selection of
concrete components according to compressive strength (Rn), the proposed coefficients
are different. Especially significant. Therefore, the study and supplement of the data to
determine the calculation coefficients will have high practical significance and be
mentioned in the research of the dissertation. To test the coefficients of formula (2), the
thesis has conducted experiments of gradients in Table 3.1, the research results are
presented in Table 3.13.

No
1
2
3
4
5
6
7
8
9
10
11
12

Table 3.13. Relationship compressive strength of concrete using
(fine sand, raw sand) and X/N ratio
Compressive strength,
Volumetric
Slump,
day-age, MPa
Symbol Mdl
Kd
X/N
mass,
cm
kg/m3
3
7
28
CP1
1.6
1.37 1.80
2400
17.0
16.3
29.2
33.2
CP2
1.6
1.53 1.80
2390
16.5
15.7
28.7

32.5
CP3
1.6
1.23 2.00
2420
11.0
19.3
35.6
40.5
CP4
1.6
1.39 2.00
2400
9.5
18.1
33.5
38.9
CP5
1.6
1.23 2.30
2450
8.0
33.5
45.5
50.8
CP6
1.6
1.41 2.30
2430
7.5

32.1
43.2
49.7
CP7
1.2
1.16 2.00
2410
10.0
17.3
31.2
35.1
CP8
1.2
1.33 2.00
2400
7.5
16.2
29.9
34.0
CP9
1.9
1.39 2.00
2420
12.5
21.4
39.5
44.1
CP10
1.9
1.56 2.00

2400
10.5
20.5
38.1
43.2
CP11
2.5
1.38 2.00
2430
14.5
22.8
43.1
47.7
CP12
2.5
1.55 2.00
2410
13.5
22.1
42.5
46.6

Based on the experimental results, CP concrete (1,3,5) were used with preferred
mortar residues for Rn and formula (2), coefficient B was kept fixed by -0.5. When
keeping the coefficient B constant, then for each pair (Rn - X/N ratio), one factor
An can be determined. The results of determining the An coefficient for each pair
of values and values for each material option at the age of 28 days are different,
presented in Table (3.14, 3.15).

14

Table 3.14. An coefficient with fine sand C2 and scale (X/N = 1.80; 2.00; 2.30)
coefficient An
No
Symbol
Mdl
Kd
X/N
1
CP1
1.6
1.37
1.80
0.51
2
CP3
1.6
1.23
2.00
0.54
3
CP5
1.6
1.23
2.30
0.57

Research results Table 3.14 shows that for the same Mdl=1.6 and the X/N ratio
varies from (1.80÷2.30), the factor An is equal to 0.51; 0.54; 0.57. Therefore, it is

possible to choose an average value of 0.54 (corresponding to X/N ratio=2.00), this
X/N ratio is used to study the properties of concrete and concrete mixture. concrete
using sand with different modulus of magnitude, so that An coefficient can be
determined for design work to select concrete components according to R n.
Table 3.15. An coefficient with different types of sand modulus and the same X/N ratio = 2.00

No
1
2
3
4

Symbol
CP7
CP3
CP9
CP11

Mdl
1.2
1.6
1.9
2.5

Kd
1.16
1.23
1.39
1.38

X/N
2.00
2.00
2.00
2.00

coefficient An
0.47
0.54
0.59
0.64

Research results Table 3.15 shows that An coefficient tends to decrease with
decreasing modulus of sand size. The study results also showed that the A n
coefficient increased as the X/N ratio increased and there was a significant change
according to the sand module. These values of An factor can be referenced and
used in the design of concrete component selection for concrete pavement surface.
With the above An recommended coefficient, when using cement (PCB40, PC40)
and superplasticizer can make ratio concrete (Rn/Rku), MPa is: 40/5.5 and 50/6.0
corresponds to the correlation of Rn/Rku ratio reaching level 2 level.
3.2.1.2. Relationship compressive strength of concrete using fine sand combined
limestone grit with compressive strength of cement and X/N ratio
To check the coefficients of formula (2), experiments of gradients are shown in Table 3.2,
the research results are presented in Table 3.16.

