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Cau 1: Trinh bay trang thai cau tao rong cua VLXD. Do rong va t/c cua lo rong a/h toi cac t'c chu yeu cua VLXD ntn?

1/ Trang thai cau tao rong cua VLXD:

- VL cau tao rong la nhung loai VL co nhung lo rong lon nhu be tong kho, be tong bot, chat deo to ong hoac nhung loai VL co lo rong rong be (VL gom dung phu gia chay, dung du n°Ûc).

- Trang thai ctao rong cua VLXD dac trung boi do rong. Do rong r la ti le cua cac the tich o rong so voi tho tich tu nhien r= Vr/Vv .100%

Duoc xac dinh bang phuong phap do the tich Áv va kluong rieng Á

r= (1- Áv/Á) .100%

- Lo rong trong VL go^'m lo rong kin va lo rong ho

+ Lo rong ho la lo rong thong voi mtruong ben ngoai '! co the trao doi chat voi mtruong ben ngoai

+ Lo rong kin la cac lo rong nam trong VL, ko trao doi chat voi mtruong ben ngoai

- Doi voi VL dang hat con phan ra lo rong trong hat va lo rong giua cac hat

- Do rong cua VL dao dong trong 1 pham vi rong tu 0÷98%

2/ Anh huong toi cac t/c chu yeu cua VLXD

Do rong: + cuong do, k/n chiu luc cua VL: VL rong co kha nang chiu luc, cuong do nho hon cac VL cung loai dac si't.

+ Do chong an mon kem hon cac VL dac cung loai, tinh chong tha^'m kem' hon

+ K/nang cach nhiet va cach am tot hon

T/c cua lo rong: +VL chua nhieu lo rong kin co cuong do cao hon VL chua nhieu lo rong ho

+ VL chua nhieu lo rong kin cach nhiet tot hon

+ VL chua nhieu lo rong ho thi hut am tot hon

Cau 2: Cac chi tieu danh gia chat luong voi ran trong khong khi:

- Voi ran trong khong khi con goi tat la voi, chat luong cua voi cac tot khi ham luong cao cang cao va cau truc cua no cang tot (de t/d voi nuoc).

- Phuong phap xac dinh: De danh gia chat luong cua voi la xdinh 1 cach dinh luong hoac dinh tinh ham luong cao qua 4 chi tieu sau day:

1/ Do hoat tinh cua voi (x%)

- K/n: la ti le cua CaO+ MgO co trong voi:

- Phuong phap xac dinh: Phuong phap chuan: luong HCl dung de chuan co nong do 1N la V(cm3) va kluong voi dem thi nghiem la g (g) thi x= (v.0,0284/g) .100%

- Y nghia: Do hoat tinh cao xe"90% '! voi tot

2/ Nhiet do toi va toc do toi

- K/n: +Toc do toi la tgian (phut) tu khi cho 1 luong voi t/d voi 1 luong nuoc nhat dinh cho toi khi dat t° cao nhat.

+ Nhiet do toi la nhiet do cao nhat dat duoc trong qua trinh toi voi (°C)

- Phuong phap xac dinh: Phuong phap chuan, cho 1 luong voi t/d voi 1 luong nuoc nhat dinh, dung dong ho bam giay va nhiet ke xac dinh nhiet do cao nhat trong qua trinh toi vat hoi gian tu khi toi'! dat nhiet do cao nhat do/

- Y nghia: Voi cau truc hop ly va hoat tinh lon thi voi se co toc do toi nhanh va t° toi cao (>90°C) '! voi tot.

3/ San luong voi:

- K/n: la luong voi nhuyen (l) do 1 kg voi song sinh ra

- Phuong phap xac dinh: Cho 1 luong voi song t/d voi 1 luong nuoc nhat dinh '! voi xuat hien cac vet nut chan chim '! do the tich voi nhuyen

- Y nghia: Khi do hoat tinh cua voi lon thi luong voi nhuyen sinh ra nhieu (1,5 ÷3 lan) '! voi tot

4/ Ham luong hat suong (hat non lua va gia lua)

- K/n: la hat khong bi toi lai tren sang N063 sau khi sang voi nhuyen trong nuoc.

