INFLUNCE OF INCREASING WATER:CEMENT RATIO ON THE SOME PROPERTIES OF CONCRETE CONTAINS LOW CONTENT OF POLYMER

1-Abstract This research includes the variation effect of (W/C) water: cement ratio on the properties as compressive strength , flxural strength , density and workability of concrete contains low Polymer SBR ratio. 1:2:4 (cement: sand :gravel) by weight mixes were used . The polymer was added as percentages of cement weight and it was 2%. Reference mix was made. Water cement ratio (w/c) were used are 0.2 , 0.3 , 0.4 , 0.5 and 0.6 respectively and 0.35 (w/c) was used for reference mix . The density of concrete varied between 2030 kg/m 3 and 2360 kg/m 3 .


1-Abstract
This research includes the variation effect of (W/C) water: cement ratio on the properties as compressive strength , flxural strength , density and workability of concrete contains low Polymer SBR ratio.

POLYMER PORTLAND CEMENT CONCRETE (PPCC) .
American concrete institute committee 548 [1] defines the PPCC as an ordinary concrete mix with emulsified polymers added during mixing .The result is a uniform polymeric mesh within the hydration products of concrete.

CONCRETE .
SBR Polymer is the most widely used in concrete. High adhesion occurred between the polymer films that forms and cement hydrates. This action gives less strain compared to ordinary concrete and improves the properties of concrete such as flexural and compressive strength and gives also a higher durability (2 ) .

.PRINCIPLES OF POLYMER MODIFICATION.
Polymer latex modification of cement mortar and concrete is governed by both cement hydration and polymer film formation. The cement hydration process generally precedes the polymer film formation process by the coalescence of polymer particles in polymer latexes (1 , 2 ) . In due course both cement hydration and polymer film formation processes form a co-matrix phase.
The co-matrix phase is generally formed according to the simplified model given by Ohama (1) , and also by Schwiete ( 3,4 ) , shown in fig (1).
Some chemical reactions happens between polymer and cement hydration that leads to improve the bond between cement hydrates and aggregates (1) . ٢٨

Cement
Ordinary Portland Cement (OPC) ASTM Type I from Kubaisa cement factory is used. The cement is complied to Iraqi specification No.5/ 1984.

Aggregates
Coarse aggregates from Aljrayeshi area in Al-Anbar Governorate was used . The grading of both coarse and fine aggregate which were found according to to (B.S. 410: 1976) (5) are shown in tables ( 1 ) and (2 ).

Polymer
Styrene butadiene rubber was used in this work. The chemical composition of which is shown in table (3). The polymer (SBR) was used as a ratio by weight of cement of 2%.

4-MIXING AND COMPACTION OF CONCRETE
Mixing operations were made in the concrete laboratory in the civil engineering department of Al-Anbar University. A 0.07m 3 pan mixer was used.
Pouring both the coarse aggregates and fine aggregate made mixing and cement in two alternate times and mixing them dry while adding the polymer until a homogenous dry mix is obtained. The water is added then and mixing continued until final mixing mix is obtained.
The concrete mix is poured, in three layers, in the molds. An electrical vibrator made compaction for not more than 10 sec.

5-CURING
The specimens were unmolded after 24hrs.in laboratory. They were submerged in water and in the age of 72 hrs. specimens taken out of water until time of test

6-THE MIXES
The mixes which is used in this rsearch is shown in Table 4. The weight of every specimen was recorded air-dry and dimension prior to test.

7.3.Compression Strength Test:
The compression strength tests were performed according to B.S.1881:Part 116:1983 (7) . A100X100X100mm cube steel moulds were used .The moulds were lightely oiled before filling with concrete.ELE machine with a 1000kN load capacity were used for that test.

Density -Polymer Content Relationship:
The results of polymer modified concrete revealed that the lowest 28-day density (air-dry) reached 2030 kg/m 3 for mix2 which it had a w/c=0.2 . The highest was 2360 kg/m 3 for mix4 of w/c=0.3 . The density of reference mix (mix1) (without polymer) is 2360 kg/m 3 .
The water:cement ratio effect is clear in increasing density (see Fig(4)).
This can be attributed to the effect of water in decreasing friction between the agg. Particals.

Slump(workability)-water : cement ratio relationship:
As we see in table (4) and Fig:(6) , the effect of (w/c) is more than 0.3 .
The effect of low content of polymer SBR was not appear clearly in the mixes of low water : cement ratio .
Compressive strength at 180 day age of reference mix (mix1 , w/c=0.35) was equal to 24.7 Mpa. That means low content of SBR polymer which equal to 2% developed the compressive strength only when the w/c is low value , so that at very low water : cement ratio and high water cement ratio the effect of low content of SBR polymer was not appear clearly in developing of compressive strength.