No
1
2
3
4

5
6
7
8

Table 3.16. Relationship compressive strength of concrete using
(fine sand combined with grit, rough sand) and X/N ratio
Compressive strength,
Volumetric
Slump,
day-age, MPa
Symbol Mdl Mdlhh
Kd
X/N
mass,
cm
kg/m3
3
7
28
CPM1
1.2
2.2
1.38 2.00
2430
10.0
21.3
38.8 43.7
CPM2
1.2

2.2
1.54 2.00
2420
9,0
20.4
37.4 42.8
CPM3
1.6
2.4
1.37 2.00
2440
11.0
22.1
40.4 45.6
CPM4
1.6
2.4
1.53 2.00
2430
10.0
21.2
38.5 44.5
CPM5
1.9
2.6
1.37 2.00
2440
13.0
23.2
42.1 47.8

CPM6
1.9
2.6
1.52 2.00
2440
11.5
22.1
40.8 46.3
CP11
2.5
-1.38 2.00
2430
14.5
22.8
43.1 47.7
CP12
2.5
-1.55 2.00
2410
13.5
22.1
42.5 46.6

Based on the experimental results, CPM concrete (1,3,5) and CP11 were used with
preferred mortar residues for Rn and formula (2) (coefficient B was kept fixed by 15


0.5). When keeping the coefficient B constant, then for each pair (Rn - X/N ratio),
one factor An can be determined. The results of determining the An coefficient for
each pair of values and values for each material option at the age of 28 days are

presented in Table 3.17.
Table 3.17. An coefficient with fine sand of different magnitude modulus coordinate
with grit, coarse sand and the same rate of X/N = 2.00
Coefficient An
No
Symbol
Mdl
Mdlhh
Kd
X/N
1
CPM1
1.2
2.2
1.38
2.00
0.59
2
CPM3
1.6
2.4
1.37
2.00
0.61
3
CPM5
1.9
2.6
1.37
2.00

0.64
4
CP11
2.5
-1.38
2.00
0.64

The research results show that the An coefficient tends to decrease when reducing
the magnitude modulus of (fine sand combined with gravel, coarse sand). A n
coefficient (concrete using fine sand combined with grit) is higher than A n factor
(concrete using fine sand), this shows that when adding limestone dust mixed with
fine sand, the coefficient An increase. The coefficient of An increases when the
ratio of X/N increases and there is a big change when changing the magnitude of
small aggregate module. These values of An can be referenced in the design of the
selection of concrete components for cement concrete pavement when using fine
sand and crushed stone. With the above An recommended coefficient, when using
cement (PCB40, PC40) and superplasticizer can make ratio concrete (R n/Rku), MPa
is: 40/5.5 and 50/6.0 corresponds to the correlation of R n/Rku ratio reaching level 2
level.
3.2.2. Relation tensile strength of concrete with tensile strength when bending of
cement and X/N ratio
According to Y.M. Bazenov, formula (1) can also be used to select concrete components
according to tensile strength in bending. Then the coefficient B is taken as a value of - 0.2.
and formula (1) has the form:
Rbku = Aku . Rxku . ( - 0.2)
(3)
In which: Rbku, Rxku - Flexural tensile strength of concrete and cement, MPa; Aku material quality coefficient according to tensile strength when bending; X, N - Amount of
cement and water in 1 m3 of concrete, kg. In which, Aku coefficient varies depending on
the quality of materials used. It can be seen that, although the studies use formula (3) as a

basis for the selection of concrete components according to tensile strength in bending
(Rku), the proposed coefficient has significant difference. Therefore, the study and
supplement of the data to identify the calculation coefficients has high practical
significance and is mentioned in the research of the dissertation.
3.2.2.1. Relation tensile strength of concrete using fine sand with the tensile strength of
cement and X/N ratio
To test the coefficients of formula (3), the thesis has conducted experiments of gradients
in Table 3.1, the results are presented in Table 3.18.
16


No
1
2
3
4
5
6
7
8
9
10
11
12

Table 3.18. The relationship of tensile strength when bending of concrete used
(fine sand, rough sand) and X/N ratio
Tensile strength when
Volumetric
Slump,

bending, day-age, MPa
Symbol Mdl
Kd
X/N
mass,
cm
kg/m3
3
7
28
CP1
1.6
1.37 1.80
2400
17.0
3.35
3.93
5.52
CP2
1.6
1.53 1.80
2390
16.5
3.96
4.34
5.78
CP3
1.6
1.23 2.00
2420

