29-09-2014, 12:34 PM
Recent Trends in Replacement of Natural Sand With Different Alternatives Project Report
Recent Trends.pdf (Size: 335.86 KB / Downloads: 80)
ABSTRACT
Cement, sand and aggregate are basic needs for any construction industry. Sand is a prime
material used for preparation of mortar and concrete and which plays a major role in mix design. Now a day’s
erosion of rivers and considering environmental issues, there is a scarcity of river sand. The non-availability or
shortage of river sand will affect the construction industry, hence there is a need to find the new alternative
material to replace the river sand, such that excess river erosion and harm to environment is prevented. Many
researchers are finding different materials to replace sand and one of the major materials is quarry stone dust.
Using different proportion of these quarry dust along with sand the required concrete mix can be obtained. This
paper presents a review of the different alternatives to natural sand in preparation of mortar and concrete. The
paper emphasize on the physical and mechanical properties and strength aspect on mortar and concrete.
Keywords- Sand, Quarry Stone Dust, Alternative Material, Physical Properties, Mechanical Properties.
INTRODUCTION
Cement, sand and aggregate are essential needs for any construction industry. Sand is a major material
used for preparation of mortar and concrete and plays a most important role in mix design. In general
consumption of natural sand is high, due to the large use of concrete and mortar. Hence the demand of natural
sand is very high in developing countries to satisfy the rapid infrastructure growth. The developing country like
India facing shortage of good quality natural sand and particularly in India, natural sand deposits are being used
up and causing serious threat to environment as well as the society. Rapid extraction of sand from river bed
causing so many problems like losing water retaining soil strata, deepening of the river beds and causing bank
slides, loss of vegetation on the bank of rivers, disturbs the aquatic life as well as disturbs agriculture due to
lowering the water table in the well etc are some of the examples. The heavy-exploitation of river sand for
construction purposes in Sri Lanka has led to various harmful problems [1]. Options for various river sand
alternatives, such as offshore sand, quarry dust and filtered sand have also been made (W.P.S. Dias et al
2008)[2]. Physical as well as chemical properties of fine aggregate affect the durability, workability and also
strength of concrete, so fine aggregate is a most important constituent of concrete and cement mortar. Generally
river sand or pit sand is used as fine aggregate in mortar and concrete. Together fine and coarse aggregate make
about 75- 80 % of total volume of concrete and hence it is very important to fine suitable type and good quality
aggregate nearby site (Hudson 1997). Recently natural sand is becoming a very costly material because of its
demand in the construction industry due to this condition research began for cheap and easily available
alternative material to natural sand. Some alternatives materials have already been used as a replacement of
natural sand such as fly-ash, quarry dust or limestone and siliceous stone powder, filtered sand, copper slag are
used in concrete and mortar mixtures as a partial or full replacement of natural sand (Chandana Sukesh et al
2013)[9]. Even though offshore sand is actually used in many countries such as the UK, Sri Lanka, Continental
Europe, India and Singapore, most of the records regarding use of this alternative found mainly as a lesser
extent of practice in the construction field [3].
DIFFERENT ALTERNATIVES MATERIALS TO RIVER SAND
The world is resting over a landfill of waste hazardous materials which may substitutes for natural
sand. Irrespective of position, location, scale, type of any structure, concrete is the base for the construction
activity. In fact, concrete is the second largest consumable material after water, with nearly three tonnes used
annually for each person on the earth. India consumes an estimated 450 million cubic meter of concrete annually
and which approximately comes to 1 tonne per Indian. We still have a long way to go by global consumption
levels but do we have enough sand to make concrete and mortar? Value of construction industry grew at
staggering rate of 15 % annually even in the economic slowdown and has contributed to 7-8 % of the country’s
GDP (at current prices) for the past eight years. Thus, it is becoming increasingly discomforting for people like
common people who talk about greening the industry to have no practical answer to this very critical question.
In fact we have been sitting over a landfill of possible substitutes for sand. Industrial waste and by-products
from almost all industry, which have been raising hazardous problems both for the environment, agricultural and
human health can have major use in construction activity which may be useful for not only from the economy
point of view but also to preserve the environment as well. Some of the researchers did the work to find the
alternatives for natural sand and they concluded about different industrial waste and their ability to replace the
much sought after natural river bed sand.
