Housing and Building National Research Center,Cairo,Egypt

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1 Green Bricks Units using Different Cement Types and Recycled Aggregates Hanan Elnouhy 1, a, Anwar Mahmoud 1, b 1 Housing and Building National Research Center,Cairo,Egypt a hanan_elnouhy@yahoo.com, b anwarm79@yahoo.com Keywords: recycled aggregates, green bricks, cooling techniques, blended cements ABSTRACT The aim of this study is to produce innovative bricks using 100% "green" building materials. Normal Portland cement CEM Ι 32,5N, Limestone Blended cement CEM ΙΙ B-L32,5, and Slag cement CEM ΙΙ A-S32,5 were used. Two types of coarse aggregates were used: dolomite and concrete rubble as recycled aggregates. Also, two types of fine aggregates were used: sand, and concrete rubble. The manufactured bricks were tested at ages 3, 7, 14, and 28 days. After 28 days of curing, selected mixes were exposed to elevated temperatures of 300 С and 600 С for 2 hours. Afterwards, they were subjected to different cooling regimes. The cooling regimes were air cooling, water cooling (sprayed every 5 minutes for 1 hour immediately after removal from oven), and quenching (immersed in water for 15 minutes immediately after removal from oven). Tests were conducted according to both Egyptian Standard Specifications (ESS) and American Society for Testing and Materials (ASTM) in order to determine compressive strength, absorption percentage, and oven-dry weight. The results showed that all tested mixes, including those subjected to the various cooling techniques satisfied the conditions of load-bearing units and were also of normal weight according to both ESS and ASTM. 1-INTRODUCTION Bricks are a widely used construction and building material around the world. Bricks are either produced from clay with high temperature kiln firing or from Portland cement (OPC), consequently, contain high embodied energy and have large carbon footprint. To reduce the use of OPC, the incorporation of high-pozzolanic industrial by-product content for making concrete masonry blocks becomes a preferred choice. A study investigated the effect of replacing (OPC) by 20% of basalt, as natural pozzolana, on the physico-chemical properties of blended cement in comparison to silica fume, granulated blast furnace slag, and limestone. The results showed that basalt has lower pozzolanic activity at early ages than that of silica fume and slag, but increased at later age. It was concluded that basalt has low pozzolanic activity and has a better filling effect on cement hydration with better physico-mechanical properties than other pozzolanic materials. Extensive research has been conducted on production of bricks from waste materials. However, the commercial production of bricks from waste materials is still very limited. This is possibly due to potential contaminations from the waste materials used, the absence of relevant standards, and the slow acceptance of waste materials-based bricks by industry and public. For mass production of bricks from waste materials, further research is