11.0
4.13
5.06
6.24
CP4
1.6
1.39 2.00
2400
9.5
4.21
5.34
6.51
CP5
1.6
1.23 2.30
2450
8.0
5.36
7.31
8.20
CP6
1.6
1.41 2.30
2430
7.5
5.73
7.47
8.45
CP7
1.2

1.16 2.00
2410
10.0
3.64
4.53
5.97
CP8
1.2
1.33 2.00
2400
7.5
3.95
4.81
6.29
CP9
1.9
1.39 2.00
2420
12.5
4.43
5.53
6.76
CP10
1.9
1.56 2.00
2400
10.5
4.57
5.72
7.02

CP11
2.5
1.38 2.00
2430
14.5
4.95
5.98
7.50
CP12
2.5
1.55 2.00
2410
13.5
5.20
6.29
7.72

Based on the experimental results, CP concrete (2,4,6) were used with preferred
mortar residues for Rku and formula (3), coefficient B was kept fixed by -0.2. By
keeping the coefficient B constant, for each pair (Rku-X/N ratio), an Aku coefficient
can be determined. The results of determining Aku coefficients for each pair of
values and values for each material option at the age of 28 days were presented in
Table (3.19, 3.20)..
Table 3.19. Aku coefficient with fine sand C2 and ratio (X/N = 1.80; 2.00; 2.30)
Coefficient Aku
No
Symbol
Mdl
Kd
X/N

1
CP2
1.6
1.53
1.80
0.40
2
CP4
1.6
1.39
2.00
0.41
3
CP6
1.6
1.41
2.30
0.45

The research results in Table 3.19 show that with the same Mdl=1.6 and the X/N
ratio varies from (1.80 ÷ 2.30), the A ku coefficient has a value of 0.40; 0.41; 0.45.
Therefore, it is possible to choose an average Aku coefficient value of 0.41
(corresponding X/N ratio=2.00), this X/N ratio is used to study the properties of
concrete mixtures. and concrete using sand with different modulus of magnitude,
from which to determine Aku coefficient for design work of selecting concrete
components according to Rku. This ratio (X/N=2.00) is consistent with the chosen
X/N ratio when determining the value of An coefficient in section 3.2.1.1, and is
also suitable for selection in calf components. concrete using fine sand and grit in
Section 3.1.1.2.
Table 3.20. Aku coefficient with different types of sand modulus of different sizes

and the same X/N ratio = 2.00
Coefficient Aku
No
Symbol
Mdl
Kd
X/N
1
CP8
1.2
1.33
2.00
0.39
2
CP4
1.6
1.39
2.00
0.41
3
CP10
1.9
1.56
2.00
0.44

17


4

CP12

2.5

1.55

2.00

0.48

Research results Table 3.20 shows that the Aku coefficients tend to decrease when
reducing the modulus of sand size. The study results also show that A ku increase
coefficient when X/N ratio increases and there is a significant change according to
tissue simulating the size of sand. These values of Aku factor can be referenced and
used in the design of concrete component selection for concrete pavement surface.
With Aku coefficients recommended above, when using cement (PCB40,PC40) and
superplasticizer can make road concrete with the ratio (Rn/Rku, MPa) is: 40/5.5 and
50/6.0 corresponds to the ratio correlation (Rn/Rku) ratio reaching level 2 level. It
can be seen that when the mortar residual coefficient increases, R ku of concrete
using fine sand tends to increase. Based on the above research results,
recommendations and selection tables of material quality coefficients (An, Aku) can
be used for reference in the practical application of calculating the selection of
concrete components using fine sand for roads when using cement (PCB40, PC40)
and superplasticizer, is presented as follows:
- When designing and selecting concrete components using fine sand according to
compressive strength, the reasonable mortar residue coefficient shall be used in
the table. Use the formula:
Rbn = An.Rxn.( – 0.5) (4) (with An material quality coefficient according to Table 3.15)
- When designing and selecting concrete components using fine sand according to