PHYSICAL AND MECHANICAL PROPERTIES DIFFERENT ALTERNATIVES
Copper slag:
The slag is black glassy particle and granular materials in nature and has a similar particle size range
like sand. The specific gravity of the slag is 3.91. The bulk density of granulated copper slag varies from 1.9 to
2.15 kg/m3 which is almost similar to bulk density of convectional fine aggregate. The hardness of the slag lies
Granulated Blast Furnace Slag:
The granulated blast furnace slag (GBFS) is glassy particle and granular materials in nature and has a
similar particle size range like sand. The specific gravity of the slag is 2.63. The bulk density of granulated slag
varies from 1430 kg/m3 which were almost similar to bulk density of convectional fine aggregate. The water
absorption of slag was found to be less than 2.56 %.The presence of silica in slag is about 26% which is
desirable since it is one of the constituents of the natural fine aggregate used in normal concreting operations.
The fineness of slag was 2.37.
Investigation was carried out on cement mortar mix 1:3 and GBFS at 0, 25, 50, 75 and 100%
replacement to natural sand for constant w/c ratio of 0.5 is considered. The work is extended to 100%
replacements of natural sand with GBFS for w/c ratios of 0.4 and 0.6. The flow characteristics of the various
mixes and their compressive strengths at various ages are studied. From this study it is observed that GBFS
could be utilized partially as alternative construction material for natural sand in mortar applications. Reduction
in workability expressed as flow can be compensated by adding suitable percentage of super plasticizer [6].
The strength characteristics of conventional concrete and slag concrete such as compressive strength, tensile
strength were found. Six series of concrete mixtures were prepared with different proportions of CS and FS
ranging from 0% to 100%. The test results of concrete were obtained by adding of Copper Slag (CS) and
Ferrous Slag (FS) to sand in various percentages ranging from 0%, 20%. 40%, 60%, 80% and 100%. All
specimens were cured for 7, 28, 60 & 90 days before compression strength test and splitting tensile test. The
results indicate that workability increases with increase in CS and FS percentage. The highest compressive
strength obtained was 46MPa (for 100% replacement) and the corresponding strength for control mix was
30MPa. The integrated approach of working on safe disposal and utilization can lead to advantageous effects on
the ecology and environmental also. It has been observed that upto 80% replacement, CS and FS can be
effectively used as replacement for fine aggregate. Further research work is needed to explore the effect of
CS+FS as fine aggregates on the durability properties of concrete [
CONCLUSION
1. An improvement in the compressive strength, split tensile strength and flexural strength of concrete by
addition of copper slag can be seen. The density of concrete increases with replacement of copper slag in
concrete. There is increase in the flexural strength of the beam by 21% to 51% while replacement of copper slag. By partial replacement of sand by copper slag, the strength increase is observed up to 40% replacement.
Copper slag replacement at higher level leads to segregation and bleeding due to less water absorption capacity
of copper slag. Author was also observed that the sand replaced copper slag beams showed an increase in energy
absorption capacity.
2. It was also observed that the increase in compressive strength of cement mortar with the replacing the GGBS.
This increase is not significant. But for 100% replacement the strength decreases a little bit compared to 100%
natural sand. Author concluded that GGBS sand can be used as an alternative to natural sand from the point of
view of strength and recommended to replace up to 75%.
3. It can be concluded that 30% of Washed Bottom Ash (WBA) can be replaced with sand in concrete is the
optimum amount to get favorable strength, saving in environment and reducing the cost.
4. There is improvement in the compressive strength of the concrete by partial replacement of quarry dust with
sand. Due to absorption of the water by the quarry dust, decreases the workability of concrete with increase in
quarry dust quantity. The recommended percentage of the replacement of sand with the quarry dust is between
55% to 75% in case of compressive strength. The 100% replacement of sand can be achieved by addition of fly
ash along with quarry dust. For mortar, stone powder is well suitable to choose it as an alternative of sand. The
availability of the stone powder is depends on the locality and its price is mar vary. If the stone powder is
available in the market, it can be used as an alternative to sand and it is observed that concrete made stone chip
will have higher compressive strength compared with that of concrete made with brick chips. This may be due
to inferior quality brick chip, poor workmanship, and improper proportions of mixing. Since brick chip is
inexpensive and normally available, hence used for the low strength structures.