2 needed on standardization, government policy and public education related to waste recycling and sustainable development [1-3]. Using by-products and waste materials, such as ground granulated blast furnace slag(ggbs), cement by-pass dust (BPD), run-of-station ash (ROSA), basic oxygen slag (BOS), plasterboard gypsum (PG),incinerator bottom ash aggregate (IBAA), recycle crushed glass (RCG),recycled bricks (RB), steel fibre (SF), and PVA-fibre for the production of environmentally friendly paving blocks was investigated. The test results confirmed that a concrete paving mix containing 6.3%GGBS,0.7%BPD and 7% OPC by weight can decrease Portland cement content by 30% in comparison to the percentage currently being used in most factories, without having a substantial effect on the strength or durability of the paving blocks produced in accordance to BSEN 1338:2003[4]. The behavior of high volume fly ash (HVFA) concrete blended with ground granulated blast furnace slag (shortened as slag) under the effect of elevated temperatures was studied. Cement was partially replaced by a Class F fly ash (FA) at a level of 70% to produce HVFA concrete (F70).F70 was modified by partially replacing FA with slag at levels of 10% and 20% by weight. After curing, the specimens were exposed to elevated temperatures. The incorporation of slag showed negative effect on HVFA concrete before and after different heat treatments [5]. Sadek examined the effect of using aircooled slag (ACS) and water-cooled slag (WCS) in solid cement bricks. The behavior of the bricks was evaluated at ambient temperature and after exposure to elevated temperatures. Mixes were prepared in which sand was replaced either partially/fully by either ACS or WCS individually. Results indicated the possibility of recycling ACS and WCS without processing as fine aggregates in bricks production. The use of ACS resulted in a higher deterioration after exposure to elevated temperatures although it increased the compressive strength of unheated specimens. On the other hand, the bricks which contained WCS were thermally more stable than natural sand (NS) and ACS bricks [6].Also, another research was conducted to investigate the behavior of both normal and high strengths concretes subjected to elevated temperatures and subsequently to different cooling regimes [7]. An experimental investigation was conducted on the effect of thermal shock during cooling on residual mechanical properties of fiber concrete exposed to elevated temperatures. Various cooling regimes were used including natural cooling, spraying water for a series of durations from 5 to 60 minutes and quenching in water. Results proved that the rapid cooling regimes such as quenching in water, or water to concrete for 30 minutes or more, caused an action of "thermal shock" to concrete under elevated temperatures. The experimental results indicated that, compared with natural cooling, thermal shock induced by water quenching and spraying water caused more severe damage to concrete, in terms of greater losses in compressive strength, splitting tensile strength, and fracture energy[8]. In this study, the effect of elevated temperatures and various cooling regimes on the properties of aerated concrete was investigated. Air cooled materials were tested at room temperature and in hot condition after exposure to fire. Water quenching effect was determined by testing the material in wet condition right after the quenching and in dry condition at room temperature. Unstressed strength of the material tested hot is relatively higher than air cooled unstressed residual strength up to 600 С. On the other hand, water quenching decreased the percentage of the strength particularly when the material was wet right after the quenching; strength was lost gradually as the temperature rose. As a result, if the quenching effect is disregarded, temperature rise does not have a considerable effect on the strength of the aerated concrete approximately up to С [9]. In this study, the residual compressive strength of concrete with expanded perlite aggregate (EPA) and pumice aggregate (PA) after it was exposed to elevated temperature and then cooled in three cooling

3 conditions (natural, water, and furnace cooling) was investigated. EPA and PA replacements of fine aggregates were 10%, 20%, and 30%. Test results showed that the compressive strength of concrete cooled in water cooling after being exposed to the effect of different mixtures with EPA and PA is higher than that cooled in natural and furnace [10]. 2-Materials and Methods 2.1 Cement Portland cement CEM Ι 32,5N, Limestone Blended cement CEM ΙΙ B-L32,5N, and Slag cement CEM ΙΙ A-S32,5N were used in accordance to ESS /2009.Oxides percentages of cements are presented in table1. Table1:Oxide percentages of used cements Type SiO 2 Al 2O 3 Fe 2O 3 CaO MgO SO 3 L.O.I Na 2O K 2O Total Ins. Res CƖ Na 2OEq. LSF C 3A CEMI 32.5N CEM II/BL 32,5 N CEM II/A-S 32.5 N LSF: Lime Saturation Factor 2.2 Fine Aggregates (sand, and concrete rubble) Siliceous sand and concrete rubble were used with 4.75 mm maximum particle size in this research program. Table 2 gives the physical properties of fine aggregates. Table 2: Physical properties of fine aggregates Property Sand Concrete Rubble Specific gravity Volumetric weight (tons/m 3 )