tensile strength when bending, it is recommended to use mortar residual coefficient
higher than the table lookup value from 0.15 to 0.20. Use the formula:
Rbku=Aku.Rxku.( -0.2) (5) (with Aku material quality coefficient according to Table 3.20)
3.2.2.2. Relations of tensile strength when bending of concrete using fine sand
combined with limestone grit with tensile strength when bending of cement and
X/N ratio
To test the coefficients of formula (3), the dissertation has conducted experiments
of gradients in Table 3.2, the results are presented in Table 3.21.
Table 3.21. Relations of tensile strength when bending of concrete used (fine sand
combined with grit, rough sand) and X/N ratio
Tensile strength when
Volumetric
Slump,
bending, day-age, MPa
No Symbol Mdl Mdlhh
Kd X/N
mass,
cm
kg/m3
28
3
7
1
4.70
5.94
7.62
CPM1
1.2
2.2
1.38 2.00

2430
10.0
2
CPM2
5.05
6.31
8.01
1.2
2.2
1.54 2.00
2420
9.0
3
4.89
6.19
7.95
CPM3
1.6
2.4
1.37 2.00
2440
11.0
4
5.21
6.57
8.35
CPM4
1.6
2.4
1.53 2.00

2430
10.0
5
CPM5
5.09
6.43
8.25
1.9
2.6
1.37 2.00
2440
13.0
6
CPM6
5.42
6.84
8.68
1.9
2.6
1.52 2.00
2440
11.5
7
2430
4.95
5.98
7.50
CP11
2.5
-1.38 2.00

14.5
8
2410
5.20
6.29
7.72
CP12
2.5
-1.55 2.00
13.5

18


Based on the experimental results, CPM concrete (2,4,6) and CP12 were used with
preferred mortar residues for Rku and formula (3) (coefficient B was kept fixed by 0.2). By keeping the coefficient B constant, for each pair (Rku - X/N ratio), an Aku
coefficient can be determined. The results of determining A ku coefficients for each
pair of values and values for each material option at the age of 28 days are
presented in Table 3.22.
Table 3.22. Aku coefficient with fine sand of different magnitude modulus combined
with grit, raw sand and the same X/N ratio = 2.00
Coefficient Aku
No
Symbol
Mdl
Mdlhh
Kd
X/N
1
CPM2

1.2
2.2
1.54
2.00
0.50
2
CPM4
1.6
2.4
1.53
2.00
0.52
3
CPM6
1.9
2.6
1.52
2.00
0.54
4
CP12
2.5
-1.55
2.00
0.48

Research results show that Aku coefficients tend to decrease when reducing
modulus of small aggregates (fine sand combined with grit, coarse sand). The
results showed that Aku coefficient (concrete using fine sand combined with
crushed stone) is higher than Aku coefficient (concrete using fine sand), this shows

that when adding limestone dust mixed with fine sand, the system A ku number
increases. The Aku coefficient increases as the X/N ratio increases and there is a big
change when changing the magnitude modulus of fine sand and gravestone. These
values can be used as reference in the design of preliminary selection of concrete
components using fine sand mixture and stone grit for concrete pavement surface.
With Aku coefficients recommended above, when using cement (PCB40,PC40) and
superplasticizer can make road concrete with the ratio (Rn/Rku, MPa) is: 40/5.5 and
50/6.0 corresponds to the ratio correlation (Rn/Rku) ratio reaching level 2 level. It
can be seen that when the mortar residue ratio increases, the R ku of concrete using
fine sand combined with stone grout also tends to increase. Based on the above
research results, recommendations and selection tables of material quality
coefficients (An, Aku) can be used for reference in the practical application of
concrete composition calculation using fine sand and dust. stones for sugar when
using cement PCB40, PC40 and superplasticizers, are presented as follows:
- When designing and selecting concrete components using fine sand and stone grit
in accordance with compressive strength, use reasonable mortar residues to
investigate tables. Use the formula (4) with An material quality coefficient according
to Table 3.17.
- When designing and selecting concrete components using fine sand and stone grit
in accordance with tensile strength when bending, it is recommended to use mortar
residual coefficient higher than the sheet value of 0.15 to 0.20. Use the formula (5)
with Aku material quality coefficient according to Table 3.22
3.2.3. Correlation between compressive strength and tensile strength of concrete
using fine sand and concrete using fine sand combined with limestone grit
3.2.3.1. Verify the ability to improve tensile strength when bending of concrete
using fine sand
19