- Phuong phap xac dinh: sang N053 (124 lo/cm2)

Cau 3:

V= 2432kg/m3; 1:x:y(z) =1:2:4 (0,6)

Á= 2,6g/cm3); Áv= 1500kg/m3

±=?

Luong vat lieu dung cho 1m3 be tong:

X= 2432/(1+2+4+0,6)= 320 kg

'!C= 2X =640kg

D= 4X= 1280kg

N= 0,6X= 192kg

CT tinh luong da dung cho 1m3 be tong la

D= 1000/(±.r/Áv +1/Á)

trong do r=1 Áv/Á= 1- 1,5/2,6 =0,423

1280= 1000/ (0,423.±/1,5 + 1,5/ 2,6) '! ±= 1,407

Cau 3:

Go 2x2x3 cm; W=12%; P= 2240kg;

Xd Rnd voi W=15; 20; 25; 30; 35;40 (%)

Wbh= 34%; ±nd= 0,04;

Bai giai:

Cuong do nen doc tho o do am 12% la:

R12nd= P/S= 2240/ 2.2= 560 (kg/cm2)

Cuong do nen doc cua go o do am tieu chuan:

R18nd= R12nd [1+ ±nd(12-18)]

= 560. [1+0,04(12-18)]= 425,6 (kg/cm2)

Tinh cuong do cua go o cac do am khac, khi Wd" 34= Wbht

Ta co:

RWnd= R18nd/ [1+±(W-18

= 425,6/ [1+ 0,04.(15-18)= 483,6 kg/cm2

W=20% '! R20nd= 394,1 kg/cm2

W=25% '! R25nd= 332,5 kg/cm2

W=30% '! R30nd= 287,6 kg/cm2

W=34% '! R34nd= 259,5 kg/cm2

Khi W> Wbht= 34% thi lay cuong do bang cuong do o diem bao hoa tho

W40= W35=W34=259,5 kg/cm2

Cau 1:

Cuong do cua BT nang? Anh huong cua cuong do da XM den cuong do BT?

1/ Cuong do cua BT nang:

- K/n: la dai luong dac trung cho BT o trang thai pha hoai duoi t/d cua luc

- Su '! cua cuong do BT theo thoi gian:

Rm/Rn= lgm/lgn

m,n: tuoi cua BT

m,n e" 3 ngay (3÷90 ngay)

Tuoi tieu chuan danh gia: 28 ngay

- CT danh gia: Rbt =A. Rx (X/N ± 0,5)

A: he so ke den anh huong cua cot lieu

Rx: mac xi mang

- Phuong phap xac dinh: + pha hoai mau: 150x150x150

+ kop ha hoai mau: sung bat nay, sieu am

2/ Anh huong cua cuong do da XM '! cuong do BT

CT: Rb= A.Rx (X/N ± 0,5)

Neu Rx lon "! cuong do da xi mang cao thi cuong do BT cao va nguoc lai

Cau 2:

Khoi luong the tich cua VLXD:

1/ K/n: la khoi luong cua 1 don vi the tich VL o trang thai tu nhien

2/ CT: ÁV = m/VD (g/cm3; kg/m3; T/m3)

m: kluong cua VL

V0: the tich

3/ Phuong phap xac dinh

- VL co kich thuoc hinh hoc: can va do kich thuoc

- VL ko co kich thuoc xd: can khoi luong va do V= phuong phap chat long chiem cho (neu chat long tham nuoc thi phai boc 1 lop nen)

- VL roi thi can va do V = cach do VL tu 1 chieu cao nhat dinh xuong 1 cai ca biet V truoc

4/ Cac yeu to anh huong

- VL cung loai, cau tao khac nhau thi ÁV khac nhau

Neu VL co cau tao lo rong thi' ÁV nho hon VL cung loai

- ÁV phu thuoc vao moi truong kho am khac nhau: Neu moi truong am thi ÁV lon hon

5/ Y nghia

- Phan doan 1 so tinh chat nhu cuong do, do rong

- Lua chon phuong tien van chuyen VLXD thich hop

- Tinh toan trong luong ban than ket cau

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