4 2.3 Coarse Aggregates (crushed stone) Dolomite and of 10 mm maximum particle size was used in this research. Table 3 shows the physical properties of coarse aggregates. Table 3: Coarse aggregate physical properties Property Dolomite Concrete Rubble Acceptance limits Specific gravity Volumetric weight (tons/m 3 ) Absorption Percentage Not more than 2.5% (1) Clay and other fine materials (%) 2 1 Not more than 3% by weight (2) Impact value (%) Not more than 30% (2) (1) According to the Egyptian Code of Practice issued 2007 (2) According to the Egyptian Standard Specifications 1109/ Mix proportions for solid cement bricks and methods The control mix design for the manufactured product was selected from previous research work [11]. Six mixes were cast and tested at ages 3,7,14,and 28 days (except mix 6, which was tested at ages 3,7,and 28 days). Three types of cements were used. After casting, and until testing age, all specimens were sprayed twice daily. Mixture proportions and testing matrix are given in table 4. Solid cement bricks 26 x 12x 6 cm were manufactured by conventional equipment. Concrete rubble was used as replacement for both coarse and fine aggregates. The manufacturing process involves compaction of the mixed constituent materials in a mould followed immediately by extrusion of the pressed product so that the mould can be used repeatedly. Since the finished product is required to be self-supporting and able to withstand any movement and vibration from the moment they are extruded, very much drier, higher fine aggregate content and leaner mixes are used than in the normal concrete work. The demoulding ability is an essential criterion for manufacturing solid cement bricks. The water contents of the solid cement bricks were adjusted based on this criterion. The (w/c) ratio was adjusted to maintain an almost zero slump. It is worth mentioning that the high water content is imperative despite of the dryness of the mixes due to the low cement content. A series of tests were carried out according to ASTM C 67-03a [12] to determine compressive strength, water absorption and Oven-Dry weight, values of the brick samples. The brick samples were tested for compressive strength. The compression load was applied on the face of the sample of dimensions 26 x12 cm. The compression strength was determined by dividing the maximum load with the applied load area of the brick samples.

5 Water absorption and Oven-Dry weight values were obtained as follows: The samples were submerged in water for 24 hours. Then, they were dried with a cloth to remove any water on their surface, and then reweighed. The obtained weight was the wet weight of the sample. The samples were placed in the oven at 105 С and dried to a constant mass and then taken out of the oven and weighed at room temperature. The obtained weight was the dry weight of the sample. The water content of the samples in both its wet and dry state was recorded. The Oven-Dry weights were calculated by dividing the weight of the bricks (in the dry state) by their overall volume. Water absorption values were obtained by dividing the weight difference in both the wet and dry state by the overall volume.. After curing for 28 days, the samples were exposed to 300, and 600 С in an electric oven. Then, the furnace door was opened and the samples were allowed to cool. The temperature was maintained at the respective temperature for 2 hours to achieve a thermally steady-state. Samples which were exposed to 300 С were cooled both naturally and by water cooling (sprayed every 5 minutes for 1 hour immediately after removal from oven), while those which were exposed to 600 С, were also cooled by the two previously mentioned regimes, in addition to, quenching(immersed in water for 15 minutes immediately after removal from oven). Concerning specimens that were exposed to 600 С, compressive strength was determined after applying the three cooling regimes, while absorption was determined after exposure to air cooling and water cooling only. Mixture proportions and test matrix are presented in table 4. Table 4: Mixture proportions and test matrix Constituents Materials (kg/m 3 ) Cement Fine aggregates Crushed Stone Water Slump Zero-1 Mix no. Cement types Aggregates Testing Cooling Regimes after 28 days of Coarse Fine Ages Temperatures casting 1(control) R.T. 300 С Air cooling CEM Ι 32,5N С Water cooling 7 2 CEM ΙΙ B-L32,5N 3 CEM ΙΙ A-S32,5N Dolomite Sand CEM ΙΙ B-L32,5N Concrete Rubble 5 CEM ΙΙ A-S32,5N 600 С Quenching