Tensile strength when bending, MPa

Tensile strength when bending,
MPa

The dissertation has conducted
8,00
using a number of CP
7,00
representative gradients (8,4,10) in
6,00
Table 3.1, refer to the results in
5,00
Table 3.2 of Decision No.
4,00
778/1998 / QD-BXD. The results
Rn/Rku grade 1
3,00
are shown in Figure 3.18. The test
Rn/Rku grade 2
2,00
results show the ratio of
Rn/Rku - fine sand
1,00
compressive strength to tensile
0,00
strength when bending of concrete
0
10
20
30

40
50
60
Tensile strength, MPa
using fine sand in the 2 level area.
This proves that with the use of
Figure 3.18. Correlation between compressive strength and flexural
PCB40 cement, polycarboxylatetensile strength of concrete using fine sand at 28 days
based superplasticizer, and increase mortar residual coefficient, it is possible to improve
the tensile strength of bending of concrete using equivalent fine sand raw sand with the
modulus of magnitude, meeting the technical requirements of the tensile strength when
bending for concrete to make the level 1 road.
3.2.3.2. Compare the tensile strength of bending concrete using fine sand and
concrete using fine sand combined with limestone grit
10,00
The dissertation has conducted
9,00
using a number of CP
8,00
representative scales (8,4,10) in
7,00
Table 3.1, CPM (2,4,6) in
6,00
Table 3.2 and refer to the
5,00
results in Table 3.2 of Decision
4,00
No. 778 / 1998 / QD-BXD, to
Rn/Rku grade 1
3,00

Rn/Rku grade 2
compare the flexural tensile
2,00
Rn/Rku - fine sand
strength
improvement
of
1,00
Rn/Rku - Fine sand and stone grit
concrete using fine sand and
0,00
0
10
20
30
40
50
60
concrete using fine sand in
Tensile strength, MPa
combination with stone grit.
The results are shown in Figure Figure 3.19. Correlation between Rn/Rkuc ratio of concrete used (fine
sand, fine sand combined with grit) at the age of 28 days
3.19. Research results show
that the ratio (Rn /Rku) of concrete using fine sand combined with gravel is higher
than that of fine sand and is located on the level 2 area. PCB40 cement,
polycarboxylate - based superplasticizer, fine sand in combination with crushed
stone (40% replacement rate of fine sand) and increase mortar residual coefficient,
can improve the tensile strength of bending concrete. using fine sand and grit, and
achieving a higher value than when using fine or coarse sand alone. Meet the

technical requirements for cement concrete pavement to grade I (with tensile
strength when bending over 5.0MPa and abrasion less than 0.3g/cm2).
3.2.4. Abrasion of concrete
20


3.2.4.1. Abrasion of concrete using fine sand
Abrasion of concrete using fine sand was studied on CP gradients
(7,8,3,4,9,10,11,12) in Table 3.1. The abrasive results for concrete are presented in
Table 3.24.
Table 3.24. Abrasion of concrete used (fine sand, coarse sand) at the age of 28 days
Abrasion, g/cm2
No
Symbol
Mdl
Kd
1
CP7
1.2
1.16
0.40
2
CP8
1.2
1.33
0.45
3
CP3
1.6
1.23

0.39
4
CP4
1.6
1.39
0.44
5
CP9
1.9
1.39
0.31
6
CP10
1.9
1.56
0.33
7
CP11
2.5
1.38
0.20
8
CP12
2.5
1.55
0.24

Research results show that when the modulus of sand increases, the abrasion of
concrete at 28 days of age has a decreasing pulse (increased abrasion resistance).
Increasing mortar residue coefficient increases abrasion (reduced abrasion

resistance). The abrasion values of concrete using fine sand are in the range of
(0.3÷0.6)g/cm2, only meeting the technical requirements of abrasion for the
concrete surface for grade IV roads and yard.
3.2.4.2. Abrasion of concrete using fine sand combined with limestone grit
The abrasion of concrete using fine sand combined with limestone grit was studied
on the gradients shown in Table 3.2. The results of determination of concrete
abrasion are presented in Table 3.25.
Table 3.25. Abrasion of concrete used (fine sand combined with gravel, coarse sand)
at the age of 28 days
Abrasion, g/cm2
No
Symbol
Mdl
Mdlhh
Kd
1
CPM1
1.2
2.2
1.38
0.24
2
CPM2
1.2
2.2
1.54
0.28
3
CPM3
1.6

2.4
1.37
0.22
4
CPM4
1.6
2.4
1.53
0.26
5
CPM5
1.9
2.6
1.37
0.18
6
CPM6
1.9
2.6
1.52
0.23
7
CP11
2.5
-1.38
0.20
8
CP12
2.5
-1.55

0.24

Research results show that when the modulus of the magnitude of (fine sand
combined with grit, rough sand) increases, the abrasion of concrete at 28 days of
age has a decreasing pulse (increased abrasion resistance). When adding grit
combined with fine sand used in concrete, the abrasion resistance of concrete is
significantly improved, which is a reduction in abrasion compared to when using
fine sand alone and achieving a value of (0.18÷0.28)g/cm2 is equivalent to the
abrasion of concrete using coarse sand with the same modulus of magnitude. It can
be seen that combining grit with fine sand is one of the solutions that can improve
21


the abrasion resistance of concrete using fine sand. Thereby, it has improved the
level of application road from grade IV and yard (when using fine fine sand) to
grade I (using crushed stone combined with fine sand).
3.2.4.3. Verify the abrasion resistance of concrete
The concrete mixture used (fine sand, fine sand combined with grit) is relatively
homogeneous without stratification (no water separation, no mortar separation).
This can be proved that the use of grit combined with fine sand for concrete can
completely meet the technical requirements for concrete pavement for roads of all
levels.
Conclusion of Chapter 3:
1) Concrete using small aggregate is fine sand (M dl=1.2÷1.9) combined with 40%
stone grit (Mdl=3.6) with cement (PC40, PCB40), superplasticizer admixture
Polycarboxylate (1% by weight of cement) and large aggregate can usually reach
Rku over 5.0 MPa, abrasion (0.2÷0.3)g/cm2, equivalent to rough sand concrete
(Mdl=2.5) and can be used to make concrete pavement for roads up to grade I.
2) Concrete using small aggregate is fine sand (Mdl =1.2÷1.9) but not combined
with stone grit, with cement (PC40, PCB40), polycarboxylate based

superplasticizer (1 % by weight) cement) and large aggregate can usually reach R ku
over 5.0MPa, but the abrasion is only (0.31÷0.45) g/cm2, so it can only make
cement concrete pavement to the road level IV or yard.
3) Some relationships serving the design of road concrete components using small
aggregate are fine sand (Mdl=1.2÷1.9), fine sand combined with gravel (Mdl=2.2÷
2.6) with polycarboxylate-based superplasticiser has been drawn as follows:
a) Correlation between mixing water - slump and properties of concrete mixture:
The amount of water mixed with concrete mixture increased from (148÷157)l/m3
(with Dmax=20mm, The slump =1÷2 cm) when the module of small size of small
aggregate decreased from 2.6 (fine sand combined mites) to 1.2. For Dmax and the
other slump, the rule is the same as the instructions (Decision No.778/1998/QDBXD). In fine sand concrete (Mdl=1.2÷1.9), the separation of mortar (2.2÷2.6)%,
while this feature is not found in small aggregate concrete, is coarse sand or finegrained sand.
b) Reasonable mortar balance coefficient for concrete (Kdu - preferred mortar
residue coefficient)
When applying the priority mortar balance factor (Kdu) like ordinary concrete
(Decision No. 778/1998/QD-BXD), it shows that Rn reaches the highest value, the
abrasion reaches the lowest value; When increasing Kdu coefficient by 0.15±0.05,
reduced compressive strength (2÷4)%, tensile strength when bending increases
(4÷10)%, increased abrasion (0.04÷0.05) g/cm2. The selection of Kdu coefficient
can be made according to the priority criteria.
c) Correlation of intensity
- The compressive strength of concrete with the compressive strength of cement
and the N/X ratio is consistent with the Bolomey - Skramtaev formula, with a
22