6 6 CEM ΙΙ B-L32,5N Concrete Rubble 7 28 R.T. 3- RESULTS AND DISCUSSIONS Properties of bricks are herein presented using two approaches: the first one by considering the effect of the different cement types, recycled aggregates, and elevated temperatures to which the specimens were exposed to, while the second one by considering the effect of different cooling regimes. At ages 3,7,14, and Compressive strength The compressive strength was tested at ages 3,7,14, and 28 days for mixes 1to 5. Mix 6 was tested at ages 3, 7, and 28 days. All specimens were sprayed twice daily till testing age It is worth mentioning that the method of testing in the ESS is the same as that in the ASTMC 67. The ASTM states that only three specimens should be tested and did not mention the method of curing nor at what age should the specimens be tested at [12]. Figure1 presents the effect of the three cement types on compressive strength at ages 3,7,14, and 28 days. Sand and dolomite were used as virgin materials in the three mixes. As expected, as age increases, compressive strength increases. At all ages, CEM ΙΙ A-S32,5N (mix 3) provided the highest strengths, while CEM Ι 32,5N (mix 1) yielded the lowest strengths. The limit of load-bearing units was met at age 3 days for the three types of cements, indicating that it is feasible to use the produced bricks after 3 days as load-bearing units (average compressive strength was greater than 13.1 MPa). Regarding non-load bearing limit, it is suggested that cement content be reduced, as the compressive strength was much higher than required (average compressive strength was higher than 4.14 MPa). The effect of using recycled aggregates on compressive strength is shown in figure 2. Mixes 1,4, 5, and 6 satisfied the limit of load-bearing units at tested ages. These results indicate that it is possible to have such bricks in the market at age 3 days. Mix 6 contained CEM ΙΙ B-L32,5N and fully recycled aggregates in order to produce Green bricks. As mentioned earlier, five mixes were exposed to 300 С and 600 С for 2 hours after 28 days of curing. After exposure to 300 С, the specimens were cooled using two cooling regimes: air cooling, and water cooling. Figure 3 presents the effect of the cooling regimes on compressive strength. The results demonstrated that air cooling provided higher compressive strength than water cooling regarding the five mixes. Again,the mixes met the limit of load-bearing units regarding both Egyptian Standard Specifications (ESS) and American Society for Testing and Materials (ASTM). Specimens which were exposed to 600 С were cooled using three cooling conditions: air cooling, water cooling, and quenching. Figure 4 shows the effect of the three cooling regimes on compressive strength. The figure shows that, air cooling resulted in higher compressive strength regarding the five mixes, as opposed to, quenching, which provided the lowest strength. These findings are in agreement

7 with previously research work [8].Yet again, the three cooling conditions satisfied the limit of loadbearing units. Table 5: Strength and Absorption Requirements [13-15] Compressive strength, min,(n/mm 2 ) Average net area Water absorption, max, (Kg/m 3 ) (Average of 3 Units) Weight Classification-Oven-Dry Weight of Concrete, (Kg/m 3 ) average of 3 Units Light weight Medium weight Normal weight Loadbearing units Nonloadbearing Units Less than ( ) or more 208 Fig1: Effects of cement types on average compressive strength

8 Fig 2: Effects of cement types and recycled aggregates on average compressive strength Fig 3: Effects of the two cooling regimes on average compressive strength after exposure to 300 С

9 Fig 4: Effects of the three cooling regimes on average compressive strength after exposure to 600 С 3.2 Oven-Dry weight and water absorption percentage There are three classes of solid cement bricks: normal weight, medium weight, and light weight according to both ASTM C90-03[13] and ESS /2005[14]. The two criteria that specify the categorization of weight are the Oven-Dry weight and water absorption. The results are shown figures 5 to 8. The limits of Oven-Dry weight and water absorption are given in table 5. The average absorption in figure 5 show that all tested specimens provided absorption values less than 208 Kg/m 3 at tested ages regardless of the type of cement. Figure 6 also show that the use of fully recycled aggregates also resulted in water absorption lower than 208 Kg/m 3 at tested ages. Tables 6 and 7 demonstrate that the average unit weight of tested specimens were higher than 2000 Kg/m 3. Consequently, all tested specimens fall in the category of normal weight bricks. Figures 7 and 8 present the effects of the two cooling regimes on average absorption after exposure to the two elevated temperatures. After exposure to 600 С, specimens were tested for water absorption after being exposed to two cooling regimes: air and water.

10 Fig5: Effects of cement types on average absorption Fig 6: Effects of cement types and recycled aggregates on average absorption

11 Fig 7: Effects of the two cooling regimes on average absorption after exposure to 300 С Fig 8: Effects of the two cooling regimes on average absorption after exposure to 600 С

12 Table 6: Unit weight of tested mixes (*1000)kg/m 3 Mix No. Tested days & Aggregate type Coarse Aggregate Fine Aggregate CEM I 32.5 N Dolomite Sand CEM ΙΙ B-L32,5N Dolomite Sand CEM ΙΙ A-S32,5N Dolomite Sand CEM ΙΙ B-L32,5N CEM ΙΙ A-S32,5N Concrete Rubble Concrete Rubble Sand Sand CEM ΙΙ B-L32,5N Concrete Rubble Concrete Rubble Table 7: Unit weight of tested mixes after exposure to elevated temperature (*1000)kg/m 3 Mix No. Temp. &cooling regimes Coarse Aggregate Fine Aggregate 300 C Air cooling 300 C Water cooling 600 C Air cooling 600 C Water cooling CEM I 32.5 N Dolomite Sand CEM ΙΙ B-L32,5N Dolomite Sand CEM ΙΙ A-S32,5N Dolomite Sand CEM ΙΙ B-L32,5N CEM ΙΙ A-S32,5N Concrete Rubble Concrete Rubble Sand Sand

13 4- Conclusions Based on the experimental results obtained from this study, the following conclusions can be drawn: 1) At all tested ages and when virgin aggregates were used, CEM ΙΙ A-S32,5N (mix 3) provided the highest strengths, while CEM Ι 32,5N (mix 1) yielded the lowest strengths 2) The limit of load-bearing units was met at age 3 days for the three types of cements 3) Mixes which were exposed to 300 С and cooled by air and water met the limit of load-bearing units regarding both Egyptian Standard Specifications (ESS) and American Society for Testing and Materials (ASTM). 4) All tested specimens were of normal weight irrespective of cement types, aggregates types, testing ages, and cooling regimes. References [1] L.Zhang, Production of bricks from waste materials-a review, Construction and Building Materials. 47(2013) [2] P.Chindaprasirt, T.Cao, The properties and durability of high -pozzolanic by-products content concrete masonry blocks, Eco-Efficient Masonry Bricks and Blocks. (2015) [3] M.Saraya,Study physic-chemical properties of blended cements containing fixed amount of silica fume,blast furnace slag,basalt and limestone, a comparative study, Construction and Building Materials. 72(2014) [4] E.Ganjian,G.Jalull,H.Sadeghi,Using waste materials and by-products to produce concrete paving blocks, Construction and Building Materials. 77(2015) [5] A.Rashad,An investigation of high-volume fly ash concrete blended with slag subjected to elevated temperatures, Journal of Cleaner Production. 93(2015) [6] D.Sadek, Effect of cooling technique of blast furnace slag on the thermal behavior of solid cement bricks, Journal of Cleaner Production. 79(2014) [7] C.Rao, R.Kumar, A study on behavior of normal strength concrete and high strength concrete subjected to elevated temperatures, International Journal of Civil, Structural, Construction and Architectural Engineering. 9(2015) [8] G.Peng,S.Bian,Z.Guo,J.Zhao,X.Peng,Y.Jiang,Effect of thermal shock due to rapid cooling on residual mechanical properties of fiber concrete exposed to high temperatures, Construction and Building Materials. 22(2008) [9] L.Tanacan,H.Ersoy,U.Arpacioglu,Effect of high temperature and cooling conditions on aerated concrete properties, Construction and Building Materials. 23(2009) [10] M.Karakoc, Effect of cooling regimes on compressive strength of concrete with lightweight aggregate exposed to high temperature, Construction and Building Materials. 41(2013) [11] H.Elnouhy, Current and Future Management Plans for Recycling Construction and Demolition Waste in Egypt. Ph.D. thesis (2004), Faculty of Engineering, Cairo University. [12] ASTM C67-03: Standard Test Methods for Sampling and Testing Brick and Structural Clay Tile. Philadelphia,PA: American Society for Testing and Materials [13] ASTM C 90-03: Standard Specification for Loadbearing Concrete Masonry Units. [14] ESS1292-1(2005): Concrete Masonry Units, Part 1: loadbearing Concrete Masonry Units. [15] ESS1292-2(2005): Concrete Masonry Units, Part 2: Non-loadbearing Concrete Masonry Units.

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